Proper insulation helps keep your home cool in the summer, and warm in the winter. It comes in a variety of types including mineral or organic material, plastic foam, spray foam, glass fibers, batts, blankets, rigid foam-board or fiberboard. Insulation performance is measured by R-value, which refers to its ability to resist heat flow. The higher the R-value, the better. However, different R-values are recommended for walls, attics, basements and crawlspaces, depending on the area you live.