green building materials
The building industry is responsible for a significant portion of total global environmental impact. When assessing this impact, it’s worth considering:
- 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
These are subjects many manufacturers don’t want to think about, let alone inject into a complex accountancy exercise. As consumer demand increases, an increasing amount of products provide this assessment for independent certification. Organisations exist that list such products.
In Australia, ecospecifier (www.ecospecifier.com.au) offers a free website service to compare products. The search tool is a bit clumsy and the analysis can be brief, but it’s still a great resource. 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 EASIEST WAY TO START
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 (and with little thanks from the locals). Pretty much every science fiction film shows Utopia as a tropical rainforest – we can’t imagine a perfect world without one. There’s nothing like that anywhere in the known universe. Yet we’re happy to get rid of the little bits left on earth because the pool needs a new deck.
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 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. We’ll assume most Australians would refuse such housing (although it’s affordable) so here’s the lowest 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, 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 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.