Or shall we go back to using straw, as the palaeolithic hunter-gatherers did when they stopped being nomadic and put down roots and cultivated grasses? Down on the farm, at the Centre for Alternative Technology (CAT) in Machynlleth, Powys, Wales, they are building a children's theatre, 12m by 12m square and seven bales high, entirely from straw. At CAT, in a cluster of offices and shops, restaurants and visitor centres and performance spaces, they test-drive sustainable and low- energy buildings. Some are made of earth under thatch, others of wood, roofed with lawns sprouting daisies.
CAT is a hippie-ish sort of place which, in the 25 years since it began, has turned Establishment after being invited to advise on Government green policy. It's a living, working laboratory for green ideas.
A team of builders and gardeners live and work among the buildings to demonstrate renewable energy and new uses for age-old materials. Enthusiasts visit to learn about hand-built houses and low heating bills - about 80,000 of them every year. Reedbeds filter and clean all the recyclable water. Even the lavatories function using peat shavings.
Their new theatre will be made out of straw, but no amount of huffing and puffing - even gales whistling down from the foothills of Snowdonia - will dislodge it. Nor will it burn. If you plunge an oxy-acetylene torch into a compacted straw bale it will go out, which will surprise all those who confuse straw with hay; hay cut green from the field will sometimes even self-combust. Straw, on the other hand, is made from dead stalks, wheat heads, leaves cut from oats, rye, barley, any grain crop.
The straw-bale theatre will be built over four weeks by course-workers who pay CAT for the privilege of learning the skills. First the foundations were laid in a narrow trench, to have minimum impact on the landscape. Then the timber frame was raised, in a scene straight out of Witness (in which Harrison Ford helped raise a barn in an Amish community). Tractors delivered hundreds of bales to the dun-coloured field ringed with birch trees, and 12 course- workers raised the walls seven bales high.
Koji, an architect, even flew from Japan to join in. This week, the pitched roof - it rains a lot in Wales - of slate and turf will be laid over the crossbeams. People come from all over the world to gain practical experience under the expert eye of Barbara Jones, who runs the summer course on straw- bale building. "I can't get them to stop for tea. They're all smitten by bale frenzy," she says.
Barbara Jones is also at the commercial sharp end of this alternative form of building, with her own building business in Yorkshire. AmazonNails is the phonetic name she chose to underline the fact that she needs neither hammers nor nails to make shelters out of straw. Hazel hoops are wound around the corners in the same way that gardeners truss sweet peas to stop them falling over. Baling-twine ties the big bales on to a timber frame set into a low trench in the ground. "We try to impact upon the landscape as little as possible," says Barbara Jones. The knot system used is basically the same used by truckers to tie loads on to lorries. AmazonNails has built 13 straw-bale buildings, including community centres in North Yorkshire and a family house in Ireland for five people, costing less than pounds 30,000. She learnt her craft in the States on a Winston Churchill fellowship. Apparently, beneath sensible stucco on many a thick-walled, century-old mansion in the US lies bedded straw - though lime washes are preferable because they let the straw breathe. As any gardener growing strawberries knows, straw won't decompose. It keeps warm and dry, "cosy", as Barbara Jones says. It smells nice, too.
"Cosy" isn't a word architects usually rate. Patrick Hannay, from the Welsh School of Architecture, really put the CAT philosophy among the pigeons last month when he accused the "whole earth" movement of not caring about aesthetics. As Europe's leading environmental education centre, CAT is sending out the wrong signals, he believes. "There would appear to be little aesthetic leadership here," he writes in Touchstone, the magazine he edits for the Welsh School of Architecture.
He blames frugality, which so often accompanies self-sufficiency. He does give one example of unadorned aestheticism that he admires: the frugal, honed look of the Shakers. "Has anything CAT created come anywhere near the aesthetic quality of the Shaker community products, those famous self-build communities in the States? `No' has to be the resounding answer," he thunders.
"Yeah, he's right, none of the buildings here is architecture with a capital A," says Peter Harper, a CAT resident. "But then I'm just the bloody gardener." A biochemist, he explains how function drives the form at CAT. So when they decided to run a steam railway, rather than build a concrete water tank (cement is the one material they really don't like at CAT) to feed the hopper, he made a lake and ringed it with aquatic plants. Often unheroic and unexciting, the thoughtfully executed buildings at CAT are a reaction against the abstract formalism of modern architecture. They're not architect-designed, and reflect no classical precedents.
Peter Harder was disappointed by Hannay's article. "I suppose he likes the handful of buildings at the Earth Centre in the disused colliery in Doncaster, which set out to make sustainability entertaining because they were designed by architects. Here, we're just builders and gardeners. We build to test materials, so that, 80 years on, they will have matured nicely to fit into the landscape.
"We've got away from the precariousness and fashionableness of what currently passes as good aesthetics. We're not trail-blazers. Nor are we setting standards."
CAT are too modest. They are setting standards of which planners should take note. When the Welsh Assembly opens, they can expect some lobbying on behalf of changing planning regulations. And The Whole House Book, by Pat Duran and Cindy Harris, is used by the Government for advice on sustainability in construction.
The oldest building on the CAT site, a Waites house built to test insulation after the 1973 oil-price hike, turns out to be both highly efficient and ugly as it weathers. Insulation boards in the thick brick walls block any warmth seeping through to the external walls. Consequently the bricks have leached, or "squalled" as they say in the hard-hat business, in great, grey splashes. Inside, sound echoes Tardis-like because of quadruple glazing. A historical piece of the Apocalyptic Seventies, it is now used as the environmental information complex to test "new" materials, such as wool for insulation and packed-earth columns, which termites discovered.
"Everything is very much a testbed rather than a showcase. We live and work among the buildings, to demonstrate renewable energy. Lots of things we do are just wacky kite-flying," Peter Harper explains. "My guess is that no, we won't build blocks of flats out of straw bales - but you never know." Their shop is made out of earth, a building material the Egyptians pioneered millennia ago, but rather than great earthen vaults they used packed earth for load-bearing columns within. Straw bales are relatively cheap and provide fantastic insulation, but are not very strong, which is why the windows are minimal, cut out of the timber frame (this has the side-effect of keeping the interiors relatively dim for video-screening).
The CAT crowd are not a band of Merrie Olde Englanders in hair shirts and earth shoes, pretending that the digital age isn't upon us. In another building experiment, they use green-oak timber frames set in pairs, much smaller than the thick planks used by our Tudorbethan ancestors, to run wiring, cabling, fibre optics and insulation in the spaces between.
But aesthetics don't necessarily go out of the window. The constraints of working with cumbersome straw bales tied with baling twine don't faze Barbara Jones one bit. "We get very beautiful semicircles and curves in straw, and thick walls around small windows, just like those Devonshire cottages that bed and breakfasters pay a fortune for," she says. "The floor is the natural shale already on site in Wales. All it needs is a green-oak verandah."
You can find out more about straw-bale building by visiting www.cat. org.uk/ news.tmpl
... Meanwhile, back in London, two architects who worked on the CAT project have adopted a similar idea for their own city home.
HOW CAN two modern architects design a London house-cum-studio made out of straw bales that doesn't look like a barn? What appears set to be Britain's greenest home and office for its two designers - Sarah Wigglesworth and Jeremy Till - is on site in Islington.
It is too soon to say if their attempts to reconcile cutting-edge architecture with folksy, green materials which are bulky and awkward, have worked. But the spirit with which they have sought to build a smart London home out of straw and corrugated steel is already a talking point. Instead of a waste disposal unit, they tip their household vegetable clippings into a peat lavatory that eventually turns sewage into leaf-mould compost. A lawn sewn with strawberries roofs the house. Walls on the cold north side are made out of straw bales behind corrugated steel panels, curling around to insulate the bedroom on the mostly glazed, sunny south side. Facing the railway, the fourth wall is made from gabion crates filled with the kind of boulders that are used on motorways to stop embankment erosion, and which also act as sound insulation.
It was while moving straw bales about the fields at the Centre of Alternative Technology in Machynlleth, Powys, Wales, on a building course with Barbara Jones, that Till and Wigglesworth became convinced that compacted straw was the building material of the future. A bale costs as little as pounds 1. Half-a-metre thick, one bale can cover a lot of ground, economically and swiftly.
Wigglesworth can't understand why property developers haven't latched on to straw. If the party walls in terraced houses were made from straw bales, she argues, their sound-deadening qualities and excellent insulation would have big implications for house-building prices.
The couple convinced Islington Council that straw would be the ideal material to build their house, situated on wasteland near a railway line. Fire was the one objection, which they overcame with reports from Canadian and American loss adjusters that straw bale infill with an internal plaster coat resists fire better than conventional timber- frame construction. It chars, rather than burns.
The design doesn't wear its conscience on the outside. "We're not green lobbyists," says Wigglesworth. "We just want to build a responsible home and bring some of the ecological issues into mainstream conversations about architecture."
A double-height steel frame soars vertically, emphasised by the wood- burning stove's steel flues, and long, open-plan living space uninterrupted by support columns. Timber-frame technology would not support such long spans without load-bearing columns to hold up the roof. So the pair settled for steel, and restricted the timber inside the steel frame as a support to tie in the straw-baled insulation. Once built, the only sign of its straw padding will be revealed behind transparent corrugated polycarbonate cladding. They would have liked a greater area of polycarbonate, but since it is a potential fire hazard, they replaced it with corrugated galvanised steel. By using glass and steel with style, they have shaken up the earnest Shaker image of timber and straw.
At the University of Sheffield School of Architecture - where they both work - the Bale Project, as they call their home, is seen as a research project. Practical work of this kind supports Wigglesworth's time away from Sheffield, but not Till's. Because funding in universities is based on research papers, most architects in academia find it impossible to actually practice. The impact of this split between pragmatists and polemicists has marginalised the ecological movement from mainstream architecture. Germany's legislative framework better integrates the two, which is why Germany currently leads Europe on green issues in architecture.