Will spray polyurethane insulation lose R-value over time?
When first installed, spray polyurethane foams R-value is about 10 for a one-inch thickness. Over time, the R-value drops to between 6.5 and 7.0 (one inch) and stabilizes at that value. The time it takes to reach an R-value of 6.5 to 7.0 depends on a variety of factors, including total foam thickness. We report a six-month aged R-value. Many industry studies indicate that a one-inch thick sample of foam will stabilize after six months and maintain that approximate R-value for decades.