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CAT Gets New Green Education Building

Posted: 06/06/2006

Work is about to start on The Wales Institute for Sustainable Education (WISE), a new complex intended to showcase the very latest thinking in environmentally-conscious building design at the Centre for Alternative Technology (CAT), near Machynlleth in Wales.

Consulting Engineer Buro Happold has been appointed structural engineer and the architects are Pat Borer and David Lea. It 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.

Among the innovative features of the building will be construction of rammed earth walls in the Institute’s lecture theatre, the use of natural ventilation where possible, a biomass-fuelled combined heat and power system, solar photovoltaic cells on the roof and extensive use of timber. These features will help keep the carbon dioxide (CO2) emissions from the building low during its operation. Use of local resources where possible, such as timber from stewarded forests in the region, will also keep control of the CO2 created by the construction process.

The 7.2m high rammed earth walls, which are load-bearing and made of excavated subsoil, exemplify this approach. The clay content of the soil means no additional binding material will have to be added. The walls are packed down in layers, using hand-held pneumatic compactors, between temporary formwork.

“This is an excellent opportunity to demonstrate the benefits of rammed earth construction. As well as the energy savings in construction, the result is a building with a greater thermal mass than its conventional equivalent – ideal for a building with high thermal loads, such as a theatre,” says Toby Hodsdon, Buro Happold’s project engineer and a structural engineer with experience of rammed earth construction.

“Rammed earth is also a surprisingly flexible material to work with, as the circular design of this building shows, and gives a more interesting, tactile finish. The project is a great and unique opportunity for us and we’re proud to be working with such forward-looking architects and client on this project,” Toby adds.

As well as reducing the project’s use of cement, which consumes significant amounts of energy during manufacture, the rammed earth walls will help absorb heat and moisture from inside the building and help reduce the need for mechanical air conditioning in the lecture theatre.

Alongside the lecture theatre is a substantial three-storey complex of other spaces, and the split-level building enclosing all these spaces will make extensive use of timber. Glulam beams will be used to create a framed structure, supporting an innovative solid timber floor to maximise spans and create the soffit to the space below. Timber will be locally sourced, from forests accredited for their sustainable stewardship.

Between the structural posts and beams of the building, a lime and hemp fill material will be used, chosen for its excellent insulation properties and sustainability credentials. This will be pumped into place using a novel technique developed by Lime Technology, a specialist contractor.

The entire site is scheduled to be complete in late 2007.

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