Diary Of An Eco-Builder

The world would be a happier place if our first intuition was to treat nature as a university

Reflecting on our guiding metaphor, I am struck by how freely we draw on the natural world to illuminate our own, yet rarely return the favour with any sympathy, perhaps because projections of our manufactured world on to the natural landscape tend to expose uncomfortable truths about the relationship between the two. At best, the biosphere is a garden, more often a playground, warehouse or rubbish dump.

The world would be a happier place if our first intuition was to treat the natural world as a university, a place to seek wisdom, skills and technology. This approach is most fully articulated by the advocates of "biomimicry", who point out that many of our energy-intensive, pollution-saturated technical achievements have long been realised in the natural world at ambient temperatures with minimal resources and entirely beneficial side effects.

The lotus stays clean in Asian swamps because dirt particles cannot hold to the microscopic mountain ranges on the surface of its leaves. A spider excretes a material for web-building that, weight for weight, is five times stronger than steel. The abalone shell is one of the hardest materials known, yet it is made in the sea rather than in a furnace (see www.biomimicry.org).

Trees are fine examples of biological engineering, but our efforts in Clapham to build a house that "works like a tree" are focused on achieving the ecological performance of a tree without necessarily using arboreal technology. A tree harvests solar energy using tiny organic photosynthetic solar cells, largely made from air and water, whereas our photovoltaic solar roof is made from highly refined materials, leaving behind a significant trail of energy emissions and waste.

The nearest we shall get to working like a tree is in our use of wood. When you chop a tree down, the transport of water and sugar within wood ends immediately, but the extraordinary strength that sustained the tree remains. In fact, the best timber comes from inside the tree, where the wood is effectively already dead. As a tree grows and its trunk thickens, the tree packs oils and resins into its core. This heartwood protects and strengthens the tree and helps to support the sapwood around it, where living processes continue.

Although most timber sold commercially is heartwood, it sometimes comes with edges of sapwood. These are vulnerable to insect attack but the heartwood will only get munched if it has already decayed, usually because of prolonged exposure to damp.

So don't rush to spray your home with pesticides if you see tiny holes in timbers, as this is likely to be expendable sapwood. Such "flight holes" are usually historical anyway: your guests may have left decades ago. Where wood treatment is unavoidable, use boron-based products which have low toxicity to both humans and the environment.

Foreman Steve is not entirely persuaded by our branching roof, as not all of the branches are strictly necessary. Happily, though, we are not inspired by hard-line modernism but by a tree; and in the natural world, lots of things are not strictly necessary: abundance is the reward of truly sustainable design.