# How to Calculate the Shading Coefficient

Windows are things that most people take for granted. Glass has been around since the beginning of civilization. Archaeologists have found evidence of glass being manufactured in the Middle East as early as 3000 B.C. As the science and engineering of glass have become better understood, many advances have been made. In the late 1950s Sir Alastair Pilkington introduced the "float" glass production method, which is still used to manufacture approximately 90 percent of the glass produced today.

## Step 1

Locate the National Fenestration Rating Council (NFRC) label on your window. Most new residential windows are rated by the NFRC, and should have a label.

## Step 2

Note the solar heat gain coefficient (SHGC) on the label. It has replaced the shading coefficient (SC) as the standard indicator of a window's shading ability. SHGC is expressed as a number between 0 and 0.87. SC is expressed as a number between 0 and 1. You can use the following formula: SHGC = SC --- 0.87.

## Step 3

Divide SHGC value by 0.87 to compute SC.