Glass Glossary

The Shading Coefficient (SC) is a measure used to quantify the solar heat gain of glass in comparison to a standard piece of 1/8 inch (3mm) thick clear glass, which has an SC of 1.0. It is a ratio that indicates the ability of a particular type of glass to reduce solar heat gain compared to the reference glass. The SC of a glass unit is determined by measuring the amount of solar energy that is transmitted and absorbed by the glass and then reradiated into the interior of a building. SC values typically range from 0 to 1, with lower values indicating better shading and heat-reducing properties.

SC is a useful consideration in window selection, as it correlates to the thermal comfort of the occupants and the energy efficiency of the building. By choosing glass with a lower SC, homeowners and building managers can reduce the need for air conditioning and save on energy costs.

However, SC is used less often to measure solar heat gain and has been replaced by Solar Heat Gain Coefficient (SHGC), which is a more comprehensive measurement. SHGC accounts for both the directly transmitted solar energy and the proportion of absorbed solar energy that is re-radiated into the building. While SC only considers the solar energy that enters through the glass, SHGC includes all sources of solar heat gain. Consequently, SHGC is typically used as the primary metric for evaluating the solar performance of windows in energy-efficient home and building design.