Resistance, Thermal (R-Value)

A measure of the ability to retard heat flow. R-value is the numerical reciprocal of "U" or "C," thus R = 1/U or 1/C. Thermal resistance R-value is used in combination with numerals to designate thermal resistance values: R-11 equals 11 resistance units. The higher the "R," the higher the insulating value. I-Punits are °F – ft2 – hr / Btu; the SI units are °C – m2 / W.