Designing Ecological Habitats - Gaia Education

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Materials
Most houses built in the western world today rely on industrial materials,
steels, alloys, plastics, wood that has been shaped and impregnated, often
chopped up and put together again, and various forms of artificial stone.
These modern materials represent an enormous energy cost in terms of
production and transport.
If we take as our starting point the cost of felling, sawing and transporting
timber, estimated at 580 kWh/tonne, we can compare other materials:
• Timber 580
• Bricks 2,320
• Cement 2,900
• Plastic 3,480
• Glass 8,120
• Steel 13,920
• Aluminium 73,080
Stone
Because of its weight, transport over long distances is expensive but if you
have stones lying around on your site, you can save lots of money. Stone
requires skill to work with. Unless you are an experienced dry-stone wall
builder you need to use a cement matrix to hold the stuff in place. You need
to be aware of the geology; some stone weathers badly.
The easiest and most effective way of using rough stone is to build a box
of wood and fill this with stones, cement and reinforcing. These wooden
boxes can be built in sections which are dismantled as the cement sets, and
which can then be moved along to make the next section.
Earth
You can make a test of your particular earth by taking a sample, shaking it
in a jar of water, and letting it settle for a few hours. The courser material
will settle at the bottom, the finer in the middle, and the organic matter on
the top. Ideally a mixture of between 50-70% sand, 10-20% clay, and a good
addition of chopped straw is the best for an all round plaster. The simplest
plaster I’ve used was just a mixture of earth, sand and a little cow dung to
make it hard.
Adobe are earth bricks, dried in the sun, and cemented together using the
same earth mixture as a bond. Pisé involves building a framed box, ramming
damp earth in hard, letting this dry and then moving the box upwards to
then ram in the next layer. In both cases with an earth plaster finish on the
inside and outside, you have a heat retaining wall, thermal mass, breathing
qualities to give good air and a healthy inner climate.