nkhan

It takes 40 years of energy savings from the insulation (CO2 saved at the powerplant) to "pay back" the injection of HFC into the atmosphere that occurs when blowing foam using the typical spray foams. For this alone, if you have to use foam, at least go with the foams that have the reduced content of petroleum-based polyols, and that are water-blown, free of HFCs and PBDEs, until even better products come into the market. Like the Icynene - http://www.sprayfoam.com/npps/story.cfm?nppage=230. Air krete sounds interesting...