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fogged thermopane
By johnlm, Section Solar Posted on Tue Jan 24th, 2006 at 05:21:13 AM MST
can it be fixed?

I've been planning on building a batch hot water heater and found a 34 X 76 inch used patio door double pane glass at a local glass dealer that is somewhat fogged up (lost its seal). He will sell it for $5.00. Im wondering if there is any way to clean up the internal fogging without totally separating the two panes of glass. I thought I might try drilling a few holes through the aluminum spacer and trying to force air through it to dry it up and then temporarily sealing the holes back up with silicon sealant during a period when the humidity was very low - which is pretty often around here - to be repeated if it fogged up again. Or maybe just leaving the seals open enough that enough air gets through that it doesn't permanently fog while keeping any direct moisture from entering the holes. Anybody tried this? Or is a fogged thermopane not a significant problem for loss of solar transmission in a solar collector application? I haven't taken possession of the glass yet to test the transmission through the fogged areas with my solar insolation meter.
Suggestions?
Johnlm

fogged thermopane | 16 comments (16 topical, 0 editorial)

Re: fogged thermopane (3.00 / 0) (#1)
by ghurd on Mon Jan 23rd, 2006 at 11:45:29 PM MST
(User Info)

Best guesses?

It will greatly reduce the transmission.
However texturing can reduce the surface reflected radiation. Maybe thats only for the front surface?

My folks picture window lost a seal and fogged. The window guys (who sell windows) said it was etched or pitted and could not be fixed. Something related to the gas in the window?

Interesting. Keep us posted on the findings.
G-

Re: fogged thermopane (3.00 / 0) (#2)
by Gordy on Tue Jan 24th, 2006 at 01:22:03 AM MST
(User Info)

John,

If you or a freind have a mig welder with an argon filled tank/bottle your set.

remove window from frame, and apply silicone sealant to the entier edge of the glass and old seal (unless you can see where the leak is, then just fix that part).
once thats dried, drill a hole in the seal at the top and bottom.
Back to the welder, disconect the gas/argon hose from the back of the welder. And an adapter to fit the hole you drilled.
with the window standing up, conect the hose to the top hole. With the flow meter set at 10 cfm it should only take a minute or so to force the heavier moist air out the bottom hole. Then seal the holes.

A guy I worked with did this and it worked.

Gordy

[ Parent ]

Re: fogged thermopane (3.00 / 0) (#3)
by johnlm on Tue Jan 24th, 2006 at 07:21:49 AM MST
(User Info)

Thanks guys. Gordy, your process sounds pretty reasonable, the only problem is I don't have a MIG welder so no Argon. I will be picking the window up today so I will asess how bad it might be. I had only seen it sitting outside along his building and it had been there for awhile so was pretty dirty - not sure how much was dirt and how much was fogging. If the fogging is minimal, I may just try to reseal it. It is already out of the framework. I did an internet search and found that some company claims to have a process to defog these windows but it gives very little detail, mostly a sales pitch and asking if you want to be a dealer.

John

Re: fogged thermopane (3.00 / 0) (#4)
by zap (bell47g5a at comcast dot net) on Tue Jan 24th, 2006 at 09:01:41 AM MST
(User Info)

Hey John it sounds like a good find. I'm assuming you're still in Penrose and if so and if your batch heater isn't needed immediately, I'd set the pane in the sun and let it bake for a few days. Usually this will clear up the condensation. Dad lives in Pueblo West and got snow the other day, if you got it in Penrose also this may slow down the evaporation some. If the unit is straight glass with no coatings you may end up with clear glass, if the unit is Low-E then you may have problems such as ghurd's folks. It all depends on how much moisture was sucked into the unit and how long it's been there. You may want to ask the guy if he knows if it was a Low-E unit.

If you decide to go with some type of gas or compressor use VERY low pressure. With such a large area for the gas to act on it doesn't take much pressure to start bowing the glass and possibly breaking a pane. Since it has fogged check for failure of the seals or a capillary/breather tube that was never pinched off.

Even if you do end up without completely clear glass, Penrose gets some very good sun and the unit should still do quite well. Good luck and post some pics of the project.
zap
[ Parent ]

Re: fogged thermopane (3.00 / 0) (#6)
by johnlm on Tue Jan 24th, 2006 at 10:18:31 AM MST
(User Info)

Zap,
Yup Im in Penrose. I guess I did mention that on this board some time back - good memory on your part. Where are you? Do you just know the area because of your familiarity with Pueblo West?
When I picked the unit up this am I noticed that one of the panes has separated from the spacer for about 18 inches. The guy could bend it out slightly to make a noticable gap between the glass and the spacer - so the seal is pretty much shot. I forgot to ask if he knew if it was low-E or not. Are you suggesting the low-E units corrode up more inside if they get moisture in them? I may just separate the halves and clean them up and then mount them only semi sealed - much like a window / storm window approach but with maybe 1/2 inch of spacing between them. From experiments Ive done, and looking at R ratings of double pane sealed verses single pane window / storm window the R values are not all that much different.

John

[ Parent ]

Re: fogged thermopane (3.00 / 0) (#8)
by zap (bell47g5a at comcast dot net) on Tue Jan 24th, 2006 at 10:55:08 AM MST
(User Info)

I'm in Denver :( this town's getting too big! Built the house in P.W. for my Dad about 2 years ago but Dad worked mines all around your area and we used to visit old friends down there quite often years ago.

If the seal has given up the ghost then your cleaning idea should work well. If the seal is still holding strong on the majority of the unit it could be a real hassle getting it apart but heat can help to loosen it. Moisture alone could stain the glass whether it's Low-E or not. Some Low-E use silver and can corrode with moisture and may even etch the glass as ghurd suggested although I've never seen this happen but I've heard of galvanic corrosion from the silver and spacer.

If you do get them apart and clean them I'd suggest sealing them back again tight but that's your call, I guess there wouldn't be much of a penalty to your batch heater if you didn't seal them back up.
zap
[ Parent ]

Re: fogged thermopane (3.00 / 0) (#9)
by fishfarm on Tue Jan 24th, 2006 at 11:23:31 AM MST
(User Info)

If you decide to separate them, here's a site with good info on the various types.

Quote from article: "Manufacturers install glass in window frames in three different ways: with gaskets, adhesive tape or caulk. We'll show each method, starting with the easiest."

http://www.rd.com/content/openContent.do?contentId=18213

[ Parent ]

Re: fogged thermopane (3.00 / 0) (#5)
by crashk6 (crashk6(at)solarstormtechnologies(dot)com) on Tue Jan 24th, 2006 at 10:14:02 AM MST
(User Info)

Although I like Gordy's process for refilling the glass with argon much better you could try this if you can't manage the argon. If you can find the leak, Let the window bake in the sun until the fogging subsides, then seal it. If you can't find it separate and reseal the unit with GE silicone II. The secret here is that you put silica jell inside the window to control the moisture problem. If defogging method one is used you will have to drill the frame and deposit the jell inside. I have done this with success on a couple of these units. And actually have a canister of silica jell on my shelf for such things. I found mine in the floral section of the local hobby store chain being sold as "Microwaveable flower drying art medium"... Listed ingredients: Silica Jell.
--
crashK6

Re: fogged thermopane (3.00 / 0) (#7)
by johnlm on Tue Jan 24th, 2006 at 10:25:54 AM MST
(User Info)

Thanks - that sounds like a viable option also.
John

[ Parent ]

Re: fogged thermopane (3.00 / 0) (#10)
by johnlm on Tue Jan 24th, 2006 at 01:22:53 PM MST
(User Info)

I got the unit home - actually I bought 2 of the same size 34X76. The one I initially looked at and discussed above actually had about half of the seal totally loose (looks like sticky back adhesive black tape for the sealant) so I took the panes apart anc cleaned them up. There is a bit of etching on the glass but I reduced it considerably using tile spray and also a mild abrasive powder (bon amie). I get 80% light transmission through the cleaned up glass which is in the ballpark of what I see through normal double pane glass. The second unit was 3/16 thick double pane so it was heavier than h---. I havent looked at it real close yet but is is only mildly fogged. Havent decided what to do with it yet but these are reasonable chunks of glass considering $5.00 per unit. I havent decided yet whether to seal the the unit I took apart totally back together as described above with just normal (pick a real dry day) air inside or just mount it as slightly sealed storm window style.
Thanks for all the help.

John

Re: fogged thermopane (3.00 / 0) (#11)
by Volvo farmer on Wed Jan 25th, 2006 at 05:07:22 AM MST
(User Info)

There are glass shops out there that can professionally reseal these. I built a half dozen PV solar panels out of cells and old tempered windows that had failed like you describe. I took the two panes of glass in to them, they fitted a new aluminum spacer around the edges, poured a bunch of silica dessicant inside the aluminum, and resealed the whole thing with some sort of heat gun that melted the black sticky stuff in place.

There's not many glass guys who will do this anymore due to warranty issues and the fact that it's easier and less labor intensive to just buy factory-sealed panes with warranties than to reseal them.

Anyway, these glass guys I met were very interested in what I was doing and would seal up these 28x72 windows for about $30 each, but I think I was getting the "bro" deal. Call around, you might be able to find an old-timer who has the right tools and supplies to do these and might take pity on your project.

Volvo Farmer

May you always have success in your quest to irritate those who you despise. -Ben Goode
[ Parent ]

Re: fogged thermopane (3.00 / 0) (#12)
by GaryGary (gary@BuildItSolar.com) on Wed Jan 25th, 2006 at 03:48:15 PM MST
(User Info) http://www.BuildItSolar.com

Hi John,

Here is a thought.

Take the thermopane apart, and use each pane separately to make a batch heater that has twice the glazed area. This will get you a lot more hot water than the one double glazed panel. This might not work if the two panels that make up the thermopane are different, but you could probably determine this beforehand by looking at the edge of the panel.
Most commercial solar collector panels are single glazed.

You may have these already, but here are the rules of thumb for sizing batch heaters:

30 gallons of storage person (eg family of 3 = 90 gals)
not more than 2.5 gallons of storage per sqft of glazing.

(so, 36 sqft for the family of 3, 90 gallon example)

This is for a "temperate" climate.
Colder climates want more glazing per gallon of storage, warm climates less.

If you have not settled on a batch heater plan, I have a bunch of free ones on my site here:
http://www.builditsolar.com/Projects/WaterHeating/water_heating.htm

I would be nice if some inventive Otherpower person could figure out a way to automate the lid on the Maine Solar design (at the link above) -- I think this would be a real winner. Maybe a PV panel powered tiny winch? or?

There is a great book on batch solar heaters called: "The Integeral Passive Solar Water Heater Book", David Bainbridge. Its out of print, but may be available on Amazon.com used books or the like.

Gary
Gary gary@BuildItSolar.com www.BuildItSolar.com

Re: fogged thermopane (3.00 / 0) (#16)
by johnlm on Tue Jan 31st, 2006 at 08:34:36 AM MST
(User Info)

Gary,
I have been brainstorming for awhile on how to automate a lid to close at night, or maybe an insulative blanket that gets pulled across the inside of the glazing at night. The sensing electronics would likely be photocell controlled. The lid closing approach might be simpler but I worry about having a lid sticking up in the air when we get some of these 50 to 70 mph chinook wind gusts during the winter.
Im still in the thinking about it stage.

By the way I think I saw your site from a search I did a few weeks ago. Very handy site.

Thanks
John

[ Parent ]

Re: fogged thermopane (3.00 / 0) (#13)
by Clifford on Wed Jan 25th, 2006 at 11:00:50 PM MST
(User Info)

A few years ago I replaced the window felt on my car.

At the "Car Detail Shop", they had a claulking tube of this black tar like stuff... I guess I should have written down what was in it, but I must admit that it was the best caulking/sealant/glue that I've ever seen. Anyway, rather than using Silicone or something for the sealant, try to find a "professional" sealant.

Typically I've observed clouding in the windows after the seals are broken.. I guess that it what you've been talking about with the etching. No idea if you can reseal your window on a low humidity day (not sure if you need a hot low humidity day or a cold low humidity day... in theory, if you have, say 50% humidity at 33 degrees and 50% humidity at 90 degrees, you actually have a much lower humidity on the cold day.

As someone mentioned, it might be worth comparing single paned to double paned Hot Water collectors. Presumably you wouldn't worry too much about night-time losses at the panels.

Re: fogged thermopane (3.00 / 0) (#14)
by zap (bell47g5a at comcast dot net) on Wed Jan 25th, 2006 at 11:43:02 PM MST
(User Info)

Where John lives humidity isn't usually much of a big concern! : )

zap
[ Parent ]

Re: fogged thermopane (3.00 / 0) (#15)
by Clifford on Thu Jan 26th, 2006 at 09:51:26 PM MST
(User Info)

However, humidity may be a concern when building air-filled sealed double paned windows.

Keep in mind, the moisture carrying content of the air drops as the temperature drops. And, of course, pressure increases as the temperature goes up.

[ Parent ]

fogged thermopane | 16 comments (16 topical, 0 editorial)

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