[ ahr-val-yoo ]
/ ˈɑrˌvæl yu /
a measure of the resistance of an insulating or building material to heat flow, expressed as R-11, R-20, and so on; the higher the number, the greater the resistance to heat flow.
Origin of R-value
1945–50; R, symbol for resistance
Dictionary.com Unabridged Based on the Random House Unabridged Dictionary, © Random House, Inc. 2019