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One measure that you may have heard of when researching window film, is the Solar Heat Gain Coefficient or SHGC. It’s a term used in the building industry and it sounds complicated, but it isn’t. We’ll break it down for you below and explain how it’s used with window film.
The Solar Heat Gain Coefficient (SHGC) is a measure of the amount of solar radiation that enters a building through its windows, doors, and skylights. It represents the fraction of solar heat gain that is transmitted through the glazing and absorbed into the building’s interior.
The SHGC not only measures the heat that is transmitted through the filmed glass, but it also includes any incident heat that may enter the house through convection (the warmed glass).
The Solar Heat Gain Coefficient is a standardized measure that the National Fenestration Rating Council uses to rate the efficiency of windows, glass doors, and window film. The NFRC is the official rating agency of the window and window film industry. It’s a non-profit agency that governs standards.
The NFRC sets the standards against which windows, doors and window films are measured so consumers can more easily compare products across brands.
The SHGC is expressed as a number between 0 and 1, with a lower number indicating less solar heat gain and a higher number indicating more solar heat gain. For example, a window with an SHGC of 0.25 will transmit 25% of the solar radiation that strikes it, while reflecting or absorbing the remaining 75%.
The SHGC is an important factor to consider when selecting windows, doors, and skylights for your home or building, as it can have a significant impact on the building’s energy efficiency, cooling load, and indoor comfort. Windows with a lower SHGC are generally more energy-efficient, as they allow less solar heat gain to enter the building, reducing the need for air conditioning and helping to lower energy bills.
Just like with glass, the solar heat gain coefficient can be measured for glass with window film applied. SHGC is an important measure that you can use to determine the ability of the window film to block solar energy from entering your home.
Remember that window film blocks solar energy by both reflecting and absorbing the sun’s rays. So filmed glass often feels warmer than unfilmed glass. But you can rest assured that any convection heat from the warmer glass is included in the SHGC calculation.
And it’s something you can compare across different types and brands of window film. Any window film you purchase should offer you the film’s performance specifications which will include SHGC.
Let’s take a look at Concord’s ComforTech™ Ceramic Series Performance Specifications:
In the chart above, you can see the fifth column shows the solar heat gain coefficient. The first row gives you the SHGC for 1/8” clear glass as a reference (this is the standard industry benchmark used). So, clear glass has an SHGC of .84 meaning it allows in 84% of the solar radiation that hits it.
Below this, you will see each of the shades of ComforTech™ Ceramic Series window film from 45 – 05. Remember that as the product number decreases, the darker the film gets and the better it will be at blocking the sun’s rays.
ComforTech™ 45, our lightest film, has an SHGC of .48 which means it will transmit 48% of solar radiation hitting the window. Conversely, our darkest film, ComforTech™ 05 will only allow in 18% of solar radiation.
Now that you understand window film specifications, you may be asking yourself, why wouldn’t I always go with the lowest SHGC? And the answer lies in your personal preferences and individual aesthetic!
As we stated before, the better the SHGC, the darker the film. And the exterior of the film also becomes more reflective. This is great for rejecting the sun’s heat and for daytime privacy, but you may not want to change the look of your home (or may not be able to in the case of a condo or association).
It’s best to check out the shades before you purchase. At Concord Window Film, you can do that two ways: with our product simulator and with our sample kits. The product simulator approximates the look of each shade of the film in a room. The sample kit gives you a 5”x7” piece of each shade of film (plus our matte white privacy film and Silver 15 reflective film) to view in your home.
We hope this helps you understand Solar Heat Gain Coefficient (SHGC). It’s a crucial factor to consider when selecting window film for your home or building. While choosing the lowest SHGC number may seem like the best option, you need to consider your personal preferences. It’s important to note that the film becomes darker and more reflective as the SHGC improves.
Overall, understanding SHGC and its application in window film can help you make informed decisions to select the right product to improve your energy efficiency and indoor comfort!
