The importance of good ventilation in classrooms has been recognised since Victorian times, but many of today's schools fail to reach even basic levels of indoor air quality. Ewen Rose reports on a growing health crisis.
Montgomery Primary School in Devon is the UK's first zero carbon, climate – change ready school. Andy Pearson takes a look at the fabric first, 'tea cosy' principles behind the design of this award-winning building.
When it comes to achieving outstanding results Montgomery Primary School, in Exeter, is top of the class. The UK's first zero-carbon school, it is also the country's first Passivhaus school and its first climate-change-ready school. If all that were not enough, this pioneering £8.9 m scheme was recognised by CIBSE at the Building Performance Awards 2014, at which it won the New Build Project of the Year award for schemes under £10m.
The zero-carbon target for the 420-pupil school was set by the client, Devon County Council, in 2008. The council had secured additional funding from the Priority School Building Programme - along with a grant from the Zero Carbon Task Force - to create an exemplar zero-carbon school that would help to increase knowledge and understanding of low-energy school design. The council worked with engineers Hamson JPA, and their architect and quantity surveyor affiliates at NPS Group, plus Exeter University's Centre for Energy and the Environment, to develop the design. The team set out to pioneer a new approach to primary school design. The simplest solution to meeting the client's zero-carbon aspirations would have been to construct a conventional Building Regulations-compliant building, which could be transformed into a zero-carbon solution using a biomass boiler for heat and hot water, and a green electricity tariff for electrical power. Such an approach was considered unsustainable by the design team.
'This solution is without value because it relies on the continued use of precious resources,' says the project's quantity surveyor, Chris Rea, from NPS Group. By contrast, Montgomery Primary School has been designed to minimise its use of resources, so that all energy for heating, lighting and power is generated on site.
“The space heating requirement of the school is now so small that the primary source of heat input is body heat from the pupils and teaching staff”
The starting point for the resource-lean design was to minimise fabric heat losses. The new two-storey school has been built within the grounds of the 1930s primary school it has now replaced. It is oriented north-south, with the majority of classrooms facing north and the more flexible teaching spaces to the south. A double height, central atrium-corridor divides the spaces. Passivhaus standards were adopted for the design of the building fabric. These set a limit of 120 kWh/m' /year primary energy use, and 15 kWh/m'/year for heating and ventilation - significantly lower than the 55 kWh/m'/year for a typical school. To meet the heating target, the school's walls have been assembled from highly insulated, precast concrete sandwich panels, comprising 100 mm of high performance, rigid foam insulation, sandwiched between a 100 mm-thick concrete inner leaf and 70 mm outer skin.
Concrete was selected for its high thermal mass, which was deemed essential in enabling the step-up from Passivhaus to zero carbon. Pressure to complete the 2,786m2 building in time for the school term forced the design team along the precast, modular route. At the time the modular fabric solution was being developed, building services design was not sufficiently advanced to enable these to be incorporated into the precast units.
On top of the precast walls is precast concrete roof deck, blanketed with 200 mm of extruded polystyrene insulation. Underneath the building is a 150 mm layer of expanded polystyrene to insulate the cast, in-situ raft foundation and floor slab from the ground. 'We've adopted the same principle as a tea cosy, with insulation placed on the outside of the building to allow the thermal mass of the concrete structure to be fully exploited,' explains Rea.
Compliance with Passivhaus standards has ensured the school is exceptionally airtight. 'We followed the maxim "build tight, ventilate right",' says Rea. An air-seal barrier layer was defined in the modular wall, roof and floor constructions at the outset In addition, construction joints were carefully detailed and unavoidable service penetrations and other openings were kept as regular circles or rectangles to match the pipe or duct, and to make them easier to seal. To ensure the detailing was flawless, regular workshops were undertaken with all members of the construction team; for some of the more critical details, samples were prepared and tested on site to verify their performance.
The team's efforts were successful. The Passivhaus air-leakage standard is o.6 air changes per hour at 50 Pa; the focus on air tightness at Montgomery has enabled the building to achieve an impressive 0.28 air changes per hour at 50 Pa.
The fabric-first approach dramatically reduced the space heating requirement of the school. In fact, this is now so small that the primary source of heat input is body heat from the pupils and teaching staff.
A mechanical ventilation system with heat recovery ensures optimal thermal comfort is maintained throughout. Warmed fresh air is supplied to the teaching spaces. This returns to the air handling unit (AHU) through a high-level transfer grille into the building's central atrium-corridor, from where a high-level grille allows the air to return to the AHU in the plant room. This enables excess heat to be moved from high-occupancy spaces to spaces with a lower occupancy and a demand for heat.
Top-up heat is provided by electric heating elements mounted in the air supply ducts. The electric elements are set to operate on manual boost or fabric frost protection only. To protect against overuse, the boost feature is restricted to returning the room to the design set-point temperature. The advantage of this simple heating system is that it has zero losses when not in use and is almost 100% efficient in operation. 'Using electric heaters enabled us to offset this electricity using roof mounted photovoltaic panels.' says Rea.
The ventilation system operates in two modes. In winter, when heat is required, the building is predominantly mechanically ventilated using a variable air-volume strategy under control of the Building Energy Management System (BEMS). This uses temperature and C02 sensors to control dampers to alter the volume of air supplied. The BEMS also varies the speed of the fans in the building's AHU to minimise expended fan energy, while keeping the system in balance.
Energy consumption in the AHU is further minimised by a reversing regenerator unit. This uses two metal heat-exchanger packs to absorb heat from the exhaust air stream, and a series of dampers to reverse the airflow through the unit mechanically, once every minute. Initially, warmed exhaust air passes through one of the aluminium regenerator units, heating it before it is discharged. Simultaneously, cold supply air passes through the other, warmed, regenerator unit, where it picks up heat before it is supplied to the school. After 60 seconds, the control dampers reverse the airflow direction so that the regenerator warmed by the exhaust air now imparts heat to the incoming air, while its twin is regenerated by the warm exhaust air stream. The system is claimed to operate with 93% heat-recovery efficiency.
In summer, the building operates on a natural ventilation strategy. Each classroom has manually opening, triple-glazed windows that allow cool, fresh air to enter the room. This fresh air drives stale, warm air upwards to the transfer grille, and out into the central atrium-corridor, where large roof Iights open under control of the BM S to create a stack-driven, low-pressure, ventilation system. The effectiveness of the design was proven by modelling using IES: Virtual Environment software.
Summertime overheating of the highly insulated school is mitigated by the high thermal mass of the building fabric. In extreme circumstances, the natural ventilation system can operate overnight to remove excess heat to pre-cool the thermal mass for the following day.
In the same way that the building fabric was modularised, so too are the building services. Early involvement of the building services contractor, NG Bailey, enabled the ductwork and lighting assemblies to be supplied as modules and lifted into place. To reduce the lumen output of the lighting, the rooms all have light-coloured walls. In addition, absence detection and daylight sensors turn off lights in unoccupied spaces to minimise energy consumption.
On-site renewable sources are used to enable the school to meet the zero-carbon, in-use target Photovoltaic panels were found to be the most appropriate technology to meet the school's predicted 166,000 Wh/y energy requirement. Around 900 m' of Sanyo HIT N-235 SE10PV of PV panels are located on the south-facing pitch of the roof. The electricity these generate is fed into the national grid.
Electricity generated by the PVs is not used to heat the hot water, although it is used for the trace-heating system, which keeps the water warm in the distribution pipe work. Instead, the hot water is heated throughout the year by a high-temperature, C02 air source heat pump, which picks up heat from the kitchen extract. Modelling showed this solution to have the lowest overall energy use of all possible options.
To enable the teaching and facilities staff to familiarise themselves with the innovative technologies and solutions employed at the school, the client specified an extended commissioning period in the contract. In addition, the team used the BSRIA Soft Landings approach for the handover and follow-up visits.
'The structure provided by this approach enabled the school staff, design team, client and contractor to work together to identify and resolve issues that - if left unsolved – would have compromised the school's low-energy operation and client's satisfaction with the scheme,' says Rea.
The design complies with the requirements of Building Bulletin 101: Ventilation of School Buildings. Unusually, the school has a 60-year design life. The scheme has been modelled by Exeter University and found to be sufficiently robust to ensure conditions remain comfortable, without overheating in the school, even as the climate changes up to 2080.
“The scheme is sufficiently robust to ensure conditions in the school remain comfortable. even as the climate changes up to 2080”
The scheme was completed in October 2011. Its measured energy performance figures are: 12 kWh/m'/year space heating and 167,358 kWh/ year total energy, including energy used in the kitchen. Despite these outstanding low-energy credentials the building has only managed a DEC band B because of its reliance on electricity for top-up heating. Monitoring has shown that, over the course of a year, the amount of electricity generated by the PVs is equal to that imported from the grid.
From the school's perspective, its carbon neutral performance means that the manager doesn't have to budget for heating and electricity costs over the coming year. Instead, any savings on the utility bills can be used to support future maintenance and educational budgets, to make the school a zero-carbon, self-sustainable, stand-alone environment of learning.
Pearson, A. (2014) ‘The full Monty’, CIBSE Journal, April 2014, pp. 4-8
Zero carbon is great as a political aspiration but will it stack up effectively as a policy? Richard Hillyard examines Government aims to impose zero carbon targets on the construction industry. Back in July 2007 the Government published the Building a Greener Future statement. This policy document announced that all new build homes would be zero carbon from 2016.
The definition of zero carbon requires new dwellings to take into account:
- emissions from space heating, ventilation, hot water and fixed lighting,
- exports and imports from the development (and directly connected energy installations) to and from centralised energy networks.
Note:- Expected energy use from appliances is excluded from zero carbon definition.
By following this policy the Government expects new buildings to have net zero carbon emissions over the course of a year.
The definition of zero carbon consultation subsequently introduced by the government, sought views on the Government's proposals. This consultation ran from 17 December 2008 to 18 March 2009 and goes on to explain how to achieve net zero carbon emissions.
The Government also announced that from 2019 all non-domestic new builds will also be required to have zero net carbon emissions, with earlier dates for schools (2016) and public sector buildings (2018).
Wisely, the government set boundaries to what it meant by zero carbon. The embodied energy content of construction materials is not covered, and neither is the transportation of materials. Additionally, transport emissions associated with developments are not included as the government intends to deal with these through other policy instruments.
Given these omissions, it could be argued that Government's proposals do not equate to zero carbon. Even if it is not possible (nor cost-effective) to construct a building without generating any greenhouse gases, how far could we get by dramatically improving the efficiency and sustainability of construction methods?
In any case, does it really matter? Less than one per cent of the UK's existing building stock is replaced every year, and it's been estimated by the Department for Communities and Local Government (CLG) that 87 percent of the current housing stock will still be around in 2050. That means that the UK cannot meet its carbon reduction targets without a far-reaching retrofit programme for existing buildings.
The UK Green Building Council's proposal for a Code for Sustainable Buildings will play an important role in improving the focus on energy efficiency in existing buildings. But this is just one of a hierarchy of measures that the Government says will be needed.
The consultation document proposes a three-stage hierarchy for designers to achieve zero-carbon. The first step for energy efficiency requires compliance with Part L of the Building Regulations. This stage may also encompass other regulatory instruments, such as a mandatory requirement to design to Level 6 of the Code for Sustainable Homes.
The second stage proposed by Government is something called Carbon Compliance', which essentially is the use of on-site micro-energy generation. A report by the UK GBC Zero Carbon Definition Task Group believe over 80 per cent of homes in the UK to be unable to achieve zero carbon targets this way. The development of near-site and off-site low and zero-carbon energy generation is also being proposed.
Initially there were reservations over whether the use of biomass technologies could be included in the zero carbon strategy. However, the government appears to be in full support of using biomass systems both within new homes and as a source of direct heat from nearby off-site generation.
The third stage in the zero-carbon strategy is what is known as allowable solutions', which is a buy-out fund or form of carbon offsetting through high quality international investment in low and zero carbon projects.
This third way will, it is believed, only be permitted where energy efficiency and carbon compliance are unable to be achieved totally through on-site and near-site measures achieve the goal of zero carbon - in other words the residual emissions.
The government is proposing a system of credits to permit off-setting to occur. Credits will be awarded to developments that have a range of energy-saving criteria. For example, energy-saving appliances and low and zero-carbon technology capable of exporting energy to the grid will earn credits to enable an offset of residual carbon emissions.
The government would prefer off-site low and zero carbon technologies to be included in this part of the hierarchy by feeding into the national grid.
So will the policy work? The first two parts of the hierarchy - energy efficiency and carbon compliance - are signs of forward thinking. With a few tweaks, off-site low and zero carbon energy generation could play an integral part of reaching the zero carbon target, but only if the contribution from the grid can be guaranteed to be clean.
Other questions remain to be answered. For example, with allowable solutions, will off-setting contribute to reducing carbon dioxide emissions enough for claims of zero carbon to stack up - not just initially but over a sustained period? Or is it, as some might argue, just a way of covering up holes in the system, and easing collective guilt?
Off-site low and zero carbon energy generation technologies sounds like reasonable measures, but if they are supplying to the grid as opposed to supplying directly to a development, what guarantees will there be that this clean energy will not be lost in the overall electricity generation? This is a key issue, especially when it's mixed with the output from the proposed eight new coal power stations (each potentially generating eight million tonnes of CO2 per year) that the Government is keen to build.
These questions highlight the credibility gaps that still exist between intention and delivery in Government's push for a low carbon and sustainable energy future. Whatever transpires following the zero-carbon consultation, tackling the issue effectively will not only significantly affect the environment, but also our pockets.
Zero carbon targets on the construction industry, [Online], Available: http://www.bsria.co.uk/news/article/clean-home/ [18 March 2014].
In part 1 of a 2 part article, Mark Siddall of Low Energy Architectural Practice: LEAP [www.leap4.it ] observes that there appears to be mounting confusion about the Passivhaus standard and Passivhaus Certification. Here he reflects upon the implications of such misunderstandings. It’s time to straighten out some the facts. The government has undertaken a legal commitment to reduce carbon emissions by 80% by 2050 and is developing tools and strategies to try and ensure that this commitment is satisfied. This has led to the rise of the Code for Sustainable Homes and a series of net- zero carbon targets for new build projects - whereby homes are to be net-zero carbon by 2016; schools and pubic buildings by 2018; and commercial buildings by 2019. However, recent research by Leeds Metropolitan University has found that homes built to energy performance standards, including Building Regulations, are not performing as required. This fact alone raises some important concerns. Quality assured Passivhaus buildings have been proven to perform in accordance with theory. However, in the UK, there are growing number of projects that people claim to be Passivhaus buildings but upon closer analysis do not appear to satisfy the rigorous quality assurance requirements established by the Passivhaus standard. This introduces risks that could damage the growing reputation of the standard before it has been properly established.
A quick recap
In case you didn't know, the Passivhaus standard, is the world's leading energy efficiency standard and it can be applied to all manner of building typologies including homes, offices, schools, care homes etc. Of late I've been to a number of meetings and conferences where it has emerged that people tend to think that the Passivhaus standard is 'a number' or perhaps a series of 'energy performance parameters.'
The basic, well publicised, performance requirements that tend to be recited include:
• an annual energy consumption for space heating of s 15kWh/m2.yr
• a primary energy requirement of less than 120kWh/ m².yr (best practice being less than70kWh/m2.yr)
• an air leakage of less than O.6ach@50pa when tested in accordance with EN 13829
• perhaps they are also aware that the risk of overheating should be s 10% (with best practice being less than 5%).
What is not recognised in these statements is the background to these standards. Supporting these basic requirements are a number of other, less widely
appreciated requirements that serve to deliver thermal comfort and energy performance, all via a carefully structured quality assurance system.
Towards a need for quality assured buildings
Rather than discuss the process of delivering low energy buildings, people seem to have a fascination with design targets. The question is, do these targets turn into a reality? When asked how he got involved in working on low energy buildings, Dr Wolfgang Feist, founder of the Passivhaus Institut (PHI) said; "I was working as a physicist. I read that the construction industry had experimented with adding insulation to new buildings and that energy consumption had failed to reduce. This offended me - it was counter to the basic laws of physics. I knew that they must be doing something wrong. So I made it my mission to find out what, and to establish what was needed to do it right."
In this respect I personally find the above statement by Dr Feist rather intriguing for it indicates to me that in Germany, just as the UK, quality assurance is key to the delivery of truly low energy buildings.
In the context of a Passivhaus building, what is meant by 'quality assurance' needs to be clearly understood. Here it includes the correct building physics concepts,
the correct application of these concepts during design and specification processes and finally the correct implementation on site. Various aspects of these quality assurance issues will be considered in more detail below, but first it is useful to provide a little background as to why this quality assurance is required. A little bit of history will serve to make a point.
The history of the low energy standard
In 1983 Sweden developed an energy performance standard that limited the space heating 50-60kWh/m².yr (the theoretical performance of the 2006 UK building regulations). In Germany it was recognised that the average German home uses 200kWh/m².yr for space heating and that if Swedish energy standards were to be adopted then a factor four reduction in energy demand could be achieved; this led to the rise of the largely unofficial voluntary 'low energy standard.' This eventually led to a tendency for architects and builders to make claims about having built low energy houses simply because they orientated the house in a southerly direction or applied an extra couple of centimetres of insulation. After a while newspaper articles began to crop up with statements such as 'family uses more energy in their new low-energy home than in the old heritage building they previously occupied', 'mould problems in low-energy houses', or 'low-energy houses are only for the hardiest, as they stay quite chilly in winter to save on energy.' Anyway you get the point, the buildings were not delivering the required performance and the public felt duped as they understandably began to believe that there aren't any real benefits from 'energy efficient' buildings. In this context it is not surprising that German research into building physics found that low energy buildings did not always perform as expected - eerily, as recorded by Leeds Metropolitan University, this finding is reflected in UK experiences. As noted in the quote above it was with this in mind that Dr Feist set out to understand what was going wrong.
Later, in order to overcome the failures in quality assurance, RAL 965 was developed for the low energy buildings. This simultaneously created a definition for low energy buildings, protected the design standard from abuse and, as a basic term and condition for delivery and sale, provided the people requiring low energy buildings with a quality assured product. Interestingly, the most recent version of RAL 965, issued in 2009, also includes the Passivhaus standard and requires that both Low Energy buildings and Passivhaus buildings are designed using Passivhaus Planning Package (PHPP). In many respects the energy performance standards delivered by the CarbonLite Programme, which was developed by the AECB, seek to establish a programme that is akin to the RAL standard, both in terms of its numerical prescription and the development of trained and informed builders and designers.
Delivering quality assured buildings
After the successful completion, and perhaps more critically, the validation of the original Passivhaus project in Darmstadt (1991-93) Dr Feist and his team at the Passivhaus Institute began to develop the PHPP. This design tool is a simplified means of ensuring that all the requisite aspects of the comfort criteria and building physics are addressed in the appropriate manner and in the necessary detail. Whilst detailed discussion of these criteria is beyond the scope of this article, suffice to say that PHPP carefully considers heat losses and gains associated with airtightness, ventilation, thermal bridging, solar gains, internal gains and the like.
For a Passivhaus the use of PHPP is the most fundamental aspect of the quality assurance process. One of the principal benefits that PHPP offers is that the designer does not have to return to first principles as a number of assumptions have been researched, established and validated by PHI and then included in the design tool. In addition, not only does the tool include all the necessary aspects of building physics that need to be considered, but it also establishes a datum that allows one Passivhaus to be compared to another. In this respect it should be recognised that PHPP establishes a number of conventions which can simplify the design process and enable validation. At this time not all of the conventions in PHPP agree with UK methodologies, often for good reason. The heating energy demand, as calculated by PHPP, has been validated against the monitored heating energy consumption of more than 500 new homes.
Gerit Horn, in a paper on the legal aspects of designing and constructing Passivhaus buildings, remarked that the 'agreement to plan and construct a Passivhaus means that the calculation methods used in PHPP apply for the determination of compliance with the Passivhaus standard.' On this basis the requirement for a Passivhaus should form a part of the contractual obligations of the design team and the contractor, furthermore, these requirements should be clearly defined as otherwise the client will not be able to demand compensation based upon the PHPP calculations.
Recent claims in the UK
Recently I have found that I have had the issue of quality assurance in mind when I read the various articles in the press where people (journalists, clients, architects or builders) have made claims about schemes that have been designed to the Passivhaus standard or having completed Passivhaus buildings.
At first I always find the reports of a new Passivhaus very encouraging but after a while, as I read the article, I repeatedly find tell tale signs - errors and omissions - that suggest that the projects are not actually Passivhaus buildings at all, Worst of all in some cases there are even claims of building in accordance with Passivhaus 'principles' - these projects are certainly not Passivhaus buildings. Whilst they are no doubt designed and built by well meaning individuals, the projects have not been subjected to the same level of rigorous analysis (leading to inappropriate specifications), they have not used the correct design tools (leading to erroneous assumptions) and they have not been subject to the same standard of quality assurance (which means that errors can creep in and as a consequence theory and reality will not converge).
Now I can hear you, the reader, say "Do such claims matter?" To me the obvious answer is a resounding 'yes'. For instance, imagine if someone claimed to have a 'BREEAM Outstanding' office. Would you expect them to have certification to prove it, or would you think it OK for them just to pass it off without actual substantiation - just because they tried harder than usual? At the moment what I have witnessed is that this kind of thing is happening with the Passivhaus standard - here and there people are making ill-informed, often unsubstantiated, and false claims. Whilst energy efficiency is the focus of the Passivhaus standard it is an over simplification to suggest that it is 'simply' an energy standard. It is in this respect that it should be recognised that Passivhaus is also a quality assurance standard. In order to deliver buildings that perform as predicted, as a quality assurance system, Passivhaus works on a number of levels and includes; certifiers, designers, components and ultimately buildings.
Is all this quality assurance required? Perhaps it is worth considering the need for quality assurance in the context of building performance. There is mounting evidence to suggest that buildings that are being designed to achieve thermal performance standards, including the Building Regulations, are in some cases consuming in excess of 70- 100% more energy than the predicted values. In light of the recent discussions at Copenhagen, if there was ever a need for quality assured construction it is now. The old adage 'you cannot manage what you cannot measure', would seem particularly true here.
Certification schemes such as BREEAM and the Code for Sustainable Homes (CSH) are well meaning. However, by being broad-brush design tools they do not focus sufficient attention upon the key details that can influence a building's design and ultimately its energy performance aspects. By not focusing attention on the important details it is unlikely to perform appropriately when the building is realised - leading to increased energy costs, increased carbon emissions and greater occupant discomfort. In this respect BREEAM and the CSH fail to offer a sufficiently rigorous quality assurance and, furthermore, this kind of tool has been shown to incorporate what can only be described as perverse incentives that can actually encourage designs that run counter to the greater ambition.
It was in this context that, within the UK, the AECB launched its CarbonLite Programme as a means of improving the quality of the buildings that are constructed. The programme has, to date, concentrated upon improving the quality of design skills, and though practical training for builders is yet to be commenced, much of the current course could be beneficial to contractors and sub contractors as it would serve to raise awareness of key issues.
Evolution or revolution?
The rise of the CSH has led to a dearth of 'innovators' each with their own untried and untested super product/ concept. Whilst it is great that the UK construction industry is finally thinking, there is an inherent danger of reinventing the wheel at great expense. Perhaps we could in fact be learning from projects that have already been developed, trailed, tested, verified and proven to work.
The Darmstadt Passivhaus was a research project funded by one of the state governments. The building physics models for the project were complex and dynamic; much beyond what is required, affordable and replicable for normal construction. The physics was then tested by building a real house that was occupied by families for years, rather than weeks, and was rigorously monitored throughout this period (in fact the houses are still occupied). This is a far cry from the 'demonstration' houses at the BRE Innovation Park.
After all this complex research and analysis the Passivhaus Institute went on to develop a simplified design tool that that would enable mainstream construction to replicate the results. This tool became the Passivhaus Planning Package (PHPP). Since then the Passivhaus standard has been proven to be cost effective time and again in studies across Europe, meanwhile much of the UK construction industry is wasting time, and money, trying to corner a market and score a bit of brand recognition. I just find myself asking whether it would it be wiser to learn from experience. When given the choice of evolution or revolution, I'd choose evolution.
Why are such issues of building physics and quality assurance vital? In light of the threat of climate change the government has undertaken a legally binding commitment to reduce the UK's carbon emissions by 80% by 2050 and other issues deserving attention, such as fossil fuel depletion and fuel security, there is a significant challenge to the status quo. This reduction target is not theoretical, to address climate change no amount of accountancy will solve the problem, this target must be achieved in reality.
It is in this context that the research by Leeds Metropolitan University becomes so powerful for they have found repeatedly that homes can, and are, failing to perform in accordance with design standards. As the theoretical targets become more stringent so the gap appears to widen. It is worth recognising the systematic errors that can occur in low energy or 'super-insulated' buildings designed to something akin to PassivHaus 'principles':
• the appropriate building physics design model is not used from the beginning of the design process, ie. not using PHPP - this leads to systematic errors
• the correct area and geometric conventions are not used to establish the energy performance - heat losses and energy consumption figures can be distorted
• incorrectly calculated U-values lead to an under estimation of the heat losses (an error of 30% is possible)
• the notional Passivhaus U-values are used - leading to an increase in energy demand (using this method it is unlikely that the 1 5kWh/m2.yr target will be achieved)
• thermal bridging is not accounted for appropriately which can lead to increased heat losses. (Poorly defined and inadequately designed details can result in 50-100% more heat loss than intended)
• incorrectly specified windows and doors can lead to heat losses being 60% higher than expected due to additional heat losses via the frame and spacer bar
• incorrectly specified heat recovery ventilation systems can lead to an increase in energy consumption of 25% (specifically by the use of uncertified heat recovery systems without due consideration for impact upon efficiency of the system as a whole - this will be discussed in more detail in part two of this article.)
• pressure tests are not conducted, ie. actual performance cannot be verified. The resulting error can mean that infiltration heat losses are >300% higher than required
• it can be concluded that no space heating is required which leads to ludicrous claims of affordable 'zero heating' and 'going beyond Passivhaus' (there is not space here to discuss this matter in detail, but suffice to say that it was the recognition that the reality of 'zero heating' was in fact impractical that lead to the Passivhaus standard being structured as it is. This matter was also explored in AECB/CarbonLite report 'A Comparison of The Passivhaus Planning Package (PHPP) and SAP.)
• poor construction details (failure to design for construction and inability to design out defects that will impair thermal performance - thermal bridging, poor airtightness, thermal bypass etc)
• poor site quality assurance - poor airtightness, gaps in insulation leading to constructed thermal bridges, thermal bypass etc. Instances of poor workmanship are inexcusable for the simple fact that the skills that are required are, in their own right, not complex. All we are talking about is attention to detail which was once customary practice and takes no more time than a more sloppy approach.
These failings, many of which also are commonplace within the construction industry, have a number of impacts, including the fact that the owners and occupiers of modern buildings are not reaping the full benefits of reduced fuel bills and improved thermal comfort. It also means that theoretical carbon emissions are not actually being achieved and as a consequence will not deliver the government's legal obligations. In this context it is notable to consider that where a building fails to satisfy the legal and/or contractual obligations mandated by performance standards, ie. Passivhaus or Building Regulations, designers and constructors may be exposed to claims of professional negligence.
Returning to Dr Feist's quote it can be seen that the goal of the Passivhaus standard is not simply to 'design to a number'. It is much more than that. The ambition of the standard is to close the gap between design and practice; to have theory and reality converge. If the UK is to achieve an 80% reduction in carbon emissions by 2050 the quality of the buildings that it builds, and refurbishes, needs to be vastly improved. This may be achieved by Introducing the appropriate quality assurance systems throughout the design and delivery process. Buildings without the rigorous quality assurance are far less likely to succeed in their aims and ambitions, particularly in very low carbon/energy buildings. It is in this context that the purpose of this article was to shed some light on the subject of the Passivhaus standard and the quality assurance that is associated with delivering such buildings at a national level and on individual building projects.
Accessed online: 7th August 2014 http://www.greenspec.co.uk/building-design/quality-assured-passivhaus-1/
Paul McAlister Architects were delighted to win an open tender for the provision of architect led design team services for the provision of the new CREST Centre for South West College Enniskillen. This project is one of the most sustainable projects in Ireland and will be the first commercial building in Northern Ireland that will achieve the Passive House Certification. The project is distinguished as it will achieve all of the following three sustainable credentials:
- Passivhaus Certified for Energy efficient envelope and ventilation system
- BREEAM excellent in terms of the BRE sustainable benchmark for UK commercials buildings
- The building will also be Zero Carbon, this means that the building can provide, by renewable energy, it own source of heat and lighting.
Whilst a combination of these sustainable criteria has been attempted in other parts of the UK, this will be the first example in Northern Ireland or Ireland and will become a benchmark building for sustainability.
South West College is one of six Further and Higher Education Colleges in Northern Ireland and was formed as a result of the merger of the former Colleges of Fermanagh, Omagh and East Tyrone on 1 August 2007. South West College services the geographical area of Counties Tyrone and Fermanagh. There are five campus locations at Cookstown, Dungannon, Omagh, two at Enniskillen (main campus and Technology and Skills Centre) and a number of out centres. The College has approximately 500 full-time staff and a similar number of part-time staff and an annual budget of £39M. The college offers a wide range of vocational and non-vocational courses, training courses such as Training for Success, Steps to Work and provides a service to the community, local schools, business and industry. It provides courses ranging from basic skills to Higher National Diploma and Degree Level programmes.
The CREST centre will provide industry Research & Development, demonstration and testing facilities for new renewable energy products and sustainable technologies. The facilities will be used by small companies within the region who have ideas for new products but who currently do not have the physical and/or technical capacity to develop, test and commercialise these. Within CREST facilities and staff will be accessible to develop, demonstrate and test new technologies and show how these can be integrated practically and sensibly to achieve energy savings. The CREST centre will form one component of a wider bid for European funding to support Research & Development in renewable energy and smart technologies within small businesses in the border regions of Northern Ireland, Ireland and western Scotland.
The CREST centre will comprise of three areas; the Pavilion, Research & Development Lab and Hub. The Pavilion will be newly developed and the Hub and Research & Development lab will be integrated into the existing Skills Centre building.
The Hub will form the central office area within the CREST centre and will comprise modern office and meeting space where the CREST team will meet with companies to discuss their requirements and outline the services available. Within the reception area of the Hub, real time visual data monitoring screens will be located. These will display easy-to-understand graphs and tables to analyse the energy performance of a variety of renewable energy installations (e.g. wind turbines, solar panels) located within the region and provide useful data such as information on CO2 savings and energy output. The CREST centre in Enniskillen will form the core of a larger network of satellite facilities in Sligo, Cavan and Dumfries in Scotland, and modern electronic communication facilities will be required within the Hub to link with these sites (e.g. Videoconferencing, web conferencing etc). The hub will be accommodated in the existing building which will require adaptation. Within the Research & Development lab a range of advanced prototyping, testing and development facilities will be available to enable staff at the centre to support companies with practical hands-on new product development. The Research & Development lab will comprise a large workshop facility which can be divided into smaller project workspaces. It is envisaged that some of the CREST projects will involve the development of highly innovative ideas for which IP protection will be required and thus some of the project workspaces will need to be screened from public access to prevent disclosure issues. Equipment within the Research & Development lab will include a laboratory scale wind turbine, biomass heating apparatus, heat exchangers, heat pumps, solar heating and photovoltaic and various monitoring, testing and ancillary equipment. This lab facility is to be accommodated within existing accommodation which will require adaptation. The Pavilion area of the CREST centre will provide demonstration and testing facilities to showcase innovative products and processes and the use of renewable technologies in construction. The Pavilion will be designed to engage industry through experiencing (seeing, touching) new sustainable technologies and materials allowing for a deeper engagement in and understanding of the techniques on display. Products and processes will include new construction technologies – building materials e.g. hempcrete, insulation etc. and renewable energy applications e.g. heat pumps, solar panels. It is planned that the Pavilion will be a dynamic facility which will allow for annual/biannual reconfiguration to include emerging technologies.
Poorly insulated window frames and single glazed windows account for up to 20% of heat loss in the average home. If you upgrade to energy efficient windows, you can help reduce your energy consumption and save money!
In recent years, windows have undergone a technological revolution to bring them up to today's insulating standards. Upgrading single glazed windows with energy efficient ones will not only make the property more secure, warmer and more comfortable to live in, but they will also help reduce your home's energy bills and enhance your property's overall appearance. The wide variety of materials, sizes, and colours for windows has opened a new world of design possibilities, which is limited only by your imagination and budget!
Above: Passive House standards can now be achieved with these Upvc/Alu-clad windows from Internorm (Passion Vetro Design and Thermoj). They are triple glazed as standard and come in a range of shapes and colours. Visit www.ecoglaze.iefor more information.
So what are energy efficient windows?
They are windows that help contain and conserve heat with i n the home, resist condensation and benefit from solar gain. They can be made using any frame material aluminium, uPVC or timber or even a combination of materials. Energy efficient windows are easy to recognise - simply look for its energy rating, as classified by the British Fenestration Rating Council (BFRC), where 'A' is the most efficient. The BFRC scheme assesses the total energy performance of a complete window (not just the glass) and allows accurate comparison of the performance of windows under identical conditions. The most energy efficient windows (A being the most efficient) also carry the Energy Saving Recommended logo issued by the Energy Saving Trust. NB. Glass doors are to be included in the BFRC rating scheme in 2009. Conservatories are currently excluded.
How much do energy efficient windows cost?
The cost varies not only between the various ratings but is also dependent on the frame materials, type of glazing used and the size and style of the overall window. A-rated windows will cost more than B, C, 0 and E rated windows, but when offset against the energy savings you will make, this is comparatively low.
How much would I save on my energy bills?
According to the Energy Saving Trust, when you replace single glazed windows with Energy Saving Recommended double glazing, you can cut heat lost through windows by half, as well as saving around £140/€160 a year on your heating bills (which at the time of writing this, was the equivalent of around 400 litres of home heating oil!) It can also save you around 720kg of carbon dioxide (CO2) a year.
How much could I reduce my carbon footprint by?
It is generally recognised that if you live in a single glazed house and install energy efficient windows you could reduce the energy you use by 0.30 tonnes (or 18%) per year. This calculation is based on 'an average, semi-detached house'.
The material used to manufacture a frame not only governs the physical characteristics of the window, such as thickness, weight, and durability, but it also has a major impact on its thermal characteristics. Since the frame represents 10-30% of the total area of the window unit, the frame properties will definitely influence energy performance and looks.
uPVC - A derivative of plastic, this material requires no painting. The choice of colours and textures has grown, from imitation timber to stand alone colours. They can easily be cleaned and aren't subject to attack from woodworm and insects. However, they can warp or discolour over time.
Timber Wood - this is a natural and sustainable material which comes in a variety of colours depending on the type of timber being used. It's warm to touch and can be stained or painted to suit your interior style. Minor maintenance is required to prevent moisture building up and rotting the frame.
Aluminium - This is perhaps the strongest and most durable of materials as it maintains temperature in accordance with the seasons and has an excellent lifespan. However, when it's freezing outside, aluminium can be exceptionally cold to the touch, which is why some window manufacturers have introduced Alu-Clad systems which have aluminium outside and another material inside. The aluminium protects against rain, hail, UV light, dust and air pollution, and comes in a range of colours or even timber effect finishes. On the inside, timber, vinyl or uPVC can be used to provide a warmer and decorative finish.
Above: These vertical sliding sash windows combine the elegance of traditional sash windows with all the benefits of modern uPVC - strong, won't rot, warp or require repainting. Available in cream, white or oak with brass, chrome or white window furniture. BFRC rated 'C and available from Camden Group, www.camdengroup.co.uk
There are three fundamental approaches to improving the energy performance of glazing products (two or more of these approaches may be combined).
1. Alter the glazing material by changing its chemical composition or physical characteristics, ego tinted glazing.
2. Apply a coating to the glazing surface.
Reflective coatings and films were developed to reduce heat gain and glare, while low-E coatings improve both heating and cooling performance. There are even coatings available for the exterior to break down dirt!
3. Add multiple layers of glazing with low conductance gas to the spaces between the layers; and use thermally improved edge spacers between the panes.
Upgrading your glazing to include specialist coatings will help you save money controlling solar gain. www.pilkington.com
Understanding the Jargon ...
Double Glazed - Two panes of glazing with air spaces in between.
Triple Glazed - Three panes of glazing with air spaces between each.
Low-E (emittance) Coating - The coating is a microscopically thin, virtually invisible, metal or metaIIic oxide layer deposited on the inside of glazing primarily to reduce its Uvalue. The effect is reduced heat loss and better solar gain.
Argon &. Krypton Gas - Originally, the space between panes was filled with air or flushed with dry nitrogen just prior to sealing. However, if the space is filled with a less conductive or slow-moving gas like Argon or Krypton, it minimises the convection currents within the space and the overall transfer of heat between the inside and outside is reduced. Argon is inexpensive, nontoxic, nonreactive, clear, and odourless, while Krypton has a higher thermal performance but more expensive to produce.
Tinted/Obscured Glass - Tinted glass is usefuI in controlling glare but solar heat gain and visible light transmission may be reduced, which is a benefit in summer but not in winter. The tint has no effect on the U-value. Obscured glass is used to protect privacy, but it can also reduce solar light.
Spacers - Higher quaIity spacers between panes can reduce 'fogging' and condensation, while some can incorporate a thermal/warm-edge for better insulation. This is particularly effective if you have aluminium or uPVC frames.
Safety Glass - Glass can be toughened (via repetitive heating and cooling processes) or laminated, both of which are difficult to break and ensure injury is reduced if they are. Laminated glass is a sandwich of two layers of glass with a plastic sheet 'filling'.
- Windows and roof lights should be positioned where they will maximise solar gain.
- The minimum standard for an 'energy-efficient' house is Low E, Argon filled cavity double glazing.
- Ensure draught proofing seals and spacer bars on windows are working effectively - move a candle along the edge to see if it flickers. This may indicate air is leaking
- Replacement windows & doors must comply with current building legislation on thermal performance, fire safety and ventilation. Ask your supplier to certify this before installation.
- Decorate & Improve Your Home.
When you select a window, there are numerous operating profiles to consider. Traditional profiles include projected or hinged types like casement and French windows; or sliding types like double/singlehung and sash windows. In addition, the current window market includes storm windows, sliding/folding and swinging glass doors, skylights and roof-mounted windows, and window systems that can be added to a house to create a bay or bow. The choice is vast' Modern profiles may also offer additional benefits of 'tilt-in' or 'tilt and turn', which make cleaning exterior panes possible from inside the house.
Heat loss is a major concern for today's home owners and one of the key reasons we opt for multiple glazed units with gas infill. However, if your period property has traditional timber sash or casement windows, you won't want to replace them. Frank Clissmann from sashwindows.ie says the best way to make traditional timber sash windows more energy efficient is to draught proof the frame. He adds, "replacing single glazing with double glazing can reduce a room's heat loss by around 6%. However research from Glasgow Caledonian University found draught proofing an old sash window can reduce heat loss by around 86% without replacing the single glazing. This method is also more environmentally friendly because there is no waste."
- Acoustic Performance - Noise is an environmental problem and makes life very difficult for some people. One way to reduce noise in your home is to use thicker glass or more of it and improve the seals around the window.
- Security Performance - Window locks and thicker glass or multiple panes can improve safety.
- Warranty – Lifespan and installation warranty will vary between manufacturers.
Did You Know...?
- Trickle vents on windows will provide sufficient ventilation to reduce the build up of condensation and odours, and also control heat loss in your home. Shutters and thermal blinds or lined curtains and can help minimise heat loss at night.
- Replacing single glazed windows with energy efficient windows can help increase the resale value of your property.
- Shutters and thermal blinds or lined curtains can help minimise heat loss at night.
What is an Eco house?
The name is banded around and is ultimately misunderstood by the general public. It has also become a generic term encompassing all things ecological and sustainable in terms of building and living in an environmentally friendly home. There is actually no simple definition of an eco house and it could be said that any house which incorporates technology, such as renewable energy solutions, may be considered an eco house to a degree. Another ‘Green’ concept would be to build a house using some overtly ‘green’ material such as sheep’s wool insulation or straw bales for insulation of the external walls. The commitment to build in these greener materials indicates a strong statement in terms of the ‘greenness’ of the build but without a holistic approach to the dwelling the green opportunity of building a new dwelling may be lost.
The global problem of build-up in CO2 gases in the atmosphere and the knock on effect of global warming, and damage to the ecosystem, is a manmade phenomenon which needs to be addressed for a sustainable future.
In the UK 30% of CO2 is produced as a result of the energy requirement of the housing stock, which means the homes, that we all live in, produce a significant amount of all CO2. Governments have recognised this and have a target, enforceable by building regulations, for all new homes to be carbon neutral by 2016. This would be achieved by a series of incremental increases in the energy efficiency of dwellings and the increased use of renewable technologies.
The energy efficiency of dwellings is therefore the one area in which the individual may play a major part in reducing their ‘carbon footprint’ making a contribution to reduce CO2 emissions.
An added benefit of an energy efficient home is the actual running costs of the house itself. An initial capital investment providing a super-insulated envelope for the building and suitable means of energy efficient ventilation may have a payback period of 5-10 years, depending on specification. After this period the house is saving money for the occupiers, as it is possible to design passive houses that need no additional heat source except in severe weather conditions.
If we identify energy efficiency as one of the key elements in environmentally friendly building design then it would seem appropriate to focus on this area, as a key element in the design and specification, were the correct choice of building materials and construction techniques will make a significant contribution to the home. The use of renewable energy sources also has a role to play and the investment of relatively common technology, such as solar panels for hot water heating, should be considered for any new home striving to be energy efficient.
The other element of Eco build that makes an environmental impact is reducing water supply needs by recycling of rainwater from roofs. This water is stored and reused for washing and flushing toilets whilst the waste produced from the home may be filtered by reed beds.
Finally the choice of material to construct the eco home brings more choices to be made in terms of Green materials. The concept of embodied energy, the energy required to produce the material, becomes a deciding factor and also the amount of CO2 used in the production of the material. The use of timber as a building material, from sustainable and managed forests, is an obvious ‘green’ material as the trees themselves absorb CO2 when growing. The use of recycled or natural material also has environmentally green credentials. The judgement may come to personal preference or the financial implications of some of the less mass produced products may make their use prohibitive.
In the end market forces and government legislation will determine changes in building design. There is a strong argument to future-proof new dwellings for the lifetime of the home occupier and for generations to come. This investment will ensure a sustainable future for our housing stock and makes the Eco house concept one that becomes the prudent benchmark of new homes.
Ventilation, in all its forms, is about a lot more than fresh air. As homes become ever more airtight there is the irony that increasing thought has to be given to how they are ventilated, since a constant supply of fresh air is vital for the health of both the occupants and the building’s fabric.
Without ventilation, there will be a build up of condensation, pollutants and odours and the safe and sustained performance of some combustion appliances cannot be guaranteed.
Importantly, be the homes new build or retrofit, the ventilation has to be controlled: as the adage goes it is about building tight, ventilating right. Effective ventilation must be achieved by design rather than accident and the latest revisions of Approved Documents Part F (Means of Ventilation) and Part L (Conservation of Fuel and Power) of the Building Regulations, which came into force on 1 October, underscore this.
Part F and Part L are intrinsically linked explains Lee Nurse, chairman of TEHVA’s (The Electric Heating & Ventilation Association) ventilation committee and marketing director at Vent-Axia. “Both documents include a number of major revisions that include minimum energy efficiency levels for all ventilation systems. The launch of Part L’s new Domestic Building Services Compliance Guide highlights ventilation performance levels. Here for the first time a specific fan power requirement of less than 0.5 watt/sec is included for intermittent fans used in new build developments.”
To further lower dwelling emission levels, homes need to be increasingly airtight but not at the cost of good air quality. Changes to Part F include guidelines for airtight properties with infiltration rates tighter than 5m3hour/m2 at 50pascals. Where intermittent or passive stack ventilation systems are employed in airtight dwellings the guidance increases background ventilation rates by 50 per cent.
Nurse believes this looks set to cause some developers to re-evaluate their designs and move any new planning applications away from intermittent fans since the previous provisions in Approved Document F 2006 have already been difficult to achieve when using trickle ventilators in windows. “Our belief is that new regulations will clarify any grey areas to ensure that, as buildings become more airtight, ventilation levels are maintained,” says Nurse.
William Wright, energy and sustainability consultant at Inbuilt, is more circumspect. “The new Approved Document Part F gives many welcome revisions and guidance in specifying and commissioning. However, research on the old Part F has shown that ventilation issues were often ignored or poorly implemented in practice, causing indoor air quality problems. Good ventilation is as much about the implementation as the theory.”
Clearly housebuilders must now consider how the revisions will affect ventilation strategies and the impact on air quality and occupant comfort. As intermittent fans fall out of favour, changes to Part F and Part L look set to increase the uptake of continuous ventilation since it performs better in SAP (Standard Assessment Procedure), is easier to specify and easier to standardise, as trickle vents are not required.
In the short-term it seems likely that there will be increased adoption of whole house Mechanical Extract Ventilation (MEV) systems and decentralised Mechanical Extract Ventilation (dMEV) systems where individual fans in different rooms operate continuously. In the longer term, as airtightness requirements and Code for Sustainable Homes levels rise towards 2016, Mechanical Ventilation with Heat Recovery (MVHR) will become increasingly prevalent.
“MVHR or continuous extract can be advantageous in achieving current building regulations but MVHR will become practically indispensable in economically achieving the carbon savings for Code Level four,” says Wright. “As a broader understanding of issues around MVHR is gained by UK industry, it will more easily be designed into our buildings from the outset.”
Typically whole house, multi-room ducted MVHR systems combine supply and extract ventilation in one unit and use a heat exchanger to extract heat that would otherwise be exhausted to the outside.
Wright highlights noise, positioning of the unit and maintenance as key considerations. “If the fans are noisy, occupants may be inclined to try to turn the ventilation rate down or even turn the unit off.
The new domestic ventilation compliance guide gives particular attention to the issue in designing the ducts to be quiet. Ultimately, best practice may require baffling on the ducts as is sometimes used in Passivhaus and this can be quite bulky.
“With MVHR finding its way into apartments and smaller houses, due attention must be paid to where the unit is placed, with room for ductwork and consideration of noise issues. MVHR might need a dedicated cupboard in the dwelling if a particularly efficient, therefore large, unit is needed for Code compliance, although less efficient units can mount to the ceiling. The ducts to the outside air should be kept shorter for greater efficiency, which may mean mounting the unit in the roof void, assuming there is one,” explains Wright.
When it comes to maintenance there is one particularly worrying issue to consider. The NHBC Foundation review, ‘Indoor air quality in highly energy efficient homes’, states: “Recent BRE discussions with UK manufacturers of MVHR systems suggest that there is no market for replacement filters with several reporting no filter sales at all. This suggests that maintenance is not being undertaken – even at the most basic level.” Wright says air filters must be replaced regularly to maintain efficiency and prevent build up of pollutants. “The occupants need to know how to do this or it must be scheduled by the maintainers. Housing associations will need to think about accessibility of MVHR units for maintenance. An operation and maintenance manual will be distributed to private occupiers, but how many will take on the obligation to maintain the system over the years?”
John Kelly, marketing manager at Airflow Developments, says MVHR units are becoming increasingly more efficient, recovering over 90 per cent of heat generated within the building that would otherwise be wasted. “This is usually the damp extract air from the wet rooms – kitchens and bathrooms – of a dwelling. What would normally be lost is, in fact, a valuable resource to warm the fresh, filtered incoming air from outside and distribute it to the living areas of a dwelling.”
MVHR reduces excessive moisture in the air so it combats condensation and subsequent mould growth, saving money on long and short-term maintenance and decoration. The resulting better indoor air quality also has the dual health benefits of reducing microscopic fungal growth and eliminating the conditions in which house dust mites thrive, both of which are linked to allergic reactions and asthma.
Kelly warns that care needs to be taken when selecting a heat recovery system. “It is important to ensure that this is combined with an air distribution system that enables it to operate with optimum efficiency. Ducting, pipework and fixings must be of high quality and installed correctly.
“Traditional methods like flexible ducting are easily torn, high on system resistance and are often squeezed around bends and between joists, further reducing air flow. Likewise, plastic flat ducting is often ill-fitting, with sharp bends causing dust traps, time consuming to install and wasteful of materials.”
Another key feature to be aware of is ‘summer bypass’ and, at Inbuilt, Wright warns that not all units provide this. “Summer bypass means that heat is not being brought back into the building when not needed. However, we have come across several MVHR units coming to the market that omit summer bypass as a cost saving exercise.
Summer bypass is not explicitly required by building regulations, and omitting it could cause significant overheating problems in summer leading to complaints from purchasers.”
Another point to consider is that, for the first time, Part F requires post-completion testing of ventilation equipment to ensure it not only delivers the required airflow, but does it efficiently and quietly. “Post-installation performance policing is critical to ensure air quality in increasingly airtight homes. This is especially important with the increased adoption of highly efficient ventilation systems, like MVHR, which require trained competent installers,” believes Vent-Axia’s Lee Nurse.
Traditionally it has been the electrical contractor who has installed ventilation equipment. One interesting consequence of the new Regulations is likely to be a change in the contractor base because, with the pipework required for ducting and the knowledge and calculations needed to comply with the Regulations, the skill set is much more akin to plumbing.
Bovis Homes is one housebuilder which often employs MVHR. Michael Black, group development director, says that the company has sought to ensure that it has the most efficient systems installed whilst, at the same time, ensuring their operation and maintenance requirements are not difficult for its customers.
“In fact, we’ve just completed drafting an installation guide with a major MVHR manufacturer to assist our site teams and subcontractors in ensuring that the systems are properly installed and commissioned.”
IF you are building or renovating a house you will inevitably hear the term ‘passive house’ or ‘passivhaus’, the word ‘passiv’ with a Teutonic clip of its ‘e’. For the uninitiated, this term, and the cheery declaration of ‘passivhaus standard’ slapped on a range of energy-efficient products, can be confusing. Passivhaus standards, or an approximation, will increasingly become the industry norm for house building, as all new homes are constructed to be carbon neutral, emitting no harmful gases as we heat our rooms and water.
Turn up the body heat
or a house to be deemed passive, it must draw a minimal amount of active external energy, if any at all (excluding solar), to run its space and water heating and keep it cool, where needed. Passive houses are sometimes termed ‘body heat houses’, as the warmth emanating from the people who live there, and the passive heating coming through the windows, is enough to keep them cosy.
In their most developed forms, these sustainable houses can become very active, selling energy back to the national energy grid. If you want to find out more about energy-positive housing, Google ‘Villa Åkarp’, the first of a new league of super homes constructed in Malmø Sweden.
Setting the standard
The energy standard for the true Passivhaus, is set by the PassivHaus Institute in Germany, and despite its rigorous demands, it remains a building concept not a brand. The concept was developed by Professors Bo Adamson of Sweden, and Wolfgang Feist of Germany and the first Passivhaus dwellings were constructed in Darmstadt in 1991. The criteria for a passive House per m² living area include a maximum of 15 kWh/m²yr annual space-heat requirement and no more than 42 kWh/ m²yr annual total amount of energy input.
A semi-detached, two storey Irish house built in the mid 1970s before the introduction of thermal insulation standards would have a space heating requirement of over 200kWh/m²yr and have a total primary energy demand of over 400 kWh/ m²yr. In short the energy efficiency of the Passivhaus is 90% better.
A passive house is highly insulated throughout every centimetre of the envelope, including walls, roof, floor slab, windows and doors, and has no ‘cold-bridging’ where heat jumps across one material to another. It’s air-tight to prevent thermal loss and uncontrolled air ingress. The ventilations is carefully managed through a mechanical and heat ventilations system, abbreviated as a MHRV (75% of the heat from exhaust air is transferred to the fresh air by means of a heat exchanger). In warm weather the Passivhaus will use passive cooling techniques, including strategic shading. A successful build means a comfortable temperature year round, healthy humidity, fresh, clean air, no draughts whatsoever and laughable fuel bills.
Setting the standard
Certified passive houses have been built here in Ireland since 2005 to the correct layout and orientation and with the key materials and techniques, achieving Passivhaus energy performance through a highly exacting, rigorous build. Retrofit projects (which have different Passivhaus standards) are also becoming very popular. When developing new housing, or renovating existing house stock, builders have been enthused to reach beyond the building regulations towards near passive standards with low-energy designs and materials. There are actually only 20,000 certified Passivhaus builds in the entire world. If something is certified fit to go into a Passivhaus (when perfectly installed), you can be fairly sure it’s top notch in terms of its insulation properties for example.
Passivhaus Beats BER
An energy efficient BER ‘A’ rated house shares a lot of common ground with a Passivhaus. However, an ‘A1’ rated house in BER terms is not necessarily worthy of Passivhaus certification, and a Passivhaus may not reach a BER ‘A1’ rating, as the two are surveyed using different methods. The only downside voiced by the industry for passive builds is in terms of the increased cost to build and one or two lifestyle challenges. The whole house is at one temperature for example, annoying if you prefer a cool bedroom and warm living room.
Worth the expense
If you’re keen on building a Passivhaus or renovating your home to as close to passive standards as possible, the capital investment will be greater. For renovations the layout of the house may have to change and improving the insulation performance of the entire house will be vital. However, the long range rewards in terms of running costs and the potentially increased value of a superbly well built house make it well worth consideration. Part ‘L’ of the Building Regulations has done a lot to pull new housing and improvements towards high energy efficient buildings. Exceeding the standard and aiming for passive or near passive performance is a sound guiding principle.
By Kya deLongchamps
Ireland has woken up to the Passive House. Seven years ago Tomas O’Leary built Ireland’s first certified passive house in Wicklow – a home that showed Germanic influences in looks as well as energy performance. A new development at Grange Lough, Rosslare, reveals that passive can be made Irish – both in terms of what they’re built with, and how they look. Grange Lough in Rosslare, Co Wexford is the country's first commercial passive house development, and as such it's a landmark in the story of Irish construction. This is the first time that a speculative developer has looked at the market and decided it wanted passive houses. Not only that, but the scheme represents perhaps the most Irish take on the passive house you'll find. Its design is traditional- it does not look German, and incorporates much of what you'd expect in an Irish house, even a chimney. Most especially however, it has been built using Irish products and Irish expertise.
The design team is Irish, the developer is Irish, the thermal envelope manufacturer is Irish, the company which is certifying the house as passive is Irish, and almost all of the technology used in the house - including the windows and doors - is Irish.
"The passive house is a German concept but I think it's very important to localise it," says passive house guru Tomas O'Leary, director of MosArt and founder of the Irish Passive House Academy. "In Rosslare, they decided from the very outset that they wanted a fireplace and they weren't willing to roll over and accept no for an answer. You really wouldn't know it was a passive house walking around. It's traditional and I don't mean twee by traditional- it's just got a lot of the components that Irish people like."
There are three separate forces behind this project - developer Michael Bennett, Donal Mullins of Shoalwater Timber Frame who designed and fabricated the thermal envelope, and low energy designer Seamus Mullins of Seamus Mullins and Co. Both Donal Mullins and Michael Bennett have been building timber frame houses for the past decade, while Seamus Mullins has provided much of the design know-how. He recently completed the certified passive house designer course with the Irish Passive House Academy. Throughout their working relationship, the team has graduated to incrementally more efficient homes. The day we met in Rosslare, Bennett was finalising the sale of an A3 rated house in another of his developments in Enniscorthy.
With rising energy prices and the recession focusing minds on the energy performance of their homes, Bennett believes that the time is right for this kind of development. But location is also vital- Rosslare Strand has long been a summer holidaying Mecca. "We won't have first time buyers here," says Bennett, adding that the first house in the development carries a price tag of €490,000. "We'll have I expect retiree-type clients, with maybe an odd one returning from overseas, but as the houses are three and four bedroom, we are also catering for families and permanent residency." Given this profile, it was always vital that the house wear its passive tag lightly. "The Irish are very slow to change," he says. "If you built a state of the art glass house, would you sell it to anyone? I don't think you'd have a hope. People would come and look at it and ooh and ahh over it but they wouldn't buy it."
Giving the house a traditional look isn't all about meeting the market's aesthetic expectations. Irish houses need to be designed to cope with Irish conditions. "We've higher wind-speeds than mainland Europe, it's not as cold but we've more rainfall," Seamus Mullins explains. "The moisture levels mightn't impact so much on the thermal efficiency of the house but it will impact on the quality of the build. The detailing in Europe stands up in Europe but when it's put into wind-driven rain situations; suddenly you're going to start getting leaks." Moreover, the design incorporates elements of Irish design that have always made sense. The draft lobby, for example, is a standard feature of many of the houses in the area.
There will eventually be eight houses in Grange Lough, which is a very private wall enclosed site. "There will only ever be one house for sale here at a time," says Bennett. The design and construction team have however been very careful to ensure that early arrivals won't be living on a building site. All services and preparatory work for the eight houses are in place, all footpaths and roads have been constructed, while sites due to begin later are now landscaped and will remain so until construction can begin. Come construction time, the houses will be built behind hoardings, and as Seamus Mullins is quick to point out, the enhanced sound insulation of a passive house means noise is unlikely to be an issue.
The first challenge facing Seamus Mullins was achieving the right orientation for eight houses on an elongated, restricted site. "If you haven't got a front elevation facing south, you've a rear elevation facing south," he says. "So it's a matter of changing the internal room layout. Nearly all of the four designs have a central core around the stairwell that faces south." Glazing to the west had to be amended due to overheating issues turned up by the PH PP software. The houses themselves are not large by recent standards - the designs vary between 1,860 square feet and 2,200 square feet. "They're not large," says Mullins. "That's an important aspect as well, because to comply with passive certification there's a ratio of floor area of around 35m2 per person ... That's to try and get a better use of land, money and space." When he began his timber frame business eleven years ago, Donal Mullins of Shoalwater set out to ensure that any work that could be done in the factory was done in the factory. In order to preserve quality and continuity, the team that manufacture the frames also erect them onsite. He says that when he began building timber frame houses almost thirty years ago, the first panel taken from the back of the lorry was always the last to be used, and invariably suffered from constant handling. Bearing this in mind, Mullins developed a process of packaging the building system in bales and, and loads it to ensure minimal handling. "The first panel you take off should be the first panel you use." He says.Extreme attention to detail has been the hallmark of the build. Achieving passive certification was vital to the commercial success of the project, says Bennett. "We had to be certain of our certification before we started. Anyone starting to build a house like this without their homework done and all their planning and all their issues addressed are on a hiding to nothing. There's no way can you get passive certification without it." To facilitate this, the house was built on paper long before a sod was turned onsite. Because of all that preparatory work, says Donal Mullins, the construction stage didn't throw up any real stumbling blocks. "I wouldn't say there were huge issues during the build," he says. "The big issues were in the learning curve itself. Because of all the work we had done previously, we had a base of knowledge to build from." All three have been continually attending seminars and conferences in order to up-skill and keep abreast of best practice.
Achieving and then keeping airtightness is of course the perennial bugbear of low energy construction. It helped in Grange Lough that no subcontractors were used, and that many of the trade’s people had been working with Bennett for more than a decade. "If you don't bring your trades people along with you, if you don't educate them, if they don't know what they're trying to do, how in the hell can they work towards it?" says Michael Bennett. "We've done a lot of work on our people here."
Responsibility for achieving airtightness in the first place fell to Shoalwater, who have won an excellent reputation for themselves in this field using the Pro Clima system of membranes, tapes and adhesives. "When we were finished, we did our first blower door test," Mullins explains. "We got an air change rate of 0.51 [ACH at 50 Pa]. That was very good. Then Michael could go and say to his electrician, his plumber, this is our airtightness, this is what you have to have when you guys are done. If it goes up, it's because of something you guys did. Now they're far more conscious and far more careful." A blower door test after each phase not alone kept tabs on how the air change rate was being maintained relative to the passive house standard of 0.6, but also revealed who was responsible if the number went up.
One key issue that arose was with the Stovax stove. The blower door test immediately following the installation of the stove drove the air change rate above the 0.6 threshold. Repeat visits from Stovax improved the door sealing, which is where the problem lay, and moved the rate back down to acceptable levels. Surprisingly, the unit is still not a room-sealed unit. Though most of the air required from combustion is piped in externally, a small proportion is still taken from room air.
A potential issue also arose with the Beam central vacuuming unit. Though bin and turbine are both located within the sealed envelope, air could theoretically have escaped through an extract pipe which terminates outside the house. "We could have had a problem there," says Seamus Mullins, "but we were never going to find out if we didn't put it in. From a cleanness and dust elimination point of view, the central vacuuming system is superb. The filtering system really fits with the passive principle in that you're creating this quality comfortable living environment." The solution which Beam came up with was a motorised valve, kept shut while the unit is not in operation, and triggered to open when switched on. The blower door test however u
ncovered no leakages in the system so the valve was not fitted.
The windows are from Munster Joinery's Future Proof range. "Passive house windows generally cost people about €650 a square metre:' says Brendan Harte of the company.”We wanted to bring the price down, we wanted to put value for money into the market but still achieve the passive house standard. The glass section is 52mm triple-glazed and the PVC profile that we went with in Rosslare is a 90mm section, fully foam-filled all the way through." Two Munster Joinery windows are currently with the Passive House Institute in Darmstadt undergoing certification. The Passive House Institute was heavily consulted during research and development of the window range to ensure that the onerous certification requirements would be met. The windows are the first Irish products submitted to the institute for certification. "I think that's very exciting because windows typically are the most expensive element in the passive house:' says Tomas O'Leary.”They're often imported and I think in these times, if we can generate local employment in construction, that's better for everyone."
"People are amazed when they hear that the windows are Irish, says Seamus Mullins.”People think we should have Austrian or maybe German windows, we shouldn't have Irish windows, and are surprised to hear of the product range advancements that Munster Joinery have made." But using local products isn't just about local pride, says Donal Mullins. ''That window is a brilliant window and we can get it in Ireland in a two week delivery date. It's so much easier to run a schedule when your window manufacturer can have them in ten days to two weeks, at this quality and with an Irish fitter. You've got any kind of little latch or lock problems, you ring him up and the serviceman is here." One of the most interesting findings of the project was in relation to cost. Seamus Mullins tracked expenditure throughout, and presented a paper at the SEAl See the Light conference in Croke Park last September. He found that the cost of upgrading a project from A3 to passive came in at 02 per square foot. "That's in our first attempt:' he says.”We should be able to pull that down." The Grange Lough house is currently awaiting confirmation of its BER, which Seamus has calculated at high A3. He refers to Bennett's A3 house, just sold in Enniscorthy. "The funny thing is both the passive house and the Enniscorthy house are A-rated. In Rosslare, the running costs for all your heating and hot water, are going to be in the region of €500 - €600 a year, on the basis of an energy demand of 10 kWh/m'/a, while in Enniscorthy, the A3 rated houses is going to have an energy requirement of 67 kWh/m'/a - which is approximately six times more. It might not be six times more expensive to heat, but if it's three times more expensive, that means the Enniscorthy purchaser is spending an extra 0,500 to 0,800 a year for the life of that house."In order to meet the passive house standard, the house must be designed to have an annual heating demand of not more than 15 kWh/m'/yr. In Rosslare, the calculations are coming in at 10 kWh/m'/yr, 33% below the standard. Michael Bennett explains that they needed to aim high in order to provide sufficient comfort to ensure that certification would be achieved. "But we're going to get better at this, and more efficient at it:' he says. Being the first passive house in the scheme, everyone involved invested a huge amount of time and effort in achieving the right results. Bennett sees this time as an investment in skills and experience, and believes that from here on in, each house will go up within three months.
These houses are finished with the high end of the market in mind, but Bennett believes that it's entirely possible to provide the same quality of build for the lower end. "I would hope, if not this year then in two or three years down the road we'll be starting a small scheme somewhere. Ten or twelve houses, and they'll be 'white deal passive', to give passive certified houses to entry level buyers." Donal Mullins agrees. "Why not get into a position where we can supply passive houses at affordable prices to the county councils?"
The 2011 update of BREEAM will produce a streamlined methodology for assessing new non-domestic buildings, presented in a single document and more closely aligned with emerging European Standards. Other major changes will reflect the new carbon reduction requirements of Part L and a greater focus on the sustainable management and handover of buildings after construction during the initial phase of occupation An updated and significantly streamlined BREEAM methodology for UK non-domestic buildings will be released this spring. BREEAM's regular biennial revisions are designed to ensure that it remains up-to-date, representative of best environmental practice and a driver for innovation in sustainable building design and construction.
BRE Global began work on revising and updating the current BREEAM 2008 UK version (launched in August 2008) in the spring of 2010. A key part of this exercise was a wide consultation with BREEAM users and specifiers, assessors and other industry stakeholders. "The feedback we received from individuals and organisations was essential in shaping the update of the UK scheme and also our thinking on our longer-term direction," explains BRE Global chief executive, Carol Atkinson.
A major element of the 201 1 update has been the re-classification of a number of existing BREEAM environmental assessment issues to ensure an efficient, relevant and flexible methodology that focuses on the key issues. This has led to the consolidation of several assessment issues into a smaller number of new, re-focused categories. For example, the current BREEAM Offices 2008 includes 13 assessment issues in the 'health and wellbeing' section; under the 2011 version there will be about half that number, focusing on key environmental areas and impacts.
"This does not mean that we are unnecessarily cutting assessment criteria from the scheme and diluting the method," says Tim Bevan of BRE Global. ''What we have done is reviewed the existing assessment criteria and identified the key priority issues that define a sustainable building, ensuring that criteria focus on the key aspects of those sustainability issues. "Indoor air quality is a key issue for occupants' health and wellbeing, for example. It is affected by a number of factors, such as ventilation, VOCs and external pollution. Previously, these would have been listed as separate assessment issues, but they are now consolidated as one - indoor air quality - in the 'health and wellbeing' section:'
The result is that in BREEAM 2008 there were around 100 individual assessment issues, while in the 2011 version this has been reduced to around 50.
The re-classification process has enabled BRE Global to align the BREEAM methodology more closely with emerging European Standards on the sustainability of construction works, and their metrics and terminologies. "This will enable a version of BREEAM that is compliant with those standards whilst maintaining a flexible assessment and rating system that is easy to use," says Bevan.
The consolidation of assessment criteria has also enabled BRE Global to present the BREEAM methodology in a single document, rather than several documents each covering a different building type - offices, industrial units, schools, etc.
Bevan continues: ''We have been able to pull all the separate schemes together so there is one scheme document for all non-domestic buildings, instead of a shelf-full of very similar documents. To have done that with the current version would have produced a complex and confusing manual. Now, a design team will be able to consult a single BREEAM manual whether they are designing offices, retail premises or school buildings:'
BREEAM will maintain its flexible and robust approach in defining differing sustainability attainment levels, where necessary, for different types of non-domestic buildings and end-users. For example, the levels of acoustic quality required in schools will still be different to those required in offices - although many other issues will be common to all building types.
BREEAM 2008 can be applied to both new buildings and refurbishments. The updated 2011 version, however, will focus specifically on new buildings and will be known as 'BREEAM New Construction'.
A new BREEAM scheme focusing specifically on assessing refurbishments and fit-outs of nondomestic buildings will be developed to cater for the wide-ranging refurbishment projects that are undertaken. It will be similar to the BREEAM Domestic Refurbishment scheme, which has recently been tested in an extensive pilot project and is now nearing completion.
Until the new refurbishment scheme is available, it will be possible to continue using the BREEAM 2008 version to assess refurbishments and fit-outs or, where deemed appropriate, the BREEAM 2011 version can be used to assess major refurbishment projects.
One of the aims of the BREEAM 2011 update is to encourage those responsible for designing and constructing the building to take a greater role in its post-construction commissioning, handover and initial period of occupation.
A building is a complex mix of interacting structures, systems and people. Common sense tells us, and experience confirms that if a building is not operated as envisaged, it will not perform in the sustainable manner in which it was designed.
"In the 2011 version we have strengthened the criteria and increased the rewards for the sustainable procurement and handover of the building - in particular, introducing new credits for committed occupant aftercare, building performance monitoring and post-occupancy evaluation," says Bevan. "These often-overlooked aspects are vital in transforming a sustainable, BREEAM-rated building from design concept to operational reality:'
In addition to strengthening the sustainable procurement criteria in the 'management' section of BREEAM, BRE Global has updated its approach to end-user consultation. To this end, a new assessment issue, 'stakeholder participation', has been added to the BREEAM 2011 version. It aims to foster the design, planning and delivery of accessible, functional and inclusive buildings in consultation with current and future building users and other stakeholders.
The 2010 version of the Building Regulations Approved Document Part L2A in England and Wales requires a 25% aggregate improvement in C02 emissions from buildings (i.e. percentage reduction on 2006 Building Regulations for non-domestic buildings).
In response to this, and to align with the government's goal of achieving zero-carbon buildings, the assessment issue, 'reduction of C02 emissions', in the 'energy' section will be significantly amended. The awarding of credits in the BREEAM 2011 version will now be based on a zero-carbon hierarchy of:
- Reduced energy demand (built form/fabric efficiency)
- Reduced energy consumption (systems efficiency)
- Reduced carbon (use of low- and zero-carbon energy).
Building performance will be assessed against three steps based on the hierarchy:
- Energy-efficiency of the building - a performance measure of the assessed building's actual energy demand relative to a minimum standard, i.e. Building Regulations compliance (Part L2a 2010 notional building).
- Energy consumption of the building - a performance measure of how efficiently the assessed building meets its energy demands, i.e. its energy consumption relative to the notional building's energy consumption.
- Carbon performance of the building - a measure of the building's performance in terms of carbon dioxide emissions.
Although BRE Global is changing how BREEAM credits are awarded for energy-efficiency/carbon emissions performance, it will continue to align with the industry methodologies/software and their outputs used to determine Building Regulations compliance, i.e. the National Calculation Method (NCM).
Simon Gill, BRE
You've been told many times about the need to insulate your home to a high standard. This is indeed by far the most cost-effective way to lower your fuel bills, not to mention comply with the energy requirements of the building regulations. But insulation and airtightness go hand in hand. After the insulation is fitted, an airtight membrane/ vapour control layer must be applied to the warm side of the insulation, otherwise all the hard work you put into insulating and protecting your home will literally leak at the seams! Airtightness, or 'air-flow-control' (a term that takes into account the risk of condensation as well the air exchange rate), is often associated to highly energy-efficient homes. But that's not always the case. In fact you can make your house airtight with standard trickle vents, or 'hole in the wall' ventilation. With regards to the building regulations, it doesn't matter which ventilation system you choose because during the airtightness test all of the vents, extracts (be they mechanical ventilation, trickle vents, passive stack, etc.) and chimneys are required to be sealed. But be aware that too little ventilation in an airtight home will invariably lead to moisture and mould problems. Where there is no mechanical ventilation, the wall vents are the only means of moisture management and this may not suffice! When sealing the building envelope to achieve a good airtightness standard the moisture generated in the home (as well as airborne pollutants/gases) requires a direct exit through mechanical ventilation or wall ventilation in each room. So if you are only relying on trickle vents for ventilation, it is good practice to open your windows to the front and rear of the home for 30 minutes two to three times a day as this will clear moisture from the building.
Your 'airtightness strategy' will need to be conducted very early on in the process and take into consideration moisture management. It is essential that all members of the construction team understand the process involved in maintaining airtightness; it's very easy for an electrician for example to cut an opening in the airtightness membrane for his cable without then resealing it. It is therefore highly recommended that your builder ensures that every subcontractor on site understands the process. And if you are a self builder it is up to you to ensure that your subcontractors seal any penetrations as they go, otherwise the end result is likely to be poor and require remedial works to pass the regulatory standards currently applicable.
The first step is to take pen to paper. Get the plans of your building and place a pen at a start point of your choosing (internally on the section) and then draw a continuous line around the entire building where you will have a continuous airtight envelope. Any potential air leaks are when you have to pick your pen up from the paper, and as you may have guessed, particularly prevalent areas for air leakage are dormer windows, roof lights, windows, doors, junctions between floors and walls, loft hatches, etc. The rules for creating airtight seals at such junctions are as follows:
• When the membrane meets a block wall (at a gable end for example) you will need to use a proprietary mastic to seal the edge of the membrane to the blockwork. It is important to emphasise that standard cavity blockwork is not airtight until it is plastered. Therefore it is recommended that the blockwork is plastered with a scratch coat prior to using the mastic.
• Where the membrane overlaps or meets a smooth or hard surface, you can seal the membrane using proprietary tape.
Remember to think about every single section of your building. It's easy to see that your pen would lift off the paper when a floor meets a wall; this is another critical junction and the solution for maintaining airtightness depends on the type of floor construction. For a hollow core floor it is recommended that a section of airtightness membrane be laid on top of the wall on which it is to be placed. The membrane then wraps up the side and over the top of the hollow core flooring; the blockwork for the upper floor is then laid on top of the membrane. This section of 'wrapping' membrane is then fixed to the wall or vertical membrane. In the case of a timber floor, you have two alternatives. You can either use the hollow core floor technique or you can use tape to seal around each Joist to a plastered wall.
In the case of timber frame construction, you will have to fix an airtight membrane internally on the entire envelope. In standard plastered blockwork, cavity walls are typically considered to be airtight as long as they are plastered externally and internally with a minimum of two coats (scratch and finish). Potential air leakages occur where the walls are penetrated (with doors and windows for example) and adequate airtight sealing has not been considered at these junctions.
As for cavity blockwork construction-it is now common practice to insulate walls internally with insulated plasterboard (normally a 50mm board with 38mm insulation and 13mm plasterboard) but this may not necessarily be airtight as the junctions between the boards may not be sealed adequately: a skim coat does not provide an airtight barrier, nor does plasterboard tape!
The solution therefore is to scratch coat the blockwork walls first and then fix the insulated plasterboard. You will still need to pay particular care at window and door reveals to ensure the airtight barrier is maintained by applying an airtight seal or using proprietary tapes. The main thing to remember is that your structure is not airtight at junctions where you are only relying on the thickness of the finishing coat of plaster.
An alternative method for applying an airtight barrier to a cavity blockwork construction is to apply a similar technique to a timber frame wall. That is to batten the unplastered internal blockwork wall and then to apply the airtight membrane to the battens. As well as creating an airtight envelope you are also creating a cavity for any services such as electrics or plumbing, thereby eliminating any chasing. The final stage then is to apply the membrane over a cross-batten and then plasterboard and skim.
While mould growth used to be associated with badly insulated homes, now it's often due to airtight homes with poor ventilation
What the building regulations say.
Building a home that is airtight will not only improve comfort, it's also an essential component of the building regulations'. It is now a legal requirement for any new house to be air-pressure tested; both ROI and NI currently have the same air permeability requirement of l0m3/(h.m2) at 50Pa. This figure basically says that an air leakage of no more than 10m3 per hour per m2 of building envelope area (at a pressure differential of 50 Pascal between inside and outside the building), is permitted". Compliance is verified by doing a blower door test; this is where a door or window is removed and replaced with a blower fan. The house is then pressurised (both positively and negatively) to measure the air leakage from the airflow rate through the fan. This identifies the pressure difference between the inside and outside of the building structure. The bigger the number the worse the result; greater than 10 fails the building regulations, less than five is doing well, less than three is quite good. Bear in mind that the airtightness results will have a significant impact on the A to G rating you will get under your Energy Performance Certificate / Building Energy Rating.
*In ROI refer to building regulations' technical guidance document Part L and in NI the building regulations' F1 booklet.
**Air Permeability (q50) and Air Changes per Hour (n50) are two different measures: air changes are based on the volume 01 the building instead 01 the envelope area. Air changes are often quoted to demonstrate the airtightness 01 a building but this is not the measure used by the building regulations.
Illustrated guide - Airtight Walls
At the floor junction, note how the membrane continues and is sealed down to the floor: the critical Junctions when fixing the membrane using this method occur where the membrane meets a penetration such as an opening or where it meets another material such as at a floor or a gable.
Roof member/beam: Detail showing how to seal around a roof member to the airtightness membrane.
Cables: You will need to comprehensively seal every cable penetration to ensure airtightness. Some manufacturers provide a specialist tape that is more supple and easier to fold around cables than the standard, thicker tape.
Ventilation: Here we see the sealing around the pipework for a mechanical heat recovery ventilation system in the ceiling; this applies to all sorts of piping (vents, water, etc.).
Open fires: A standard open fireplace is frowned upon in an airtight construction: at best an open fire is only 5%-20% efficient and even a multi-fuel stove will extract some of the heated air in the room in order to ignite the fire. Therefore in a 'super airtight' house, you must ensure that the air which feeds the fire comes from the outside; you can now obtain specifically designed multi-fuel stoves that address this issue.
You don't have to spend a lot of money to build a home that doesn't need central heating - what's required is the right specification and the correct installation. Patrick Waterfield finds out what it's like to inhabit an energy efficient space, in a family home in Co Down and in a holiday house in Co Donegal
Received wisdom tells of a law of diminishing return where insulation is concerned and thus an optimum level based on purchase price compared to the cost of energy saved. This is true up to a point - the point at which a central heating system is no longer needed! Then the whole equation gets tipped on its head because you save the cost of the heating system, as well as the fuel it would have used over the lifetime of the building.
The No Central Heating standard was designed with this concept in mind, developed by the author of this article and by a local timber frame company specialising in energy efficient dwellings (whose standard product consists of a highly insulated fabric with high levels of airtightness and mechanical ventilation with heat recovery). Arriving at the No Central Heating standard was 'simply' a matter of improving the fabric insulation further and specifying high performance glazing, as well as ultra-low air permeability levels.
The result is a system which, for little overcost on normal construction, can achieve levels of performance of Passivhaus standards. A number of house-building systems are available, notably from other European and Scandinavian countries, which provide excellent levels of energy performance but at a considerable cost premium. Key to the cost effectiveness of the No Central Heating system is the use of industry standard components, such as 140mm timber stud, and local factory and on-site construction. Additional costs for insulation, glazing, mechanical ventilation and high levels of airtightness are offset by the avoidance of a central heating plant (such as boilers) and heat emitters (for example radiators) plus associated pipework, valves and controls.
The walls, roof and floor of the No Central Heating houses are of layers of insulation of different materials, in order to provide excellent thermal performance without the risk of interstitial condensation. All windows, including rooflights and glazed doors, must be inert gas filled, triple glazed units with low emissivity coatings and insulated spacers.
While both the Co Down and Co Donegal houses share a similar fabric make-up and services (no boiler or radiators of course!) one is continually occupied and the other intermittently, which gives us a chance to assess the dynamic as well as steady-state performance of the system.
The mechanical ventilation systems continually extract air from the waste areas (kitchens and bathrooms) and recover up to 85% of the heat content which is transferred to the incoming fresh air. In this way, the dwellings benefit from continuous, filtered fresh air with a greatly reduced energy requirement and improved comfort levels. The system thus also acts as a means of transporting heat around the house, and is sufficient to heat the bedrooms and ancillary rooms to the required comfort levels. In most conventionally-built dwellings this mechanism would not work - the heat loss through the building fabric would be too high and there would also be too much air leakage in and out of the building. But in a super-insulated fabric with very low air permeability it can.
The homes are oriented towards the south, with high areas of glazing on the main facades, thus making use of available solar heat gains directly into the main living spaces. These, combined with heat from cooking, equipment and even people collectively termed "incidental gains" - contribute significantly to the heating of the dwelling. Again, in a normal house, these incidental gains would be insignificant compared to the rate of heat loss. However, combined with very low heat loss from the fabric and through ventilation, the incidental gains reduce the "heating season" to around three months, half that of a normal house. Additional heat, when it is needed, is provided by a room heater in the main living area, where higher comfort temperatures are usually required. The mechanical ventilation system, as explained above, helps to distribute this heat throughout the dwelling.
Integral to the concept of these low energy homes is the provision for intermittent heat into the bathroom areas, which also require a slightly higher temperature than elsewhere in the house. This can be provided by a towel radiator, either electric or wet - in the latter case being run on a small pumped circuit off the hot water cylinder. Sensible time control of the towel radiator will limit energy and cost consumption and does not dilute the No Central Heating concept. Furthermore, most of the heat generated in the bathrooms is thus distributed, via the ventilation system, to the rest of the house. Use of masonry walls around the room heater acts as thermal mass, helping to store heat generated and also acting as a heat sink to reduce the risk of overheating in summer - though high insulation levels also reduce excessive solar heat gains into the building.
One and a half storey timber frame
One and a half storey timber frame
0.l3W/m2K for walls, 0.11 W/m2K for roof, 0.11W/m2K for floors and 1.0W/m2K for window units 0.l3W/m2K for walls, 0.11 W/m2K for roof, 0.11W/m2K for floors and 1.0W/m2K for window units
Airtightness < 2 m3/(hm2) at 50Pa
House size 2,000 sqft1,700 sqft
Energy rating BA2
Space heating heat recovery ventilation pre-heatsheat recovery ventilation pre-heats air; 5.5kW wood-burning stove;air; 4.5kW wood-burning stove with bespoke towel radiators fed by hotback boiler; towel radiators for water system, both approx.bathrooms fed by hot water system - 100W in size200W and 400W in size
Hot water heating Approx. 6m2 of flat plate solar36 evacuated tubes supplemented by panels supplemented by an air the stove with back boiler source heat pump (COP of 3)
The County Down house
The County Down House, which is owned and occupied by Darren and Ashleen Annett and their two young children, sits on a site between Darren's parents' house and that of the parents of Darren's long-term friend and architect John Lavery. The house comprises a main open plan living/dining/kitchen area, plus additional first floor living room, three bedrooms, two bathrooms, a study and a utility/shower room.
A plasterer by trade, Darren was more aware than most people of the opportunities for influencing all aspects of the design of a dwelling, including the energy side. He was also open to considering innovative products and practices - within cost constraints-of course. As the design phase took shape Ashleen was expecting their first child and the cost factor became even more important in their minds. The prospect of removing, at a stroke, the single greatest running cost of most houses, appealed greatly to them both.
The house faces more or less due south, fortunately dictated by the tight site, and incorporates a high level of glazing on the south facade and correspondingly low levels on the north side. The only fixed source of heating in the home is a wood-burning stove, located in the main living room. During the last severe winter, the timber frame provider became concerned for Darren and Ashleen and rang them to check that they were warm enough. He needn't have worried! Even with outside temperatures around -10°C, internal temperatures were maintained around 20°C. Ashleen reports that they needed to light the woodburning stove most days for three months during the winter. This required a certain level of intervention, which perhaps would not suit everyone. However, the same heat input could be provided readily by, say, a wood-pellet burner with automatic ignition start, controlled on a timer.
Unlike the Co Donegal house the wood burning stove provides heating only, the solar hot water panels (located on the main roof pitch) being supplemented by an air-source heat pump. The heat pump comes as an integrated package with the hot water cylinder and can be controlled on time and/or temperature to fill in the gaps left by the solar panels. This approach has the advantage over the Donegal house of separately controlled heating and hot water systems. As with the Donegal house, small towel radiators in the bathrooms are run off a loop from the hot water cylinder.
Naturally, the heat pump runs on electricity and represents a certain energy and cost component (the latter of which can be reduced if operated on a night rate tariff). Darren reports that their electricity bills are around £40 a quarter more than normal, which also includes the ventilation system fans. However, some small gains are made through savings in lighting, which is almost all LED. Overall, the cost benefit is clear, the additional electricity cost being far outweighed by that of running a central heating system in a standard (or even well insulated) new build property.
The saw-tooth profile indicates day to night readings. Even during the coldest part of the winter from mid-to-end December 2010 (outside temperatures about -5°C) the internal temperatures are maintained at 18°C to 20°C, occasionally rising much higher when the occupants demanded it. The high variation in temperatures is due to the heating system not being controlled.
The County Donegal House
The house featured here was the prototype of the No Central Heating House and was built for myself and family. The house is intermittently occupied, being used currently as a second home. It faces southwest, to avail of views and solar gains while also addressing privacy with respect to neighbouring dwellings. High levels of glazing are deployed on the southeast and southwest facades and correspondingly low glazing ratios on the other sides.
The house comprises three bedrooms, plus a study/bedroom and two bathrooms, in addition to open plan living/dining and kitchen areas and a large porch. Heating for the whole dwelling is provided by a small wood-burning stove located in the main living area, which is open plan to the dining area and kitchen. The stove is fitted with a back boiler which produces hot water, fed via a simple gravity system to the hot water cylinder. This complements, seasonally, an evacuated tube solar water heating system located on the south-west roof pitch. Indeed, the two systems complement each other so well that the electric immersion backup has never been used.
It was always intended that towel radiators either wet or electric - would be installed in the bathrooms. During the past cold winter, it was found that, in running the wood burner sufficiently to maintain comfort conditions in the living area, an excessive amount of hot water was produced there being no means of separately controlling the two outputs from the stove. Wet towel radiators were thus installed into the bathrooms, run off a pumped circuit from the hot water cylinder. This had a triple effect - not only was a heat leak provided for the hot water cylinder and comfort temperatures improved in the bathrooms, but the distribution by the ventilation system of heat from the bathrooms reduced the load on the wood burner.
Lighting is all LED, mostly "warm-white" 4.5W downlighters, which provide a similar light output and quality to halogen fittings while using a fraction of the energy. Of course LEDs produce much less heat than incandescent lamps. However, it is a much more efficient strategy to let the heaters produce heat and the lights provide light.
The intermittent occupancy of the house means that it takes a little while to warm up on first arrival - but this is of the order of a couple of hours after firing the stove, rather than a couple of days in the case of a standard masonry built dwelling. The house is built in an exposed location facing the Atlantic coast so you might expect us to get lots of noise, but the high level of airtightness, combined with very well draught proofed triple glazed windows, makes for an almost eerily quiet interior, even when the westerly winds are blowing their hardest...
In order to build a dwelling that's comfortable to live in and does not require central heating, you will need to bear in mind two major cost considerations: the extra insulation and the triple glazing required to achieve the necessary thermal performance. Other costs such as mechanical ventilation with heat recovery (MVHR) and solar water heating might have been incurred in any case on a conventional build, although both are central to the concept of the No Central Heating house - the MVHR because it preheats the home and the solar collectors because there is no boiler to produce hot water.
I would estimate a cost of about £4,000 for the solar panels, £4,000 for MVHR, £4,000 for the additional insulation (above the cost of complying with the building regulations), and £2,000 for the higher specification on the glazing (overcost as compared to building regulations compliant double glazing), or equivalent in euros.
Towel radiator costs are minimal and stoves could have been specified as room heaters anyway, although prices were approximately £1,000 for the Co Donegal house and about £1,800 for the Co Down house.
Against this, about £10,000 is saved on a boiler and heating. In addition, the cost of fuel saved each year is likely to total £1,000, so that means that within about four years the extra cost of making your house thermally efficient will have been amortised. It also means that after this time, if you have chosen the central heating route, you will be paying more than if you hadn't!
An important factor with these two houses is that they were built without recourse to grants and full costs were paid for all components and systems, although the Annetts were able to avail of the (soon to be defunct) Low Carbon Homes scheme two-year rates rebate. This shows that ultra low energy housing is affordable - indeed, the No Central Heating system has also been used recently in six social housing units in East Belfast, with the promise of very low running costs and a considerably reduced risk of fuel poverty. Following the County Down and Donegal houses, two other private houses of this specification have been completed with more underway.
As we draw ever closer to the Government's target date of 2016/17 for "carbon neutral" new dwellings, all new housing will need to adopt these principles. Self-builders in particular can move well ahead of legal minimum requirements and future-proof themselves against rising energy costs by adopting this concept. The experience of these houses shows that it works not only in theory but in practice, with very little impact on lifestyle except for a greatly reduced carbon footprint and low energy bills!
Note: All costs include supply and installation but note that these are very rough estimates. When calculating your payback you should also consider the electricity cost of running the MVHR fans and, if there is one, of running the heat pump, though these should each be under £lOO/year or €lOO/year, where relevant, for the equivalent to the dwellings featured here .
The house was occupied for one day around 20 Nov 2010 and from 29 Dec 2010 to 1 Jan 2011, during which time the wood burner was fired up. The occupied period was not during the very coldest part of the winter and the wood burning stove was not run at its highest output. The impact of the heating system can be seen during occupancy; when the house is vacant internal temperatures follow outside temperatures. Night time losses during unoccupied periods are high because no curtains were drawn. Note that the impact of solar gains on the internal temperature are reflected in the spiked profile indicating day to night readings.
Patrick Waterfield is a Chartered Engineer and a Fellow of the Energy Institute based in Belfast, www.drpatrickwaterfield.co.uk
A 1940's semi has become the first building in the UK to both reach the Passivhaus retrofit standard and be certified by a UK based certifier. Low carbon engineering consultants Encraft were appointed by housing association Orbit House of England to retrofit one of its 14,000 homes as part of a pilot scheme.
The housing association hope to learn how adapting existing properties to Passivhaus and other low carbon standards will help slash tenants’ energy bills.
The 1940s semi in Elliott Drive Wellesbourne, Warwickshire, is expected to see heating consumption drop by around 85% as a result of the £100k project. Not only is it the first building in the UK to achieve EnerPHit (Passivhaus retrofit) certification from a UK certifier– it is also the first Wimpey no-fines (sand free concrete) construction house in the world to achieve the standard.
The Elliott Drive house was one of a number of speedily built properties built to tackle the post war demand for new housing whose construction is well known for creating condensation, providing poor insulation and thus generating high heating bills.
A 70 sq m house of this type would typically cost around £1,100 a year to heat, and Encraft estimates the transformed building should now cost just a couple of hundred to run.
The Passivhaus principle is to construct or retrofit a house to minimise its need for heating and cooling by maintaining a constant temperature through effective insulation, airtightness, triple glazed windows and the installation of a mechanical ventilation heat recovery (MVHR) system.
The project saw Encraft oversee the installation of improved insulation in the walls, roof and floor which involved digging out the floor to install 200mm of under concrete insulation and 200mm of insulation around the foundations to minimize thermal bridging. It also required raising the roof level to accommodate thicker insulation, installing new triple glazed windows and doors, attaching airtight rubber grommets around soil, gas and water pipes, installing Mechanical Ventilation and Heat Recovery and a small gas heating system. Although they were not strictly a requirement of a Passivhaus, it also involved installing a new kitchen and bathroom, and fitting solar PV tiles.
Energy reduction is being monitored by Coventry University and the savings are being compared with those achieved by the other half of the pair of semi-detached houses which Encraft also retrofitted but in a less extensive, more affordable manner.
A growing number of housing associations are keen to explore the benefits of Passivhaus construction and retrofit to enable tenants to reduce their heating costs and avoid or escape fuel poverty.
Encraft are also working with several other housing associations on Passivhauses and on a newbuild site in Coventry as part of a project to compare Passivhaus standards to Code level 6 on two adjacent properties on an infill plot donated by Coventry City Council.
Encraft Passivhaus consultant Helen Brown explained: “This project marks a turning point in the UK Passivhaus and EnerPHit sector. Not only is it the second EnerPHit project, and the first to be certified by a UK-based certifier, it has also achieved higher air tightness results than those required by Passivhaus standards, thus dramatically reducing energy bills for tenants.
“58 Elliott Drive was the first Wimpey no-fines house in the world to be retrofitted to this standard. It shows what can be achieved with this kind of building and how it can be applied to the rest of the UK housing stock.
This gives us hope that in these times of austerity and fuel poverty, we can really make a difference to thousands of families on a limited income, in a cost-effective way and with respect for the environment.
“Because the triple glazed windows remain at 17 degrees even if it is below zero outside there is no need for traditional heating such as radiators under the windows. The temperature remains constant and additional heat can be delivered via the MVHR system which has ducts to every room. Background heating can be fitted as an additional source of warmth but a 100 sq m house only needs a 1kw boiler compared with a 12 to 20 kW model required in a traditionally constructed home.”
Formed 5O to 60 million years ago, the Giant's Causeway is a promontory of basalt columns along four miles of the northern coast of the Antrim plateau between Causeway Head and Benbane Head, jutting out of the cliff faces as if they were steps creeping into the sea. The Giant's Causeway and its coastal environs were bequeathed to the National Trust in 1961, and it was subsequently designated a UNESCO World Heritage Site in 1986, the only such site in Northern Ireland. The site plays a major part of Ireland's heritage and tourism, attracting visitors from around the world each year. It is Northern Ireland's most visited tourist attraction, with 500,000 to 700,000 visitors per year - and over 5,000 visitors on peak days. Background to the Project Upgraded visitor facilities were opened by Moyle District Council in 1984, but as the Peace Process in Northern Ireland took hold and tourism increased, it became clear that larger facilities were required. The situation was exacerbated in May 2000 when a fire caused by an electrical fault engulfed the visitor centre. Due to the sea breeze, 80% of the building was damaged before the Fire Service arrived. By July, the site was cleared and temporary facilities installed.
In 2003, a Management Plan for the World Heritage Site was developed and an international competition was held to design new visitor facilities. The design competition called for financially sustainable entries that could cater for an increasing number of visitors to the Causeway, deliver a world-class visitor experience and be highly regarded for the quality of its architecture and exhibition design.
The winning design, selected from over 200 entries, was by Heneghan Peng Architects, of Dublin. Utilising the large difference in level across the site, the design creates two folds in the landscape. One, extending the line of the ridge, accommodates the building. The second, extending the level of the road, screens the car park from view. The Centre is designed as a partially underground facility to integrate with the landscape and to avoid interrupting the ridge line. The Visitor Centre building and landscape therefore become integrated and the visual focus shifts from the man-made elements to the landscape and stones. Following appointment of the remaining members of the Design Team in 2006, work commenced on the design and Environmental Statement for the new Centre. However, funding, political and planning issues dogged the project in the early stages and it was only in November 2007 that the impasse was resolved when Moyle District Council agreed in principle to lease its holdings at the Giant's Causeway to the National Trust to allow the Trust to take the lead in development of new facilities. Design was able to recommence and the planning application for new visitor facilities was finally approved on 27 January 2009. Construction of temporary visitor facilities was undertaken in 2010 to allow the old facilities to be demolished and the new centre constructed. The success of this temporary scheme was demonstrated by reduced traffic problems which had been evident on their previous visit had disappeared and the improved management of the site. The main Visitor Centre building project was tendered in March 2010 and Gilbert Ash were subsequently appointed as the Contractor for the works, with possession of the site granted in December 2010.
The building design has already achieved a BREEAM 'Excellent' award, which measures overall sustainability in design, materials, energy, construction management and ecology. Incorporated within the design of the Centre are a number of sustainable ecological, social and economic elements: • The design life of the building is 100 years, with minimal services intervention required during subsequent refurbishments • Income generation has been factored into the design to ensure ongoing economic sustainability of the Visitor Centre • The concrete used has a high recycled aggregate content to give a 'Green Guide' A rating • The basalt is locally quarried in Northern Ireland • Local specialist stonemasons (S McConnell & Sons) employed to achieve the high quality polished stone finish required • The green roof assists with insulation and minimises impact on the landscape • Indigenous grasses and wild flower seed collected from the surrounding area are used for the green roof planting to maintain the sensitive ecology of the site • The 'Park and Ride' system based in Bushmills reduces traffic congestion at the Causeway site and provides sustainable economic links with the town • The site car parks all feature Sustainable Urban Drainage Systems (SUDS) to avoid increasing the load on the local storm drainage infrastructure
Building Services and Low Carbon Design
The unique design of the building and the sensitivity of the site have resulted in a servicing strategy never before contemplated for a major public building. Boilers, flue and AC condensers were not permitted under Planning conditions and the visual impact of Solar thermal, wind turbines and photovoltaic panels precluded their use on the site. The architectural aesthetic also required that the interior of the public areas was exposed concrete and no ductwork, conduits, pipe¬work or other services were to be visible. The low carbon target set by the M&E consultant from the outset was to achieve an 'A' Energy Rating on the EPC and to make the design as passive as possible. This also reduces the size and complexity of the services installation.
The first stage was to get the building thermal envelope as efficient and airtight as possible. The retaining walls and roof are externally insulated using HD polystyrene. The earth itself also provides an insulation value and in summer, evaporative cooling helps keeps roof temperatures down. The external walls are 150 cavity walls, with 100 thick PIR insulation. The glazing is frameless and is double glazed argon fill low-e glass with a glazing Uw of 1.1 W/m2K. The outer layer of glass is 10mm thick for robustness (the roof lights can be walked on) and is 'extra white' grade to allow more daylight through. Due to the dimensions of the glazing panes, it was not technically or economi¬cally possible to use triple glazing.
Although the building itself can operate passively once occupied, a heating system has to be provided to warm the building up and to temper the incoming fresh air to meet occupancy requirements. The building is designed to operate at -15°C external temperatures for a prolonged period - whether any visitors can get to it is another matter! A 72 kW ground source heat pump system has been chosen to meet the heating requirements for the Centre.
This comprises a horizontal collector mat under the main car park (boreholes were not permitted as the underlying basalt rock is protected). The total collector pipework length is 4.5km. To maximise system efficiency the LTHW circulation temperature is 35°C, which gives a favourable COP of 4.2 and a nett carbon factor of 0.10 kgC02/kWh, 48 % better than natural gas and 62% better than oil. Underfloor heating has been provided to the building perimeter. The AHU coils have been sized to deliver their design heating duty using 35/30°C LTHW. DHW requirements are met by a separate high temperature GSHP unit to avoid compromising the COP of the main heating system.
Ventilation & Comfort Cooling Strategy
The deep plan and underground configuration of the building necessitates the use of mechanical ventilation to meet occupancy fresh air requirements at 12 I/s/person (20% higher than Building Regulations). The ventilation also has to provide sufficient cooling in summer to meet internal and solar gains. Solar gain is minimised in the architectural design of the walls ¬the external basalt columns are deep and angled such that solar gain can only take place in the late afternoon on the front (South) elevation. The design strategy comprises a low-carbon displacement ventilation system, which delivers air at low velocity at 19-21°C directly to the occupied zone and warmed air rises by buoyancy to the extract points at high level.
The fact that supply air only has to be cooled to 19-21°C means that displacement ventilation can use fresh air directly from outside for most of the year without mechanical cooling and can save substantial energy compared with conventional systems. Extensive research has also indicated that displacement ventilation systems also give better internal air quality than conventional ventilation, due to the segregation of exhaust air by the stack effect.
Earth Pipe Ground-Coupled Heat Exchanger
A unique ground-coupled ventilation and cooling strategy has been incorporated which uses the coolth stored in the ground at a depth of 1.5m (ground temperatures normally between 8-14°C) to pre-heat or pre-cool the building supply air. The system comprises a groundair heat exchanger matrix (or 'earth pipes') using specialist Rehau Awadukt underground heat transfer pipe with an antimicrobial inner layer. Air is routed through a total of 1 km of underground heat transfer pipes before entering the plant-room. The minimum supply air temperature from the ground heat exchanger matrix in winter is 3°C and the maximum supply air in summer is 21°C. Higher summer and lower winter temperatures will result in greater heat transfer and therefore more cooling or heating performance. A cooling coil has been added to each of the two main air handling units to guarantee a supply air temperature of 19°C for summer cooling. These coils use low grade cooling directly from the primary (brine) GSHP circuit at 14-18°C on the ground source collector loop. As an added benefit this 'recharges' the GSHP collector during the summer months and therefore acts as a large seasonal heat recovery exchange mechanism. Thermal Mass & Night Cooling The building includes very high levels of thermal mass - 4,900 tonnes of concrete are exposed to the internal space and supply air plenum. This mass forms a key element of the comfort cooling strategy for the Centre, ensuring that temperature rises due to peak gains from solar or high occupancy are 'damped out' by the absorption of excess heat, particularly into the roof slab where the air temperatures are highest. The thermal mass effectively averages day and night temperatures within the building. Night cooling is a technique employed in passive and low carbon buildings to take advantage of thermal mass to pre-cool the thermal mass of the building using cool night or early morning air. The Building Energy Management System will compare internal and external temperatures at night and will activate the night cooling function as required using the main air handling systems.
The Invisible Air Curtain
Any visitors to the Giant's Causeway will be immediately aware that the Visitor Centre is on top of a ridge and the site is very exposed. Draughts are a potentially serious problem. The required capacity of conventional heated air curtains to protect the door sizes used exceeds the entire heating system capacity and using electrically heated air curtains was out of the question. The building has therefore no air curtains on the entrance doors to deal with draughts in winter and is instead protected against draughts by a combination of external facade treatment at the entrances and innovative ventilation design. A revolving entrance door has been provided on the main entrance - this ensures that the 'wind tunnel' effect, which is evident on buildings even where draught lobbies are used (due to simultaneous open doors at either end of the building) is negated. The rear tunnel entrance which has conventional sliding doors is protected partly by the topography of the landscape and the external tunnel entrance design encourages wind to be directed through the vehicle access road tunnel instead of the pedestrian entrance tunnel. The final door 'air curtain' protection is provided by positive pressurisation of the main concourse space to 15-20 Pa. This is similar to the pressure control regime employed in surgical operating theatres and clean rooms to keep dust and bacteria out. When the doors are opened, the pressurised air is released out through the door and helps protect against draughts. This is achieved with no additional heating or fan power ¬in fact, less fan power is used as there is no powered general extract system. Pressure relief louvres are controlled via the BEMS to ensure the building is not over-pressurised.
The Centre has been designed with a good natural daylighting via rooflights integrated into the green roof design to help reduce the use of artificial lighting. Lighting and conduits have been cast into the concrete using proprietary boxes which contain bespoke recessed or spot fittings. For flexibility and future proofing additional boxes have been provided on a grid based system throughout the building so the light fittings can be moved around to suit future internal layout changes as required. The lighting is generally a mix of high efficacy metal halide fittings and LED feature lighting. Within the interpretive exhibition area fittings are fast-response low voltage IRC tungsten display lighting fittings linked to a Dali lighting control system to allow scene changing for the dynamic multi-media displays. Emergency lighting is via a central static inverter system. The emergency luminaires are also used for quick-response pilot lighting for safe access when the building is not open. Back of house lighting is via T5 high frequency fluorescent luminaires and PIR automatic lighting controls are fitted to the back of house areas and public WCs.
The Centre incorporates the following heat recovery systems: • Back of house ventilation ¬mechanical ventilation with heat recovery • Catering refrigeration - all major refrigeration equipment is cooled by the primary (brine) GSHP circuit which contributes to Centre heating in winter. • IT I Comms racks are cooled by the cooled by the primary (brine) GSHP circuit which contributes to Centre heating in winter. • Use of the primary (brine) GSHP for comfort cooling purposes during summer recharges the GSHP collector for winter use by seasonal heat recovery I storage • Heat is extracted from the grey water recovery system from washbasins and used to generate DHW primary LTHW at the same time as cooling the recovery water to prevent microbiological growth. The warm water also increases the COP and efficiency of the DHW heat pump.
The main supply intake is rated at 145 kVA to include for the electrical heat pump load and electrical catering equipment. An emergency generator connection point has been provided. Planning restrictions preclude the installation of a fixed stand-by generator and the National Trust will hire a generator as required. Comprehensive sub-metering has been provided, including separate metering for the catering which is franchised. Electrical floor boxes with power and IT/comms outlets have been provided in a 3m x 3m grid in the floor to allow for flexibility and future internal layout changes. 50% of these electrical points are concealed under the stainless linear floor grilles in non-active sections and the main electrical distribution routes follow the line of the grilles for maintenance access. Fire alarm and PA points have been cast into a grid in the roof slab using proprietary boxes and conduit in a similar fashion to the lighting. Incoming IT cabling and links between the adjacent Causeway Hotel and Innisfree (overflow car parking) are fibre-optic. The IT system also interfaces with the radio system covering the car parks, pathways and stones. A twin electric vehicle charging station has been provided in the main car park - one of a number of designated key locations in NI. Even the hand dryers have been carefully selected for optimum performance and efficiency, with the lowest drying time available (10-12 secs) and a heated high velocity air jet at 224 mph, giving a high green rating of 3.8.
Water Conservation and Management
The Centre has the highest standards of water conservation and recovery. With over 5,000 visitors on a peak day and virtually all of them using the toilet facilities at least once, the load on the local water infrastructure and annual water consumption is potentially very high. The following water conservation and management features have been incorporated by the M&E Consultants: • Low water dual flush WCs - 4 litre I 2.8 litre • Waterless urinals - downdraught type specified as the frequency of use is too high for the standard cartridge type • Rainwater recovery from green roof and rooflights used for toilet flushing • Automatic taps with quick response shut-off •Grey water recovery from washbasins in the toilets used for toilet flushing and roof irrigation • Condensed water from earth pipes in summer is recovered and recycled.
Dominic Lawson Published Sunday Times: 1 April 2012 The gap between comfort and chaos in modern civilisation is alarmingly narrow and defined by a four-letter word: fuel.
If we needed a reminder, thepanic buying of petrol in preparation for a possible tanker drivers’ strike provided it.
Those with longer-term concerns about the survival of the good life will also have felt a spasm of fear at the news that the plug has been pulled (so to speak) on plans to build six new nuclear reactors.
Last week the two German energy giants Eon and RWE decided that the subsidies being dangled by the British government were not sufficient to justify the investment of £15 billion or so of their shareholders’ money.
It has been asserted that the companies had come under pressure from Berlin — pathologically opposed to nuclear power since the Fukushima reactor meltdown. It seems more likely that their directors sensed the way the political wind was blowing across the continent as a whole. For a nuclear programme to be confident of the subsidies required, there needs to be a long-term commitment to swingeing carbon emission reductions on a pan-European scale. Since nuclear power stations emit no CO2, they would have been the prime beneficiaries.
Yet it is
becoming clear that this commitment is weakening across the chancelleries of Europe — even though no government is publicly admitting it — and for a number of obvious reasons. They now recognise there is no possibility that the leading energy users in the developing world such as China and India will agree to any binding limits on their emissions; and if they don’t, neither will America, even under that nice Barack Obama.
So the Kyoto treaty is as dead as Monty Python’s parrot — although since its full implementation would have cost hundreds of billions of dollars in forgone economic growth to reduce global temperatures by about a fifth of 1C in 100 years, it should always have been a complete non-starter on any conventional cost-benefit analysis.
When the western economies were booming on a tide of apparently limitless credit, it was easy for politicians to imagine that the problem of economic growth had been solved and their semi-religious plans of environmental self-sanctification were affordable.
The government, although not yet ready to say so, has finally rejected the bogus economics of climate change The tax revenues would just keep rolling in and the banks would always be able to lend what governments couldn’t raise. Goodbye to all that: now governments across Europe have begun a rapid disassembly of their most grotesque subsidies for “renewables”.
Germany, where almost half the world’s solar energy is produced — in a country with just an hour of sun on an average December day — is now drastically cutting back (as is the much sunnier Spain, whose central plains are littered with bankrupt solar farms).
And which energy source is ecologically correct Germany now developing faster than any other? Lignite, otherwise known as brown coal, the most carbon- intensive fuel known to modern man.
This makes the countries on the European Union’s eastern borders (notably Poland, for which indigenous coal is a dominant energy source) even more reluctant to accept the national emissions targets promoted by Brussels. Eight of these nations launched a legal challenge and last week they won a ruling by the European Court of Justice that Brussels had exceeded its powers in imposing such limits. The court brushed aside the European commission’s complaint that it would not otherwise be able to “protect the integrity of the EU-wide market of [carbon] allowances”.
The most telling point is that this verdict gained almost no coverage. As Benny Peiser, director of the Global Warming Policy Foundation, observes: “In the past, Poland’s intractable hostility to green unilateralism was greeted by protestation in capitals around Europe. Today it is hardly noticed by the media, while green campaigners have become limp . . . Other and more pressing concerns are taking precedence and are completely overriding the green agenda.”
In Britain, where our great coal seams are depleted, if not exhausted, this is much less of an issue anyway. Gas is another matter. The advocates of gigantic subsidised programmes of offshore wind power (who had captured the Department of Energy and Climate Change) based much of their economic arguments on the point that we were running out of indigenous gas and the international price of the stuff would rise inexorably. So “green” energy would not just “save the planet” but actually made financial sense, too.
This was always fanciful: the department’s own figures of two years ago showed new electricity provided by conventional sources of gas coming in at upwards of £55 per megawatt hour, while offshore wind starts at about £150 — almost three times as expensive. This was without taking into account what has rightly been described as the “shale gas revolution”. As a result of new drilling techniques, the US energy scene has indeed been revolutionised, with such vast supplies being brought on stream that a country once terrified of becoming dependent on imported gas (Iran, anyone?) will soon be in a position to be a net exporter of the stuff.
This sudden supply of cheap energy is not only a reason why the US economy is recovering sharply while Europe remains in the doldrums: it is even causing a repatriation of manufacturing from China back to America. As Jeremy Nicholson, director of the Energy Intensive Users Group, notes, if the British government means what it says about retaining our manufacturing base, we have to find a way of emulating the Americans, “rather than continuing to engage in the puerile game of my emission reduction target is bigger than your emission reduction target”.
Over the past few years open-market gas prices in Britain and America, which used to be closely linked, have now spectacularly diverged — and not necessarily to our advantage (to quote Emperor Hirohito’s observation of the state of play on August 14, 1945).
Fortunately, last September the US company Cuadrilla announced that it had found a gigantic shale gas field beneath and around Blackpool. It is thought to contain a scarcely comprehensible 200 trillion cubic feet of gas (vastly more than any of our remaining North Sea reservoirs).
Yet Chris Huhne, the energy secretary at the time, would not pay this potential source of cheap, indigenous and secure energy a single visit even though Lord Browne, the former boss of BP and a director of Cuadrilla, said shale gas in Britain could create about 50,000 jobs and that “if they had the will they could become the centre of shale gas for Europe, much as Aberdeen became the centre of oil and gas for Europe”. Unlike nuclear, not to mention the unavoidably intermittent wind and solar, this will require not a penny of public subsidy — which would make it, in the real sense of the word, sustainable.
On BBC’s Newsnight last Thursday, in the wake of the nuclear démarche, we could see two advocates of renewable energy chorusing that solar and wind power were more economic than gas. They were described as “energy experts” yet that cannot be because if they knew anything about the subject they could not believe such a thing.
Anyway, the government, although not yet ready to say so, has finally rejected the bogus economics of climate change or, more likely, it always knew the figures didn’t add up but is now desperate for the internationally competitive cheap energy needed to keep our industrial base from wholesale emigration. Whatever the reason, there’s no need to panic over the threat by subsidy-seeking nuclear power brokers to pull the plug on Britain. We can keep the light on without them — and more cheaply, too.
All was not well when work began on this impressive Co Cork home and its architect had to pull out the stops to make the eco-home fit the brief
A problem with the design of a passive house in Co Cork made its designer, John Morehead, go hot and cold. A fault in the climate information, that was used to regulate the airtight, ventilated and draught-proofed house, meant the house was too cool. Passive house designs are so sensitive to the environment and climate that even heat from a plasma television can throw the controlled temperature off kilter.
Morehead, an architect with the Cork firm Wain Morehead Architects who specialises in designing passive homes, was concerned to get all the details right when he embarked on a new project on the shoreline of the upper Owenabue estuary, in Carrigaline.
Building had just started on the two-storey, four-bedroom family home and, while the greatest care had been taken to find ecological and energy-efficient materials, it was clear that everything was not as it should be.
“We commissioned the job of sourcing climate data to specialists in Britain,” says Morehead. “We were working off Dublin data, not local data, and suddenly we found we didn’t meet the passive-house criteria. By this stage, we were already on site. We didn’t eat for a week — it was that serious.”
It took three weeks for Morehead and his team to put the mistake right. Intensive research was carried out to try to find out what was putting the data out of sync. Readings put the house at a temperature that was far cooler than first anticipated. There was also less radiation, which can have a big impact on passive-house technology.
“It turned out there was a fault in the way the climate data was being generated,” says Morehead. “It operated on peak-data information — the extremes rather than the averages. To make the house passive again, we had to tweak the specifications. We did this with the help of a local climatologist, but it was three weeks before we were back on an even keel.”
The result, though, is an impressive and unusual contemporary house in a lovely setting with striking views. It is the home of Sally and John O’Leary and their three children. The couple approached Morehead about building an energy-efficient home in August 2008, and work began the following year. They had been refused planning permission to build a previous modern design on the site.
The refusal was based on context rather than aesthetics, and the fact it would be built on a sloping site that ran into the Owenabue estuary was also a concern.
Around that time a neighbouring house was being developed, so it was important for both the O’Learys and their new neighbour to maintain privacy and preserve views, as well as to keep the planners on side.
“Our brief was to design a four-bedroom family home and to be as ecologically friendly as possible while sticking to a budget,” says Morehead. “Our clients were interested in an energy-efficient home and one that would bring the outside space in, merging into the interior.
“The family also wanted natural finishes and a design that was relatively simple. There had to be a focus on food and cooking because that is what they love to do.”
Morehead came up with the modern yet simple passive house in Carrigaline, which was completed in April this year. It has almost 2,600 sq ft of living space over two floors. The home is at the cutting edge of passive-house design, and is one of six certified passive homes in Ireland. A name plate by the front door proudly displays its Certified European Passive House status.
The project did not begin with the intention of building a passive house. “It was originally intended to be an A-rated passive solar project and the decision was made to seek passive-house certification as late as the tender stage,” says Morehead.
Passive house certification is a quality-assured energy-performance and comfort rating that demands stringent control of both the design and construction process.
To make the most of the views and to accommodate the sloping site, the living area was put upstairs. It overlooks the estuary and contains a central winter garden, which enhances the notion of bringing the outdoor space in.
The area has become a multipurpose room, whose use changes with the weather and the seasons. “It is a busy spot, encouraging participation in activities by young children at the principle accommodation level, irrespective of weather,” says Morehead.
“The room is fully insulated from the remaining accommodation, so it can become an outdoor space without compromising the rest of the house or thermal envelope,” he adds.
“Both the expansive glass wall from this room to the hall and the screen to the deck fold away to make a versatile indoor/outdoor space penetrating deep into the bowels of the dwelling.”
Particular care was taken to ensure the home was as airtight and insulated as possible. A cement substitute made from the by-product of the iron and steel industry was used instead of conventional concrete, a decision that saved more than 16 tonnes of CO2. The walls were clad in panels of fibre-cement. It is a low-maintenance material, a consideration that was important in the coastal setting.
Because so much of the work was undertaken during the recession, Morehead and the O’Learys hired local tradesmen and builders when they could.
The upper walls and roof were made from closed wall timber-frames, also manufactured locally. “This construction had exemplary insulation and airtight characteristics,” says Morehead.
“These walls also assist with moisture transfer during periods of high humidity. The upper walls were covered with a rain screen of a carefully selected and detailed untreated Austrian larch cladding.”
To achieve a home that maximises heat gain, Morehead sought out technology to minimise heat loss. Triple-glazed windows with low-iron glass increase transmission of solar heat. The air temperature is controlled to such an extent that no internal surface temperature within the house deviates by more than 4C, even if it’s -10C outside.
The kitchen is an important feature for the O’Learys, who had stressed that they were keen cooks, and it has been given a linear corner window that not only frames views of the river, but also maintains privacy by preventing it from being overlooked by the neighbouring house. The room has direct access to the multipurpose area and the upper garden.
On the upper level there is also a guest bedroom, laundry, study and family room.
The brief had also asked that the needs of a growing family were taken into account. The house should adapt to the children as they grow. To meet this request, the children’s bedrooms surround a large, open multipurpose play area.
The kitchen, along with the living and winter garden areas, has an innovative infrared heating system that Morehead developed himself and is now patenting. “The infra-red emitters heat the occupant, not the air,” he says. “Therefore a level of individual comfort control can be enjoyed independently.
“As with the sun’s energy, 40% of which is infrared, the occupant and indeed any warm-blooded creature, absorbs and responds to this energy through their skin and their inbuilt circulatory system. Heat is then distributed evenly and at a pace to suit the comfort criteria of the body.”
Solar water heating comes courtesy of tubes at roof level and rain water is used for both sanitary and gardening use. While Morehead is coy about the overall cost of the build, he is keen to press home the savings that can be made on home heating, especially at a time when energy companies are raising prices.
“You can heat a home like this for just €150 to €200 a year,” says Morehead. “You are independent of all the price hikes and can live with consistent comfort levels.
“The project confirms that a carefully tuned passive solar design can meet the passive-house standards cost effectively.”
Insulation is a fundamental component of any energy efficient and sustainable building. Most now agree that the 'energy saving potential' of insulation, measured over the lifetime of a building, should be the dominant factor in its specification. In fact, the lifetime differences between various insulation products are small. The most important factor of all is to ensure that the insulation is correctly installed. Over the past few years choosing an eco-friendly insulation material was quite simple. All you needed to do was select one that did not use CFC or HCFC blowing agents in its manufacture. However, with the successful phase-out of ozone destroying gasses by EU law (based on the Montreal Protocol) it became a less clear-cut decision.
So how can we choose the most environmentally sustainable insulation to use in our buildings? Many might argue that 'natural is best' but others counter with 'natural cannot promise durability'. It is true that some insulation applications are accessible enough for us to replace them occasionally throughout the lifetime of the building if we so wish but, likewise, some application decisions are 'whole building life' choices. Let's take a look at some of the environmental issues that may apply to building insulation.
Embodied impact - does it matter?
For a number of years now, insulation materials, among many others, have been compared on the basis of embodied energy (the energy used to build the construction elements). However, if energy saving is high on your agenda, I believe that it is the balance of the embodied energy against the 'in-use' energy consumption over the lifetime of a building that is more important. Indeed, due to the fact that insulation, by its very nature, is there to save energy, it has become widely accepted that the embodied energy of any insulation material is insignificant compared with the energy saved by it over the lifetime of the building in which it is installed.
However this should not allow us to become complacent. The above statement will only hold true whilst we continue to design buildings with quite high levels of energy consumption. All this will change if and when our buildings have low or zero heating/ CO2 emission requirements. This can only be achieved by using insulation wisely at appropriate thicknesses and by detailing our buildings properly to ensure airtightness. Only when our buildings get to low or zero heating levels will the embodied energy of the insulation choice become significant enough to worry about.
One measure of embodied impact is the rating system used in the BRE's Green Guide to Building Specifications. This publication rates products from A+ to E on a basket of environmental impacts, including embodied energy. These ratings are based on generic life cycle assessment (LCA) data. You will find that almost all insulation materials, for which data is given, get the top ratings of A+ or A. The common exceptions are cellular glass, extruded polystyrene and high-density (128 kg/m3 and higher) rock mineral fibre; this is a clear reflection of the fact that the embodied impact of insulation materials is relatively insignificant. However, it does illustrate that it is important to consider the density of the insulation material, as more dense insulants may have a low embodied impact per kilogram, but not per m3 or m2.
How in-use energy is far more significant than embodied energy
Interestingly when the impacts for insulation are combined with the impacts of other materials that make up, say, a wall or a roof, the different ratings of insulation products become largely irrelevant as they are masked by the impacts of the other materials in the construction. In the guide it is perfectly possible for a wall insulated, with extruded polystyrene, to get an overall A+ rating, even if the insulation itself does not, (some might argue that this is a failure of the rating system used). It is equally possible for a wall insulated with an A rated insulation material to get an overall E rating because it is the rating for the whole construction that counts as far as the Green Guide data is concerned. Accurate and unbiased embodied energy / embodied impact figures for insulation materials are difficult to find, other than in BRE's life cycle analysis (LCA), and therefore should be treated with care.
It is widely accepted that reducing "in use' energy consumption of buildings is the key to their environmental sustainability. Therefore, the major parameter on which to compare insulation materials must be their ability to deliver their specified thermal performance over the lifetime of a building. This is one of the key themes of an independently produced report on the sustainability of insulation materials, funded by BING (the European trade association for manufacturers of rigid urethane insulation products), which brought to bear the concept of risk factors. These are all factors which could detrimentally affect the thermal performance of individual insulation materials, sometimes in very different ways, and hence the environmental sustainability of buildings. These risk factors may include the impacts of:
• liquid water or water vapour
• compression or settling.
On the whole it will be poor site work that will allow these risk factors to come into play. On-site installation practices are notoriously uncontrollable and all materials will perform badly if installed without due care and attention. However, for some insulation materials the problem may stem from what is claimed for the product in the first place.
Adherence to common rules for thermal performance claims should be checked. The EU Construction Products Directive has created a set of harmonised product standards for insulation which demand that the thermal performance of all products is quoted in a comparable way that takes account of ageing and statistical variation. It is called the Lambda 90:90 method. All major UK insulation manufacturers have adopted this approach to quoting thermal performance. It is worth noting that the introduction of the harmonised product standards added about 10% to the thermal conductivity of the insulation products that are covered (i.e. made them 10% worse). However, at the present time there are a number of smaller scale products for which there is no harmonised standard available and therefore no consistent method that takes account of statistical variation. No doubt these will be brought into the fold soon but, until then, inconsistency will reign. One particular case in point is that of multi-foil insulation.
Once the global issues have been considered it is then time to consider less pressing, but still important, issues such as recycled content, local sourcing, disposability etc. The key to the environmental sustainability of any product is a balance of all these issues. Taking just one issue and over-focussing on it could be counter-productive.
Recycled content of products is going through something of a revolution in the UK construction industry. The Government has funded a body called The Waste & Resources Action Program (WRAP) to promote materials that have a recycled content. It gives very specific rules as to what counts as recycled content and what does not. These rules follow the definition cited in the ISO standard on Environmental Labels and Declarations>.
Some insulation already contains recycled content. However, when examining the recycled content of insulation materials please bear in mind that recycled content is the proportion, by mass, of recycled material in the product. Only pre-consumer and post-consumer materials should be considered as recycled content." This means that surplus material cut from the edges of products during their manufacture and shredded and added back in at the start of the process don't count.
Another, often overlooked aspect of the performance of insulation materials is their performance with respect to fire. This is quite a complicated area but, roughly speaking, there are two facets to consider: reaction to fire and fire resistance. Reaction to fire is measured by the 'Class 0' type rating system enshrined in Approved Document B to the Building Regulations in England & Wales or the risk categories shown in the Technical Handbooks in Scotland. These ratings can be achieved by reference to the new Euroclass system for reaction to fire or by the tried and tested BS 476 Parts 6 and 7.
There is a debate in the insulation industry, at present, as to which route is best. What has caused this confusion is the fact that the new Euroclass rating system for reaction to fire is irrelevant when applied to 'naked' insulation products, as the system was developed for wall and ceiling linings and insulation is rarely used as such. The reaction to fire test has slightly more value when used for products tested 'in application', since insulation products are then tested mounted as they would be in practice for example behind plasterboard. '
Proponents of the Euroclass system suggest that 'naked' products lie around bUilding sites all the time and that the products are expOsed when, say, holes are cut in walls, but I cannot understand how testing a product as a wall or ceiling lining can relate to packs of products lying on the ground. Regardless, the test still gives no indication of a product's ability to resist fire. It is this crucial distinction that
can make all the difference to the ability of a building to withstand a fire and maintain structural integrity long enough to enable occupants to leave safely, and allow emergency services more time to get the blaze under control and salvage the building. Mistakenly choosing a material based on its reaction to fire, without taking into account its resistance to fire, may therefore at best be costly, and could at worst prove fatal.
The crux of the issue is that some materials have excellent fire resistance qualities but relatively poor reaction to fire ratings, whereas others have the best reaction to fire ratings but relatively poor fire resistance properties.
What about the Code for Sustainable Homes?
There are a number of different insulation materials that, if installed correctly, can meet the low energy requirements of the higher levels of the Code for Sustainable Homes (CSH) - introduced in Chapter 2. For example, the thickness of insulation required, and whether this impinges on useable space, needs to be considered.
But having excellent levels of insulation is not enough - it is vital to also consider the overall impact of the materials used, and their effectiveness over the lifetime of the building. In the past the environmental sustainability of insulation materials has been compared on the basis of embodied energy. However, this may not deliver a true picture of environmental impact and it is now recognised that a much wider range of issues needs to be considered, not just embodied energy.
LCA techniques provide a good, holistic tool to achieve this but it is also important to look at the whole construction and not just one component of it. The CSH has endorsed this approach by awarding credits based on the BRE Green Guide ratings for the roof, external walls, internal walls floor and windows of a house construction which are themselves based on LCA analysis. If all 5 elements achieve an A rating then just 2.7 credits are awarded if they all get an A+ then a maximum 4.5 credits can be awarded.
It is also important to recognise that it is operational energy use that creates the vast majority of environmental impact, and this too has been reflected in the CSH in the balance of credits allowed for reduced CO2 emissions versus those allowed for materials: 17.6 and 4.5 discretionary credits respectively. However, there is one vital aspect of environmentally sustainable buildings which is not addressed by the CSH, and that is the point that the longevity of the standards of operational performance is critical.
For example, the performance of some insulants, such as rock mineral fibre, can deteriorate rapidly if exposed to water penetration, moving air penetration or compression. This may increase operational energy use and hence compromise the environmental sustainability of the finished building to an alarming degree. Other insulation materials, such as rigid phenolic and rigid urethane insulation, are not vulnerable to any of these problems. The question of longevity is particularly important in the light of the requirement for energy performance certificates for all houses. These certificates are an important part of the resale or let process, tracking the energy performance of homes over time.
So when it comes to achieving the best standards, and meeting some of the key objectives behind the CSH whilst still delivering reliable long term performance, there are three important considerations: in the first place, work to the lowest possible U-value regardless of insulation type, design out the risk of the chosen insulant not performing as specified, and, if you can't, choose an insulant that is at low risk of failure.
In this way the industry knows that it can deliver housing that meets the increasingly tough criteria for carbon dioxide emissions, without having to rely on expensive technology or worry about site restrictions. In other words, a smart solution that keeps the numbers of new projects and higher standards within the realm of both the achievable and the realistic.