ABSTRACT
The U-value is the rate of heat flow per unit area from the fluid (usually air) on the warm side of the element to the fluid (again usually air) on the cold side. The procedure for U-value calculations is given in numerous references1,2,3 along with thermal conductivities for various materials. Values of thermal conductivity vary somewhat according to the reference consulted. Manufacturers will provide the most accurate test data for their products.
