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Today I had a customer reach out to ask about our film’s shading coefficient. I happily obliged, providing the information, but was surprised by the technical nature of the question. So, I asked the customer if he wouldn’t mind telling me why he was asking about that particular specification. He told me that his utility company is offering a rebate for window film installation and had a minimum shading coefficient requirement. Since this is a term specific to windows, window film, and glazing, I thought I’d write a post about it for anyone (else) who likes to geek out on window film terminology.😊
The shading coefficient (SC) is a measure used to evaluate the effectiveness of window treatments or glazing materials in reducing solar heat gain. It is a dimensionless value that ranges from 0 to 1, with lower values indicating better shading performance. The shading coefficient is determined by comparing the solar heat gain of a particular window or glazing material to that of a single layer of clear, 1/8-inch-thick (3.175 mm) glass under the same conditions.
A lower shading coefficient means that less solar heat is being transmitted through the window or glazing material, which can help reduce cooling loads in buildings and improve energy efficiency. This is especially important in hot climates or in buildings with significant exposure to sunlight.
When choosing window treatments or glazing materials, it’s important to consider both the SC and other factors like visible light transmittance, thermal insulation, and aesthetics to find the best solution for a specific building or climate.
And apparently, some local utilities in warmer areas (like this one in Orlando) are using shading coefficient as a measure of a window film’s efficacy for rebate or incentive programs.
Below is a chart of all five ComforTech™ shades’ performance specifications including their shading coefficient.
Like most measures – with the exception of UV control, the darker the film is the better the film will control solar heat gain. For the shading coefficient you can see that our lightest film, ComforTech™ 45, has an SC of .57 and as the shades get darker, this measure improves. Our darkest film, ComforTech™ 05, has an SC of .20.
In the case of our Orlando customer, to be eligible for the window film rebate (which by the way is a cool $0.55/square foot!) the film needs an SC of at most .5. So, our ComforTech™ 05, 15, 23 and 35 meet the criteria. The utility also required an invoice and specification documentation of the film’s performance. You can download a PDF of our performance specs here.
If you run into any questions about our performance criteria or are unsure whether our film meets an outside requirement or not – please don’t hesitate to reach out!
