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How can I know if my windows have Low E glass?

Posted by frenchman (My Page) on
Fri, May 22, 09 at 15:10


I am replacing a sliding patio door with a French door and have the choice between Low E and not Low E glass. I was going for Low E and then the door reseller said that if my other windows are not Low E I may want to get the same not Low E glass because the Low E will have a tint and it may look weird (the French door will be 4 inches away--a pillar--from a big floor to ceiling window).

There is some engraving on the glass of my window:

tempered safety glass
21 16 CFR 1201-II
2 07 1-1984

I don't see a tint but I also don't know how much it would be.

How can I find out, or at least make a decent decision re: Low E versus not. (Non Low E will also save me ~$170 at order time).


Follow-Up Postings:

RE: How can I know if my windows have Low E glass?

Hold a flame to the window in the dark and count the reflections.

The easiest is to hold a lighter (or other open flame) near the glass and look at the reflection in the window. If you have Low-E, and it is on the #2 or the inside of the exterior lite surface, then you will see three flames reflected in the glass. If you are doing this test from the inside of your house, the two "flames" farthest from you will be close together and then a space and then the third flame.
If you perform this test outside, there will be two flames close to you and then a gap and one flame further away.
The center flame will be a slightly different color than the two flames that bracket it.
It is best to do this test in the dark, although you can do it in daylight as well. It is simply easier to see it in the dark.
The middle flame will be the reflection from the Low-E coating.

RE: How can I know if my windows have Low E glass?

Three or four reflections? It seems that I see two sets of two flames and matchsticks. Each flame in a set is extremely close to the other one (at most a millimeter or so) and the other one is about what I'd guess the distance between the two panes of my windows are.

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