Diary of an Eco-Builder

We're refusing to compromise on our dream design, even if it leads to delays

What does it cost to build green? This ought to be a straightforward question, but the straightforward answer - more! - is wrong some of the time and misleading all of the time.

What does it cost to build green? This ought to be a straightforward question, but the straightforward answer - more! - is wrong some of the time and misleading all of the time.

The ordinary builder's bottom line (and I'm not talking ill-fitting jeans here) does not take account of any environmental costs. Nor does it reflect the long-term value of durable materials, a healthy living environment and low running costs. Tree House may not be the cheapest self-build in Britain today, but once we're in we will have no monthly fuel bills and we'll be able to enjoy a consistently comfortable, draught-free home that is filled with natural light and free from toxic pollutants.

Building professionals will also tell you that doing anything non-standard is unpredictable, risky and therefore more expensive. This argument is a little closer to the knuckle at the moment: we are currently paying a price for our ecological ambition in our embarrassingly absent super-structure. Our beautifully prepared slab, endlessly nipped and tucked by ever-patient foreman Steve, is beginning to feel like a launch pad for a rocket that left long ago, a lingering concrete impression of ever-receding dreams.

Last month I belatedly discovered that the company we originally approached to supply our timber frame had no evidence that it came from a sustainable source, despite the fact that their website was plastered with the Forestry Stewardship Council logo. Fortunately, we were able to find a manufacturer, James Jones and Sons (www.jji-joists.co.uk), and a supplier, Ridgeons of Sudbury (www.ridgeons.co.uk), who were willing to pull out their FSC stops for us. But some re-engineering of our ultra-efficient walls was also required, adding to the delay.

Happily we have a contractor, Martin Hughes, who does not see this as an opportunity to slap some extra costs on us but instead has jiggled his schedule, bringing forward some jobs to fill the gap, so that the costs of the delay will be limited to some hard-bitten nails. Our contract with Martin is not the result of competitive tendering but of a series of discussions led by our architect that began early in the design process, a "negotiated contract", which is especially appropriate for an unusual build that is difficult to price. If you don't go out to tender you risk being ripped off but the reward of a successful negotiation is a set of working relationships based on trust and a shared commitment to the building itself.

Enthusiasm for the building has proved to be a major benefit of our ambition, a payback for our determination to push beyond the fluffy green foothills of eco-design and into the more challenging landscape of energy self-sufficiency. This includes everyone from our very supportive neighbours to Chris the concrete man, eager to tell me about his recycled aggregate.

If you are embarking on a building project, however small, you will be under pressure from day one to stick to the familiar. But if you want professionals who are really going to take an interest, don't compromise. Whatever your design fantasies might be, eco or otherwise, let them rip. You can always sew them up neatly again if circumstances dictate.

Back on site, I remain nervous that one delay will lead to another, despite the best of all our intentions. Hopefully our engineered timber beams will arrive any day now and, amid a flurry of sawdust, Clapham's first carbon-neutral Apollo mission will finally leave the ground.