How can you determine if windows are Low E

larrylwillApril 18, 2009

I have some picture window panes I want to replace.

One possibility is to just re frame what I have. They are 4' x 4'5" glass, 6 of them. They are double pane looks like about 3/4" between panes and look slightly tinted. At night the house lights reflect back off them even white walls hurting my view of the distant city lights. I assume they are between 10 and 20 years old but are not leaking.

They are under a porch roof so no direct sunlight will enter except for very late evening. Mainly I want to keep the heat in, in the winter and heat out in the summer.

Is there any way to determine if they are low E? If not I will replace them. They are in a metal frame which I would replace.

Would a IR bulb do the job? I could compare them with my newly installed Low E double hungs.

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oberon476

larry,

The simplest way to see if your windows have LowE glass is to hold a lit flame (match, lighter) next to the glass when it is dark. If you have a LowE coating you will see three flames reflected in the window. The center flame will be a different color than the outer two.

If you see only two flames in reflection then you don't have LowE.

    Bookmark   April 18, 2009 at 8:40AM
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larrylwill

I have some new Low E with argon in the rest of the house. So I held a flame to them and see 4 reflections. 2 very close, a space and 2 more. On the ones in question I see exactly the same thing except the first 2 are further apart than the 2nd 2. The new Low E windows the furthermost flames are slightly different (faded) The ones in question all look the same.
It wasn't dark so I held a black object on the outside if the glass.

    Bookmark   April 18, 2009 at 2:02PM
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larrylwill

Doing some more research I found this. I also found that if the sun hits the windows you want Hard coat to reflect it back, if not you want Soft coat to reflect the temp back.

" Windows in warm climates, where cooling is the primary concern, should have the low-E coating on surface 2 as shown in the figure below. In cold climates, the coating should be on surface 3. "
You should see 4 reflections. I live in North Alabama and have it on the proper surface #2 However the ones in question have none.

Outside 1..2.....3..4 Inside

Sleeves that site looks like its for people that want to buy new window units, I'm really making my own just buying the glass.

    Bookmark   April 18, 2009 at 2:48PM
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windowsonwashington

Larry...sounds like you have two surfaces of Low-e with the 4 reflections.

    Bookmark   April 18, 2009 at 5:21PM
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larrylwill

http://www.progress-energy.com/custservice/flabusiness/efficiency/CA/library/BUILD001.asp

here is where I got the info I posted, I also found a similar post in this forum and some others.
Only 1 reflection is a different color of my 4.
I also get 4 in the windows I want to replace but all the same color. I also checked my door. No low E
thank you

    Bookmark   April 18, 2009 at 11:19PM
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oberon476

Typically you do see four reflections - I apparently had a bit of a brain cramp when writing my original reply.

As you noted in your last post, the different colored reflection indicates the location of the LowE coating - or if all the reflections are the same then there is no coating.

"Doing some more research I found this. I also found that if the sun hits the windows you want Hard coat to reflect it back, if not you want Soft coat to reflect the temp back."

To follow-up on your post, hard coat LowE works well when you want high solar gain thru the window and into your home. But if the sun hits your window and you want to block it, then you want a dual or, better yet, triple silver softcoat.

A hardcoat will allow almost as much solar heat gain thru the window as will clear glass while the multi-layered softcoat will block direct solar heat gain.

    Bookmark   April 19, 2009 at 10:01AM
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larrylwill

Ok now the question is
How can you tell if its Hard coat or Soft?
I want to keep the heat and cold in. I have No sun problems.

thanks

    Bookmark   April 19, 2009 at 2:44PM
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oberon476

The best way for you as a homeowner is to simply ask the window manufacturer what coating they are using.

Maybe 85% (give or take a couple percent)of LowE coating used in the US is softcoat. Hardcoat is generally only available in the north.

You want maximum efficiency so you want either or a dual or triple silver softcoat.

Again, your best bet is to ask the window manufacturer what they are using.

    Bookmark   April 19, 2009 at 8:34PM
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