16 Oct 2014

Fast forward


Every issue i-build follows Will Anderson as his self-build adventure unfolds. In this installment, his project moves fast as winter approaches.



It took about a month for our timber frame to go up. That was quite slow by the standards of Touchwood Homes, however, their small team included two novices – my cousin and myself – both on steep learning curves. We climbed these curves as quickly as we could, hauled up by the patient and cheerful guys from Touchwood. It was a great experience.

The frame was complete by the end of August, which was fortunate as we had a slot booked with the Green Building Store to install our windows and doors starting on September 1st. On this date three Yorkshiremen turned up in a van with our made-to-measure, triple-glazed Ecocontract windows. The job didn’t take long, as the holes in the frame were, as expected, just the right size. Nonetheless it certainly wasn’t straightforward, principally because triple glazed timber windows are incredibly heavy but must naturally be handled with great care. Thankfully all went well.

We also moved quickly to get our roof on. Touchwood had left us with some chunky rafters and a layer of chipboard, the foundation for a seriously ambitious roof which will keep the heat in, generate electricity and even provide us with fresh air – as well as keeping us dry, of course.

The basic design of our roof is a ‘warm deck’: a thick layer of insulation laid on top of the rafters that is finished off with a continuous weather-proof membrane. We used an Alwitra membrane supplied by ICB, who also supplied the exceptionally efficient Sunpower solar panels. The roof membrane was installed by Steve and Ashton from SW Roofing, based up the road from us in Battersea, south London. Steve was an old hand and clearly took pride in the quality of his work, carefully welding together all the pieces of the membrane as if it was a gigantic tapestry.


One of Steve and Ashton’s first tasks was to cut and lay the insulation. Because we are building an exceptionally low energy house, we wanted an unusually large amount of this: 300mm of high performance Kingspan TR27 roof insulation. This was slightly off the scale for Steve and Ashton, who had never laid this depth of insulation before. By the time it was all down, they were persuaded that our heating bills will be almost non-existent.

At the very top of our roof, three curious alien beings look down upon the solar panels and roof windows. These are our heat-recovery ventilation cowls, designed and supplied by Ventive. These days, mechanical heat-recovery ventilation systems are usually specified for low energy houses: whole house ducted systems, driven by fans. But why use a machine when you can get the result you need without one? The system we are installing is entirely passive, driven by the buoyancy of the internal air and by the wind outside. They look pretty cool too.

Time pressure

The roof was a big job and took nearly three weeks to complete, during which time not a single drop of rain fell. We ended up hoisting a hosepipe onto the roof to make sure that the membrane did its job properly. Sure enough, all the water quickly ran to the one outlet at the rear of the roof where a temporary downpipe currently takes the rain away from the unfinished walls.

That’s the next task: the week after the roof was finished, I took delivery of seven thousand beautiful handmade bricks from the Northcot brickworks in Gloucestershire. It’s all been a bit non-stop and I am beginning to feel exhaustion creeping in. But there’s no rest for self-builders, let alone the wicked. Winter is coming and I need to get inside soon.

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