SIPs are certainly designed to reduce the amount of energy a house consumes, but does that make them green?
To find the answer to this, I called David Johnston who is a green building consultant and author of Green Remodeling. David is pleasant and easy to talk with but when you bring up SIPs he can get excited. I asked him about the argument that SIPs are not green because they consume petrochemical products.
“This whole idea that plastic can’t be green is silly,” he said. “When plastic is used inside the wall, it’s a lot more green than driving your pickup truck to the lumber yard.”
The reasoning is that once the EPS is expanded it becomes inert and no longer reacts with the environment (there are disposal issues that I won’t go into now). If the house just sits there, the material used will not be contributing to global warming.
So this EPS house is pretty benign as long as it gets recycled.
Urethane and XPS panels are a little more complicated because they do discharge HCFCs into the environment during manufacture and for a short while after construction. As far as the OSB that is used for most SIPs skins, according to Johnston, there are two good qualities of OSB. First, the wood pulp used is from fast growing softwood trees that are a renewable resource (typical cycle is 35-45 years). Second, the glue is a phenolic resin that does not emit substantially more formaldehyde than the wood itself.
So I’m going to go out on a limb and say that SIPs are green. Are they perfect? Nope. Is anything perfect?
This might come pretty close.