Stained Glass Window Film

Archive for the ‘Window Film’ Category

Thanks to a recent email from one of our readers,  the question came up on whether installing window film can cause problems for window glass.  I thought it was an excellent question and wanted to share the answer and a little more detail here in this post for others who may have had similar questions.

A common question for decorators or homeowners considering applying window film is whether or not window film can cause glass damage. Specifically, since many homes today have insulated double pane windows, what is the impact on these types of windows? Will window film cause glass breakage?

There is good news and bad news. The answer is not very cut and dry. In researching several manufacturers websites as well as a respected window film associations’ information, I feel confident in saying that the odds are very much in your favor that window films by themselves will not cause breakage. However, it is good to understand a little of the science behind this answer and know the limitations of my statement above.

First, the plain and simple fact is that window glass breaks because of stress. Specifically the types of physical stress and the associated details are listed below. This information was taken from the International Window Film Association’s website. It is excellently layed out and if you want to read more of their information, feel free to check out their website here:

Source: http://www.iwfa.com

Glass breaks when stressed. There are five types of stress which may cause glass breakage:

1. Thermal Stress–from absorption of solar radiation.
2. Tensile Stress–from the weight of the glass itself.
3. Mechanical Flexing Stress–from wind.
4. Impact Stress–from flying objects, hail, baseballs.
5. Twisting Stress–from building or window frame sagging or settling.

The first type, thermal stress, is the only one which window film may affect. The use of window films will increase the thermal stress on sunlit glass. However, there are also other factors which will increase thermal stress such as: partial shading of windows from overhangs, tightly fitting drapes or blinds, signs or decals on windows, heating and cooling vents directed at glass. In addition, different types of glass (annealed versus tempered, clear versus tinted) have different solar absorption rates and will withstand different degrees of thermal stress.

The window film manufacturers have recommended film-to-glass tables for use by factory-trained dealer installers. If a consumer is ever in doubt, he/she should request a copy of such guidelines. Listed are some glass types or conditions where the use of a solar control (not clear safety) type of window film is not recommended without extreme caution.

* SINGLE PANE GLASS LARGER THAN 100 SQUARE FEET.
* DOUBLE PANE GLASS LARGER THAN 40 SQUARE FEET.
* CLEAR GLASS THICKER THAN 3/8 INCH.
* TINTED GLASS THICKER THAN 1/4 INCH.
* WINDOW FRAMING SYSTEMS OF CONCRETE, SOLID ALUMINUM, OR SOLID STEEL .
* GLASS WHERE SEALANT OR GLAZING COMPOUND HAS HARDENED.
* VISIBLY CHIPPED, CRACKED OR OTHERWISE DAMAGED GLASS.
* REFLECTIVE, WIRED, TEXTURED, OR PATTERNED GLASS.
* TRIPLE PANE GLASS.
* LAMINATED GLASS WINDOWS.

So as you can see, there are recommendations and cautions to consider when installing solar window film.  Remember, the absorbtion properties of the window film will increase the temperature of the glass.  This can cause thermal stress.   In modern day insulated windows, this stress is minimal…but it still present.

Another good resource to consider is from one of the big players in the window film industry. 3m window film has a helpful FAQ  here.   Specifically one of the points found here also mentions this:

The application of 3M™ Scotchtint™ will increase the temperature of your sunlit glass which will increase the stress on the glass edges. The quality of those glass edges and several other factors (external shading, interior shading, glass history, type of film, size/shape of glass, indoor/outdoor temperature) all contribute to the potential risk of glass breakage.

So in summary,  there is a lot of knowledge and expertise along with science that has gone into minimizing the risks associated with glass breakage.   While it is possible that glass could break due to the increased thermal stress added to it by window film, it is unlikely to happen as long as you do proper research and consult with a local expert who can advise you on your specific installation.