At this job we installed R-20 in the roof and R-13 in the walls. We actually can still meet the building code requirements with these R-values. Talk to Peter Jr for information regarding that. At those R-values we are stopping almost 90 percent of the heat coming the wall/roof. Adding more R-value really would not enhance the performance at this point. This works because foam is an “air barrier”. We are stopping the movement of air which is the largest transport of both heat and moisture! This is a great product that has been on the market for 35 Years! We love it and have had great luck with it.