I heard about this really neat construction system at a meeting recently:
This company, Strata International Group (website navigation requires Flash, so is unnavigable in my current Firefox), has invented a method of making small structures (I believe the height limit is two stories) out of foam and a thin layer of concrete. They sell a polymer that you mix into the concrete before spraying or troweling it onto the foam, which keeps moisture out (concrete normally will let moisture through).
And on their header, which shows on every page, is the phrase “Sustainable Building.”
It’s a really awesome system, but I have a hard time understanding how foam, which is made from fossil fuel, is sustainable. And without knowing what the special polymer is made from, that, too, might not be sustainable. Oh, plus there’s the adhesive used to attach the foam pieces to each other. Probably not made from renewable resources. Can it be recycled? Does it biodegrade? I’m dubious. And what about offgassing of the polymer? Maybe it’s completely inert once it dries/cures.
I know there have been some advances made in the manufacture of plastics, like making plastics than can be truly REcycled, not just downcycled (ignoring for a moment the plant-based, biodegradable plastics), but they have not reached a scale where ENORMOUS BLOCKS OF FOAM are being produced in a sustainable way. Perhaps there is a better recycling method out there for foam than I have heard of; I am not the world’s most expert expert on recycling.
Of course this is better in some ways than making a house entirely out of concrete, which has a significant carbon footprint. And it looks like a pretty fast process, because you’re just gluing big chunks of foam together and then spraying concrete on them, and inexpensive; a 400sf house in Mexico was built for about $2500. Yes, that’s a small house. But that’s a trivial amount of money for a solid structure (the guy at the meeting said the company has tested the system in wind tunnels, and they can definitely stand up to hurricanes, because they survived 400mph winds in the testing).
The pictures of projects in process (also requires Flash) are pretty awesome, even if they look deeply wrong. You can’t build a house out of foam like that! Except yes, yes you can.
But I am deeply bothered by the labeling of this method as sustainable, because it isn’t, and diminishes the meaning of the word.