There are two main types of fiberglass insulation: fiberglass batting and loose blown-in fiberglass insulation. According to the U.S. Department of Energy, fiberglass insulation will have a variable R-value based on the thickness of the batting. The average R-value for fiberglass is 2.9-3.8 per inch of batting and 2.2-2.9 per inch for loose blown-in fiberglass.