U-Value or K Value

Describes the rate of Thermal energy passing through a material due to conduction, convection,

and radiation under specific environmental conditions.

It is calculated using material thermal conductance and surface emissivity values

which are intrinsically measured.

Lower values describe lower rates of heat energy transmitted through a material

and hence improved insulation values.

For glazed areas, the surface emissivity of glass can be dramatically reduced

by high performance coatings and this is a major factor in reducing this value.

U-Value is expressed in units of Btu/hr ft