Large banks of windows are a popular building amenity, but the extra daylight can seem like a double-edged sword on sunny days.
Plentiful daylight is generally healthy for occupants and can contribute to productivity, but can also result in distracting glare and an influx of heat that’s expensive to manage.
Retrofitting your existing windows with window film can help you achieve your energy, aesthetic and productivity goals at a fraction of the cost of a window replacement, according to Darrell Smith, executive director of the International Window Film Association.
Investigate these five ways window film could benefit your building.
1) Less Glare and Lower Bills
Some window films can block different parts of the solar spectrum to minimize glare, heat and dangerous UV rays, Smith explains.
Sunlight contains three parts:
- Ultraviolet radiation – the part that contributes to skin cancer and fades interiors. This section makes up about 3 percent of the sunlight spectrum, according to Smith.
- Visible light – literally, the part that you see. This section is about 44 percent of the total and is responsible for causing glare.
- Near infrared light – which is invisible but contributes to heat gain. This makes up the other 53 percent of the spectrum.
Understanding the difference between these qualities is key to selecting the right window film if solar control is a priority, Smith explains.
“Products today will block 65 percent of the heat and allow 65 percent visibility,” Smith says. “Think of the windshield of a car. They’re equipped with factory-tinted glass that looks almost clear, and by law that can’t be darker than 70 percent visibility. This window film is almost that light but would block 65 percent of the heat coming through because it has high infrared reflectance.”
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Films with high insulating values keep heat in your building in the winter and seal in air conditioning in the summer so that you’re not paying to condition the whole neighborhood. Some can also reflect infrared light back into the room to help heat it, giving you additional winter savings.
“Standard window film products still make up the majority of window films sold,” says Smith. “There’s a lot of single-pane or clear dual-pane glass that was installed 20 to 40 years ago that needs better energy control or an aesthetic upgrade. Just by tinting that window, you can save as much as 30 percent in the summer months.”
2) Customized Reflection and Transmission
Dual reflective films have made a big splash in the last five years thanks to the flexibility they offer building occupants, Smith explains.
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“On the outside of the building, you may want a reflective bronze look, but people on the inside of the building looking out may not want to see a bronze color,” Smith says. “The interior may be blues or grays. Manufacturers can change the reflectance and transmission values so that you see different colors depending on which side of the glass you’re on.”
3) Aesthetic Benefits and Branding
Window film with decorative patterns is growing in both variety and popularity, Smith says.
“You can now get window films that look like frosted or stained glass or that has a bamboo-style pattern. Some patterns are actually screen-printed into the film itself to accent a window. Those same films can be specified with or without energy control or in a thick version that holds glass together whenever the glass breaks.”
4) Life Safety and Security
Window film buyers sometimes believe that window film can make glass shatterproof, a longstanding myth in the market. The truth is that window film can’t prevent glass from breaking, but it can hold glass fragments together when the glass is broken.
That usually means that the broken glass also stays in place in the window rather than scattering everywhere, keeping wind and rain out of your facility during a storm and making it harder for an intruder to get into your building through the broken window.
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“It does mitigate the danger, but only in terms of what’s called glass hazard mitigation,” Smith says. “It reduces the dangers of flying glass fragments. It will not prevent glass from breaking. We’ve seen those claims and we refute those statements whenever we can.”
The risks of flying glass shards are considerable, however, so it’s still worth investing in security films if you have large windows that put the inside of your facility at risk.
5) Producing Energy
New research on window film may allow building owners to generate more energy from their windows rather than just reducing the amount of energy wasted by the HVAC system. Engineers at the University of California, Berkeley, developed a thin film that uses pyroelectric energy conversion to turn low-quality waste heat into electricity.
“We know we need new energy sources, but we also need to do better at utilizing the energy we already have,” says Lane Martin, senior author and associate professor of materials science and engineering. “These thin films can help us squeeze more energy than we do today out of every source of energy.”
The film is less than 100 nanometers thick and can generate up to 526 watts per cubic centimeter at 19 percent efficiency. The research team will now focus on optimizing the thin film materials to specific temperatures and waste heat streams.
Today’s window film carries a warranty of 15 years or more, Smith explains, and the cost has come down considerably despite the new innovations in the market.
Dual reflective films and other high-tech products range around $7-$11 per square foot, while window films that have been on the market for a while are typically $4-$7.
“You can get almost the same performance by putting a window film on an existing window, so why would you replace the window unless the frames are in disrepair or the window has air leakage around it?” Smith says.
“In many cases, there’s nothing structurally wrong with the window and it just needs to be upgraded. If that’s all that needs to be done, window film is a great solution for that.”
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