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Does window efficiency film work?

Posted by admin on Sep 29th, 2008
Sep 29

About two weeks ago I wrote that I was going to try to make our single paned windows in our home more energy efficient by using a window film that claims to block around 70% of the suns radiant heat. This weekend I finally completed enough of the project to get an idea on if I’m heading in the right direction. It seems that I might just have wasted my time and money on this.

Of the 12 “panes” on the window, I put the film on 11 of them. I left the top middle pane untouched so I could test the difference in temperature between the filmed and non-filmed sections. I went to Harbor Freight to pick up a cheap infra-red thermometer ($10 – and I plan to use it around the house to find hot and cold spots). Since it was doing the testing on glass, I wanted to make sure it wasn’t skewing the test results when I checked the window temperature so I first put a large washer on the two test panes (the top left pane and the top middle pane) and checked the temp. Hmm – 106 degrees for the non-filmed pane, and 104 degrees for the filmed pane. Whoa.

Okay, maybe the metal washer is making a difference. I decided to put a paper mailing label on each window – that way I would have a surface to test that wouldn’t potentially accumulate heat due to the material it is made from. It did make a difference, the temperatures dropped about 5 degrees for each pane, but they were still 2 degrees apart. The filmed pane was 99.3 degrees and the non-filmed was 101.3.

That’s very disappointing. I’m going to double check the directions, and look for some tips online from others who may have tried the film and see if they have any suggestions on what the problem might be. If I can’t find that I’ve done something wrong then I’ll start looking for alternate ideas to make the windows more efficient.

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