R-value of half-inch glass

vegomatic(z5 BHSD)August 6, 2007

Hi group,

I'll bet someone here knows the answer to that question. We came across 7 sheets of 3'x5'x.5" tempered glass from the front of a remodeled bank. They weigh about 60 pounds per sheet.

I tried googling the answer to no avail.

In the middle of a major home-remodel, we substituted one of the panes for an exterior door that had to go. Great view and the houseplants love it!

To us, it seems as good thermal-wise as the double-pane insert with enclosed blinds in our front door. In other words, a hand on the glass in sun is as warm on one as the other. In some late frosts earlier this spring, only once did it have a spot of frost on it.

We'd like to use several of these in a sun-room addition if they are at least close to double-pane in R-value.

Thanks!!

-Ed

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dcarch7

Glass is not a very good insulator. Air space is.
1/2" thick! Bullet proof! Don't know the R value. Sorry.

Make a few table top with them.

dcarch

    Bookmark   August 6, 2007 at 11:00PM
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vegomatic(z5 BHSD)

Thanks. Yeah, from a bank. Bullet-proof would be good, lol!

But, we figure it was enclosing an interior space and you know how miserly banks can be!

Single-pane is R .91. Adding more panes .5" apart adds a bit more than one R-value per layer. Triple-pane is about the same as a solid-core door.

If .5" solid glass is say, R-2, I'm well within shooting distance if I add a storm, for example. Or I could silicone spacers between two panes and be ready for anything, lol!

-Ed

    Bookmark   August 6, 2007 at 11:36PM
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kudzu9(Zone 8a - PNW)

I found a site that gives R-values for 1/4" and 1" glass. The increase is essentially linear as the glass gets thicker. If you graph their values and select 1/2" off the graph it gives about 1.25 as the R-value at that thickness.

Here is a link that might be useful: Glass R-values

    Bookmark   August 7, 2007 at 1:23AM
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birdwidow

Ed: 1/2" glass alone won't give much insulation, but I know a whole bunch of aquarists who would kill to get their hands on your glass sheets, to use in building large custom tanks. I'm one of them.

    Bookmark   August 7, 2007 at 2:08PM
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dcarch7

"Ed: 1/2" glass alone won't give much insulation, but I know a whole bunch of aquarists who would kill to get their hands on your glass sheets, to use in building large custom tanks. I'm one of them."
Not really. Tempered glass has distortions. You need plate glass.

dcarch

    Bookmark   August 7, 2007 at 5:56PM
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vegomatic(z5 BHSD)

That's interesting, thanks for all the replies!

To tell the truth, I wouldn't know plate from tempered. There's no imprint, and it's all one layer, so maybe it is plate.

There are some edge dings and minor chips, but I see six very useable out of the seven sheets.

Our front double door glass inserts look to be about 1.65 give or take. 1.25 is not all that far off. A simple storm would add 1 to that. Still not as good as a solid core door, but not that bad for a huge window. We heat primarily with wood, it's fairly easy to keep the room warm.

OTOH, if they are plate and their value is higher to an aquarist, that might buy large windows that actually open. This is raw glass with no frames.

I have a pic of one in place I can post later.

Thanks!!
-Ed

    Bookmark   August 7, 2007 at 6:48PM
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vegomatic(z5 BHSD)

Here it is in temporary service.
-Ed

    Bookmark   August 7, 2007 at 7:51PM
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birdwidow

"Tempered glass has distortions. You need plate glass."

For big breeder and/or grow out tanks, it makes no difference. I know some who use fiberglass stock tanks for grow outs, and they do give a lot of water capacity for the bucks, but nothing beats being able to observe them from the front, and for that, you need a transparent side wall.

If I lived closer to vegomatic, I'd make him an offer, because a single, huge tank, to run the entire length of my GH is high on my wish list, but there is no way I can even consider a single sheet of glass, 3 ft wide X 16 ft. long, so it will have to be built in sections, with supports every 2 - 3 ft. 1/2 inch thick would be just right for me. Ah well.

    Bookmark   August 7, 2007 at 10:33PM
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vegomatic(z5 BHSD)

Checking aquarium and glass websites, I only found one price of $9/sq.ft for 1/2" plate. That would make these panes $135 each new.

We paid $100 for all seven, so I guess we did alright. We got them from a friend who was moving out of state. He got them to make a greenhouse but never got around to the project.

-Ed

    Bookmark   August 8, 2007 at 11:22AM
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