This impact may be through energy that is consumed during manufacture. It could be what is thrown away in the process, and equally important, how waste is disposed of. It might be a question of where raw materials are sourced, if that source is renewable, if something natural was degraded along the way.

Under pressure to build quickly and cost effectively, there often isn't enough time to think this through. The hard truth is that green material selection does not yield the same cost dividends as, say, designing for energy efficiency. There must therefore be a different raison d'etre here, since an ethical choice cannot rely on fiscal logic alone.

The difficulty for any designer, inclined to do the right thing, is that environmental impact is not only hard
to sell, it is hard to explain. There is no one standard for materials, no index that says it all. There is, in place, a complexity created by the marketplace and research. The industry affects the environment in so many ways, through such a wide range of products, that green specification writing has become an expertise in itself.

Compounding this complexity is the lack of awareness of what, really, is green. At a Green Materials Exhibition in Beijing recently, I asked one supplier if his product was green. He pulled out a colour chart and declared proudly "yes, we have green". He was not in the minority. Of some 200
plus exhibitors, only half a dozen had anything
that was pro-environment. One exhibitor explained
to me that China has its own notion of green, very different from the rest of the world (which he calls 'international green'). In China, he said, green is
a cross between healthy and modern. A PVC floor finish at this exhibition was touted as green because it is easy to clean and looks contemporary, never mind that it is pollutive to manufacture.

This then leads to the third problem of green material selection: the lack of industry support. And this is a problem not just in China. Without suppliers and manufacturers coming onboard and volunteering meaningful information, making an informed choice takes a lot of effort.

This article takes a stab at a few issues in green material selection. It is not definitive; nor can it be (there are other criteria and materials that the reader is encouraged to explore). Ultimately, making a judgement requires an understanding of tradeoffs as a product may be green in one way, but not in others.

Some products are reconditioned, which means they've been spruced up for re-use. Others are made from reconstituted materials. This means that a material, usually post consumer waste, underwent a process of retrieval and recycling. In Singapore, for instance, reconsituted timber made from waste wood is sold under the name 'technical wood'.

Other recycled products are made from post industrial waste. Some road pavers, for instance, use copper slag. Slag, is waste from ship repair yards that might otherwise have been dumped into landfills. Similarly, carpet manufacturers are known to use by-products from the manufacture of the carpet itself, collected and re-introduced into the production chain.

While the details may vary (with it, real environmental impact) it's best to begin by asking a supplier if a recycled alternative exists.

Natural materials, like wood, have low embodied energy, because they can be processed in a relatively simple manner from tree to plank. Aluminum window frames, on the other hand, require the extraction of minerals form Earth. The complexity of aluminum production further adds to its embodied energy, making it many times that of wood.

In general, it's best to start with natural materials or materials that have a simpler production process, but always ask if these come from sustainable sources. Go with an option that comes from regional sources. Of two identical products — one from say, Europe, the other, Thailand — the latter will consume less energy getting to a project site, if that site is in East Asia.