Rammed Earth Bricks

New homes built of mud or straw, with a lawn on the roof, sheep fleeces for insulation and heat from the ground or a boiler fired with sawdust – this is one vision of the future for our green and pleasant land.

The Centre for Alternative Technology (CAT) in Machynlleth, the ancient Welsh capital, opened in 1975. The centre, in a former slate quarry, is blessed with mountain streams, which help fire up some of the energy projects.

Many of the techniques currently being explored are not new – indeed, much of the work at CAT revolves around materials and methods that have been used for centuries. It is often a case of "looking forward to the past".

There's nothing new about rammed earth walls, for example. Ancient cob cottages built by labourers trampling mud and straw have survived for hundreds of years, provided they had "a good hat and boots" (roof and footings).

Among the energy-saving building techniques being developed and used in public buildings are grass roofs and rammed earth bricks covered with hemp and lime render. These, unlike traditionally fired bricks and clay tiles, use hardly any energy in their manufacture.

Traditional bricks may become museum items and housebuilders will have to use other materials to give their properties what estate agents call "kerb appeal".

Indeed, the production of cement for building is known to account for more than five per cent of global carbon dioxide emissions. CAT recommends 'limecrete' be used instead of cement-based concrete.

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