A measure of heat gain or heat loss through glass due to the thermal conductance and the difference in indoor and outdoor temperatures. As the u-value decreases, so does the amount of heat that is transferred through the glazing material. The lower the u-value the more restrictive the fenestration product is to heat transfer; reciprocal of r-value.
A process of applying a specific design or pattern to glass. The design is made by placing a screen over a piece of glass and then pressing ceramic frit by means of a large squeegee through the pores of the screen. After the frit is applied the glass goes through an infra-red oven to dry the frit and then through a tempering furnace to fire (bond) the frit to the glass permanently.
The amount of heat gained through glass taking into consideration the effects U-value and shading coefficient. The English System relative heat gain is calculated as: RHG = (Summer U-value x 14°F) + (Shading Coefficient x 200). The Metric System is calculated as: RHG = (Summer U-value x 7.8°C) + (Shading Coefficient x 630). The lower the RHG the more the glass product restricts heat gain.
Thermal resistance of a glazing system expressed ft2/hr/°F/BTU (m2/W/°C). The r-value is the reciprocal of the U-value. The higher the R-value, the less heat is transmitted through the glazing material.