What is an R-value?
An R-value is an assigned number derived from a specific testing procedure (or calculation) to determine a materials (or building assemblage) resistance to conductive heat transfer. The higher the R-value, the more resistant a material (or building assemblage) is to conductive heat transfer. Reflectix can provide verification for all R-values stated for all products and applications.
The R value is the material’s thermal resistance to conduction heat transfer. In simple terms, the R value shows how a material retards heat flow. So 3 1/2″ thick piece of wood has an R value of 4, while that same thickness of fiberglass batt insulation has an R value of 13. If we go to 3 1/2″ of polyisocyanurate foam, the R value jumps to 23, since that type of foam has the highest R value of common building materials. So the higher the R value, them more the material resists heat flow, that is to say, the higher the R value, the better the insulation value of the material. It’s valuable to remember the basic insulation values per inch for common insulations: R value per inch of insulation 1. Fiberglass batt insulation 3.5 2. Molded expanded polystyrene foam board (white board) 4 3. Extruded expanded polystyrene foam board (blue board) 5 4. Polyisocyanurate foam board (foil backed board) 6.5 The following US Department of Energy site http://www.eere.energy.gov/consumer/your_home/insul
