Gottfried Green

A: R-value relates to thermal resistance. Thermal resistance is the measure of a material's ability to retard heat flow. An R-value represents the amount of time (in hours) that is required for one Btu to be transmitted through one square foot of a material (or structure) when there is a temperature difference of one degree Fahrenheit between the two surfaces of the insulation. Since R-values are a measurement of the ability to retard heat flow, the higher the R-value, the higher the insulation value. Materials which have the same R-value, regardless of thickness, weight, or appearance, are equal in insulation value.

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