Commonly used fiberglass batt insulation has an R-value in the range of R-2.9 to R-3.8 for every inch of thickness. High quality batt can have an R-value between R-3.7 to R4.3 per inch. The exact R-value for batt insulation depends on the specific batt used.
Batt insulation is a blanket-type of insulation typically placed between wall studs, floor joists or rafters. Most modern batt insulation is made from strands of fiberglass, but batt can also be found made from mineral wool, natural and plastic fibers. In addition to serving as insulation, batts can also be purchased with fire-resistant facings for increased safety.
The R-value of insulation represents the thermal resistance of the material. Thermal resistance is a measurement of a material's resistance to conductive heat flow. The higher the R-value of insulation is, the more resistant the material is, marking it as more effective for use as insulation. The R-value of batt insulation depends on the material used to create the insulation, its thickness and the density of the material. The thicker or denser the insulation, the greater the R-value. The greater the R-value for most batts, the greater the energy efficiency of the structure into which the batt is installed.