Window Film Benefits, Types and Techniques

Whether you want to lower your cooling bill or help safeguard your home, there’s likely a window film perfectly suited to your needs. Sometimes, the line even blurs between window films that enhance insulation and those that provide security – you may be able to find one that offers the benefits of both types.

Here are some important tips to consider as you select and install your window film.

Insulating Window Films

For year-round comfort, consider an insulating or thermal window film. Insulating films reflect the sun’s heat during the summer while helping retain the home’s warmth during the winter. This translates into lower cooling and heating bills – which means they actually pay for themselves with the money you save. Insulating window films also block up to 99 percent of UV light. This helps prevent fading of your furnishings and floors. Insulating window films may also reduce VT – visible light transmission – to some extent. This helps darken the room and reduce glare on televisions and mirrors. If you want more light, select a film that allows VT instead.

Some insulating window films may qualify for a local, state or federal tax credit. You may also find that your insulating film qualifies for points towards LEED certification for homes (a standard of energy efficiency and “green” building design).

Safety and Security Window Films

Specially designed security window films offer your home protection. They actually increase the shatter resistance of your window glass; some security films are rated strong enough to hold broken window panes and fragments in place even when shot by small caliber gun, and possibly during an explosion, according to the manufacturers. This means increased safety for your family in the event of a natural disaster such as a hurricane, or from a robber aiming for a quick smash-and-grab.

When shopping for security window film, check the UV blocking ability, the VT rejection rate and other features. Look at the specifications, such as what it’s made from and the thickness of the material. Do your homework: Considering the purpose of this film type, comparison shopping is a good idea.

Key Concepts

Knowing these terms will help you understand the slight differences in window films while you shop.

  • Light Transmission: Police officers use a light transmission score to determine if an automobile’s windows are tinted too dark for state law. For accuracy, they must use a special instrument that measures the light transmission; the lower the number it scores, the darker the tint. For a home, a film measuring around 50 percent light transmission balances glare reduction with light visibility.
  • Shading Coefficient: In the energy field, the shading coefficient is a measure of the net benefit of a window treatment to prevent or reduce heat gain from the exterior (the sun and environment). Films with a shading coefficient of .50 or even lower are best.
  • UV Rejection: The sun emits ultraviolet A and B rays. A UV-rated film blocks a given amount of these rays. UV rays are largely responsible for fading carpets, furniture, decorative items and flooring.
  • Visible Light Transmission and Reflectance: While shopping, you’re likely to see mention of VT or even visible light reflectance. VT reflectance is a measure of the amount of VT that’s reflected away from the window due to the film. The higher the film scores, the shinier it will appear from the outside.
  • Solar Energy Rejection: This refers to the film’s effectiveness at repelling UV and VT rays as well as infrared heat – the warmth that radiates from the sun via infrared light waves. The higher the number listed on your film, the more it insulates your windows.
  • Film Thickness: Each film will list a product thickness, expressed in either microns or millimeters (1 mil is equal to 25 microns). The thickness becomes extremely important when selecting security films. The thicker the film, the stronger and more shatter-resistant it is. Quality security window films generally measure from 4 mil to 14 mil or greater.


Here are a few tips to keep in mind during your film selection:

  • Never apply window film to broken, chipped or cracked glass. Any film can create a rise in temperature within the glass, which can lead to shattering.
  • As a general rule, do not apply window films to tinted glass to prevent overheating from thermal absorption, which may cause the window to shatter. Also avoid Plexiglas and similar glass replacements. Tint, when applied to Plexiglas, may create outgassing – the release of chemicals in the plastic.
  • Avoid altering the film. Applying chemicals, cutting a decorative pattern or cleaning with abrasive cleansers may damage the film or lessen the intended benefits it offers.
  • If your window is curved, look for a film designed for use on curved surfaces.
  • Some films are removable and reusable. Others are permanent, so look for the kind you prefer.
  • Look at the warranty offered before purchasing. The longer the warranty, the more you can expect it to perform well for a greater length of time. Check for a guarantee against cracking, bubbling and fading.

Window Film Installation Techniques

While you can hire an installation professional, it’s not necessary. Installing window film is typically a rather simple DIY task. The most important things to keep in mind are to take your time and pay attention to detail. Patience and determination will help ensure a successful installation.

Before you start, always completely read the product installation instructions. These may vary somewhat from general instructions found here. For instance, security film will specify to cut the film slightly larger and then attach the film to the window frame as well. Always follow the manufacturer’s instructions when there’s a deviation from general guidelines.

Install your window film on a mild day when the temperature is between 50 and 60 degrees. Freezing temperatures or extremely hot, sunny weather may interfere with application and curing time. Curing time may range from four to eight days or longer.

The basic installation procedure for most window films involves the following steps:

  • Remove the current window treatments (blinds, shades or curtains) and clear the area.
  • Cover your floors with a sheet of plastic, garbage bags, newspaper, an old sheet or other protective material.
  • Clean the window: Use a gentle dish soap and water to thoroughly clean the window and remove grease, dirt and any contaminants. This helps film adhesion and ensures that you don’t memorialize your little one’s fingerprints in the window.
  • Dry the window: A squeegee works best, and is needed later.
  • Cut a section of film, if it isn’t pre-cut, using a utility knife. Measure the window carefully and add 1 inch to the height and width to determine the film size.
  • Spray the window generously with soapy water. Wet your hands as well, and keep them moist during the film installation.
  • Remove the film backing carefully to avoid contaminating it by touching anything else. Have a helper assist you – especially if you’re working with a large window.
  • Spray the back of the film with additional soapy water.
  • Starting at the top of the window, position the film on the glass, centering and spreading it as you work down the window. Spray with soapy water as you work, and use the squeegee to move air bubbles to the film edges. The water helps prevent tearing the film.
  • Trim the film once it’s installed. Leave a 1/16-inch gap between the film and the window frame to allow the glass to expand and contract. (Security films may differ in this step.)
  • Allow the film to dry and cure. It should start to adhere within 30 minutes and cure within several days.
  • Eliminate air bubbles in the film by carefully pricking the bubble with a needle. Smooth by pressing firmly with your thumb.