Coefficient of Heat Transmission (U-Value) 1 topic · 1 source ScienceEnergyA value that describes the ability of a material to conduct heat. The number of Btu that flow through 1 square foot of material, in one hour. It is the reciprocal of the R-Value (U-Value = 1/R-Value).US DOE Office of Energy Efficiency & Renewable Energy — Glossary of Energy-Related Terms retrieved 2014-05-26 Cite