Earth wall as second skin for lecture room  (Bagnall, 2015)

CAT, the Centre for Alternative Technology doesn’t just look at renewable technologies and utilising them (for example, solar radiation and water to create electricity), but also how to construct in alternative ways which have a smaller impact on the environment. It is a known fact that concrete and steel is one of the major areas of the construction industry which creates the greatest amounts of carbon dioxide in the UK. At CAT we were taken on tours around their site to show how they have used alternative construction materials to build building.

SOLAR GAIN

The tour was done by Trisha Andrews, an architect who has worked with CAT for over 25years. Her tour started at looking how the orientation of a building can contribute to the building's internal thermal comfort. We discussed how a buildings south façade should be fitted with the most glazing compared to the other surround façade, this is to introduce a solar gain factor to the building. Solar gain looks at providing a thermal energy into the building as well as a light, so the solar radiation heats the building up as well as providing natural sunlight. By adding more glazing to the south façade, this means the benefit from a greater solar gain (sun path of the UK).

STRAW BALE CONSTRUCTION

After solar gain, we moved to the next building on the site which was one made of a latch primary frame with the main material of the walls constructed from straw bales. Trisha told the group how compact, building straw bales where used during the construction; these building bales allow construction up to 2 and a half storeys high, while also providing a good insulation to the internal building. The straw bales are an unusual form of construction material and are quite thick, however with its insulation value and how cheap it is (£10,000 worth of bricks could be replaced by £600 worth of straw bales), could mean it becomes a popular building material in the future.

TIMBER FRAMING 

From straw bales we moved onto timber frames. While looking around at the surrounding Snowdon landscape, it was quite apparent that there was a problem with the trees as seen by their colour. We were told how the latch population within the UK was dying through a disease, and latch needs to be used in the next 5-10 years, after that there may not be any latch left to use. While looking at an exterior timber frame by the visitors centre, we spoke about the different treatments which are applied to the wood before use, and how the treatments may not always be the best treatment for the wood. The wood on site used on this frame was not treated but left to dry before use (making it structural harder), however in the UK we previously used a CCA (chrome, copper and arsenic) treatment which poisoned the trees. Although now we use a CCB (chrome, copper and boron) treatment which is less toxic (still slightly toxic) and can be applied in three different ways; dipped, brushed or pellet inserted.

EARTH WALL

The final part of the tour looked at we use of Earth Wall within the visitors centre and the new WISE building. The Earth Wall was created by ramming sand, clay and water together, compressing a 100mm mixtures of the three materials into a 50mm, dense block. The wall was created in layers, each layer rammed and the next layer applied until the wall is complete.

APPLICATION TO PROJECT

COMPANIES/SUPPLIERS 

Strawworks - http://www.strawworks.co.uk/ [straw]
ModCel - http://www.modcell.com/ [straw]
Sirewall - http://www.sirewall.com/licensees/earthwall-rammed-earth-architecture/ [earth wall]



ADDITIONAL LINKS

University of Bath - http://www.bath.ac.uk/research/case-studies/straw-scientifically-proven-building-material [straw]
VSL - http://www.vsl.com/business-lines/ground-engineering/vsolr.html [earth wall]