Case study Self-build eco-home
pastures
Green
When a highly experienced building services engineer decided to construct his own house to high ‘passive’ standards, he took on more than he bargained for. But the results were worth the pain, as Ewen Rose discovers
H
aving decided to build a house from scratch, Mike Murray believed he should practice what he preached about reducing his personal carbon footprint. He also wanted to apply
the principles of ‘open book’ contracting, laid down by Latham and Egan in their seminal reports. These principles had been adopted at multidisciplinary practice AMEC Design and Management in Stratford when Murray was head of design there. Murray admits that he is a classic case of a senior
professional with masses of expertise on domestic projects. He therefore had a clear vision of what he wanted to achieve with the 4.5 acres of land in Banbury, Oxfordshire, that he planned to build upon. But he had little doubt that he would need a range of practical support to turn that vision into reality. His wife Ann had already sketched out a design for
a traditional Cotswold stone farmhouse, but Murray eventually persuaded her to tuck those away for another day. What they have ended up with is something much more unusual – a visually arresting home featuring three integrated blocks, each with its own curved copper roof. When the Murrays bought the site, it came with a
1970s Colt bungalow and planning permission to demolish and rebuild. Murray was looking to develop a 300 sq m, four-bedroom home, constructed using locally sourced materials and local firms where possible.
Thermal inertia
The outside of the building is a combination of local Hornton stone (‘softer and more mellow than Cotswold stone’) and oak cladding which, along with the heavyweight concrete block shell and the beam and block floor, has created a thermally massive structure – a key part of Murray’s low-energy approach. ‘My PhD included computer simulation of the
thermal envelope, so I was able to look at this intuitively,’ he says. ‘We couldn’t afford computer modelling in any case, but I was confident that this structure would give me the thermal inertia I needed to create an efficient
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house with minimal heat losses.’ The walls and vaulted ceilings are all heavily insulated. The foil-backed insulation in the walls, and the multi-layered foil insulation in the roof, unexpectedly turned the building into a Faraday cage so that no mobile phone signals can penetrate. However, the Murrays would not be without the
unusually shaped copper roofs, which they say make them feel happy when they wake up in the morning. They certainly enhance the sense of space. A thatched roof had been considered, but Murray applied a clear life-cycle planning approach to all aspects of the project and the thatching would need replacing in 30 years’ time (when he ‘wouldn’t really be up to it’). Life-cycle planning was done at the conceptual stage
when Murray adopted the ‘Six S’ plan pioneered by the architect Frank Duffy: Stuff (family possessions), Space plan, Services, Structure, Skin, Site – the principle being that the stuff drives the design rather than façade architecture.
We took our brief to 12 different
architectural practices – four of whom immediately walked away
‘We created a cracking brief from all of that information, which included listing absolutely everything we would need in the new house,’ says Murray. ‘Then we took it to 12 different architectural practices – four of whom immediately walked away citing their concerns about responding to such a challenging brief!’ One architect, Simon Carter, a former AMEC
colleague, was up for the challenge – including a robust environmental site analysis reflecting the sustainable design approach. However, the first lesson he learned was that architects find it hard to get good building services advice on small-scale projects – particularly when seeking to design a low-energy home from
June 2010 CIBSE Journal
27
Above and facing page: Mike Murray looked to develop a home with minimal heat losses.
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