I'm considering getting one-way mirror film for my home windows and sliding patio door. The salesperson I spoke to advised that these films could actually contribute to the breakdown of the window's seals by causing light to reflect off the film and then back through the space between the panes which generates excessive heat build-up within the argon gas insulation. There always seems to be a caveat to everything, but I am hoping this one is actually minimal and that I can proceed with the film installation with little worries.

  • Which side of the glass are you going to install the film on? And which way is the reflection? If you're installing the film on the outside and reflecting outside, then I don't see how that would heat the gas.
    – longneck
    Nov 5, 2014 at 21:16
  • @longneck The film will be installed on the inside and reflecting toward the outside so that people on the outside will have a harder time seeing in while I am able to easily see out. Nov 5, 2014 at 21:26
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    Just as an aside, if it's dark outside and the room is brightly lit, I wouldn't count on the "one way" mirror to live up to its name...
    – DJohnM
    Nov 6, 2014 at 1:36
  • @User58220 Correct. This is mainly for the day and I plan on installing some outdoor lights right above the windows to keep the surface reflective for when I do want to keep the curtains open at night. Nov 6, 2014 at 1:51

1 Answer 1


I don't like this question, simply because there are too many variables. "CAN it be detrimental?" Well...

Windows come in single, double and triple pane; made from glass or plastic; have different insulation systems between panes, have different natural coatings and compositions for various properties such as UV protection or reflection; and many other variables. Over time glass windows will flow and warp, where plastic windows will oxidize.

Stick-on Window Coverings come in various materials (plastics usually, but that's a wide range of chemical structures with subtly different properties); use different adhesion methods such as static or chemical bond; have different coatings and compositions to create various properties such as coloring, refraction, UV protection or reflections; and again many other variables. Coatings will chemically change over time.

Light from either side of the window can have different compositions, although usually the concern is natural sunlight. Sunlight comes from different angles with different amounts of atmospheric interference through the day and year. This is why it wasn't expected that UV glass can melt siding.

So again, CAN it be damaging? Sure, anything is possible.

WILL it be damaging? We really can't say until you install it. But a bit of very light Googling didn't find any actual reports. It looks more like an attempt to pass responsibility between window and coating manufacturers. I'd say check with your window manufacturer, and follow their recommendations. Ultimately, that's the expensive repair if something goes wrong.

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