A. Alex Wilson responds: Toxic chemicals are used in producing polyisocyanurate foam. But after curing, the foam is considered very stable and safe. The primary health concern with this type of insulation is exposure of factory workers to the isocyanurate resin.
The outgasing that does occur from polyiso foam is HCFC-141b, which is used as the foaming agent. This gas, trapped in the foam cells, provides the high R-value, but as it gradually leaks out the R-value drops. In the atmosphere, HCFCs (hydrofluorocarbons) contribute to the destruction of the ozone layer and to global warming, but they are not...
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