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Baldy's Garden uses locally-grown coppiced sweet chestnut

Exit eco-bling
01/04/08
Published:  08 August, 2008

FCB Studios' Century Court is clad with FSC-certified red louro

Architects' definitions of sustainable construction and their take on where timber fits into the picture are the subject of a new book from TRADA. Mike Jeffree reports

Ask eight architects and designers for their steer on the UK’s drive to build more sustainable homes and you get eight different perspectives. But TRADA, which has done just that in a new book entitled Timber and the sustainable home, also picked up on some common threads. Most prominent was that the key to unlocking the sustainable and zero carbon home conundrum is not loading housing with eco extras like wind turbines, solar panels and ground source heat pumps, but building in energy efficiency and sustainability from the outset. That puts the emphasis on design, orientation and the materials palette – and it also puts timber, the renewable construction material, firmly in the frame.
Craig White of White Design is one architect interviewed and he sets out his stall unequivocally by stating that there’s “no such thing as a zero carbon house”. But what you could have, he says, are zero carbon communities. That means shared heat and power generation and a stress on infrastructure; how people travel to work, get food and recycle waste, with housing schemes including allotments and on-site recycling.
When it comes to the sustainability of building fabrics, White Design puts increasing emphasis on carbon captured. This led to its BaleHaus project using timber frames packed with straw, then finished in render to add thermal mass. In the Innovation School at the BRE’s Offsite exhibition, it used Eurban cross-laminated solid timber panels. The zero carbon house may be a myth, but, according to White, the prototype school does score zero in terms of embodied energy, with Eurban adding to its eco points by planting 10 trees for every one it uses. 
The "carbon hierarchy", White adds, starts with "trying not to emit carbon in the first place". “This is where you look at the fabric and the design of the house and incorporate things such as renewable materials, passive design and preventing energy leakage”. You also have to teach the occupants of the building how to get the most out of it. “Engagement with people’s behaviour ensures we create buildings that are low energy long term,” he said.
American architect John Onken questions the wisdom of the UK construction sector’s rush to “jump on the carbon bandwagon”, fearing that it may lead to “a lot of alternative drivers” to sustainable construction being overlooked. But he feels the growth in the range of building methods being adopted here is potentially an environmental plus – and he’s especially positive about the increasing expertise in timber. When he first came to the country a decade ago he was surprised at the commitment to brick and block. “This method of layering one lump of dirt on another was so ingrained, I got the impression timber frame was alien.” His experience on his recent award-winning Dolphin Cottage project in the Isle of Wight highlighted how things had changed. “Everyone was much more switched on in terms of the whole process,” he said.
According to Andy Couling of FCB Studios, the Brits are still “hung up on brick and block”. But he believes this can be “unpicked”. “Most want to live in the country and timber can provide that link between buildings and nature.” 
But a challenge for timber in meeting increasingly tough sustainable construction criteria is airtightness. Wet trade building is forgiving on this front, but site-built timber frame can struggle to meet the highest standards. The answer is prefabrication. FCB, for instance, is evaluating SIPs panels and timber frame sprayed with Hemcrete, the lime and hemp concrete substitute. “This way you get greater thermal mass and improved airtightness because you’re going back to a wet trade,” says Couling.
Christopher Platt of KAP architects also favours prefab and, for his recent cuboid, shingle-clad house in Scotland, used Swedish-made closed panels. He eschews PV panels and wind turbines too in favour of the right materials and building systems, in his case partly because he thinks these technologies are not yet efficient enough. He also maintains that aesthetics are central to sustainability. “We need to create buildings that contribute to our architectural heritage,” he says.
Ben Addy of Moxon Architects is another advocate of keeping it simple and shunning “eco-bling”. His illustrates this with his recent extension for a London mews. The simple recipe is sustainable materials (including a steel and timber hybrid frame and cedar cladding), plus high passive energy performance (achieved with all-round insulation, timber rain- and sun-screening and Scandinavian double-glazed doors and windows). The route to sustainability, says Addy, also involves educating the British to accept more Continental-style high density urban dwelling which, in turn, would lead the way to more lightweight timber frame.
Meredith Bowles of Mole Architects also urges the construction sector to strip sustainability back to basics: orientation, insulation, airtightness and high-spec windows. It’s within that context that you look to employ newer products and materials. When it comes to timber elements, for instance, he talks up using
I-joists over “big lumps” of solid wood. “You use less material, [building] panels are lighter, you avoid thermal bridging and you can make them 11m long.”
The final piece of the sustainable jigsaw in TRADA’s book comes from Duncan Baker Brown of BBM Sustainable Design. It’s sourcing locally, which BBM tries to do for all materials, including wood. To date, this has constrained it to smaller timber-based projects but now it’s talking to timber framers that can take on larger structures and still use home-grown. The key to this developing, says Baker Brown, is more trees: “Schemes are in place to expand our forests and that is exactly what needs to happen.”

Editor’s note
Timber and the sustainable home is a lively, informative read and packed with pictures of the interviewees’ projects. Particularly interesting to note is the general preference for the pared down path to sustainability rather than buildings festooned with "eco-bling".
You can order your copy at www.trada.co.uk/bookshop; £10 for TRADA members, £25 for non-members.

Ben Addy

Keywords: White Design Duncan Baker Brown FCB Studios Mole Architects