eco architecture

Thermal Mass - Understanding its benefits

Thermal Mass - Understanding its benefits

Thermal mass 'Thermal mass' describes a material's capacity to absorb, store and release heat. For example water and concrete have a high capacity to store heat and are referred to as 'high thermal mass' materials. Insulation foam, by contrast, has very little heat storage capacity and is referred to as having 'low thermal mass'.

Zero energy for all?

Zero energy for all?

From 2020 onwards all newly built or renovated houses in NI and ROI will have to comply with the Nearly Zero Energy Building (NZEB) standard. How that requirement will be put into practice remains unclear but there are some general rules we already know will have to be followed ..

Embodied Energy of Materials

Embodied Energy of Materials

Total primary energy consumed from direct and indirect processes associated with a product or service within the boundaries of cradle to gate. This includes all activities from material extraction (quarrying / mining / harvesting), manufacturing, transportation and fabrication until the product is ready to leave the final factory gate.

Here's how much of the world would need to be covered in solar panels to power Earth

Solar energy is a seriously underrated resource. More power from the sun hits the Earth in a single hour than humanity uses in an entire year, yet solar only provided 0.39% of the energy used in the US last year.

The Passive House standard can't be diluted and here are the maths to prove it

The Passive House standard can't be diluted and here are the maths to prove it

“As debate ramps up in Ireland about whether local authorities in Dublin should adopt the passive house standard, and the UK government scraps its plans for zero carbon homes, Dr Shane Colclough urges passive house advocates to prepare for the lobbying battles ahead by remembering the basic science behind the standard.”

Pennine Farmhouse marries traditional style with passive performance

Pennine Farmhouse marries traditional style with passive performance

Steel Farm is the first certified passive building in Northumberland, and the first cavity wall passive house in the north east of England. It is located near Hexham in the North Pennine area of outstanding natural beauty (AONB)

The design and construction of an exemplar Zero-Carbon Primary School

The design and construction of an exemplar Zero-Carbon Primary School

In 2008 the Department for Children, Schools and Families (DCSF) identified funding for pilot/exemplar projects under the Zero Carbon Task Force (ZCTF).

Delivering Low Energy Buildings for Real

Delivering Low Energy Buildings for Real

This Guide is a unique publication which combines professional guidance from a range of suppliers and industry experts, which, when combined together, can deliver a low energy building. A variety of systems are presented ranging from ventilation systems to a range of insulation, airtightness, windows and water treatment systems. 

Invisible Fuel

Invisible Fuel

The cheapest and cleanest energy choice of all is not to waste it. Progress on this has been striking yet the potential is still vast. Improvements in energy efficiency since the 1970s in 11 IEA member countries that keep the right kind of statistics (America, Australia, Britain, Denmark, Finland, France, Germany, Italy, Japan, the Netherlands and Sweden) saved the equivalent of 1.4 billion tonnes of oil in 2011, worth $743 billion.

A Beautiful Solution - An argument for Passive House by architect Justin Bere

an-introduction-to-passive-house.jpg

The government's cynical recent energy policy announcements represent a dereliction of duty to the vulnerable and to future generations. There is an alternative, argues award-winning passive house architect Justin Bere - and it's beautiful.

Many of the UK's elderly citizens and low income residents cannot afford to maintain healthy conditions or basic levels of comfort in their homes, while those who are better off often cosset themselves in over-heated homes burning excessive amounts of precious and polluting fossil fuel. Everyone complains about the cost of energy, politicians wring their hands and try to sound as if they have a plan, but little is done to improve the UK's domestic and non-domestic buildings to make them more affordable to run.

"Those who peddle minor gestures in sustainability as if they are an al­ternative to passive house are either lacking in real knowledge, or simply playing confidence tricks on the public."

In a world where there is a rapidly growing population demanding a share of ever fewer resources, it is unrealistic folly and indeed utterly foolhardy to think that the answer to the high fuel consumption of our buildings is simply to outsource new power stations on guaranteed repayments to meet the unchecked projected future growth in demand. Yet this is exactly what the UK is currently doing. Through sloppy thinking, the UK is mortgaging the future; locking the younger generations into a level of expenditure on fuel that will most likely be completely unaffordable for them. Effectively they will be trapped in a situation with no affordable way out. What is utterly unforgiveable is that the reason for this is that the current generation doesn't want to feel any of the pain of transition. But transition will have to happen in the end and the longer we leave it, the more painful - or catastrophic - it will be.

Yet those of us in the passive house community have demonstrated that there is a solution that can deeply reduce overall energy demand in both new and existing buildings by 80 or 90% while at the same time creating ex­ceptionally healthy and comfortable buildings. New passive house buildings can be built for little or even no extra cost if design priorities are realigned with an energy saving imperative. But even where there are additional costs, such as in passive house retrofits, the costs can be paid back in a lifetime so that future generations are handed an affordable and beautiful solution.

The UK can look back with pride at how its population pulled together and responded effectively to national emergencies in the 20th century. Once again, and as much as at any time before, we need to respond with effective action to what I believe is an even bigger emergency than those faced by previous generations.

Effective action will include re-building the respect for vocational skills, the passion for making things to the best of our ability and to world-beating levels of excellence. It will include renewed respect for world-class engineers and engineering businesses. It will include a transformation of the construction industry from one focussed on what it can take from society, to one focussed on what it can give to society.

All this requires an honest, clear vision which I believe all of us in the passive house community have, and which we must promote. We must point out that those who peddle minor gestures in sustainability as if they are an alternative to passive house are either lacking in real knowledge, or simply playing confidence tricks on the public.

In An Introduction to Passive House (RIBA Publishing, £27.99), I present facts and arguments that attempt to show why passive house is the best form of building for people's health, comfort and general well being, for every age group, for fantastically low energy use, for very low whole-life costs, for the environment as a whole and for the future of the planet.

Embracing passive house technical methods does not mean that we have to turn our backs on beautiful architecture or light-filled, flowing spaces. Passive building techniques give us the opportunity to hold on to the uplifting aesthetic tenets of the very best 20th-century buildings, while at the same time transforming our technical abilities to make social progress and beauty possible in a world where excessive consumption is no longer tenable.

An Introduction to Passive House shows that the economics of passive house are clear. While shifting priorities is a simple lifestyle choice for many, for others the help of responsible, in­telligent and forward-looking govern­ments is needed in order to make it easy for individuals and organisations to make steps now, for the benefits of both themselves and of society at large, now and in the future.

Passive house is emphatically not a product, nor does it require designers to use particular products. The Passive House Institute offers manufacturers technical assistance to improve their products, and provides quality assurance certification, but passive house buildings can be built without any certified products. Passive house is a standard and an advanced method of designing buildings using the precision of building physics to ensure comfortable conditions and to deeply reduce energy costs. It does what national building regulations have tried to do. Passive house methods don't affect "buildability", yet they close the gap between design and performance and deliver a much higher standard of comfort and efficiency than government regulations, with all their good intentions, have managed to achieve.

The in-use performance data from passive house buildings shows that to provide comfort, to save energy, to reduce bills, to protect people from fuel poverty, to reduce excess winter deaths, to save money in the long run and, arguably most importantly, to reduce CO2 emissions, it is difficult to escape the conclusion that deep, energy-saving passive house retrofits and new-builds must become the norm. A deep, energy-saving retrofit programme will create jobs now at the same time as saving money on fuel imports, both now and long into the future. Vast amounts of money can also be saved by reducing the need for new power stations and for long-term storage of nuclear waste, and by reducing the serious impact upon the National Health Service of the UK's dreadful, damp and draughty buildings.

In concluding I will repeat the question that visitors to passive house buildings seem to ask more than any other: Why aren't all buildings built like this?

An Introduction to Passive House by Justin Bere (RIBA Publishing) is available now at RIBA Bookshops (ribabookshops.com/passive)

Bere, J. (2014) ‘A Beautiful Solution’, Passive House + , Issue 5, UK Edition, pp. 20.

 

Homage to Catalonia: A pre-fab straw bale Passive House 'first' for the region, by Oliver Style, ProGETIC

The Larixhaus is the first pre-fabricated straw bale passive house on the Iberian Peninsula. A project that took 7 months from start to finish, this single family home is located in the town of Collsuspina, Catalonia, Spain. Through careful bio-c1imatic design, thermal insulation with straw, an airtight envelope and high-performance windows, the Larixhaus has a projected space heating demand (calculated with PHPP) of 15kWh/m2 .a, approximately 80% less than that required by current Spanish building regulations. The project is a modest, but inspiring example of deep-green energy efficient construction, in preparation for the EU's 2020 deadline, when all newly built homes will need to be 'nearly zero energy'. Oliver Styles reports...

He huffed and he puffed...

Jordi, Itziar and their two daughters live in a small town in the hills above Barcelona, between rolling pine forests and burnt sienna escarpments. Renowned for its cool winters and even colder traditional stone houses, the area has been witness to one of the greener construction projects to have taken place in recent years south of the Pyrenees: the Larixhaus, Spain's first prefabricated straw bale and timber passive house. As straw bale building gains momentum in central Europe, with ground- breaking work from ModCell, White Design, LILAC and the University of Bath, the Larixhaus is a modest but determined example that timber and straw bale construction can move beyond the pigeon-hole of one-off self-builds and contend in the mainstream of beautiful, low-impact, energy efficient architecture. A simple, compact home which, despite the huffing and puffing of the big bad wolf, is set to brave the elements of this Mediterranean mountain region and place nearly zero energy construction on the map in preparation for the EU's 2020 deadline.

Early design: where the first steps count

The client's priority, from the outset, was to bring together a group of professionals with experience in timber and straw bale Passivhaus construction, who could design and build a small home at reasonable cost, where natural, renewable materials were married with a high level of energy efficiency and indoor comfort. In the early design stage, a simple and relatively compact building form was chosen, with 339m2 of thermal envelope enclosing a gross exterior volume of 437m3 over two floors, for a form factor of 0.78. The longest dimension of the building was aligned east-west, to provide maximum day lighting and reduce artificial lighting loads, resulting in a building aspect ratio of 1:1.3.

A location specific climate file was generated with the Meteonorm software and compared with the last 10 years of data from a weather station located 6km from the site, showing good agreement. Shading from nearby mountains was taken into account using a topographical horizon profile. The climate data was then entered into the PassivHaus Planning Package (PHPP) energy simulation and certification tool, for early stage design modelling and analysis.

Contrary to the orientation of all other homes of the street, the building's southern and most highly glazed facade was orientated perfectly south. PHPP modelling provided the required surface area of southern openings to take advantage of free solar heat gains in the winter. A combination of design strategies were modelled and tested for maintaining summer comfort with no active cooling.

To enjoy the spectacular views west to the jagged rock formations of Montserrat and east to the Montseny mountains, bedrooms are located on the ground floor, with a diaphanous kitchen, dining and living room space on the first floor. Wet rooms (bathroom and kitchen) are located in the same vertical plane, to reduce pipe runs and minimise heat losses in the domestic hot water system. To provide full fresh-air ventilation with minimal heat losses in the winter, a whole house ducted heat recovery ventilation system was chosen: careful early planning of duct routing made sure the duct lengths were kept to a minimum, reducing cost and energy losses. Operable windows on the east, north and western facades provide natural ventilation in the summer and sufficient natural light in all habitable rooms.

The skin: timber and straw bale

The timber superstructure and external cladding is PEFC certified, and was laser cut to order and delivered to the Farhaus workshop for prefabrication, 1 5km from site. The straw bales are 1200 mm x 700 mm x 400 mm, positioned vertically in the timber frame structure. The bales were sourced 1 25km away on the Costa Brava. The bales are enclosed on the outside with wood fibre breather board, followed by a 35mm ventilated gap and larch rain-screen cladding, fixed on timber battens. The ventilated wall reduces transmission heat gains in the summer and provides an exit for water vapour in the building structure - an important design consideration to avoid interstitial moisture build-up and condensation damage in straw bale construction. On the inside, the bales are shut in with 22mm formaldehyde-free OSB that acts as the air tight layer. Finally, Fermacell gypsum fibre board, over a service void, provides a dry-lined internal finish. Structural timber that spans the thermal envelope is thermally broken with cork insulation.

Two straw bale roof cassettes, with the bales positioned in the same direction as the walls, provide a thermally efficient roofing system, finished with clay tiles over a ventilated air gap, reducing transmission heat gains and summer overheating. Gravel infill on the intermediate floor adds some thermal inertia, although with the air-tightness and thermal insulation specification, combined with careful design of openings with external blinds, the building's thermal mass (calculated as 84Wh/K for every m2 of Treated Floor Area) was calculated as sufficient for maintaining summer comfort with natural ventilation. Given the site's altitude at 888m, peak summer temperatures are lower than coastal Mediterranean regions, averaging only 20°C in July and August. PH PP modelling showed that with no active cooling and a combination of glazing with a solar factor of 47%, external blinds on southern openings, and natural night ventilation, summer overheating frequency (when the indoor air temperature exceeds 25°C) could be kept below 3%, equivalent to a total of 36 hours in which the indoor ambient temperature rises above 25°C.

Despite not meeting the environmental criteria established between the client and design team, the most cost effective and thermally efficient solution for the floor slab was found to be 130mm of rigid polystyrene under the slab with perimeter insulation of 60mm around the edge of the slab.

The testing of alternative design strategies with PH PP modelling showed that an acceptable balance of heat gains and losses was achieved with triple glazing (with two low-e coatings, argon gas filling and TGI warm spacers), for a centre-pane U-value of 0.65W/m2.K and solar factor of 47%. Soft-wood Farhaus frames provide a U-value = 1.00W/m2.K, with cork insulation to reduce installation thermal bridges. The average installed window U-value is 1.06W/m2.K, not enough for cold' central European climates but sufficient in the Collsuspina climate to meet the comfort and hygiene requirements set by the Passivhaus standard.

The average weighted thermal transmittance of the building envelope is U-value = 0.21 1 W Im2K. The door blower test gave an impressive result of n50 = 0.32ACH (air changes per hour). Cold bridges were eliminated or reduced with modelling and optimisation in the design phase.

The building shell was prefabricated in the Farhaus workshop over a period of 6 weeks. It was divided into 10 separate modules, with the air tight layer and window frames installed and sealed. The modules were transported to site and the basic structure was assembled in two days. Pre-fabrication minimises on-site construction times, providing cost savings and near-zero on-site waste. The Larixhaus' embodied energy and C02 emissions derived from materials are minimised by prioritising natural, non-toxic, renewable materials with minimum processing (certified timber, locally sourced straw, cork, and gypsum fibre board).

Indoor air quality, acoustic comfort and active systems

Healthy indoor air quality is achieved through the use of non-toxic, Iow-VOC, natural materials. Exposed timber inside the home is either untreated or coated with water-based varnish. Healthy materials are combined with whole house ducted heat recovery ventilation to provide efficient, comfortable full fresh air ventilation during the winter. Cool air is brought into the home and pre-heated by outgoing stale air through a Passsivhaus Institut certified Zehnder Comfoair 350 ventilation unit, with an installed sensible heat recovery rate of 79%. PHPP simulations showed an average seasonal COP of 9. Efficient DC fan motors are essential for reducing electricity consumption: calculations showed that, given an average of 4,700 hours of operation per annum, at an air change rate of 0.40 (91 m3/h), the unit will consume only £31 of Spanish electricity each year (where household electricity is the 3rd most expensive in Europe). The ventilation unit is fixed on acoustically insulated mounts and located in the service cupboard by the entrance on the ground floor. Silencers on the indoor air supply and return ducts, combined with adequate duct sizing to control air velocities, means the system has a maximum measured sound pressure level of 33dB(A) in living spaces. The result is a quiet, discrete and efficient comfort ventilation system.

The near-zero heating demand is met by two low-cost 500W wall-mounted electric radiators in each bedroom, and one 450 W electric towel radiator in the bathroom. On the first floor, a 4kW air-tight log stove (that modulates down to 2kW) with a twin-walled concentric chimney flue, provides heat on very cold days, without compromising air tightness. Hot tap water is produced by a compact air-source heat pump unit with a COP of 3.75 (@ air = 15°C and water = 45°C) and a heat store of 300 litres. The air intake of the heat pump is located just above the stale air outlet of the ventilation unit, providing some performance improvement. The clients have set timing controls on the heat pump to make sure it does not activate between 1 1 pm and 8am in the winter, to avoid poor 'performance when outdoor air temperatures are low. Following 3 months of use, there has been sufficient hot water to meet daily demand with this control strategy.

Cooking is done on an induction ceramic cooktop with a re-circulation cooker hood. Artificial lighting is with LEDs and all white goods are A++. If the Spanish government decides, at some point in the future, to reverse the current legislation and encourage the use of renewable energy technologies rather than bending to the pressure of the large energy companies, the clients intend to install a grid-tied photovoltaic array to achieve a net zero energy balance. When the budgets allows, a rain water catchment system will follow suit (pre-installation was done during construction) .

Beyond PHPP and into the real world

A remote monitoring system will be installed in the coming months, providing quantitative data over a 2-year period, monitoring outdoor temperature and humidity, indoor temperature, humidity and C02 levels, together with electrical energy consumption for space heating, ventilation, hot tap water, lighting and equipment. It will be particularly interesting to see the in-use summer performance of the building.

Meanwhile, feedback to date from the clients shows that with outdoor night time temperatures reaching -1°C, indoor temperatures have remained above 20°C with no active heating, as long as there is some sun during the day. For successive days with no sun, they turn on the electric radiators for half an hour at night and in the morning, to maintain comfort. The first test of the log stove ended with Itziar opening the windows as it got too hot in the sitting room (!), confirming the PHPP calculated peak heating load requirement of 11 W 1m2. At least during this first mild winter, the stove seems largely redundant. The specific construction cost of the build has come in at around £1,005/m2, an estimated 14% more costly than building to current regulations in Spain. This gives an approximate simple payback time of just under 9 years, for a building with an expected useful life of 80 years.

So goes the story of the Larixhaus: a green-building homage to Catalonia and its rich history, number 10 in a growing list of healthy, comfortable, Passivhaus constructions south of the Pyrenees.

Oliver Style

Useful links:

WWW.PROGETIC.COM

WWW.LARIXHAUS.CAT

WWW.FARHAUS.COM

WWW.KLlMARK.COM

WWW.CONSTRUCTION21.EU/ CASE-STUDIES/ES/LARIXHAUS-STRAW-BALE­AND-TIMBER-PASSIVE-HOUSE.HTML

WWW.PASSIVHAUSPROJEKTE.DE/#D 3874

Project team:

Client: Jordi Vinade, Itziar Pages

Architecture: Nacho Mart, Maria Molins, Oriol Mart.

Passivhaus design, PHPP analysis, M&E: Oliver Style, Vicenc Fulcara - ­ProGETIC SCP

Contractor: Albert Fargas - FARHAUS

5tructural Engineering: Manuel Garcfa Barbero - Klimark Architectural Consultant: Valentina Maini

Project Spec:

Energy standard: PassivHaus new build Location: ColIsuspina, Barcelona, Spain Treated floor area (PHPP): 92m2 Construction type: timber construction Completion date: December 2013 Completion time: 7 months

Space heating demand (PHPP): 15kWh/(m2a) 5pace cooling demand (PHPP): 3.2kWh/(m2a) Heating load (PHPP): 11W/m2

Cooling load (PHPP): 3.9W/m2

Primary energy requirement (PHPP): 96 kWh/(m2a) Construction costs (gross) [1m2]: 1211/m2

Air tightness (n50): 0.32ACH

Envelope information:

Exterior wall: U-value: 0.127 W/m2.K: in> out

  • 13mm plasterboard (Fermacell)
  • 35mm service void between timber battens at 8%
  • 22mm 05B 4 [air-tight layer]
  • 400mm straw bale insulation [052] between timber joists at 8%. thermally broken with cork insulation [040]
  • 16mm wood fibre breather board (DFP Kronolux) Wind tight membrane and ventilated larch rain screen cladding, flxed on external timber battens

Floor slab: U-value: 0.165 W/m2.K: bottom> top

  • 130mm XP5 insulation [034]
  • 350mm reinforced concrete floor slab
  • 80mm Pavaflex wood fibre insulation [038] between timber joists at 10 %
  • 22mm timber flooring
  • 60mm XP5 insulation [034] around the edge of the floor slab

Roof: U-value: 0.122W/m2.K: bottom> top

  • 15mm timber board (Fir) 22mm 05B 4 [air-tight layer]
  • 400mm straw bale insulation [052] between timber joists at 2% 16mm wood fibre breather board (DFP Kronolux)
  • Timber battens and roof tiles

Windows / doors

  • Farhaus, Fargas window frames
  • 50ft-wood laminated wooden window frames (90mm)

Uframe = 1.00W/m2.K

Average U- value window = 1.06W/m2.K

  • Triple glazing. with two low-e coatings and argon gas fllling; 33.2/16argon/4/16argon/4; TGI warm spacer

U-value glazing = 0.65W/m2.K

g-value = 47%

Entrance door - Farhaus: Fargas door

  • Triple glazed entrance door with identical speciflcation as windows

Udoor = 1.00 W/m2.K

Ventilation

  • Zehnder ComfoAir 350 Luxe
  • PHI certifled ducted whole house mechanical ventilation with sensible heat recovery
  • Distribution in HDPE 90mm pipes

Heating system

  • Ground floor: electric radiators
  • First floor: Rika Passiv blomass stove

Domestic hot water system

  • Theodoor Aerotermo 300 Plus
  • 3.6kW thermal compact air source heat pump unit, with backup electric immersion heater.

Oliver is a certified PassivHaus designer/energy consultant and co-founder of ProGETIC, an engineering practice based in Barcelona, Spain. He specialises in passive design and building performance optimisation through energy model­ling. He has an MsC with distinction in architecture, with the Centre of Alternative Technology and University of East London. He enjoys working closely with designers, developers, engineers and free thinkers who want to build or renovate beautiful, healthy, comfortable buildings with low running costs. - OSTYLE@PROGETIC.COM

Style, O. (2014) ‘Homage to Catalonia: A pre-fab straw bale passive house 'first' for the region’, Green Building Magazine, vol. 23, Spring 2014, pp. 20-24.

 

Zero carbon targets and the construction industry

The new definiation of Zero Net carbon occurs after allowable solutions are introduced.

The new definiation of Zero Net carbon occurs after allowable solutions are introduced.

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].

Passivhaus vs Code for Sustainable Homes

Many people appear confused about how PassivHaus and the code for sustainable homes can run in parallel, 'Does one compliment the other?’

To obtain the definitive answer, we need to remember that us that Passivhaus focuses on building fabric and performance without the use of renewable technology. Typically a PassivHaus will achieve code energy rating of level 4 or 5. This means that it is an ideal methodology for achieving the higher level of the overall code rating, whilst also minimising the cost of renewables.

Principles And Performance

The term 'PassivHaus' refers to a specific construction standard for buildings which have excellent comfort conditions in both winter and summer. These principles can be applied not only to the residential sector but also to commercial, industrial and public buildings. For houses, it is claimed that this is the world's leading standard in energy efficient construction. They are designed and built using a step-by-step approach with efficient components and a whole house ventilation system to achieve exceptionally low running costs to create something which is comfortable, healthy and sustainable.

There's an interesting article in Green Building Magazine www.greenbuildingpress.co.uk written by Justin Bere about a talk given in London by Wolfgang Feist who founded the German PassivHaus Institute in Darmstadt.

The fundamental objective of PassivHaus design is unambiguously to cut energy consumption and to provide accurate design tools to measure the expected energy consumption in a clear, accurate, numerical way. Germans really don't have time for vagueness and are aware of the requirements set out in UK Building Regulations. However many of our Code level features are incorporated, no one can circumnavigate the essential requirement to produce a building designed to use less than 15kWh/m2/annum supplementary heat and no more than 120 kWh/m2/annum primary energy [total of heating, lighting, hot water, appliances and any cooling). No box ticking wood chip boiler - nothing will let the PassivHaus architect, developer or builder circumnavigates this fundamental, verifiable bottom-line requirement for PassivHaus certification.

The simple techniques necessary to achieve PassivHaus design are: Insulation [typically 30cm thick]; PassivHaus windows [airtight, triple glazed with thoroughly insulated frames achieving an overall U-value of 0.8 including the frame]; Airtight construction [max 0.6 air changes/hr under 50 pascals pressure] with very efficient mechanical heat recovery ventilation. Assuming that these three main performance targets are met, together with detailing to eliminate cold bridging and numerous other detailed requirements prescribed by the PHPP software, it is possible to eliminate the need for a boiler and the need for radiators or underfloor heating.

Comparing certain other UK building codes with the PassivHaus approach highlights difficulties in the UK codes that have been introduced in relative haste. By contrast the PassivHaus code has passed the test of time and Dr Feist is very careful to ensure that it remains truly robust. It is the very robust nature of the concept and the software that led the RIBA in a sustainability review to originally describe PassivHaus as 'The emerging European Standard.' Now there are about 17,000 buildings have been constructed worldwide, typically achieve an energy saving of 90% compared to existing housing principles.

The NHBC Foundation and Zero Carbon Hub have published 'A practical guide to building airtight dwellings'. It brings together the experiences of those who have already got to grips with air tightness for the benefits of designers and builders who have not. It provides solutions for common air leakage paths. Clearly, changes in the Building Regulations have now made air tightness an issue which cannot be ignored.

The Denby Dale Project

Typically, PassivHaus buildings are built using timber-frame construction or blockwork wall with external render. Green Building Store has succeeded in adapting the PassivHaus approach to British traditional building methods - by creating the first certified PassivHaus in the UK to use traditional cavity wall construction. Earlier this year the Denby Dale PassivHaus project in West Yorkshire received its official PassivHaus certification.

The project - built by Green Building Store's construction division Green Building Company - has pioneered the combination of low energy PassivHaus methodology with standard British cavity wall construction and building materials. Bill Butcher, Director of Green Building Store, said, "We chose cavity wall construction because most British builders are familiar with the technique and materials could be sourced easily from any builders' merchant. Cavity wall also met Yorkshire planning requirements for stone exteriors and was affordable for our clients. In addition, masonry construction, including cavity wall, offers a 'cave effect' which acts as a thermal mass, helping to keep temperatures stable in winter and summer".

It requires minimal heating - using 90% less energy for space heating than the UK average; £141 K build cost for the 118m2 three-bed detached house. Green Building Store's technical film 'PassivHaus low energy building in the UK' for building professionals is freely downloadable from www.greenbuildingstore.co.uk. The 60 minute film covers all stages of construction of the Denby Dale project.

What are the challenges?

Achieving the required level of air tightness, minimising the risk through good design and specification.

Is it costly to build?

European experience suggests an extra 6% is likely. There are not yet enough UK houses to make a proper comparison, although BRE is advising on a London project which has achieved PassivHaus for the same cost as a typical social housing one.

Are PassivHaus products widely available?

Yes but windows have at present time to be imported; they have generally been the reason for higher costs.

Will adopting PassivHaus facilitate compliance with buildings regs and the Code for Sustainable Homes?

Yes. If a compliant design specification is derived from PHPP [the PassivHaus Planning Package] and transposed into SAP, a 30-45% improvement in carbon emissions can be realised - without the use of heat-pump, biomass or other low carbon or renewable technology.

The Low Carbon Buildings Programme - Energy Saving Trust

If you are a householder in Northern Ireland interested in generating your own heat or electricity, you can apply for a renewable technology grant of up to £2,500 per property. The Low Carbon Buildings Programme incentivises householders interested in fitting their own green energy systems, such as solar photovoltaic’s, wind turbines, small hydro, solar thermal water, ground source heat pumps and Bio energy, by providing grants to contribute towards the cost of installation.

The Programme is funded by the Department of Energy and Climate Change and managed by the Energy Saving Trust. Many people claim that they want to do their bit to help tackle climate change but are put off by the costs associated with renewable technology. By taking advantage of the grants available through the Low Carbon Buildings Programme, homeowners will find small renewable technologies a more affordable option. By installing micro generation technologies, homeowners will not only play a vital role in tackling climate change but will also save themselves money in the long run.

Noel Williams, Head of the Energy Saving Trust Northern Ireland commented: "I am pleased that householders in Northern Ireland have already applied for grants to install green energy technologies through the Low Carbon Buildings Programme and hope that even more people will follow in their footsteps and reduce their carbon footprint."

To be eligible for a grant through the Low Carbon Buildings Programme, consumers must choose a certified product and have it installed by a certified installer.