Solar heat gain coefficient (SHGC) is the total percentage of solar energy at a window opening that is either absorbed and reflected into a building or directly transmitted through the window. In hot climates, like Arizona, a low SHGC helps reduce energy costs. In cold climates, however, a higher SHGC helps reduce energy costs. SHGC replaces a measurement called shading coefficient (SC). You may find references to shading coefficient in the ratings of older windows or in older reference materials. The relationship between the two ratings systems is straightforward, and the coefficients can be converted with a simple formula.
Use the formula SHGC = SC*0.87 to convert between SHGC and SC. Enter the value that you have and solve algebraically to calculate the value that you don't have.
Multiply SHGC by 1.15 to convert the value from SHGC to SC. This conversion factor is the result of solving algebraically and is a simple, shorthand version of the formula. You can use this step in place of algebraic conversion.
Multiply SC by 0.87 to convert from SC to SHGC.
- Green Building: Project Planning and Cost Estimating; R.S. Means Co.
- Residential Windows: A Guide to New Technologies and Energy Performance; John Carmody
- Building Energy Codes Resource Center: How Do I Find the SHGC for My Windows?
- Windows for High-Performance Commercial Buildings: Issues in Window Selection: Energy-Related
Chance Woods has been a personal trainer since 2002, specializing in fitness and nutrition. She holds a Bachelor of Science in dietetics.