Buildings have a large impact on our total environmental footprint. To assess this impact, we consider:
- Depletion of a limited resource
- Loss of biodiversity
- Resource degradation (includes effects on water, soils, etc)
- Energy consumption
- Re-use or recyclability
- Ethical treatment of workers and/ or animals
As consumer demand increases, an increasing amount of manufacturers account for these factors. In Australia, ecospecifier (www.ecospecifier.com.au) offers a free website service to compare products in these areas. There’s also certifiers GECA (Good Environmental Choice Australia) (www.geca.org.au), FSC (Forest Stewardship Council), Green Building Council of Australia green star system and the ABGR (Australian Building Greenhouse Rating scheme).
The worst thing you can buy
Never (except second hand) use tropical rainforest timbers – meranti, kwila, pacific maple etc. They come from one of the worlds biodiversity hotspots – once beautiful areas suffering some of the worst degradation. Pretty much every science fiction film shows Utopia as a tropical rainforest – we can’t imagine a perfect world without one. Yet we’re happy to get rid of the little bits left on earth if it makes that pool deck a bit cheaper.
Don’t buy large size timbers. They come from old growth forest. Instead buy smaller sizes (preferably pine or FSC certified), or laminated or recycled timber. Perhaps in future the fashion of big thick timber posts will be about as socially attractive as an orang-utan rug.
Comparison between materials
This can be a balancing exercise with sometimes difficult choices.
A concrete floor has higher embodied energy (energy required to make it) than a timber floor. However, a concrete floor correctly designed for passive solar can reduce the energy used in heating & cooling a house over its lifespan.
Would you prefer a treated pine post which is too toxic to burn or woodchip at the end of its life, or a naturally durable Tallowwood post, taken from a native forest where it is the major koala feed tree? (Green groups recommend the pine).
How low impact can you go?
There are plenty of peasant houses around the world made of bamboo, mud, timber, thatch, sun dried clay, etc. that have effectively no environmental impact & are actually really beautiful to look at & live with.
We’ll assume most Australians would refuse to use such housing (although it’s affordable) so here’s the lowest impact you’d likely find in an Australian context.
- Footprint: small
- Walls: Strawbale, mudbrick pressed on site with no cement, second hand timber frame.
- Footings: Apart from rocky sites, we can’t seem to get away from concrete, although it has been avoided in a pole house I know of. Sheds can use second hand concrete blocks as footings, or durable poles.
- Flooring: Local, sustainably managed, air or solar dried timber or second hand. Sealed earth floor.
- Cladding: packed clay, second hand roofing or weatherboard.
- Roofing: green roof.
- Internal: Local, sustainably managed, air dried timber or second hand. Second hand sinks, tiles, showers, taps.