Q&A: International Window Film Association

A simple fix is sometimes all that is needed to m commercial building or school that is more energy efficient and comfortable for its users. At least that’s the contention of the International Window Film Association, an industry trade association for manufacturers and professional installers of window film: A clear film that can be overlaid onto a window to provide for greater solar insulation and protection against broken fragments shooting inwards.

 

Darrell Smith, executive director of IWFA, says energy-control window film — when professionally installed on old, single-pane windows — can boost the efficiency of those windows as much as two or three times. The film also costs 20 percent to 50 percent less than top-end energy-efficient windows, according to Smith.

 

Green Building News spoke with Smith in a telephone interview to learn more about window film and how it can be applied in various settings. 

 

Q: What is window film and how is it applied in commercial and institutional settings?

 

A: Window film is a product made up of one or more layers of a clear polyester sheet. This polyester layer has either been permeated throughout, pre-surface treated or coated with certain substances. These substances can include metallic deposits, dyes or chemicals; each is selected to control a specific type of energy. The types of energy window film can control include visible light, ultraviolet energy, or near-infrared light, all of which make up the solar energy passing in through a window. Windows with window film can also control far-infrared energy, which is room heat, reflecting it back into the room.

 

In addition, window film can block sound waves, or mitigate damage from physical impacts, like a golf ball hitting glass or even bomb-blast airwaves. Windows installed with bomb-blast window film protect occupants by holding back the glass in windows so it doesn’t become a weapon and do damage inside. Window film can control what happens to the fragments of a glass window after it breaks. For example, about one month after 9/11, all of the federal buildings in downtown Washington, D.C., that didn’t already have hazard mitigation glass and were considered to have a high threat level were outfitted with safety/security window film. The Capitol building has it, for example.

 

Q: What kinds of building is window film typically installed in?

 

A: You’ll see very little in new construction. Generally, window film is used in an existing building on existing windows. The International Window Film Association only supports professionally installed retrofit window film, or film that is added to existing windows.

 

Most of the buildings with window film will be older, but some newer buildings can be installed with window film to counteract unique problems that an architect or builder didn’t anticipate when the facility was originally planned or constructed. For example, window film might be applied in a new building if the facility operator discovered excessive glare coming in through the window at different times of the day. Another example might be if a building changes use, like a facility that began as an office with one employee per so many square feet is redeveloped into a service call center. The service call center is going to house many more people and electronics inside, which in turn creates a greater internal heat load and requires more cooling capacity, possibly more cooling capacity than the building was originally designed to handle, which is where window film comes in.

 

Q: How does window film help control energy use and encourage building efficiency?

 

A: Many large, old commercial buildings still have un-efficient single pane glass windows. There are a couple measures of the energy efficiency of glass, or the entire window system, one of which is the solar heat gain coefficient. The lower the SHGC number is, the more efficient a window system is in controlling solar energy. If it’s a single-pane glass window in a large commercial building, the window might have a SHGC rating of approximately .85 to .90, which means very little energy efficiency. A rating of 1.0 means the glass lets all the solar energy in, while .90 means it lets in 90 percent of the solar energy, and so forth.

 

With window film, a contractor can take that single pane window, put a standard commercial window film on it, and easily achieve a .20 or .24 SHGC. So a building operator can go from having windows that allow 90 percent of the solar energy focused on them in, to windows that allow less than 25 percent of solar energy into the building. That’s a huge savings on air conditioning costs.

 

To test some of the savings that are achievable by making those changes, facilities managers can conduct energy analyses to determine efficiency before and after window film is installed in their buildings. IWFA manufacturers have an energy analysis program utilizing recognized computer platforms from the U.S. Department of Energy that can provide a facility operator with a building-by-building analysis of the expected energy savings, in usage and dollars, they might expect from the installation of energy control films.

 

Q: What are some ideal places on buildings for window film?

 

A: Energy control window films are ideal for managing the solar energy entering a building from the east, west, and south sides. If the building is in a colder climate, the use of low-emissivity window films may be beneficial on all sides, but especially on the north side by keeping room heat from escaping on cold days.

 

Q: Do the window film materials and types used vary from climate to climate?

 

A: Window films do not have to vary from one climate to another if the primary goal is to reduce the cost of air conditioning whenever there is a solar energy load on a window. However, since some of this reduction of solar energy might result in passive solar heat being lost during daylight hours on the coldest winter days, there are window films that also have low-emissivity, or insulative, properties. This increase in insulative properties can offset or surpass any possible loss of passive solar heating during the winter months.

 

In terms of determining which type of window film is best suited for a particular building and its occupants, that can depend on the building’s use schedule (both the time of day and the days of week), the internal heat loads existing inside it, the building’s geographic location and compass directions, and its construction characteristics (insulation, type of windows in place, heating and cooling systems, etc.).

 

The use of safety/security films is not influenced by climate except for geography. For instance, windstorm debris-hitting windows might be more appropriate in coastal states where hurricanes are a primary concern, whereas glass breakage from possible earthquake activity might be a greater influence somewhere else. Once a specific threat or hazard is determined, the proper use of specific safety/security films can be recommended.

 

Q: So, in terms of energy efficiency, window film can either be used as a quick fix on a building to achieve more efficiency, or in a large-scale retrofit project to really overhaul a low-performing building’s systems, correct?

 

A: Yes, and sometimes it can be used to delay or avoid higher capital outlays for other parts of the building. For example, if a building is being remodeled, contractors can calculate out the building’s air conditioning needs with or without window film. In turn, they can probably put a smaller HVAC system in with the installation of window film, lowering overall capital and operating costs.  

 

Q: Can window film be used toward LEED certification at either existing school buildings or commercial or institutional structures?

 

A: Window films can be used in several categories, dependent on the building type and its location and the particular film selected, toward points contributing to LEED certification. Most IWFA manufacturer members have LEED-credentialed experts on staff and will be glad to assist a facility in determining how film use can benefit their LEED program.

 

Q: What are some common questions commercial builders ask about window film?

 

A: “How long will it last?” is a big one, and “What is the durability of window film?”

Depending on the technology of the product, window film is warranted on a commercial installation. You’ll find the standard warranty to be 10 years or longer on a commercial building. Many of the new high technology window films have warrantees of 20 years.

 

Another question is, “Will it scratch?” All the window films on the market today have a scratch resistance coating, which is very durable and has been used for years on automobile windows, which undergo a lot of rubbing on surfaces, etc. So normal cleaning with non-abrasive materials will not affect window film.

 

For more information, visit www.iwfa.com.