What is a Shading Coefficient? And Why Is It Important?

With local electric companies now offering rebates for having high performance window films installed in homes and businesses, consumers are coming across some new specifications that they might not be familiar with. One of the more common terms used by power companies to describe a window films performance value is its shading coefficient.

Shading coefficients describe the ratio of solar heat gain (heat) through a given glazing (glass) system to the solar heat gain under the same conditions for clear, unshaded double strength window glass. Shading coefficient defines the sun control capability or efficiency of the glazing system relative to a standard window.


 It is usually a value ranging from 1.00 to 0.00. The lower the rating, the less solar heat is transmitted through the glass, and the greater its shading ability.

How is this relevant to the consumer? The smaller the number, the greater the heat reduction. Shading coefficient is a standard term in the glass industry used to rate the effectiveness of a glazing system compared to a "standard window". However, the glass industry is moving away from the use since a "standard window" is no longer a single pane, clear window. Until other measures are used by utility companies to express a films performance for rebate purposes, it is important for consumers to understand this term so they can better choose which product is best for them and which window films will qualify them for any available rebates