Understanding How Window Film Works
Sunlight and Glass
Solar radiation from the sun is divided into 3 components: visible light we can see, infrared we feel as heat and ultraviolet rays, which are invisible. It interacts with glass in one of 3 ways. It is reflected, absorbed or passes through. 3M films shut out up to 99 percent of the sun’s ultraviolet rays; preventing them from damaging furniture and more importantly preventing them from causing skin cancer. The same films also block up to 79 percent of the heat from direct sunlight while simultaneously preventing up to 35 percent of diffused heat from passing through a window. These help reduce energy costs by keeping a room cool during a hot summer and keeping it warm during a cold winter.
In the past several years, 3M™ window films products have been significantly improved through nanotechnology. The application this technology has allowed 3M to create a film that delivers the highest performance possible without using metal, which can corrode and interfere with digital and satellite signals.
3M™ has utilized both film and adhesive technologies to create ground-breaking advances in window protection. It is their innovation that powers 3M’s credibility to a wide range of users, from the homeowner and small business owner to the corporations and government institution.
3M films are designed primarily to protect a home or office from the harmful effects of light and to limit the transfer of heat to or from a room.
Judging the Window Film Specifications
According to the Efficient Windows Collaborative (EWC), window standards are now moving away from a previous standard referred to as Shading Coefficient (SC) to Solar Heat Gain Coefficient (SHGC), which is defined as that fraction of incident solar radiation that actually enters a building through the entire window assembly as heat gain. To perform an approximate conversion from SC to SHGC, multiply the SC value by 0.87.
The SHGC is also affected by shading from the frame as well as the ratio of glazing and frame. The SHGC is expressed as a dimensionless number from 0 to 1. A high coefficient signifies high heat gain, while a low coefficient means low heat gain.
If you receive a sample from a contractor that is cut from the roll and privately labeled, you run the risk of being fooled. Every manufacturer produces professional sample cards that give accurate information and every contractor can supply you with the AIMCAL booklet. This booklet spells out exactly what window film will and will not do, and how it works and is available from our office.
SOME HINTS ON SELECTING A BRAND OF WINDOW FILM: We believe the most important thing about a window film installation is the craftsmanship of the installer supported by a friendly and efficient staff. We have a team that beats all for great installations. However, with the plethora of manufacturers and expert advice out there, we find the selection of material to be confusing at times (we have been studying window film since 1969). We want you to be informed about your decision, contact our office for samples