[stvc]

There are varing rates of return on insulation. Lets say if you go from zero to R-60 there is a huge return. If you go from R-30 to R-40 there is a medium return. R-40 - R-60 small. Bottom line is insulation is the cheapest way to make you comfortable. If you have none, do it and go big, it costs more to get the truck and crew there than the material does. Oh, don't forget to airseal first.