Window Film is a Clear (or Tinted) Choice

by | Mar 23, 2016

window filmDarrell Smith, the Executive Director of the International Window Film Association (IWFA), said that in the past, window film installations in California schools were only done in conjunction with bigger projects. There simply was no way to assess the value of these projects in isolation and, thus, no way to qualify for state funding.


Recently, however, the California Energy Commission has approved the IWFA’s Window Film Savings Calculator as a way to measure savings. This quantification is opening a path for schools to apply for funding, which is awarded under the state’s Proposition 39, which became law in 2012.


Films are common in building and car windows. In buildings, Smith said, they work in two beneficial ways: Film – which can be clear or tinted – can stop as much as 85 percent of solar energy coming from the outside into the building. It also will retain 55 percent of the energy – in the form of heating or cooling – from leaving. Smith pointed out that untreated windows only prevent 9 percent to 11 percent of the energy from leaving. “Window film blocks solar energy during the day and, on the other hand, is an insulator during cold periods,” he said.


The cost of window film is determined by several variables, Smith said. In general, prices for fully completed window filming range from $7 to $11 per square foot. This works out to impressive return-on-investment calculations, according to figures provided by Smith. He said that return on investment (ROI) of 65 percent to 75 percent were consistently achieved in Florida. A wider range of ROIs – from 27 percent to 75 percent – were found in California.


Like reflective roof coatings and green roofs, filming existing windows is a non-invasive, inexpensive and even boring way to cut energy use. As mundane as those steps are, they pay off. Window film has two hidden benefits, Smith said: Health and less stress on the building’s interior.

The health factor is key. By cutting ultraviolet radiation, window film blocks radiation that can cause skin problems for those sitting near the window. Along the same lines, the UV rays from the sun shine on the same objects over time. Blocking the UV rays can save these objects. This type of “soft” benefit – extending the life and attractiveness of carpets, laminated desks and other objects that can’t stand up to the sun over time – improves ROI. “It’s an additional savings, but has nothing to do with direct energy costs,” Smith said.


In a sense, the fact that window film – which is used to tint car windows and similar common purposes – has been around so long is not to its benefit. People, Smith said, are not aware that the technology is evolving. In short, putting a film on a window is roughly equivalent in UV blockage as installing a new dual pane Low-E window. In other words, Smith said, putting film on an existing window can provide the same solar efficiency as a replacement – at one-seventh the cost.


The IWFA, which is holding its southeastern regional conference early next month in Atlanta, focuses on retrofits that are overlays to existing windows. Smith said that his organization is related to but distinct from the emerging smart window sector.


As the name implies, smart windows use the Internet of Things and advanced networking techniques to agilely control the amount of radiation that passes through a window. Smith points out that the connectivity necessary for smart, IOT-controlled windows is a complex undertaking. The two industries segments do not directly compete, Smith said.


Now, under Proposition 39, schools housing students in grades K through 12 can be fully refunded for standalone window filming projects. The tool – which is available at — may be adjusted in the future to be used by other states and organizations.

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