Insulation type, whether for attics or walls, and the material it is made from determine the R-value of the installation. The R-value measures how well the insulation resists the flow of heat, explains Today's Homeowner. When looking for the most heat resistance, choose an installation with the highest possible R-value.
Homes in colder locations require at least R-49 value in the attic, while warm locations only need an R-38 value in the same area, notes Today's Homeowner. The opening in the wall spaces limits the amount of installation installed, but insulation with high density exists. Spray foam insulation provides a high R-value to walls. Floor insulation in colder areas require an R-25 rating, while warmer areas only need an R-11 rating.