The United States is divided into zones, and each zone has different recommended insulation levels. We are in Zone 6, so our attic insulation should have R-values of between 49 and 60. Some attics in our area of the U.S. need more than one type of insulation. Most attics have fiberglass batts, which are very effective. But small gaps and cracks need a better fill-in, so blown-in fiberglass works well. Spray foam insulation air seals any area, including attics. The most environmentally friendly attic insulation is cellulose. Cellulose is also perfect for garages because of its soundproofing properties