As with many other things, there are myths and misinformation regarding the installation of window film, especially on dual-paned insulated-glass units. Do-it-yourselfers, lack of proper education, and window manufacturers voiding warranties due to an aftermarket product on theirs all contribute to mistruths and obfuscations. These consist of claims that glass will break and seals will fail without any regard to understanding technical parameters. As a master-accredited specialist with the International Window Film Association, these claims make my head spin.
There are several technical factors when choosing the proper products so we meet the ultimate goals. Knowing the glass type, location of any low-emissivity coatings, and compass orientation all determine product selection. As long as the job is done correctly from the start, any risk of glass thermal shock is greatly reduced, albeit extremely rare it ever happens. In most cases, the window film manufacturers provide a warranty covering the replacement of glass affected by increased solar absorption resulting in thermal shock. There may also be an included warranty covering seal failure of an insulated-glass unit as long as there is an existing warranty from the window manufacturer. Being a Llumar Select Pro dealer, their Gold Warranty can be added to an installation that covers the existing terms and conditions of your in-force window warranty for any dollar amount needed to repair the affected window. These warranties are in place to prove that window film has extremely low risk as long as guidelines are obeyed.
Using the proper film product on particular windows is crucial. There are people installing automotive film on flat-glass windows in homes and businesses. This is not proper and only results in poor performance due to the film's construction being meant for the automotive environment as well as being a very high risk of breaking glass that isn't tempered. While the automotive and flat-glass window films have similarities, they're also quite different. Please understand there is real science to adhere to in order for the job to be done correctly.
They've been around for at least six decades and have more pros than cons. The pros are being much more energy efficient than single-paned glass as well as being noise reducing. The con is when too much moisture enters the unit when the seal fails and the desiccant between the primary and secondary seals becomes saturated. This results in a cloudy appearance between the two panes and will eventually stain the glass with water spots. While this appearance is unsightly, ultimately they just need to be replaced. Seal failure is extremely common especially in geographical regions with higher humidity. Window film applications that are within approved parameters will not directly cause seal failure. In the event there is existing seal failure, the performance of window film could expose the existing failure by causing the humid air within the unit to steam with sun exposure. Film Solutions is not responsible for any seal failure of IG units, pre-existing or otherwise. Seal failure provisions within the window film manufacturer's warranties only apply if the window has a current, in-force warranty for seal failure.
A low-emissivity (or low-e) coating is usually a metalized coating that is applied to a surface of glass to reflect infrared energy, or heat. The surface where it's applied is important. Dual-paned units should be installed with the low-e coating on Side #2 (inside of the outer pane) for solar heat rejection in regions where the winter months aren't very long...such as in Ohio. When the low-e coating is on Side #3 (inside of the inner pane), passive solar heat will warm the interior area with sun exposure. This side is okay for regions that are way north, but not here. Unfortunately, this low-e location is too common and a window film installation can not only be risky because the inner pane gets hot, but the total performance to reduce solar heat gain simply can't be achieved easily. With the added risk of thermal shock in mind, only a film with very low solar absorption or an exterior film should be used. As long as the low-e coating is on Side #2 or there's no coating at all, risk factor is low and lots more options are available and acceptable and will provide excellent solar heat rejection if needed.
We've all heard of UV rays and infrared (IR), but there are myths with this area, too. Let's start with UV. We don't see or feel it. That's right...we don't feel it as heat (that's infrared). It's what burns our skin and damages furnishings. Don't be fooled into thinking because the sun isn't coming directly though a window or that blinds are installed that UV isn't present. If there's no coating to stop or reduce it, UV is present during the daytime. There are three sections to the UV spectrum. The shortest wavelength of UV radiation is UV-C. This part does not hit the earth thanks to our atmosphere. If it did, we wouldn't exist on this planet. It's used for sterilization in water treatment plants because it kills almost anything. The midsection of UV radiation is UV-B. Glass alone filters most of this spectrum. It's the spectrum that burns our skin when we're outside. Now for the longest wavelength of UV, known as UV-A: Every bit of it comes through glass unless there is a UV-absorbing barrier. It's what fades and damages floors, artwork, and anything else that is vulnerable. Window film rejects >99% of the UV spectrum that enters windows.
I probably don't need to explain what visible light is, so let's move onto infrared, or IR. This is the spectrum we feel as heat. There are three sections in the IR spectrum: Short or near (IR-A), Mid (IR-B), and long or far (IR-C). Different types of heat sources can produce different IR wavelengths depending how they are used. Beware of window film specs that claim to reject a certain amount of IR. The number may be true at a particular wavelength, but not the entire IR spectrum. Look at what wavelength(s) are being specified. This is a marketing ploy and is not a true representation of total solar performance!
Annealed glass is the type that can crack due to thermal shock. Laminated glass consists or two or more layers of annealed glass that are bonded by PVB (polyvinyl butyral), and is also susceptible to thermal shock. Window film installations on laminated glass are of higher risk due to the layer of PVB restricting glass expansion and contraction. Tempered glass doesn't care how hot it gets from solar heat. It will only break with a physical hit or twist.
While tempered glass poses no risk for thermal shock, it's very common for it to look wavy when viewed from an angle and have fabrication debris on its surface. This debris is a microscopic layer of glass dust that has been baked onto the surface during the tempering process. When window film is applied to a surface of tempered glass with this manufacturing defect, the film will expose the debris and look like dust, scratches, or hair under the film. A razor blade can be used with caution to indicate if a surface has the debris but should not be used to clean it if it does. Only a scrubby pad or fine steel wool should be used. Unfortunately, there is nothing that can be done to further prep tempered glass with this defect for a window film installation and should be understood by the customer. Film Solutions is not responsible for any existing flaws in the glass or any additional flaws from a film installation. Below is a link that explains tempered glass more in depth and there is more information out there from additional sources.