Have any of you had any experience with fixing a window with condensation?
I have a 106″ x 58″ double pane window in my living room (not safety glass) that gets condensation on a hot day. To replace this would cost over $1000 because the installation cost is ½ of the price because of the location.
I have talked to a local company who say they can fix the problem. What they do is drill a small hole in each of the four inside corners of the window. They then insert a small wand and wash the inside of the window and dry it. Then they spray a ‘no fog’ solution on the inside of the window. Then they plug the two bottom corner holes with a silicon of some type and leave the top two holes open.
They claim that on a hot day the moisture between the panes evaporates via the top two holes leaving the window clear. This comes with a 20 year guarantee at a cost of approx. $0.75 per foot, $300 total.
My concerns are:
- will it solve the problem?
- will drilling the holes cause stress points in the window which will encourage it to crack/break in the future?
Has anyone had any experience with this?
Thanks
JobJars
Replies
If they gaurentee it you have nothing to lose.
I doubt it'll work. If there is a white haze the glass has been acid etched, must be a heck of a wash if they can get that off... and having permenent holes drilled trough the glass will effectively take you back to single pane efficenciey.
The glass is not etched. I agree that the hole drilling will absolutely screw up the seal integrity. I think I will live with it as long as I can then replace.
Thanks
I drilled holes in some windows I have in which the seal had leaked and condensation had formed. I decided to try it when I found that Pella windows actually have a small vent between their window panes.
After drilling one hole in the top of the window and another diagonally in a lower corner the window dried up after a few days of sunshine. I used a drill bit which was made to do glass, ceramics, etc. It takes a while to do the drilling depending on the thickness of the glass. I actually did the same thing to a small picture window in a rental house two days ago. As the seal is already broken what do you have to lose.
Throw rock, call ins co.
Joe H
Thanks Joe. Thought about that - for a minute.
You are a funny man.Jack of all trades and master of none - you got a problem with that?
Your window fogs because the seal between the panes is broken and nothing short of a replacement will fix the real problem.
Beer was created so carpenters wouldn't rule the world.
Thanks Don, I realize that a new window would be the ultimate fix, I was just wondering if anyone else has tried this (new solution???)
Well, I shouldn't have said the ONLY fix it total replacement. Another option is disecting the window until (if?) the glass can be removed. The adhesive strips that seal and separate the glass is available so if someone wanted to, the glass could be reused. Very time consuming and not a sure bet.
If you want to try something new it can't be worse than what you have now. :-)
Best of luck
Beer was created so carpenters wouldn't rule the world.
YOU MUST BE SMOKING SOMETHING FUNNY.... IG PANES ARE NOT SEALED BY A "TAPE" IT CAN NOT BE REPAIRED OR RE-USED.... NEW GLASS OR SASH IS THE ONLY OPTION...
This is a bit off the precise topic, but since it was suggested that the homeowner might consider taking the IGU apart, cleaning the glass, and then reassembling it, I think that an explanation of spacer systems - or how the two lites are joined together - might be of interest to some folks.<!----><!----><!---->
Once upon a time, virtually all dual pane windows were made with aluminum spacer bar and a sealant/adhesive to stick the glass to the aluminum spacer bar. These early IG's were almost always “single-seal” systems that used a single “layer” of sealant to join the glass to the spacer. <!----><!---->
There were several different sealant products used for that purpose, primarily organics - such as hot-melt butyl, some urethane products, polysulfides, and some inorganic systems as well such as various silicones. Some of the sealants worked okay and some of the sealants worked a good bit less than okay – ultimately none of them worked as well as needed.<!----><!---->
The primary problem was that the products that did a good job of keeping moisture out of the space between the glass panes was often not a particularly strong structural product or else it didn’t have a high enough adhesion.
On the other hand, products that had great adhesion or that provided a good bit of structural support (to hold the glass solidly to the spacer) were often porous – moisture and sometimes even air could eventually pass thru the material. When manufacturers began to use an argon gas-fill between the panes the spacer materials of the time often did a poor job of retaining that fill for a significant period. <!----><!---->
Manufacturers were aware that the materials that were being used were simply not working as well as they needed to be working in order to have a satisfactory product. Subsequently a great deal of research went into finding a better method of building IGU’s.<!----><!---->
As a result of that research (which is still on going) there are about a half-a-dozen or so types of residential window system IG spacers in use today that fall under three broad categories:<!----><!---->
Metallic systems, non-metallic systems, and those systems that have attributes of both metallic and non-metallic…and within those categories you would find folks in the industry that may not even agree on that much.<!----><!---->
In high-end metallic systems, very thin-walled stainless steel is the metal of choice; although aluminum is still found in lower end, and occasionally, although rarely, in higher-end systems. Stainless steel has significantly less heat conductivity than does aluminum and it is also a much more physically stable material. In addition, the metallic spacer system adds some structural support to the IG which is something that the non-metallic systems do not…depending on whose window system is being discussed; the additional structural support may not be an issue at all.<!----><!---->
Most (but not all) of today’s metallic systems (and non-metallic as well) are dual seal systems. They combine two materials to seal the IG rather than the single-seal of the past. The best primary (or moisture-blocking) seal in use today is polyisobutylene or PIB. PIB is the only butyl available today that is impermeable to gas and moisture. <!----><!---->
The secondary, or structural part, of the seal, is usually silicone – used for its strength and demonstrated long-term performance – basically, it is the silicone that keeps the two lites attached to the spacer.<!----><!---->
There are still manufacturers who use hot melt butyls, polysulfides, and other materials for both the primary and secondary seals, with varied success.<!----><!---->
Probably the most widely used spacer system on the market today is a hybrid system of metal and non-metal components. This system has a “U-shaped” metal spacer that is covered by a non-metal component. The idea of the U-shape, versus the box shape of most metallic systems, is that when the glass flexes with changes in air pressure the edges of spacer can flex along with the glass. This system can be used with PIB/silicone but it is also widely used with other sealants as well. Also, the metal part of the system may be stainless steel (manufacturer recommended), but many window companies who use this system use a tin-plate steel rather than stainless…it has been reported that it can affect performance.<!----><!---->
Taking apart and “repairing” an IGU is not a DIY project. The materials used in spacer construction are often not readily available or else can only be purchased in bulk. In addition, the IG is filled with desiccant to keep the space dry. When a homeowner (or anyone) opens an IGU, the desiccant will completely saturate with moisture in a very short time. Even if the homeowner cleans the glass thoroughly and closes the IGU, the desiccant will release moisture inside the space in the right conditions – negating the “fix”.<!----><!---->
Okay – too long again. <!----><!---->
Hopefully, it made some sense.<!----><!---->
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Edited 11/5/2006 9:52 pm ET by Oberon
Interesting -- Has anyone tried making sealed glass units entirely out of glass? Two sheets with glass spacers, then melt th edges to fuse the whole shebang into one piece. Sort of like a light bulb or vacuum tube.
-- J.S.
I am not sure.But I think that the orginal thermopane units where made that way that they had a bad habbit of cracking.
Yes and BillHartman was exactly correct. Some of the earliest thermopane windows were made as you suggested but they were a number of technological problems with those units.
As a rule, a dual pane window isn't really much more energy efficient than a good (tight) single pane with good (tight) storm window. The real advantage of the dual pane is the ability to include a LowE coating and fill the space with an inert gas - that is what really makes a dual pane window a big improvement over single pane with storm.
Interesting -- Would it be possible to do a low-E coating and inert gas in small all-glass units? If they were, say, 6" by 9", that should be small enough to handle the cracking and barometric pressure issues. Then we'd need to devise some way of making a true divided lite sash with equivalent R-value thru the muntins.... Probably easier than making the small all-glass sealed lites.
-- J.S.
No one that I am aware of does all-glass anymore. In order to make an "all glass" IG it is necessary to position the two "face" lites and then to place the smaller strips around all four edges and then to heat the edges of the glass sufficiently to fuse the strips to the face pieces.
There is no way to have desiccant between the lites so that any residual moisture (desiccant would soak up that moisture) that was in the space when it was sealed then stays in the space. This results in interior condensation much more readily than in a multi-part IGU system.
In addition, the residual moisture would eventually corrode the LowE coating - IF the coating actually survived the rigors of the glass being fused.
Argon fill? No way to do it with an all-glass IG unit.
A good many technical problems to manufacture a glass unit that is in most ways inferior to a modern multi-part IGU.
If your concern is the smaller units - for TDL's, they can be easily manufactured using conventional technology.
Have you never seen how a double pain window is put together? Glass shops make them all the time and it's definitely not rocket science. :-)
Beer was created so carpenters wouldn't rule the world.
Read oberon thread..... I have been in the window/ glass repacement business for 25 yrs. If it were that easy, don't you think anyone with a work bench and a putty knife would be doing it. I have been to MARVIN, JELD-WEN, CARADCO, AND ANDERSEN PLANTS FOR ONE WEEK EACH. I know and understand the process. For you to suggest it is not "rocket science" and easy and anyone could do it is the nuttiest thing I have read here in a long time. You should look into a wrm-up act in front of Seinfeld of Leno. New glass or sash is the only practical solution. Besides, if your proposal is followed.....how much warranty do you get? Even replacement glass from a "glass house" has little or no warranty.
Besides, if your proposal is followed.....how much warranty do you get? Even replacement glass from a "glass house" has little or no warranty.
For such a glass guru aparently you haven't repaired many windows. What do you do when a model is no longer available, just replace the whole unit? And you only replace glass when your supplier will provide the waranty? Blow smoke up someone else's ars.
Beer was created so carpenters wouldn't rule the world.
Repairing a window is a different matter from replacing glass. If a model is no longer made..... there are a number of options. I have sometimes used other companies windows that are inter changable. The best option is to allways use the original window companies glass with a solid warranty. To cover your first point.... the number is in the thousands. There are allways many ways to solve a problem. I can tell you one thing..... "adhesive strips" are not used under any condition in the making of I.G.U.'s. It sounds like a band-aid...not a cure
A few thoughts on a purely hypothetical homeowner DIY repair of a failed IG in a comparable window.
First, this is a big window - 5'x9' - 45 sqft. Glass weighs 155lbs per cubic foot. Assuming two lites at 1/4", that makes this window about 150lbs. Certainly not an insurmountable weight, but this is 150lbs in two large sheets of raw glass that can break if improperly handled resulting in a number of large and relatively heavy shards of very sharp glass that will cut - possibly very severely.
Assuming that the homeowner is confident enough in his or her own ability to handle the glass, the next step is determining if this is a direct set or sash-in-frame unit - how this thing is mounted in the hole-in-the-wall. The type of mounting obviously makes a big difference in how to remove it from the opening. Again, not an insurmountable problem - especially if it is a direct-set - removal is a relatively simple and straight forward procedure and someone with even limited DIY skills should be able to determine how it is done. Of course there is still the factor of 150lbs and 45 sqft of glass to contend with.
Going to wear gloves? I would certainly suggest it since the glass edges are going to be very sharp. Professional glass handlers know that the best way to avoid cuts when handling raw glass that size is to make sure that the glass can't slide thru the gloved hand - because if it does slide it likely will be "thru the glove and into the hand". So, the homeowner needs to have a pair of gloves that are cut resistant, pliable, and non-slippery.
At this point I would suggest a trip to the local rental center to check on a pair of glass-handling suction cups. They will make the removal of the window MUCH easier and safer. I don't know what the rental fee might be, but it is worth it whatever the cost. A set of professional glass handling suction cups will cost around $200 if the homeowner decides that he wants to have a set of his own.
Okay, the glass is out of the wall - safely - so now where does he put it? This thing is still 9' x 5' and it has to be laid flat in order to separate the two lites from the spacer - and being glass - it has to be well supported or else it may break from its own weight. Glass actually has a fair bit of structural strength when vertical - it has very little structural strength when laid flat. There is a very good reason why glass companies and window companies ship glass vertically.
Since the homeowner has previously built a table to support the glass so this isn't a problem - and having a location to actually work on a window this size is certainly convenient.
Now comes the hardest part of the repair...taking the thing apart. This isn't fun - I have done it. Depending on what sort of spacer system was used in the IG construction will determine how it comes apart. If the homeowner determines that the IGU has a non-metallic spacer - then there is no way to get the glass apart without destroying the spacer - which means that the spacer will have to be replaced. So the next step will be finding a source for new spacer material - this is going to be at best difficult and depending on what spacer was used in this case it may not be even possible. Even if a homeowner could find the material, depending on the spacer type, it may be possible to apply it by hand or it may require a couple of hundred thousand dollars for the equipment required to place the spacer material.
However, since this is an older window, it is likely that it is a single seal system with an aluminum spacer - the easiest to replace. So the homeowner uses a knife to cut the bond between the glass and the spacer - being very careful to avoid running skin along the edge of the glass - still sharp - and being careful to avoid cutting into the alouminum spacer itself - it is soft aluminum afterall.
However, it is possible - depending on the spacer material - that the knife simply isn't working - not cutting the seal. In that case the homeowner may try a solvent to soften the spacer material prior to cutting it away. Isopropyl alcohol may work on some of the organics - and as a bonus it will also tend to lubricate the area between the glass and spacer making removal easier (but not easy).
Once the top lite has been cut away it is a relatively simple procedure to clean the old sealant from both the edge of the glass and from the spacer - "relatively simple" not necessarily implying either easy or simple - it is a PITA.
Once both lites are off the spacer, and assuming that neither the spacer nor the glass was damaged by the procedure, it is time to rebilud the IG. First, what sealant material does the homeowner want to use to seal the aluminum spacer to the glass? If the homeowner doesn't know what original sealant was removed there is a very real likelihood that the new sealant may not be compatible with the old material thus preventing a seal from forming.
If the homeowner decides to use a silicone to seal the glass to the spacer - what type of silicone? ALL silicones pass moisture - some more readily than others. Try one of the other spacer sealant materials? Again, where is he going to get them and how is he going to apply them? There are hand-applicated materials available and glass shops do make IG's using those materials - and no doubt the glass shop will be eager to sell these materials to any homeowner who decides to build their own IG unit.
Finally, even if the homeowner does manage to complete the "repair" - what is the likelyhood that he has done so without allowing at least a small area where air and moisture can penetrate into the enclosed space? When reusing the original spacer the likelihhod that there are no leaks is pretty much zero - and since a failed seal is what caused the original problem...
Also, while the unit was open the desiccant became fully saturated with moisture - moisture that will be released between the lites in the right weather conditions.
Suggesting that a homeowner attempt a DIY repair of an IG (especially of one this size) is probably not the best idea - and to paraphrase your earlier post, it would be time consuming and results may not be adequate - to which I would certainly agree.
Edited 11/10/2006 8:55 am ET by Oberon
Edited 11/10/2006 9:05 am ET by Oberon
Interesting desription on redoing a unit... as we had to replace a unit a couple of years ago that had everyone scratching their heads till we got it out.
We had a 2 year old fogged 6' x 6' Andersen direct set unit up about 15' interior and 30' exterior. The logo was on the wrong side and backwards???? No one knew nothing... must have been a mfg screwup but this stank to high heaven as cardinal glass rarely fails in 2 years for no reason at all.
Well when we got the unit out the birds started singing... as I was on fire, screaming mad... Seems the builder broke the outside pane and had a local glass co uninstall unit cut off broken glass side and replace with a smear of butyl to seal.
Seems no one really cared that when 4 of us where up a scaffold wrestling out one heavy piece of glass with suction cups the only thing bringing the outside pane along with the inside pane was a crappy caulk job... No one was hurt and the job was finished without tragedy but had the seal let loose a 6 x 6 piece of glass falling 15' is a day I don't want to have.
Oh and Andersen paid the entire bill for labor and new replacement glass, well over a grand... and homeowner and builder knew Andersen was getting a screwing but never realized or cared someone could have been hurt bad.
That is frightening...and certainly a dangerous situation. You really were lucky that that outer lite didn't simply fall off before you discovered what you were dealing with.
I can imagine that you handled that unit very carefully when you realized what was the issue! Good job getting it out and no one getting hurt. It sometimes amazes me how people want so badly to "pretend" that they are unaware of a problem or to something that they know is wrong that they would actually risk someone else being injured in order to cover their own behind and to not admit that they made a mistake.
I certainly understand why you were puzzled when you saw the AW logo in the wrong location. Andersen is amazingly careful to ensure that their window logo is in the correct position and they almost never have a logo that is incorrectly located.
Almost never is right... Buttt and you'd know there would be a but.
Had a 3' full round unit in an attic that was totally inaccessable. Builder painted it black and it cracked. DUH! Well he spent the better part of a day cutting his way through insulation, drywall, roof sheathing and trusses to get to the unit. We finally got the old glass unit out and the new one in... went up the ladder to clean the exterior and when I hit it with cleaner it turned purple... They glazed the low-e coating on the exterior...
Just when I think I've seen it all and know what to look for, a new level of WTF crops up.
Edited 11/11/2006 6:41 pm ET by sledgehammer
Well, luckily it was an "easy" location? (not)
I think that there is a rule of nature that states if there is a problem with one part in 100, that part will be the toughest to replace!
If it's just condensation and the glass isn't etched, you can probably just drill your own top holes and test their theory. Can't hurt -- if it doesn't work you're into a full replacement anyhow.
-- J.S.
You have a point. Since I don't believe that they can wash the inside of the window anyway and it is not etched or streaky from the condensation when it appears, I guess I have nothing to lose. But you know, I really think that the window will still collect condensation on those hot sunny days.
Oh well, drilling holes will cost me nothing and worst case scenerio is that I replace the window anyway.
Thanks
...you can probably just drill your own top holes and test their theory...
Since I've never drilled holes in glass before, how does one go about it?
>>> Since I've never drilled holes in glass before, how does one go about it?
Diamond drill bits, moderate speed, plenty of water to cool it. Steady hand.
However, this whole experiment is too fishy for me.
Oh, no, not through the glass. The way to go for small holes accessing the interior space would be to drill thru the aluminum trim on a diagonal. Then drill the surface square on, and tap it so you can cover the holes using matching setscrews. You'd need to find a cross section drawing for the unit so as to be sure to miss the edge of the glass.
Another thought if you want to experiment would be to make both top and bottom holes, dehumidify the air in the room, and use your shop vac on the bottom holes to help pull new dry air into the unit.
It is possible to drill glass using diamond bits, or a small piece of tube and valve grinding compound. You have to keep it cool, it takes a long time, and the end result won't look as good as a plugged hole in the trim.
-- J.S.
A few thoughts:
First, you have condensation between the lites because of a breach in the seal that separates the two lites. This breach has allowed moisture between the lites. In the right weather conditions, you have condensation.
I am thinking that since you are seeing between-glass condensation on hot days, then you are seeing the haze on the inner pane of glass? While your home air conditioner is keeping the inside of your home cool, it is also lowering the temperature of the inner lite to below the dew point of the air between the lites. That is what is causing the condensation to form on the glass.
I am curious though - is it specifically hot days or is it hot and sunny days? Do you notice that the haze is on the glass primarily when the sun is shining on the window?
Second, your dual pane window was manufactured with a desiccant in the spacer that keeps the two lites apart. Depending on who made the IGU (dual pane - Insulating Glass Unit) and how it was made would depend on how much desiccant is present. Ultimately, the seal breach has allowed enough moisture between the lites to saturate the desiccant so that it is no longer effective as a drying agent. As long as the desiccant is able to hold enough moisture to keep the dew point of the air in the space above the temperature of the glass, you won't have a condensation problem. But, unfortunately, your window is apparently past that point.
The folks who offer to "de-fog" your windows have an interesting gimmick. They drill holes in the glass, suck out the excess moisture, "clean" the glass and then apply an anti-fog solution between the lites. Personally, I would love to see how they clean the area between the lites in a window the size of yours using little wands that fit thru the small holes that they drill in the glass. Imagine trying to clean the surface of your window with a Q-tip on the end of a springy 5 or 6 foot rod? That is what they are suggesting that they will do for you, and they are suggesting that they can reach all over the inside surface of the glass with that set up...as I said – something I would love to watch being done.
Also, what do they propose doing about the seal breach? Remember that that was the original cause of the problem in the first place. What they propose to do about that is....nothing at all because there is nothing that they can do about it. No matter what they do to your window, the original cause of the problem remains unchanged.
Ultimately, from an energy standpoint, the fact that your window has interior condensation does not affect the performance of the unit. If they drill holes in the window, it has very little effect the energy performance either - unless the window has a LowE coating or if it was originally filled with argon (or some other) gas. In those cases, a seal breach will affect the performance of the unit because it would have allowed the gas to escape (if it was there in the first place) and if you have moisture between the lites, the LowE coating will eventually corrode because of it.
And, as sledgehammer already pointed out, if the moisture has caused etching on the interior glass surface (and that can happen) then the “fog-out” folks won’t be able to do a thing about that.
Here’s a suggestion – next time you see the condensation, use a portable hair dryer to warm up the glass where you see the moisture. Depending on the severity of the problem you might be quite pleased with the results and at a cost a heck of a lot less than $300 for a band-aid solution.
I can go into the technical aspects of how they remove the moisture - but this thing is already long enough!
Thanks for the detail Oberon. Yes the condensation is on the inside window. I say condensation but a heavy haze would also describe it. We live in Victoria, BC and most people here don't have A/C. But in late july to mid-Aug when the sun is on that window we get the haze.
I am going to call this guy tomorrow and ask him to explain to me in detail how they propose to 'clean and dry' the glass. I had to laugh when I pictured what you said about a Q-tip on the end of a springy rod - I have a hard enough time getting a window clean using windex and lots of paper towels. I will send you another note tomorrow and let you know what he says.
Doesn't sound like anyone else has ever heard about this type of fix and I guess that doesn't surprise me.
Thanks again
http://www.ccwwi.com/Default.htmlHere is one company that does this and franchise it.
It sounds like it could work if it is a legitimate business, but I'd want to see it with my own eyes first. How 'bout asking them for references, and going to see some yourself?
As far as drilling holes in the glass, it will not cause stress points nor weaken it.
Thanks Wayne. I am comforted to learn that the glass will not be stressed if drilled. I have two of these windows in the front of my house. Two years ago the other window started a little crack from the edge of one side and after three days it had expanded into a jagged crack across the entire window. That why I know how much it costs to replace.
When I speak with him tomorrow I will ask him for references and follow up on satisfaction.
Thanks again
As someone who works in this industry, I would be very skeptical of this fix. How long has this company been in buisness? Ask for referals that go back 5 years. How can they offer a 20 year guarantee when the best warranty you can get in the States on the original construction is 10 years, from a commercial fabricator. This sounds too good to be true.
If they do leave the "top holes open" they probably have a bridge in NE they can get you a great deal on. Insulated, or multiple pane glass works because of the air gap. If you eliminate the air gap you have a single pane window and a close fitting storm window. Replace the glass and/or the window and get a 25 or lifetime warranty. Please I would be interested in knowing the name of this company, or maybe I already know. Voodoo window cleaners,
It's not quite so all or nothing. I doubt that the thermal performance of the unit would be much better as is than it would be with a couple small holes in the top. And if you make the holes thru the aluminum trim, you can plug them with screws if you want.
It would be interesting to get a fair comparison between typical sealed double panes and properly installed storm windows. I'd expect the sealed units to be better, but not by a huge amount. The option to open and clean everything may well outweigh that extra bit of "R" for some folks.
-- J.S.
By defination, a storm window can only be 95% air tight. This is why you see the curved up lip at the bottom which is for drainage. If the holes are sealed again then the dead air space is not compromised, but the original post stated that the company was going to leave the top holes open. I would believe that this is so the HO would not see condensation anymore. The problem is that condensation is when warm air comes in contact with cold air and/or surfaces. Cleaning the glass will not change this, therefore the lack of condensation when they complete this process only removes the warmer glass and thus eliminates the insulating propery.
A couple tiny holes won't eliminate the insulating property of having two sheets of glass. They'll compromise it a little. How long does it take to get an air change thru them?
Conventional storm windows and traditional European casements with both inswing and outswing sash both insulate a lot better than single panes, but not quite as well as sealed units. There's no special magic that happens at the transition from a couple little holes to completely sealed.
-- J.S.
John,
Thanks for the explanation on where you envisioned drilling the holes. I thought of the same thing (drilling through the spacer material), but I figured it might be a real pain to gain access to it.
By the way, I concur with what you're saying regarding R-value and the small holes. By allowing a small amount of air exchange to occur, the insulative value is less than that of a sealed unit, but still much better than a single glaze configuration.
How is a thermo-pane supposed to work if there's air inside?
Most IGU's are sealed with air inside. Although argon or other inert gasses increase the energy efficiency of the units they aren't absolutely necessary.
Some IGU's are sealed in a vacuum chamber - this is primarily a third-party-manufacturer procedure and something that very few window companies do. Most window companies that manufacture their own IG units are not automated - and few of those that are - even those with some level of automation - use a vacuum chamber to seal their IGU's.
Although sealed in a vacuum chamber, that does not mean that there is a vacuum between the lites - rather the units are placed in the chamber and the air is evacuated to be replaced by whatever the manufacturer wishes to fill the space between the lites with. Usually argon or an argon/nitrogen mixture for dual pane units and often krypton or a krypton/argon mixture for triple pane units.
As I mentioned, the majority of window companies manufacture their own IGU (or dual pane) glass units. Most of the larger window companies buy their IGU's from an IGU manufacturer. The top IGU manufacturer uses the vacuum system exclusively - some of the smaller third-party IGU manufacturers do not.
Often when people buy windows they don't want to pay extra for the gas between the lites. In those cases, some IGU manufacturers (those with the vacuum chamber technology) replace the air with pure nitrogen in the vacuum chamber. But, since the majority of window companies don't use the vacuum chamber system, those windows are simply closed up with the air from the factory inside the unit.
For those window companies that still "hand-make" their IGU's adding argon is also an interesting exercise - they leave a gap in the spacer and quite literally "pour" the argon into the space between the lites. Since argon is heavier than air it displaces the air out the gap and replaces it. The window company then seals the gap - more or less.
Personally, I find the vacuum chamber a much more professional approach.
Hmmm -- Could they make a small all-glass krypton/argon unit, with relatively low pressure inside, and electrodes at the far edges? Hook 'em up to a neon sign transformer, and you have light at night.... ;-)
-- J.S.
Interesting thought! Argon and krypton are both inert (or noble) gasses - part of the group of gasses that also happens to include neon...coincidently enough.
Helium and neon are the two lighter gasses of the group whereas argon, krypton, xenon, and radon are the heavier gasses (heavier than air).
Currently argon, krypton, and even xenon are used in IGU construction to increase the energy performance of the unit - and as the molecular weight of the gas increases so does the ability to improve on energy performance.
So imagine a window company ultimately advertising that they use radon between the lites in an IGU - imagine the comments that that would bring!