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Our client wanted the building to be an exemplar of how to build sustainably in a protected national park, but we hadn’t really thought about the insulation until, during one public consultation, a local woman suggested we use some wool from her sheep! The idea struck a chord and led us to Second Nature UK and Thermafleece.

Second Nature supplied us with hundreds of panels for use in the roof and external walls. These were also used as soundproofing in walls between meeting rooms.

We were intrigued by the history of the company, which was set up by two sheep farmers’ wives who wanted to make use of stained sheeps’ wool that would ordinarily have gone to landfill. It’s therefore a highly sustainable product and it won’t give off any toxic fumes, unlike some synthetic insulation.

Although we considered other natural alternatives, such as a recycled paper-based product, these would have required a deeper thickness of wall and we were restricted by the width of our timber frame. We actually specified 200mm-thick Thermafleece slabs for the walls, which we compressed into the cavity.

One drawback was the cost: it was about four times the price of fibreglass wool insulation. But the client put an emphasis on sustainability and decided to cut the fitout budget instead. You can always buy new furniture, but you can’t replace insulation down the line.

Some people have raised concerns that wool insulation might rot, but as long as you keep moisture out, and have a good vapour barrier to stop condensation forming in the cavity, there shouldn’t be a problem.

We were able to achieve U-values 20% better than Part L 2006 – 0.24Wm2K for the walls and 0.20Wm2K for the roof. The building has just won the Low Carbon Trust’s Low Carbon ºÚ¶´ÉçÇø Award 2009 for Scotland.