Earth - building material of the future

The Centre for Alternative Technology will have a 200-seat lecture theatre with rammed earth walls 7.2m high - the highest in the UK.

To build the tallest earth walls in the UK, you need first hand experience of the environmentally-friendly material.

To this end, the Centre for Alternative Technology (CAT) has recruited structural engineer Toby Hodsdon of Buro Happold, to work on the Wales Institute of Sustainable Education (WISE), a new mini-university for environmental courses.

The ambitious £3.2million building at CAT will have a 200-seat lecture theatre with rammed earth walls 7.2m high - the highest in the UK.

Toby's experience of working with rammed earth was gained on a study trip to Australia, sponsored by the Educational Trust of the Institution of Structural Engineers.

"Rammed earth is well established in Australia as a modern building material," Toby says.

Although in some parts of Australia the environmentally friendly technique is very common, it is still seen as "a lifestyle choice," he says.

"It comes at a slight premium in terms of cost and management complexity, however offers the promise of a unique, stylish and thermally-stable home".

Earth is put in pre-constructed formers, and compacted in layers using hand-held pneumatic rammers.

This gives the walls an attractive, stratified finish.

CAT is planning to use rammed earth for WISE because it has a very low 'embodied energy' - the amount of energy used in its manufacture.

Cement has a very high embodied energy, so its use is minimised in WISE's design.

Rammed earth also has a very high thermal mass, stabilising temperatures in a building, therefore reducing the need for air conditioning and heating.

Builders plan to reduce emissions from transport too, as the earth will come from a local quarry.

CAT is also taking advice from Andy Simmonds of Simmonds Mills, who advised on a previous rammed earth project at CAT, and Rowland Keable of the In Situ Rammed Earth company, so is using most of the UK specialists in unstabilised rammed earth (without added cement).

WISE has been generously funded by a range of organisations and individuals including Objective 2 funding from the European Union, provided through the Welsh Assembly Government.

Beside the lecture theatre, WISE will include workshops, classrooms, en suite accommodation for 48 students, a bar, study areas, a laboratory and offices.

This is to cater for educational visits, conferences, and the increasing demand for CAT's courses covering all aspects of sustainable living.

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