Window films, also called window tints are an increasingly popular solution for reducing the heat that enters a home through the windows. So how do they work? Solar Window Films are installed on the interior or exterior of glass and they are designed to control specific solar rays to decrease heat transmission. This can lead to energy savings on heating and cooling costs and improve the comfort of a building. Short Version, films block UV Rays and Infrared Rays while allowing visible light rays. Read on for the Long Version
Here we get a bit technical: The sun heats up homes, buildings, and people by emitting radiant energy. This solar energy comprises of a wide range of electromagnetic waves, including visible light, ultraviolet (UV) rays, and infrared (IR) rays. When these rays reach the Earth's surface, they can be absorbed and re-transmitted by various objects, including windows and skin tissues on the human body. Window film works by disrupting this process.
Window Film can be made of a multi-layer, ceramic or metallic construction that reflects and absorbs very specific rays, while permitting others. By controlling specific radiation, the films can reject the solar heat gain. Most films offer 99% UV (Ultraviolet) rejection, and some high-performance films offer IR (Infrared rejection) in the 90-97%, while still allowing up to 90% visible light transmission. In this sense, we say that window film is spectrally selective, it is able to "select" specific rays in the solar spectrum and block them.
In less words: In direct sunlight, window films can reduce temperatures by as much as 9° Fahrenheit.
Window films are therefore an ideal way to reduce heat while still keeping your view, as they are designed for those that don't want to completely block out the window with a roller shade or blinds to stop the heat. Their heat rejecting qualities are similar to what is currently used in high performing glass (like Low - E Windows) but the benefit is that they are much less expensive to install. This means that upgrading your existing windows is up to 1/10th less expensive than replacing glass. Even high performance windows sometimes fall short in their heat rejection, especially in southern areas where Solar Heat Gain is extreme and in these cases Window Film can be used to reinforce these high performing windows.