Choosing and Using Window Films: Types and Terminology

Forget the cheap, ugly window films you may have grown up with. Brittle, easy to bubble, and peel – but nearly impossible to remove, it seemed – they didn’t offer many advantages.

Today, it’s a different story. From lowering your cooling bills to protecting your family and home – or merely decorating your glass – you can find a window film perfect for you. Installation is fairly simple, too. So the next time you’re working on windows, you may want to discuss window films.

Types of Window Films

When you read about window films, pay attention to which category of window film is being addressed. As the International Association of Certified Home Inspectors discusses, there are three categories of window films: tinted film, made from cellophane-like material that is applied for temporary use such as with glare-reducing retractable shades; semi-permanent films applied to the windows directly and intended to stay permanently; and permanent tint, such as the brand Heat Mirror and other low-E coating makers who develop their own coating system and apply it to the windows at the factory.

If there’s money in the budget, today’s manufacturer-applied coated glasses are a great investment. However, all homeowners can benefit from cheaper at-home films that are easy to apply. These semi-permanent films last a very long time, too. Look for specialized films such as:

Insulating Window Films

Everyone benefits from insulating window films. Well, except for the energy companies, who get to collect a little less of your money. Insulating / thermal films reflect the heat from outdoors in summer, while in the winter they help retain heat. No matter what the climate, homeowners will find these films indispensable.

Most insulating window films block up to 99-percent UV rays. This means on top of energy bill savings, you help protect your furniture, walls, and flooring from fading. Insulating window films also reduce visible light transmission (VT).  The disadvantage to this may be less light in the room, but it also means less glare on televisions and computer monitors. For more light, choose a film that specifies it allows VT.

Some insulating window films count towards local, state, or federal tax credits. Aiming for LEED certification? You may be surprised to learn that your film qualifies you for points toward it. Best of all, the money recouped from lower bills will eventually pay back what was initially spent on the film.

Safety and Security Window Films

Live in a crime-prone neighborhood or concerned about the safety of a relative? Safety and security films work wonderfully to protect your home and loved ones. These films reinforce the glass to increase the shatter resistance. Some are even rated as able to withstand a bullet from a small caliber gun or small explosions, according to manufacturer’s claims. Nature’s hurricanes and tornados, or break-ins and robberies – all can be just a little less of a worry.

You can also find UV blocking ability, and other characteristics, combined with safety and security in window films.

Decorative Window Films

Stained glass, etched designs, frosted coatings – they are beautiful, but who can afford to go replace perfectly good glass on a whim? Enter decorative window films, in such a wide variety of designs you may have a hard time deciding which one you like best. Take some time and browse the Internet for decorative window film and comparison shop first. You’re sure to get great ideas!

To their credit, decorative films aren’t just pretty. They may also block about 70- to 80-percent of the sun’s UV rays. Some are easy to remove, so you can switch them to other windows if you want. You may enjoy it so much you simply want to buy more, and at the generally affordable price for most films, you can, too.

Privacy Window Films

Blurring the lines between decoration and privacy are today’s privacy window films. Not only are they often made with pretty designs, unlike decorative films, they also make sure all view is blocked. From frosted panes to dark film (such as used in cars), crumpled tissue paper or mirrored surfaces, privacy windows make it difficult to impossible to spy inside your home.

While some privacy films won’t allow you to see in, you may find it harder to see out, as well, depending on the film. You can also expect some level of UV protection – up to 98-percent reduction, according to some manufacturers. Be sure to look for the VT rating as well.

Important Window Film Terminology

It’s not enough to know that you want a window film, or even what type of film you want. While shopping for your film you will encounter many terms. Understanding the lingo will help you buy precisely what you want:

  • UV Rejection: UV-rated products block a certain amount of ultraviolet rays A and B, which the sun emits. UV rays are harmful to the skin plus fade interiors. Look for high UV rejection rates for best results.
  • Light Transmission: Simply put, the light transmission level is how much light will pass through the film. Police officers test light transmission on vehicle tints to ensure that car tints are legal – the lower the score, the darker the tint. For home use, aim for around 50-percent light transmission to balance glare and visibility properties.
  • Visible Light Transmission and Reflectance: Visible light reflectance and transmission (often called simply VT) measures how much light is reflected away from the window. The higher the film rates, the shinier it appears outside (hence a mirrored appearance).
  • Shading Coefficient: A term used in the energy field, the shading coefficient simply measures how much a window film prevents (reduces) the heat gain from outdoors. Look for film with a shading coefficient level of .50 or lower.
  • Solar Energy Rejection: Another energy term is solar energy rejection. Simply put, it’s the measure of the film’s ability to repel UV and VT as well as infrared (radiating) heat. The higher the film’s score, the better it insulates your windows.
  • Thickness: Another important quality, the film thickness is expressed in either mils or sometimes, microns (1 mil is equal to about 25 microns). Thickness becomes particularly important in safety and security films; generally, the thicker it is, the stronger. Look for film measuring at least 4 mil – keeping in mind that 14 or greater is best.

In the end, what matters most is how the film performs for you. By understanding the types of films, what they will and will not do for you, you can better select the ideal treatment for your windows. Understanding the terms the manufacturer uses makes it much easier to translate a film’s qualities, as well. Now all you have to do is find the film you want!

1 Comment

  • John Sortore October 22, 2014 at 4:37 pm

    There is little “security” provided by traditionally installed surface applied films. Unless the film is wrapped around the edges of the glass or secured within the window frame in some way, the entire broken window lite can be removed en-mass. Security films might thwart a simple “smash and grab” attempt by a rookie, but an experienced “s and g” guy will simply push his way through and collect the booty.
    This is precisely why window films are not generally approved for use in hurricane impact situations and won’t pass Florida testing. I’m NOT saying that the films, themselves, are inferior. I’m saying that without some type of perimeter anchoring system the films cannot possibly perform in the manner that many proponents imply that they will.
    The other drawback to window film is the same drawback as that of impact glass – it doesn’t prevent breakage. In some cases, replacing a piece of, say, side-lite glass isn’t very expensive, but replacing a complete side-lite impact window assembly could run a couple grand or more.
    Whether it results from a break-in attempt, vandalism, debris impact or a rock from a lawnmower, broken glass has to be replaced when it breaks.
    On top of replacement you lose the use of the window from that point on until it can be measured, ordered, manufactured and installed. You also have to but up with the construction mess and inconvenience of the replacement process.
    Based on these facts, about the only safely that interior surface applied films can be counted on to provide is the capturing of glass shards after impact. This does increase the safety of the occupants from flying glass projectiles.
    Manufacturers will make claims of more but there is so much “hidden fine print” involved in their claims that the advertised application comes at a price far above what could be termed as “cost effective”.
    The bottom line is that window films are a great way to decorate, filter light and provide privacy. When it comes to stopping intruders, severe weather events or bullets there is way more to consider than just applying some film to the surface of glass. Caveat Emptor


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