U-factor


U-factor

Measure of the heat conducted through a given product or material—the number of British thermal units (Btu) of heat that move through a square foot of the material in one hour for every 1 degree Fahrenheit difference in temperature across the material. U-factor is the inverse of R-value.

thermal transmittance, U-value

The time rate of heat flow per unit area under steady conditions from the fluid on the warm side of a barrier to the fluid on the cold side, per unit temperature difference between the two fluids.