The house that Will built

It went from a rubble-strewn plot to a fully sustainable green house: Will Anderson pens the final chapter of his ground-breaking project

I am sitting amid the boughs of a tall multi-stemmed sycamore in a quiet corner of Clapham, south London. The heavy rain last night has brought a soft glow to the spring foliage and the delicate tassle-like flowers that shelter beneath the outstretched leaves. As the canopy is still young the sunlight easily penetrates the lattice of branches, creating a patchwork of blue and green. There is little wind but the form of the tree is full of movement and life.

This is a long-awaited moment. The first entry in my unexpectedly long-running Diary of an Eco-Builder, published in full today by Green Books, began beneath the same tree. Then I was surrounded by rampant brambles and a dense entanglement of shrubs and climbers, each fighting for space in the tiny urban wilderness that was our building plot. My current elevation into the canopy is one of the many delightful outcomes of the creation of Tree House, the rather ambitious building project that has occupied most of my waking hours for the past three and a half years.

I am writing this in the top room of Tree House where great timber trusses burst from a wall of books then branch out to support our roof. Through the glass doors that open on to our little tree-top balcony we can admire the same movement in the structure of the tree, albeit expressed in an infinitely more complex manner. Interior-balcony-canopy become one space and one experience.

The house as a whole enjoys a unity of design thanks to the guiding influence of the tree. It is risky playing with organic forms in design but our architect, Peter Smithdale of Constructive Individuals (www.constructiveindividuals.com), avoided the pitfalls by being allusive rather than literal.

Our tree has also found its way into many of the details of the house including the fences that pick up the patterns in its bark, the tree trunks that support our staircase and the dappled light created by our contemporary stained glass. There is a much more profound way in which the tree inspired the design of the house. At the core of our romantic hopes for this project has always been the crazy notion that this house could "work" like a tree.

Trees are remarkable feats of engineering. They are built to last from sustainable materials. They are well adapted to their climatic conditions, coping admirably with heat, cold and desiccation. They get all their energy from the sun. They recycle all their nutrients and enhance biodiversity by supporting a wide range of flora and fauna. Their impact on both local and global ecology is benign. They are beautiful, inspiring, sustainable structures. Not a bad specification, I reckon, for a new house built at the beginning of a century in which we must either learn to swim sustainably or quite literally sink.

We may not have met every detail of this specification but we have done the best we can on our highly constrained urban site. It will be some time before we know if our combination of a high-performance building and on-site renewable technologies achieves our goal of energy self-sufficiency but early indications are encouraging. I am quite confident, however, that one of our other core goals has been achieved. We have scored the "win-win" of making eco-design work for us as well as for the planet: the house is warm, draught-free, light-filled and an absolute joy to live in.

For me, Tree House has long ceased to be an "eco-house". It is simply an imaginative response to a tricky urban location, driven by a passion for beauty in design. As far as I am concerned, design that harms the world and the prospects of current and future generations can never be truly beautiful, so our radical ecological specification is no more than a logical consequence of this passion.

There are no green flags waving from the top of Tree House. The technology and environmental design are almost entirely hidden. Many people stop on the street when we are digging the front garden and comment on the beauty of the building; few of them are aware of the quiet beauty of its environmental specification. Although ultra-bespoke Tree House will never be a model for mass housing, the discretion with which it carries its commitment to the future offers hope for universal green architecture. I am confident that, in time, this house will become a hoary old sycamore in a forest of thriving sustainable buildings.

w.anderson@independent.co.uk

Features of Tree House

* A highly insulated and air-tight building fabric with controlled ventilation

* Lots of natural light complemented by careful summer shading

* A rooftop solar power station and solar hot-water panel, and a ground-source heat pump that draws warmth from beneath the house

* Sustainably sourced timber frame construction

* Low-impact finishes, including Kirkstone slate, reclaimed teak floors and natural paints

* Energy-efficient lights, appliances and various electronic items

* Rainwater collection for the garden, and water-efficient toilets, taps and appliances in the house

* Recycling built in to the entire dwelling

* A pond and wildlife garden installed to enhance biodiversity

* Excellent local services and public transport connections

* To order your copy of Diary of an Eco-Builder at the special offer price of £13.95 (free p&p), phone 0845 458 9910 quoting "The Indep-endent reader offer"