The grass grows greener on a timber teepee

David Nicholson-Lord visits the environmental centre that has turned itself into a living, breathing demonstration of how we can learn to build with nature ARCHITECTURE IS EDITED BY Jonathan Glancey

Turn one way in Bishops Wood near Stourport in Worcestershire and the view is of pylons, pipework and portable cabins. Turn the other and you will see a glorified hobbit's hut in the woods: an odd, conical wooden structure with grass growing on the roof, chains dangling off the sides and the all-pervasive sound of Japanese wind chimes.

John Rhymer has a theory about the conical design of the Bishops Wood environmental education centre. Four years ago, when the building was not much more than a gleam in his eye, the architects from Hereford and Worcester County Council arrived to discuss the concept. They met in an Indian tepee, erected in the grounds for one of the centre's earth education courses. The tepee shape, he believes, lodged in the architects' subconscious.

Bishops Wood is probably unique in Britain - a nature study centre where the building provides much of the nature to be studied - and Mr Rhymer is its head. It was opened last year by David Bellamy, who professed himself flabbergasted at what had been achieved. It is not, however, a folly, fantasy or architectural caprice: Iain Paul, the architect responsible for its design, believes that many of its ideas can, and should, be applied in large commercial buildings.

There has been a nature trail at Bishops Wood since the Seventies. The ancient woodlandwas chosen by the Central Electricity Generating Board as a screen for a substation. Thus fenced off, the 40-acre wood and its wildlife prospered. National Grid, the CEGB's successor, has a network of nine field study centres linked to substations. Then, five years ago, the first environmental centre, an unprepossessing assembly of portable cabins, was opened. But do portable cabins carry the right message about human relationships with the environment? Mr Rhymer thought not.

The new Bishops Wood is thus a "three-dimensional textbook". The turf roof, for example, is an exercise in how indigenous building techniques have contemporary relevance: the grass acts as insulation, protecting the waterproofing layer below. The "breathing wall" - allowing moisture and air to pass easily from the indoors to theoutside - maintains a healthy environment. The shredded newspapers and telephone directories used in the insulation consume a thirtieth of the energy used to produce conventional polystyrene insulation.

Many of the green technologies at Bishops Wood - the recycling of sewage water through reed beds, the "flow forms" that oxygenate falling water, the chains that feed rainwater from the roof gently into butts - can be seen in places such as the Centre for Alternative Technology at Machynlleth in Wales. What is distinctive is the way they have been integrated into a working building. The result is not merely energy efficiency (Bishops Wood uses between a half and a third of the energy of a conventional school or library) but a place that is kind to the spirit.

Timber, preferably home-produced, to cut down on energy costs, is ubiquitous: from telegraph poles used as support pillars to bark-lined corridors. Wood makes environmental sense as a building material because it soaks up carbon and reduces global warming, but it also makes people feel at home.

Mr Rhymer says that while children love the small, intimate interiors of the building, adults like the sense of contact with the outside world. "They like the windows, the natural light, the feeling of closeness with nature, with the birds and trees and woodland outside." The woods crowd close to the centre, but there is no risk to foundations because there are no foundations.

According to Mr Paul, the lightweight timber construction, borrowing from the ideas of the self-build architectural pioneer Walter Segal, could be widely applied commercially. So could techniques such as natural ventilation, the use of local products, the recycling of building materials. Every part of the centre, in fact, has its own biography: the water-chains are from a redundant trawler fleet, the blue paving bricks outside were rescued from a Victorian school privy.

Some of the lessons, however, are less cheering. The centre cost about £450,000, much of it paid for by cash sponsorship - National Grid, the county council, and the Hereford and Worcester training and enterprise council were the chief providers - but the rest in countless smaller gifts of time, materials and money. Because it took much thought and planning it was relatively expensive. But the process convinced Mr Paul that "as long as architects are being asked to design buildings at huge discounts on scale fees, you are not going to get environmentally sensitive buildings". Two ingredients vital to a green building - designing it for a particular place and consulting the people who will have to live and work in it - do not lend themselves to stock solutions, he points out: therefore they cost money.

Ultimately, however, Bishops Wood is as much manifesto as manual. Ten thousand children pass through every year, plus hundreds of adults on courses ranging from "greening your home" to "campaigning for the environment". The children return home to educate their parents. The adults, according to Mr Paul, "begin to understand why they feel uncomfortable in their air-conditioned, deep-plan offices. They begin to ask what is coming off paints on walls and why they are getting headaches. They begin to make the connections with their normal working environments."

Green Building of the Year Award: entries for this award, sponsored by the `Independent on Sunday' and the Heating and Ventilating Contractors' Association, should be submitted by 3 March. Details from Fiona Byrne, HVCA, Esca House, 34 Palace Court, London W2 4JG, (0171- 229 2488).