Glass Glossary

The total amount of heat gain through a glazing system at NFRC (National Fenestration Rating Council) and ASHRAE (American Society of Heating, Refrigerating and Air-Conditioning Engineers) specified summer conditions, incorporating the U-Factor and the solar heat gain coefficient (SHGC).

The conditions are 248 BTU/hr/ft² (726 W/m²) outdoor temperature of 89°F (32°C), indoor temperature of 75°F (24°C) and 6.2 mph (2.8 m/s) wind (RHG = U-Summer x (89-75) + SHGC x (248). RHG is expressed in terms of BTU/hr/ft².