By Darrell Smith
Window film can be a very cost-effective solution for a variety of building issues: minimizing cooling costs, cutting glare and heat buildup, upgrading windows to safety standards, creating privacy in places like interior conference rooms, reflecting heat inside and more. Window film can be visibly clear or nearly impossible to see through from the outside even when those inside can see out.
At the International Window Film Association, we encounter inquiries from many stakeholders, and below are several common questions the association is asked about window film.
What is window film? Is there more than one type? Window film is a flexible product composed of one or more layers of coated or chemically treated polyester that can be installed on glass. It is primarily used for retrofit applications to existing windows.
There are several types of window film products; each type specifically is designed for a particular end use. These include solar control films, insulating films, ultraviolet (UV) blocking films, safety/security films, glare control/privacy films, decorative films, and automotive films.
Quality window films offer up to 99% UV protection, and solar control films are available with different levels of insulation improvement. For exterior windows, products that offer solar control and safety/security in a single product would likely be the most beneficial. For interior windows on doors or glass partitions, decorative products or safety/security products could be used.
What are the benefits of window film? Solar-control films can block as much as 80% of the solar heat coming through glass into a building, thus decreasing the heat load on the air conditioning system and reducing energy costs. Professionally installed window film can reduce cooling costs by up to 30%.
Films can be darker for glare control or privacy purposes or appear almost totally clear, depending on the required building and customer needs. More than 250 solar control films are National Fenestration Rating Council-certified, so users can be assured of the energy performance potential of the window film. Safety/security films and solar-control films offer up to 99% UV protection as a standard feature.
Safety/security window film works when glass breaks, controlling the post-break behavior of the broken fragments, generally by holding the pieces together attached to the film. This may greatly enhance the safety of building occupants and protection of furnishings/interiors from damage caused by broken and/or flying glass pieces. These products can be used to bring unprotected glass up to certified safety standards for impact by objects and humans; enhanced blast protection, such as from a chemical explosion; and other events that create hazards from broken glass.
Decorative films can be used to make standard glass look like frosted, etched, or patterned glass in colors or in white or black matte looks, enhancing aesthetics and privacy. Although not designed specifically for that purpose, standard solar control films and decorative films have the ability to minimize a portion of flying glass fragments should the glass ever break.
Does window film prevent fading of fabrics? It is estimated 40% to 60% percent of fade is caused by exposure to UV energy; the use of window film with its UV blocking ability can prevent up to 99% of that contribution to fading. Other factors that contribute to fading are visible light and heat, so the glare reduction and energy savings properties of window film can further reduce the rate of fading that might otherwise occur.
How is window film installed? Would a facility need to be offline for a length of time? Although window film can be installed as a do-it-yourself product, to achieve the best results and obtain the maximum manufacturer’s warranty coverage, a skilled professional window film company should install it. Installation of the film can be done on a room-by-room basis or after regular facility hours with little to no disruption to normal operations.
How long will window film last? Window films typically have at least a five year manufacturer’s warranty, but products today generally have 10 to 20 years of warranty coverage from the manufacturer, dependent on the specific film and intended use. The U.S. Department of Energy Weatherization Assistance Program’s software uses a 15 year life expectancy for low- to medium-price window films on windows in older buildings. Ultimately, the actual life of quality window films may greatly exceed the warranty period.
Does window film require special care/maintenance/cleaning methods once it is in place? Installed window films can be cleaned with normal non-abrasive, non-corrosive cleaning liquids and soft paper towels just as would be used to clean glass.The films have a scratch resistant surface like the scratch resistant lenses found in many eyeglasses today.
Is there still a benefit to window films when a facility already has high performance glass? The newer the building, generally, the greater the energy control capability of the window system, so there may be less energy savings potential for the use of window films.
However, normal glass stops little UV energy, so even the addition of clear UV blocking window film offers benefits. In addition, some newer windows have extremely high visible light transmission and may create areas of excess glare. Therefore, window film may be desirable to make an area more comfortable.
Even the newest windows, which advertise added UV protection as a benefit, usually provide no more than 70% UV block. A trained window film specialist, using specific tools and guidelines from a manufacturer, can determine how much added energy savings or other benefits might be achieved by adding window film to these newer types of windows.
Smith is executive director of the International Window Film Association.