Heat rejection films are normally applied to the interior of flat glass windows to reduce the amount of infrared, visible light, and ultraviolet (UV) radiation entering windows. Such films are usually dyed or metalized (which can be transparent to visible light) to convert incoming solar radiation to infrared radiation, which is then rejected back through the glass to the exterior. Modern window film technology has created ceramic window films which are non-metallic and do not contain dyes that can result in discoloration. The ceramic and metallic window films usually cost 10–15 percent more than regular window film but can reduce energy transmission by as much as 80 percent.[4] Ceramic window films cost slightly more but provide a substantial increase in blocking UV rays and ability to control heat transfer.

To keep the sun’s heat out of the house, a low-emissivity coating should be applied to the outside pane of glazed windows. If the windows are designed to provide heat energy in the winter and keep heat inside the house (typical of cold climates), the low-emissivity coating should be applied to the inside pane of glazed windows. Such films also reduce the amount of visible and ultraviolet radiation entering a window, and are often applied to reduce fading of the contents of a room. Silvered film may also be employed to the same end. Spectrally selective films act by blocking certain wavelengths of the sun’s infrared radiation and reject heat without reducing natural light.

Security films are applied to glass so when the glass is broken it holds together, preventing dangerous shards from flying about, or to make it more difficult for an intruder to gain entry. Typically applied to commercial glass, these films are made of heavy-gauge plastic and are intended to maintain the integrity of glass when subject to heavy impact. The most robust security films are capable of preventing fragmentation and the production of hazardous glass shards from forces such as bomb blasts. Some companies have even experimented with bullet ballistics and multiple layers of security film.[5] Another key application for security window films (safety window films) is on large areas of “flat glass” such as storefront windows, sliding glass doors, and larger windows that are prone to hurricane damage. These security films, if applied properly, can also provide protection for vehicles.[citation needed] These security films are often tinted and can be up to 400 micrometers (µm) thick, compared to less than 50 µm for ordinary tint films. If anchored correctly, they can also provide protection for architectural glazing in the event of an explosion. A layer of film (of 100 µm thickness or greater) can prevent the ejection of spall when a projectile impacts on its surface, which otherwise creates small dagger-like shards of glass that can cause injury.more