Window Solar Film 

The solution to over heating through windows is to specify solar control glass or applied window film, though even the best solar control glass performs no better than the best applied window film. Solar window films can be selected for optimum energy performance in reference to geographic orientation of any given home. However, even in new construction often the cost of solar control glass exceeds the cost of standard glass to which a solar control window film is later applied. The importance of sufficient insulation in walls and roofs is well recognized and the importance of well insulated windows cannot be over-emphasized. Compared to solid walls and roofs even the best windows are poor insulators; they are often equally poor at blocking out solar energy.

 Stopping heat at the window is the most cost-effective means of lowering temperatures and decreasing HVAC operating costs. Fortunately, conventional tinted and reflective window films successfully block a significant amount of solar heat. However, these window films also reduce a significant percentage of visible light.

 Many of these conventional window films are highly reflective in daylight giving the window a mirror-like appearance when viewed externally. Most conventional window films transmit less than 34 percent of visible light – a good 36 percent less than the 70 percent necessary to be undetected by the naked eye. The result is the building’s interiors are correspondingly darkened, often necessitating the use of increased illumination. This may lead to higher electricity consumption, which may increase temperatures, which may, in turn require more air conditioning. Increased utility costs defeat the major benefit of the film – cost savings.

 Clear, spectrally selective applied window film offers the best ratio of visible light transmission to heat rejection. “Spectrally selective” refers to the film’s ability to select or let in desirable daylight, while blocking undesirable solar heat. The price of tinted window film and reflective window film ranges from $4 to $6 per installed square foot. Spectrally selective window film ranges in price from $9 to $12 a square foot installed.

 Less expensive conventional window films have a shorter payback compared with spectrally selective films. However, when factoring in the cost of extra energy used for lighting and HVAC operation due to conventional film’s inability to transmit sufficient visible light or block solar heat, the payback for conventional film and spectrally selective film becomes comparable. Given rising electricity cost, the rate of payback for spectrally selective film for solar windows is always improving – averaging less than four years.