sustainable building

Dún Laoghaire council defies Alan Kelly on passive houses

Dún Laoghaire council defies Alan Kelly on passive houses

Dún Laoghaire-Rathdown County Council could be on course for a clash with Minister for the Environment Alan Kelly after councillors voted in favour of an energy-efficient building standard over which his department has serious concerns.

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. 

The Full Monty (Zero-carbon, Passivhaus Primary School)

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

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.

 

CREST Hub - South West College

The new CREST centre will comprise of three areas; the Hub, the Research & Development Lab and the Pavilion. The Pavilion will be newly developed while the Hub and Research & Development lab will be integrated into the existing Skills Centre building; with the work on the Hub area recently completed.  

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.

From the very outset it was made clear that sustainable design was key to the successful completion of the entire CREST project, this responsible approach was to reflect the innovative aspirations of the CREST project.  We are pleased to be associated with our client, South West College, who are striving to create a sustainable centre that will form a benchmark for construction projects in the future.

The new pavilion project is the one of the most sustainable projects in the UK and will be the first commercial building in Ireland to have the following three sustainable credentials:

  1. Passivhaus Certified for Energy efficient envelope and ventilation system
  2. BREEAM excellent in terms of the BRE sustainable benchmark for UK commercials buildings
  3. The building will also be Carbon Neutral, 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.

The Hub element of the project comprises of several meeting rooms, a waiting area, small kitchen and computer desk.  During the fit out of the Hub office area, where ever possible and feasible, recycled components and sustainably sourced materials where used.

A palette of recycled materials has been used to decorate the meeting rooms.  Bangor blue slates, reclaimed from the Belturbet Convent of Mercy (demolished in 2008) and reclaimed Florencecourt brick from a house in Enniskilen (demolished 2008) have been re used on the walls of the meeting rooms.  Pitch pine floor boards from the Belturbet Convent of Mercy have been used to differentiate the meeting rooms from the rest of the Hub.

The reception desk of the new hub has been created using the same pitch pine as has been used on the floors of the meeting room; the desk is supported on gabions of handpicked stone from the only slate quarry in Ireland.

The timber cladding used for the cladding walls in the Hub is reclaimed scaffolding boards that were used as shuttering on the A5 road extension project.  Scaffolding racks and poles are used to support the desks and other furniture that has been created bespoke for the project.

The palette of materials combined with the exposed duct work have created an industrial warehouse type aesthetic that is illuminated with low energy lamps to further increase the sustainability criteria.  The design utilises these materials to create a tactile, efficient and user friendly hub for a functional educational facility. The project was completed in February 2014.

Natural Insulation Vs. Manufactured Vs Embodied Energy

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.

06 chart
06 chart

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.

In-use performance

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

• air-infiltration

• 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.

Insulation considerations

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.