Geo-Insulation offers various types of fiberglass and other insulation for both commercial and residential customers. Understanding insulation specifications is key to knowing what type you need and how much you need. Insulation levels are specified by R-Value, which is a measure of the insulation’s ability to resist heat flow. The higher the R-Value, the better the thermal performance of the insulation. The recommended level for most attics is to insulate to R-38 or about 12 to 14 inches, depending on your insulation type.