SHGC & SC
SHGC & SC
SHGC & SC
The Shading Coefficient (SC) is a measure of the heat gain through glass from solar
radiation. Specifically, the Shading Coefficient is the ratio between the solar heat gain
for a particular type of glass and that of double-strength clear glass. A lower Shading
Coefficient indicates lower solar heat gain. For reference, 1/8" (3.1 mm) clear glass has
a value of 1.00 (SC is an older term being replaced by the SHGC).
In either case, a lower number indicates improved solar control over the 1/8" clear glass
baseline. With a long air-conditioning season, it is most important to reduce solar gain
and therefore reduce air-conditioning loads.
R-Value equals a measure of the resistance of the glazing to heat flow. It is determined
by dividing the U-value into 1, (R-value = 1/U-value). A higher R-value indicates better
insulating properties of the glazing. R-Value is not typically used as a measurement for
glazing products. Both U-value and R-value are a measure of resistance to heat flow
and are referenced here to help understand U-value.
The use of a less conductive gas in an IG unit has insulating benefits but may come at a
higher initial cost compared to an air-filled IG unit. There are also concerns about
maintaining the gas fill levels over time. Argon permeation is greater than air for most IG
sealants, which can result in negative pressure in the IG air space. Argon-filled units
also cannot use breather tubes for high-altitude applications.