Polyiso foam board is one of the best performing insulation products on the market. Eco-Max, the newest foil-faced foam board from RMax, is at least 8 percent agricultural oil, reducing the amount of nonrenewable resources used in the manufacturing process. Eco-Max also uses real aluminum-foil facings, not Mylar, for maximum heat-blocking performance. This board has an R-value of 5.4 per inch.
About $750 for a 2,000-square-foot house; RMax