Beware of the "Green" labeling

It's quite natural to think that when something is considered being "green" it is safe for both the environment as well as it's inhabitants. However, this is not always the case.

The other day I was researching the Spray Polyurethane Foam (commonly known as SPF) that is widely promoted as a "green" building material for its ability to improve energy efficiency. It insulates better per inch than fiberglass or cellulose, which can mean major energy savings on heating and cooling for the home owners.  However, it the impact on the environment whether during the manufacturing of the raw material or the installation process does not turn out to be quite so "green".

SPF is a formed by combining two parts, side "A" and "B" side materials. The "A" side is known as polymeric methylene diphenyl disocyanate (PMDI) and consists of approximately equal amounts of monomeric MDI and higher molecular weight oligomers of MDI. The "B" side is a polyol blend which typically contains base polyols, catalysts, blowing agents, surfactants, flame retardants, and other additives.

Even though once the compound is mixed and cured it is supposed to be inert and safe for building re-entry after 24 hours in general but depending on the manufacturer, the Environmental Protection Agency (EPA) believes that the material is still very new and not yet well understood. They believe that the potential long-term-off gassing is not fully understood.  Furthermore, they recommend that individuals with a history of skin conditions, respiratory allergy, asthma, or prior isocyanate sensitization should fully understand the product information and consider safer alternatives. That is, if the installation is done properly by someone who is an expect in this area.  So there is still a wild card where the safety of the product is further compromised by the skill of the installer, the quality of the foam, thickness of the application, and ability to properly inspect post-installation.  Furthermore, the EPA also suggests that any maintenance or repair work that disturbs the cured compound (cutting / heating e.t.c.) is a potential health hazard.  Considering this, it is quite unsettling that this is marketed as a "green" building material that is being used during construction on weathering modifications to existing constructions.  

References:

http://www.epa.gov/dfe/pubs/projects/spf/spray_polyurethane_foam.html

http://www.sprayfoam.org/technical/faqs

http://www.greenbuildingadvisor.com/blogs/dept/musings/spray-foam-jobs-lingering-odor-problems

http://polyurethane.americanchemistry.com/Spray-Foam-Coalition/Guidance-on-Best-Practices-for-the-Installation-of-Spray-Polyurethane-Foam.pdf