What is spectrally selective window film?
Spectral selectivity is the quality of having solar/optical properties which vary across the solar spectrum. This means the material allows a high transmission of visible light but a low transmission of solar gains. Spectrally selective window film is any film that reduces the amount of heat entering a building without altering its appearance. Most spectrally selective films are virtually undetectable to the naked eye, as they allow in at least 70% of visible light.
What are the advantages to spectrally selective window film?
Spectrally selective films block a comparable amount of heat to traditional films without darkening the interior of the building. This eliminates the need for improved lighting which could cancel out any potential energy savings. Traditional films would darken storefront windows, while spectrally selective films would allow passersby to view the merchandise on display. Another advantage of spectrally selective film is that it can be applied to specific areas that receive a lot of sunlight without appearing out of place, whereas traditional films would need to be applied to the whole building for visual consistency.
Is spectrally selective window film worth the price?
Tinted and reflective films traditionally range in price from four to six dollars per square foot while spectrally selective films fall in the nine to twelve dollar range. Spectrally selective films have a longer payback time than traditional films due to the higher price, but with rising electricity and natural gas costs the payback time is becoming comparable to that of traditional films, now averaging four years. Also, if traditional films are dark enough to increase the need for lighting the additional lights can generate heat adding to air conditioning costs; this is not a concern with clear spectrally selective films. Spectrally selective films, and widow film in general, is especially cost effective when compared to the price of replacing current windows with energy efficient solar control windows. In the case of new construction, the application of window film from the start can allow the building to have a smaller more efficient HVAC system, as less cooling will be needed seeing that 40% of a building’s cooling requirements are brought about by heat entering through windows.
Does spectrally selective film block more heat?
While spectrally selective technically block less heat, they outperform tinted and reflective films when considering the amount of heat rejection compared to the amount of light transmittance. Tinted films on average need to block 63% of visible light to block 36% of solar energy and reflective films on average need to block 63% of visible light to block 56% of solar energy while spectrally selective window films only need to block 30% of visible light to block 55% of solar energy.
Is spectrally selective film completely clear?
Spectrally selective films transmit approximately 70% of visible light so while not technically being completely transparent, they will appear transparent to the human eye as we cannot visually distinguish between 70 and 100 percent light transmittance.