Andersen glass failure due to negative pressure

napagirlJanuary 12, 2007

Oberon: This question is for you since you are very knowledgeable about windows. I just read your thesis on condensation, and all I can say is - "Wow!"

Getting back to my problem. We installed Andersen 400 series High Performance windows in 1989 and maybe 7-8 yrs later I noticed an oval pattern of condensation on the inside of the glass (not between the panes). I thought it was strange but since it wasn't between the glass I thought everything was okay. Fast forward to a few months ago and I discovered a diffent window had, indeed, failed (cloudiness and smears between the panes). I went to Andersen's website to notify them and to my surprise they mention the problem of the oval condensation in the center of the window!

I rec'd an email from their rep who said the oval condensation was probably an indication of negative pressure and I could tell by measuring the space between the glass at the edge and at the center of the window. (Do this by placing something on the outside [husband's finger] and your finger on the inside.) To my amazement more than half of our windows and three 36" French doors had almost no space between the glass in the center (3.5 mm on the edge and 14 mm in the center). His email also said that it could be repaired (and did not need to be replaced). Andersen then sent out a local contractor to assess the failure. To my delight this contractor said he would have the glass replaced; that if the difference was more than 4 mm Andersen will replace the glass.

Oberon, you probably know how the glass is repaired but for those of you reading this that don't know, I will tell you what I was told: They drill a small hole in the frame releasing the pressure and fill the space with air (not Argon gas as original), then plug the hole and in their words it's "still as good as the best windows on the market," stopping short of saying "as good as before the failure."

I hope that Andersen does indeed replace the glass, but on the chance that they won't, I want to know your opinion, re repair or replacement. The contractor was here on Jan 8th so I'm thinking it will be a while before I get any real confirmation from Andersen.

Sorry this is such a long message but I thought those of you with older Andersen windows would like to know my experience so far. I know they have made a lot of improvements since my windows were made in 1989, and I still think they make a good product.

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I think your rep is feeding you a line of doo-doo on the condensation between your panes of glass. search this forum and you will find answers on other threads about condensation between panes. The only way you can fix that is replace the glass.

I suggest you contact Andersen directly. Below is a link from their webpage with the phone# and a hecklist to fill out before you call

Here is a link that might be useful: Andersen webpage

    Bookmark   January 12, 2007 at 8:18AM
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see link below

Here is a link that might be useful: condensation

    Bookmark   January 12, 2007 at 8:23AM
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Sorry, maybe I wasn't clear in describing the problem. The oval pattern of condensation was on the INSIDE [OF THE HOUSE], NOT BETWEEN THE PANES of glass. This is caused by negative pressure (too much outside pressure pressing against the panes and collapsing the glass inward toward each other). Besides the condensation problem, the window has lost most of its R-value, the reason why you bought the window in the first place!

It would be difficult to know that your windows had this problem, unless it gets so bad that there is almost NO SPACE between the glass, allowing condensation to form inside the house. I didn't know I had a problem because in the winter we don't heat the unoccupied rooms in the house. You won't have condensation if the room temperature is close to the outside temperature. However, I should have picked up on the fact that originally the removeable grids were very tight against the glass and for many years now the grids have been very loose.

I did make a mistake in my original post: I erroneously switched the measurements on the glass. I should have said the window thickness measured only 3.5 mm in the center and 14 mm on the edges.

The email from Anderson said they will replace the one window that has condensation BETWEEN the panes of glass. That window showed no negative pressure, so I'm assuming it used to have negative pressure until the seal finally broke and allowed the pressure to equalize, thus popping the glass back out and allowing moisture to form between the panes.

My reason for posting this message was to get Oberon's opinion regarding REPAIR vs. REPLACEMENT of windows with negative pressure, and also to let everyone know about this condition, and what to look for.

    Bookmark   January 12, 2007 at 3:44PM
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Napagirl, It sounds to me like you're having negative pressure issues with your glass as stated by the factory rep. I own a door & window company here in MN and have dealt with Andersen for a long time. I've been in the trade here since 1974 and love every minute of it. Andersen ha always been a very stand-up company to deal with in the cases Ive had. I know this isnÂt what everyone else thinks, but itÂs how things have been for me. Oberon is my Idol when it comes to glass. Over the many years I've spent with him on numerous sites answering door & window questions. I've come to know him very well and consumed large amounts of data from him. He's definitely the one I go to with all my questions. I can tell you first hand your glass was built in an area that is at a lower sea level than you are.

Most Insulated Glass Units (IGU) are filled with Argon or Krypton gas. They are both considered being "Inert Gases" and are used quite regularly in the industry. Argon is heavier than air and each molecule is larger, not smaller than an air molecule. When your glass was made it was more than likely built in a controlled environment that filled the IGU with Argon and sealed it shut. Ounce this is done and sealed the Argon level inside the glass is much higher than the air we breathe outside the glass. The barometric pressure is also sealed up inside matching the area where it was made. In most cases the glass was built in a lower climate and usually wonÂt be shipped to an area above 3000 ft. Usually if they are shipped over the Rockies, lets say from Minneapolis to L.A., theyÂre shipped with Capillary Tubes. These tubes are installed on the IGUs topside to let the inside air pressure adjust to the different altitudes it will pass through. Since the Argon is heavier than air it wonÂt be able to flow upwards out the tube. Capillary tubes remain open to allow for barometric pressure changes. Usually the glass has a resting period to equalize completely.

Sealed insulating glass units have always had to deal with changes in pressure and temperature. Pressure changes can be the result of changing barometric pressure, changes in altitude or changes in temperature. Pressure rises and temperature drops will cause a sealed unit to bow inwards, whereas pressure decreases and temperature increases will cause units to bow outwards. It can also be attributed to the loss of your fill gas such as Argon.

I donÂt know where youÂre located so I canÂt say itÂs a problem from shipping the IGUÂs over the mountains. In any case your completely fine by having them just replace your glass packs in each window. The rest of the window is completely fine and needs no attention from the glass issues. We replace glass all the time for all sorts of reasons. So if theyÂll replace them at no expense to you, jump on it. Just make sure they give you some type of warranty on your new glass and have it dated, just in case!!! Hope this helped!!

    Bookmark   January 13, 2007 at 11:43AM
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Guy Exterior Man:
Thank you for responding. I'm located in Napa, CA, on the other side of the Rockies.

After talking with my husband again, its his understanding that Andersen will replace the glass units that have a tolerance greater than 4 mm in thickness and repair the units that are less than 4 mm in thickness (between the outer edge and center of the glass). Many of our windows have a 7, 8 or 9 mm difference between the outer edge and center; some appear to be almost touching in the center.

Regarding the Capillary Tubes you talked about --

Does this mean that my CT's are no longer open, and thus won't allow for barometic pressure changes which resulted in the collapsed glass?

When the negative pressure gets too great, is that what causes the IGU to loose its seal and get condensation between the panes of glass?

Also, what do you think of Andersen's new exterior coating (titanium dio...?) that causes the sun to loosen the dirt and the rain to wash the glass clean? Does it really work?

    Bookmark   January 13, 2007 at 4:28PM
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Hi napagirl,

What Guy brought up in his earlier post is the more common understanding of the term "negative pressure" when discussing window performance.

Curiously, and as Guy also mentioned, both he and I have had the opportunity to share ideas on this site and a couple of others for several years - the "guy" knows his stuff (pun was somewhat unavoidable - but sorry Guy, I couldnt resist!) - but, what you have experienced is not the more common definition of "negative pressure", which is what Guy described, but a different problem relating to how your windows were originally manufactured. What is interesting to me is that I don't believe that I have ever seen your specific question on any site (that I can remember), but I do happen to know what it is that you are describing as happening with your windows.

First, the collapsing phenomenon that you have experienced is actually related to a higher quality IGU (go figure) from the timeframe and technology level from when they were manufactured.

Even today, less than half of all dual pane IGUs have argon or any other gas fill between the lites. At the time your windows were manufactured the percentage was much smaller yet. Your windows, on the other hand, were made with 100% argon fill and the reason that I happen to know this is because if they werent, then you would not have had the collapsed IGU that you are now experiencing.

Ever hear anyone say that insulating glass windows have a "vacuum" between the lites? Well, they dont intentionally have a vacuum between the lites, and while this is a not uncommon misconception, if they did happen to have a vacuum between the lites then the IGU would tend to collapse in on itself (sounding familiar?) just as you have experienced.

So, where did the vacuum come from? Well, it came about because the 100% argon between the glass panes in your windows decided that it would be better off with the 1% argon that is in the air that we breathe; and so, the little argon molecules packed up and moved out of the space. They have migrated out of the space, and since your windows have maintained their original air and moisture seal, nothing has gone in to that space to replace the lost argon thus a vacuum has developed between your lites.

On the positive side your IGU seals have performed well within the limits of the technology of the time and on the negative side well, you already know what the negative side is!

What the Andersen rep has proposed is common practice in "repairing" the particular problem that you have seen in your windows. The tech will drill a small hole in the frame allowing normal air to enter the IGU airspace which will then equalize pressure between the inside of the IGU and "normal" air pressure (remember Guy mentioned capillary tubes? Same idea, except that capillary tubes are never closed and in the case of your windows the technician will seal the hole after the IGU has reached air pressure equilibrium with normal air pressure).
Obvious question what will allowing air in that space do to your windows?

Well, first, the argon is already gone. With the glass close together because of the lost argon, the windows are less efficient. Allowing the airspace to normalize will actually increase the unit energy efficiency over what you have now.

Second, argon fill increases window efficiency linearly in other words more argon, more efficient performance and it is easily calculable a 100% argon fill increases energy efficiency by 16% - 50% argon fill increases energy efficiency by 8% - 25% argon fill increases energy performance by 4% - see the pattern? But, again, the argon from your units is gone and there really is no reliable way to refill the airspace in the field despite claims by some window "repair" folks that they can replenish argon fill (rip-off).

Third, since the air/moisture seal is intact, the desiccant in the spacer will absorb the small amount of moisture that will enter the airspace thru the small hole and in your environment you wont ever notice that little bit of moisture that entered.

There truly is no need to replace those windows that have collapsed inward and that have not displayed signs of between-the-lites moisture. The ones with seal failure need to be replaced.

As a final note, Guy mentioned that he has always had good luck with Andersen customer service. While I avoid discussing specific window companies and never compare different companies on line, I am going to say that in my opinion whatever someone thinks of Andersen, they do have the best customer service in the industry and if anyone is wondering no, I do not work for Andersen in any way, shape, or form.

And as a final note some folks might see the "solution" to your problem and think about the folks who offer to "repair" leaking IGUs by drilling a hole in the glass and installing a magic one-way valve that not only cures (according to the companies who offer this "service") moisture problems inside a failed IGU but also increase energy performance (?)Not the same thing and if anyone is curious about that particular industry I have definite opinions there as well.

Have a great day napagirl and great to see you around as well Guy!

    Bookmark   January 13, 2007 at 8:37PM
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And as finally a final note (again), the titanium dioxide coating that is on the newer Andersen products works very well.

There are two types of this coating on the market - the original version was "sprayed" on the glass surface while the glass was still molten - a pyrolytic coating.

The version on the Andersen glass is applied using a vacumm chamber process that makes for a much smoother coat (given at microscopic levels) and really excellent performance.

Andersen was the first window company in the world to offer the newer version of this coating.

    Bookmark   January 13, 2007 at 8:44PM
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Hi Oberon,

What a wealth of information, I am totally in awe of your knowledge! Thank you for explaining the cause of the negative pressure in my windows and the solution to fix them. I really, really appreciate your taking the time to explain everything.

Too bad the titanium dioxide coating wasn't available last February when I ordered $15K worth of Andersen windows & doors for our current remodel, especially the ones in the cupola on top of the roof!

Have a great day and thanks again for your response!

    Bookmark   January 13, 2007 at 10:20PM
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You are quite welcome napagirl.

Actually, it is possible that your windows have the coating - but they may not as well.

Andersen was shipping coated units for sometime before they actually started advertising the coating. The reason is that they wanted to make sure that their "older", non-coated, stock was used up before they began actually "selling" the coating...but coated glass was in the system a good while before they were advertising it.

I have been told that they were very careful to ensure that orders were either 100% coated or 100% non-coated before they were shipped in order to avoid the possibility that someone's home could have a coated window next to a non-coated window in the same wall. While the homeowner would never see the coating, it would be very possible to notice that one window was shedding water and the other wasn't shedding water after a rainstorm. That condition might look a bit odd - if only for a short time.

So, since it is always relatively warm where you are, you can check your newer windows by spraying them with a garden hose then watch the water flow on the glass. If the water beads up on the glass or seems a bit sluggish when flowing off the glass then you don't have the new coating. If there is no water beading and the water flows right off the window then you likely have the coating.

Good luck!

And as a final thought (I do that alot), I used to live in Ferndale (if you happen to know where that is) for about four years.

Have a great day!

    Bookmark   January 14, 2007 at 10:36AM
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Hey Oberon! It was great to hear you had a fun time watching the Gophers! My son and I are hoping to catch a game soon.

I'm curious about the Argon taking a trip to Hawaii and not writing home. I'm baffled as to how the Argon makes it out with-out any outside air displacing it? Since my practice is mainly the installation process I rely on your grand wisdom to fill my void. My only practical thought would be there was no Argon in the IGU from the start. Since I know most manufacturers will not ship Argon filled glass over the mountains. Does Andersen have a plant over the hills, or were they shipped from here? If they shipped out with capillary tubes, were they tipped over during the loading or unloading process and have everything leak out? Let me know what your theory might be?

My Blue Collar is showing again!! Guy

    Bookmark   January 15, 2007 at 8:45PM
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>This is caused by negative pressure (too much outside pressure pressing against the panes and collapsing the glass inward toward each other).

You're being lied to! The words are technically, but only technically, correct. They're making you think that the problem is OUTSIDE the window rather than INSIDE on purpose.

This is the reason I'm got going to spring for argon-filled double pane windows unless I can't get low-E without it. Basically what happened is that the argon in such high concentrations is better at diffusing across the glass barrier than gasses that are at lower concentrations in the atmosphere are at crossing into the window. The argon is trying to equalize with the exterior, leaving you with negative pressure that causes the glass to warp. It's a design flaw, having nothing to do with your house. Another poster and I had an argument about what would happen with argon-filled spaces between windows several years ago--I forget what he said, but I said that exactly this would happen, that the glass would warp because the argon went out faster than the others came in. (He said something somewhat close but not quite, but it didn't make sense to me--I think he got the argon going out but not the glass warping and the other gasses going in at a slower rate.)

Anyway, it has to do with partial pressures--the oxygen concentration outside the glass wants to be the same as the oxygen inside, the nitrogen and the nitrogen, the argon and the argon. The argon doesn't "care" how much oxygen is outside--it can't "see" it. Since there the imbalnace is a lot greater for argon, it "runs out" faster than other gasses come in, hence the apparent vacuum. (I know, terribly non-technical, but it should get the idea across.) If you left the pane alone long enough and it didn't fail, the pressure would eventually equalize with the exterior...and so would the levels of various gasses. Leaving you with a double-paned window with intact seals--and no argon!

If you have low levels of actual argon--that is, cruddy manufacturing--you won't get the glass deflection. But you also won't get any of the benefits.

The glass deflection itself can't be good for the glass--if nothing else, I wouldn't care to bump a window under those stresses. Plus, when the glass moves closer together, your insulation is decreased.

To me, argon is lose/lose. Snake oil in a window! If they get new/fancy cloatings, they could slow its rate of diffusion, but the windows would eventually have the same problems, and I don't like replacing my windows even every 15-20 years.

    Bookmark   January 15, 2007 at 9:57PM
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Reyesuela, for you to even post such absurd information is crazy. Oberon makes a living in the glass industry. It's his job to know all this technical data. We answer questions on a daily basis free of charge. We do it in our free time to help others get the proper information they need to solve their issues. It's people like you who cause all the frustration to others by posting this kind of information. All you do is make things worse for others who are trying to learn.

    Bookmark   January 16, 2007 at 6:47AM
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Hi Guy!

My daughter and I caught the Ala-Huntsville game earlier this year. Was actually a lot better than I expected it to be but then the Gophers did have five guys in Europe for the World Juniors so they were skating only three lines.

It was great fun!

And on to the window/IGU arena...

As you know, Andersen uses the Cardinal XL spacer system. Cardinal warranties that their system is able to go over the mountains while sealed - even when argon filled - they don't require cap-tubes for the transit. If the windows are destined to stay at high altitude then they will include cap-tubes in order to stay pressure equalized at those higher altitudes - but if only passing thru - no problem with seal failure.

On the Cardinal website there is a chart that discusses at what altitudes there needs to be cap-tubes used for the XL product. It also notes that if a window is built using an IGU with capillary tubes then there will be no argon fill. In that case the window would be filled with air. They will still use coated glass however since at higher elevation the air tends to be dry and the cap-tube does do a very nice job of preventing what little ambient moisture that there is from getting into the space - so that potential LowE coating corrosion is not considered to be an issue.

The reason that I knew (well "guessed" - but based on the facts as given) that Napagirls windows had 100% argon is because Andersen used a 100% fill at the time that the windows were manufactured and because if the windows had originally been air-filled (rather than argon filled) there would have been no IGU collapse.

In the case of argon migrating out of the airspace, it is simply that the higher percentage of argon in the space wants to reach equilibrium with the lower percentage of argon outside the space. The job of the spacer and especially the spacer seals is to ensure that this doesn't happen.

The seal systems of the time were relatively porous to argon but not necessarily to "air". It was entirely possible (obviously since it did happen!) for argon to migrate out of the space and yet the seals were still intact to where outside air would not replace the missing argon. This lead to a collapsed IGU since external pressure combined with an internal vacuum would allow the glass to collapse inwards.

The extent of this phenomena was very much dependent upon window size and profile, obviously.

With the newer spacer systems now on the market this type of window collapse is very much less common - and more commonly manufacture rather than materials related. Newer systems use materials that are capable of keeping the argon or krypton in the space between the glass much better than the older systems did. There is still some migration, but industry standard is currently 1% per year argon loss - again, knowing that you are already familiar with much of this information.

Have a great day!

    Bookmark   January 16, 2007 at 8:02AM
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A bit more of a follow-up...

Terms like "negative pressure" and "positive pressure" are used rather frequently in the window industry and not always meaning the same thing.

In the case of napagirl's windows, when the rep said "negative pressure" what he was describing was the slight vaccum between the lites of the IGU - even if he did mention that outside pressure was pushing them together. He had the right term but not necessarily the right idea.

When I first read reyesuela's response I also immediately took it as a comment on my or other poster's replies to the original question - but then on rereading it I realized that she was actually commenting on the original post by napagirl - and the comment from the Andersen rep. But I would suggest no one was "lying" to anyone - it was simply a misuse (or misunderstanding) of the terminology in question.

Ultimately, there was no reason for the tech rep to lie since they were going to fix the primary problem anyway.

As for "cruddy manufacturing" being related to lower levels of argon - I am assuming you are talking about initial fills - actually many window companies use gas mixtures when filling an IGU - on purpose. However, depending on "how" a window company fills their IGU's there can be a significant variation in the level of argon fill - and in this case - not on purpose.

Anyway, the most common mixture used in IGU manufacture is argon/nitrogen, but there are several other variations being used as well. And, as an aside, as I previously mentioned, not everyone wants to pay for argon fill and most windows manufactured today are not filled with an inert gas.

In the case of Andersen windows that are not argon filled, they are filled with 100% nitrogen rather than "ordinary" air.

And as a final aside, and a bit of trivia, ordinary light bulbs are basically a sealed glass container filled with argon in order to prolong the life of the filiment and to keep the filiment from combusting in the presense of oxygen. Point being that historically glass does a very good job of containing argon.

    Bookmark   January 16, 2007 at 8:38AM
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First, LET ME MAKE A CORRECTION. The Andersen rep DID NOT say, "too much outside pressure pressing against the panes," that was my poor choice of words to explain the negative pressure.

Thank you for telling me how to find out if my new windows have the Titanium Dioxide coating. I sprayed water on them like you said and ..... I AM SO HAPPY !!! The water just ran right off, very little was left on the glass. I sprayed one of the old windows (3-89) and the water beaded up and stayed on the glass. SIMPLY AMAZING! You really made my day!

Yes, I know where Ferndale is, on the coast just south of Eureka. In fact, DH and I stopped by on one of our many fishing trips up to the Klamath River. I seem to recall visiting a fern "grotto" there. It was quite lovely, a small canyon-like area with an abundance of native ferns. How long ago did you live there?

Have a great day!

    Bookmark   January 18, 2007 at 4:23AM
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I am happy to hear that your new windows are exactly what you wanted - but didn't know at the time to ask for at the time - very glad to hear it!

I last lived in Ferndale in 1989 - doesn't "feel" that long ago...

Anyway, I know the fern grotto quite well. Next time you are up that way, and if you have time, take a stroll thru the town. It is called the Victorian Village because of the architecture and it is worth a few minutes to explore. A truly beautiful little city.

Actually, Hollywood has used Ferndale as a "stand-in" for a New England town in several movies because it fits that part of the country quite well.

Have a great day!

    Bookmark   January 18, 2007 at 7:32AM
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Sorry! No, you were right on, Oberon--didn't mean to make you think for a second that I thought you were lying!

>In the case of napagirl's windows, when the rep said "negative pressure" what he was describing was the slight vaccum between the lites of the IGU - even if he did mention that outside pressure was pushing them together. He had the right term but not necessarily the right idea.

His term was right but the usage was definitely deceptive. The reason he'd use deceptive phrasing? 'Cuz if you fix it and the customer thinks it's weather or an act of God, the customer is grateful for the service. If the customer thinks it's the window co's fault, the customer is ticked. I didn't think he explicitly lied--I think he just chose words to make you think the cause was not really the window's fault. (It could also be that he really didn't understand what happened and thought it was an act of God himself, though.)

>And as a final aside, and a bit of trivia, ordinary light bulbs are basically a sealed glass container filled with argon in order to prolong the life of the filiment and to keep the filiment from combusting in the presense of oxygen. Point being that historically glass does a very good job of containing argon.

Lightbulbs also last only a couple of years because the filament goes, anyhow! Windows should last for 30, 50 years when maintained. I *really* think this is a case where people didn't stop and think through the physics of what they are doing.

I'd be curious to know what % argon is necessary to cause such obvious failures, though.... (Filling with nitrogen isn't bad, since the atmosphere's mostly nitrogen, anyhow. Not an enormous imbalace--air diffusing both directions should pretty much average out.)

    Bookmark   January 18, 2007 at 8:02AM
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Oberon: Thank you, Guy and Napagirl for the most helpful dialogue about escaped argon in IGUs.
After 35 years I am getting new windows and I want argon filled double panes with Cardinal soft LowE3-366 glass. The PVC windows would be made locally and the IGUs would also be assembled locally (Okanagan valley, BC)with Cardinal glass from Tumwater, WA. The local glass co is willing to use argon though they recommend against it because it seems to dissipate and cause panes to be stressed and buckle inward (as with Napagirl). They are, however, not willing to use the new E3 glass until it has been around for another 9 - 12 months.
Is the Cardinal XL edge still the one to use?
Any comments you can give will be much appreciated!

    Bookmark   February 23, 2007 at 2:26PM
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Hi Kyros,

The 366 glass is still relatively new so I can understand the window company's conservative take on that product.

The LoE366 uses three layers of silver in the coating - thus the "3" in 366. The "66" represents the visible transmittance for that particular coating.

This category of coatings was really developed for southern areas that have significant cooling requirements - especially from solar heat gain. If you are building in the Pacific Northwest then I would suggest that using a LowE2 coating would be a better bet.

While the 366 offers significant improvement in blocking solar heat gain, it offers only slight U-factor gain.

There are about eight or nine different window spacer systems currently in use by window manufacturers. Energy performance in a spacer is all about edge performance. The spacer material is going to pass heat - but how much heat the spacer passes is the question. As an energy performer, the XL probably ranks third, about 3 degrees or cooler at the edge than the top performer.

The LowE2 coating has a much greater effect on overall performance than does the spacer system, but that doesn't, by any means, mean to discount the contribution of the spacer.

Longevity and durability is a bit harder to rank, but I would suggest there are spacer systems that will last a long time, and there are spacer systems that aren't going to last a long time. The XL is in the "lasts a very long time" camp.

Although some window companies offer the consumer options about what spacer system to use, most don't have that option and if you want windows from a particular company then you have to trust that the company has made the best possible choice as to the materials that they use in their systems.

Per argon, I am comfortable that the better spacer systems (including XL) will do a very good job of argon retention. My daughter is building a home this summer - and I am sure it wouldn't surprise anyone to know that I had an input in window selection. Her windows will be argon filled and I am very comfortable with that decision.

    Bookmark   February 23, 2007 at 7:56PM
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Thanks Oberon,

I stumbled across this site and discovered that I have the same problem as napgirl. My windows also are Anderson and my home was built in 1989. I have carefully read this column and have learned a lot. I do have a question on repairing the collapsed glass. I had a repairman sent by Anderson come out and told me that the windows that can be opened would have a hole drilled through the side of the window "frame" to allow air to "inflate" the the glass. This hole would then be sealed with silicone and a plastic plug would be inserted in the frame. This sounds like a good procedure to me. However, on the windows that do not open, they are fixed, he would drill a hole in the glass, allow it to "inflate" and then seal the hole. I am not sure how he could do that.

What do you think? I really appreciate your help.


    Bookmark   March 24, 2007 at 2:00AM
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Just saw your post and would like to comment re the fixed (or stationary) windows. You've got it wrong when you said he would drill a hole in the GLASS. Both the operable and fixed units are repaired in the same way. The only difference is the wood trim (stop) inside the house has to be removed exposing the frame.

Was any of your collapsed glass greater than 4mm? We were told that anything greater than 4mm would be replaced, not repaired. The glass in many of our windows was almost touching, and therefore they're going to replace it.

Also, you may not be aware and the repairman might not know, but the color of the 1989 glass was changed around 1992-1994. I know this because we bought some at that time and the new glass was noticeably darker. For that reason, we are also replacing, at our expense, the 6 sashes that have not failed so they will all be the same.

Sorry I didn't see your post earlier. I'm usually at the kitchen forum and not over here.

    Bookmark   April 20, 2007 at 10:27PM
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Thanks for your comments. The repairman who came out to my house to analyze my windows told me that he will drill a tiny hole in the GLASS in the fixed units to equalize the pressure. This doesn't seem right to me and I am going to call Anderson to check it out.

Actually, almost all of my windows were "touching" with "0" measurements on a few and 2-3 mm on the others. Anderson did not offer to replace any of these, only to repair them. I will question them about that also.

Thanks for making me aware of the different glass color too!

    Bookmark   April 27, 2007 at 1:20AM
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I know I'm a year late but here is some more info, Andersen, Pella, Marvin and many others all use the same glass maker called Cardinal. There will be a CIG stamped in the corner of each window. This colapsed glass problem was from 1989-1992. All the companies had this problem and only Andersen has either replaced the faulty windows or repaired them with a procedure payed to Andersen from Cardinal. The others have just ignored it. The repair procedure works 99% of the time and brings the glass closely back to its original space. The drilling of a small hole into the glass is a newer procedure that works but if not carefull the Tech could break the pane. Now another problem they had is when the two panes touch together and some have been known to crack. Some home owners that don't know of problem just think someone broke the window and pay to replace it when had they known it would have been covered under warranty. The glass today does not have this problem but is better with the new Low E 4 glass. There will be a 3.8 stamped in the corner next to the logo to tell you if you have this new glass. If any of you have the 89-92 years of glass, think about getting it fixed before your 20 years are up.

    Bookmark   April 21, 2008 at 1:58PM
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I have a timber frame house built in 1991. glass is andersen from 1988-1990. I just had the third pane of glass break on my house so I once a again called andersen to get new sash. I was getting a little worried b/c 20 year warenty. they decided to send a rep out he came out this morning told me about the negative presure glass. he fixed all the windows in the house exept the broken one and the two replaed years earlier. couldn't replace my 4 skylights he said there was no fix for it. He is sending me 4 new ones. I have two bow windows with fixed center panel in the lower right hand he drilled a hole in the GLASS! let the pressure equalize and sealed it back off. I am happy to hear the fix will work. I found about half of my windows were actually touching each other. Anyway I am not impressed with the repair on the fixed panel now I have to live with a defect in my glass. I called anderen and they said it is up to the rep. I love my windows and have choose andersen on a vacation house, but not for sure a bout this repair on the fixed window.
thanks micheal

    Bookmark   October 16, 2008 at 1:34PM
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Is your concern about the hole in the glass primarily cosmetic (it looks ugly) or structural (there is a hole in the glass)?

If structural, the hole shouldn't be a problem at all; but if cosmetic then you might have to chat with the rep about that one.

    Bookmark   October 17, 2008 at 6:52AM
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I too have Andersen windows from 1990. Just this week, we experienced a cracked outside pane on a lower sash, which Andersen will replace w/ a new sash. I'm about to set up an appointment with the local rep to come to inspect all my windows, as I can now tell that we have many exhibiting the collapsing problem.

*For the techies - Oberon, Guy, etc: What's the con of the repair option (drill/equalize/reseal)? Two of my concerns are strength of glass that has been concaved for however long, then straightened out after the repair, and, possible loss of insulation.

*For those folks who chose the repair option (drill into the frame), are you satisfied?

Andersen said it would be up to us to decide if we repair or replace windows that are found be collapsing. They didn't indicate it may be repair only if a min tolerance not met. We'd certainly like new sashes, but other things to consider are: possible need to stain or clear coat, transferring the white plastic grilles from the existing sashes to the new sashes, mishandling the sash cord, and the possibility of the plastic runner cracking during the sash replacement, since theyre 18 years old. The plastic grilles have a solid plastic tip that goes into the sash, unlike the newer versions, so it seems like a real possibility these could break off. We have 18 double-hung windows, and my guess is many have the escaped argon problem.

Sounds like doom and gloom, but I have no window replacement experience. The local rep says it could cost $30 - $40 per sash for professional replacement. Supposedly they will cover the cost of any damage during replacement, but I don't know those details yet.

Thanks for any insight.

    Bookmark   October 17, 2008 at 10:00PM
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As mentioned in previous posts, the fix will improve the performance of your windows to near the level they were as originally installed.

Quoting myself from an earlier post -

"Well, first, the argon is already gone. With the glass close together because of the lost argon, the windows are less efficient. Allowing the airspace to normalize will actually increase the unit energy efficiency over what you have now.

Second, argon fill increases window efficiency linearly in other words more argon, more efficient performance and it is easily calculable a 100% argon fill increases energy efficiency by 16% - 50% argon fill increases energy efficiency by 8% - 25% argon fill increases energy performance by 4% - see the pattern? But, again, the argon from your units is gone and there really is no reliable way to refill the airspace in the field despite claims by some window "repair" folks that they can replenish argon fill (rip-off).

Third, since the air/moisture seal is intact, the desiccant in the spacer will absorb the small amount of moisture that will enter the airspace thru the small hole and in your environment you wont ever notice that little bit of moisture that entered.

There truly is no need to replace those windows that have collapsed inward and that have not displayed signs of between-the-lites moisture. The ones with seal failure need to be replaced."

The fix is simple, fast, offers minimal disruption on your time and home life, and costs you nothing. I wouldn't be concerned at all that the glass has been bowed for awhile because of the collapse. Glass is very resilient and it should easily go back to normal without issue.

On the other side, the new sash offer improved IGU technology over the originlal, 18 year old units.

They have improved energy performance based on a newer LoE coating, low conductance spacer, argon fill with improved seal/containment system, and they are brand new - not 18 years old.

On the negative side, either you install them yourself or else you have to pay someone to install them for you (recommended if you are not experienced). As you mentioned, you would have to deal with finishing the new sash.

Pro installation should be quick and easy, with minimal disruption, unless the installers run into any problems - which I would not be overly concerned about in this case.

    Bookmark   October 18, 2008 at 8:23AM
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I have some Pella windows exhibiting the negative pressure problem. What is the procedure to drill into the frame? Drill through the side of the metal frame to create a hole between the panes of glass? Is drilling on the top or bottom preferable? (I would think top.) How small of a hole? 1/16th? What's my margin of error, i.e., how much space is between panes of glass?

    Bookmark   November 9, 2008 at 11:16AM
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I am a homeowner also with Anderson windows from 1990 with the same problem as everyone else. I just thought the condensation on the inside (oval) was due to the house being too tight thought nothing of it untill some of the windows developed the milky film between the panes. Also had windows which cracked on the outside,thought a bird or something else hit them. I had replaced one myself. Then decided to contact Anderson and was told the same as everyone else. I am still waiting on a rep to come to the house to inspect all windows. I was not told about the min collapse figure to replace, will they stand behind this? Also living in Ohio cold winter months due to all the condensation running down the windows and laying and being absorbed by the wood frame of the window,they have mold,mildew and began to rotten out. I wonder if they will consider that for replacement? Also is there any class action suites for this problem?

    Bookmark   November 30, 2008 at 10:24AM
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Just a quick update. You can identify the argon depletion in the early stages with a thermal imaging camera. I have come across many and most home owners didn't even know they had a potential warrenty claim. I've been in front of many reps. No one can dispute a thermogram even when you can't see it visually yet. So if you have concerns that you might have this problem. Find a thermographer and they can quickly scan the windows. I have attached a link to a sample of what it looks like thermally.

    Bookmark   December 3, 2008 at 6:47PM
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'Andersen Owner" asked if people were happy with their repaired sashes. I just had 21 windows repaired and am awaiting 5 new sashes where the seal failed. I am the second owner of the house and am honestly thrilled that Andersen stood behind my windows manufactured in '89-'90 with no questions. I've gotten the run-around on "pro-rated" warranties in the past and expected more of the same. Andersen gets thumbs up from a customer service perspective.

As far as the repair, time will tell. I can say that on a 35 degree day, there was a 7-11 (measured) degree difference in temperature on the surface of the glass between the windows that have been repaired and the ones that will be replaced (which still have the panes collapsed). Based on amount of glass that I have, this will make a big difference in my heating bill. I already notice that sitting by a bank of windows feels warmer.

Cosmetically, I had 19 windows drilled from the side and two fixed windows drilled through the glass. Yes, there is a small hole where they drilled through the glass and then filled with clear sealant. It looks like a small drop of water on the surface of the glass. Even the windows that were drilled through the sash have a cosmetic flaw. The aluminum framing between the glass gets a dimple in it where the drill bit pushes against it. You see a dimple, not a hole. The drill bit never completely pierces (at least visibly) the aluminum - just enough to allow the pressure to equalize. Based on the specialized bits that the contractor had, this does not look like a DIY job.

All in all, I have confidence (or at least hope) that the repair will hold. If I had to purchase and replace all of my sashes, it would have easily exceeded $10,000. The small cosmetic "defects" I have from the repair are minimal compared to the unsightly condensation on the window interior and I'm now retaining much more heat in the winter months.

    Bookmark   January 3, 2009 at 8:48AM
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I have repaired thousands of sashes this way and only a handfull have failed (less then 15). Just check them all very well before the warrenty runs out.

    Bookmark   January 3, 2009 at 5:48PM
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The postings here were a great help as I investigated my own Andersen window collapse (windows built 1990). I just finished installing 20 replacement casement sashes and two sliding door panels. Andersen is a great company...reps came and measured collapse...20 of our 24 windows were bad enough to be repaired or replaced. I insisted on replacements since I suspect repaired windows may collapse more in future. It took about 30 minutes to replace each sash myself, but if your not a hands-on type I would suggest you let reps do it. Being a curious type I decided to "repair" some of my old windows, just to see if I could do it...was fairly easy. I drilled 3/16" hole in edge of permashield sash down to aluminum separator, drilled 3/32" through aluminum, let air flow in, inserted small screw covered with epoxy, then filled hole in sash with white silicone. Hole was drilled on TOP of sash. May put a couple repaired sashes in attic in case we break a window; seems a shame to discard all the rest...anyone have a use for repaired permashield sashes? Sizes = C35, C5, CW5.

    Bookmark   February 21, 2009 at 12:03PM
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Delta- For some reason casements and door panels frequently show a permanent black or grey line where the glass touched. You can drill them or remove the glazing bead and pop a hole with a dental pick through the spacer. Then cover with a silicone that is compatable... but it's probably not worth the effort.

    Bookmark   February 21, 2009 at 12:36PM
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Hmmm, I know I posted here before. Does anyone know what happened to my posts.

    Bookmark   March 24, 2010 at 9:23PM
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shammy1 - Don't know what to tell you. I did a search for your name and only came up with this thread. I even searched the entire site, not just the Window Forum. Did you post using a different name?

    Bookmark   March 26, 2010 at 4:37PM
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I signed in O.K. and have not changed any of my info. We talked about my glass failure a few months ago and I used a thermal imaging camera to detail certain temperature losses. There seems to be a whole bunch of posts by people that are not here anymore. Its ashame since this thread was so usefull. Mike

    Bookmark   March 27, 2010 at 8:40PM
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I have made the mistake several times of clicking "message view" button and then forgotten to hit the "submit message" button. Perhaps this is what happened. I've done that on a few juicy posts that contained a lot of good info and then either didn't have the time and/or desire to retype it again.

    Bookmark   March 27, 2010 at 10:03PM
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I also have the same problem with about 14 windows including both panels in a sliding door. I've already been in contact with Anderson Windows and they are sending someone out to access the situation.

My question to any of you who had the same problem is if you had a choice of repair or replacement, which route would you go? I do realize if you go the replacement route, you'll have to install the sashes myself.I really don't understand why Anderson won't install the sashes since when they repair them, you're really not getting the windows back to there original state.

I'll post after they come out and let everyone know what happened.

    Bookmark   April 24, 2010 at 10:07AM
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An interesting thing I'm seeing is the new sashes with the improved technology of stainless spacers that was supposed to correct the collapsed glass issue are doing the same exact thing.

    Bookmark   April 26, 2010 at 8:49PM
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Again, thanks to everyone for creating a great thread. I can't tell you how happy I was to finally discover the cause of my severe window condensation problem after YEARS of dealing it.

Sadly, its been a bit of a struggle to get resolution. After initially contacting Anderson, I was informed that a Anderson Repair rep would contact me within 3 business days. A week later I had not heard from anyone. I contacted Anderson a second time. The Anderson Support rep apologized for the delay, saying he would contact the Repair rep requesting that they contact me within 3 days. I requested that he (Anderson Support rep) contact me to update me on the results. Another week goes by without a word from anyone.

Yesterday, I contacted Anderson Support for the third time (a bit frustrated at this point). Again, the Anderson Support rep apologized and put me in touch with a 'Specialist'. After speaking with the 'Specialist', she contacted the Repair rep, who then contacted me within 10 minutes.

After describing the problem to the Repair rep, we setup a evaluation/repair time which is supposed to be Friday.

After setting up the repair/eval date, I inquired about the repair method, to which he replied they'd "drill a hole in the glass." I asked, "In all the windows?" He stated "Yes." I prefer drilling into the frame as opposed to drilling the glass, if for no other reason than the cosmetics. Just seems less intrusive to the overall structure of the window. Or am I being delusional??

I then inquired about the windows that have suffered significant moisture and mold damage due to the excessive condensation (even though we did our best to keep them dry; Northeast winters). The Repair rep indicated he was limited to simply repairing the collapsed IGU and could not repair/replace/refinish the moisture damaged units. In some cases, the lower portion of the sashes are blackish/grayish in color and show obvious signs off wear from years of wiping (many times several times a day during severe cold spells).

So, I've once again had to contact Anderson Support for clarification. Someone is supposed to be contacting me within 24 hours (fingers-crossed).


    Bookmark   May 5, 2010 at 4:08PM
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Somehow, I seem to have omitted the question?!? Here goes:

** For oberon or Xguy from above **
Will the 'gap' between the IGU panes vary somewhat depending on delta in external vs internal temperatures?? Meaning the colder it is outside, the smaller the 'gap' since the difference between room temp and outside is significantly greater??


    Bookmark   May 5, 2010 at 4:35PM
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Yes. The 2 panes of glass will be farther apart in the Summer and closer together in the Winter. This is one of the prime causes of seal failure.

    Bookmark   May 5, 2010 at 9:16PM
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The only thing tougher than a Andersen window is trying to long back on this site, but I made it and have upgraded to shammy2 from shammy1.

Anyway I did talk to an Andersen rep who hooked me up with the local repair shop. A very nice man came and tested the glass, I say about 70% of all the panes were bad. He drilled and plugged and ordered me some extra sashes for a couple that were on the edge including a circle top that shattered. At 19 years and 9 months into a 20 year warranty Andersen stepped up big time and I still can't believe the support they gave me.

Just wanted to say thanks to this site and this thread I have no more dripping glass and everything looks good.
And also a big thanks to Andersen for all there help.

Later, Mike

    Bookmark   January 26, 2011 at 2:21PM
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"Argon is heavier than air and each molecule is larger, not smaller than an air molecule."

Heavier yes, larger no.

Argon is mono-atomic (just Ar) and nitrogen and oxygen are diatomic (O2 and N2).
The molecules are larger than the argon atom.

"Point being that historically glass does a very good job of containing argon."

Light bulbs have a complete glass envelope with no other material used.
After the argon is introduced and flushes out the air the glass is melted closed.
The gases are not moving through the glass, but through the seals of glass to spacer in the windows.

Stopping all movement of gases is actually relatively hard.

It is actually impossible for some gases like helium.
Helium will slowly leak atom by atom through ANY container.
I can put my helium leak detector against the side of a steel gas cylinder and count the atoms leaking one by one.

    Bookmark   January 28, 2011 at 10:12AM
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great forum, could some one tell me how i can repair my own windows, they are out of warranty and i have a lot that are collasped, thanks

    Bookmark   April 26, 2012 at 9:51PM
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Windows on Washington Ltd

For lack of a better description, drill holes (provided they are not tempered glass) in the top and bottom corners (2).

This will equalize the pressure and over time, the glass should return to its normal spacing.

    Bookmark   April 27, 2012 at 10:03AM
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If you can remove the units form the window it is not al that hard to drill through the dividers used to hold the panes of glass apart.

The glass usually returns to flat almost instantly as the air rushes in.

    Bookmark   April 27, 2012 at 4:28PM
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I've repaired many collapsed glass units over the years for Andersen, and some of the info on this thread is incorrect, if not dangerous.

"For lack of a better description, drill holes (provided they are not tempered glass) in the top and bottom corners (2).
This will equalize the pressure and over time, the glass should return to its normal spacing."

What are you using to drill the glass? It's not as easy as fitting a small bit into a dremel and going at it. You are correct that this will not work on tempered glass. However, did you also know you are NOT to do this to the interior pane? Also, you do not need to drill 2 holes-that just gets you a better chance of getting moisture in the airspace, leading to fogging and eventually etching of the glass unit.

"If you can remove the units form the window it is not al that hard to drill through the dividers used to hold the panes of glass apart.
The glass usually returns to flat almost instantly as the air rushes in."
That is very simplistic, for one. Yes, in theory that works-but you do not need to drill through the spacer. You only drill up to the very interior surface of the spacer. That's why we use jigs & pricey drill bits to do the job. You need to think about this, too-is it worth the bother and liability to do it yourself? Andersen will cover the repair if you're still under the 20 yr warranty. If you're beyond that, you can still hire a trained service tech to do the job. I just last week repaired over 10 units for a total of $150. That's not even going to cover the cost of ONE sash or door panel if you break it!

reyesuela: why do you expect not to have to do ANY possible maintenance whatsoever on your windows? Do you do the same on your car? Let's think about it a little-you have windows for 21 years, just out of warranty. They've served you well & been very efficient the entire time, but now they're collapsed. Let's say you have an average 4,000 sq ft house with 80 panes of glass. If all need repair, and you are charged $10/ea to repair them-it's $800. You really are going to pitch a fit about $800 to keep your windows in prime shape? C'mon!

Another misconception I see floated around in threads all the time-"only Andersen has this problem". That's simply a lie. It was an industry-wide problem when argon was first used on a large scale in the 80s. Dirty secret-most of the largest window manufacturers use the same glass supplier-they just have proprietary technology that the supplier puts into the product. The band between the glass was the problem-it could not keep the argon from escaping. The band was redesigned in the early 90s to eliminate this issue.
Regardless, I appreciate the knowledgeable posts from the other professionals who weighed in. Happy Trails!

    Bookmark   January 22, 2013 at 4:20PM
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The window manufacturers have had better success of late at sealing their units against gas movement.

The older ones can be pretty bad.

Partial pressures is exactly what comes into play, along with leakage rates of the various gases through the less than perfect seals.

It ends up coming down to the actual atomic size if the gas molecules.

They Are NOT the same size, and smaller molecules manage to work through a porous seal faster then larger molecules.

Oxygen and nitrogen are actually O2 and N2.
Argon is a noble gas, has small atoms, and is mono-atomic.

It leaks out faster than O2 and N2 can leak in, reducing the pressure between the panes.

Large panes can even shatter from the flex they try to make.
Large tempered units make a gentle boom like a basketball hitting a wall when they let go.

A seal that stops the movement of gases is referred to as 'hermetic.'
They are very difficult to make over large dimensions, and impossible for some gases (Helium goes through solid steel slowly).

The various sealants used to joint the separate panes of glass into the unit all leak to some degree since none are actually hermetic.
It is all about expected life vs. leakage rate.

A lot of folks seem to have forgotten the basic characteristics of all gases.

One of the methods that has been used to 'repair' units is to drill a small hole through the seal between the panes of glass (NOT through the glass itself, though that is not all that hard anyway).

This hole allows the pressure between the panes to then equalize with the atmosphere.

Small plugs containing desiccants are then installed to try and limit fogging between the panes.

When the desiccant saturates, the unit start to fog.

    Bookmark   January 22, 2013 at 5:23PM
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Windows on Washington Ltd

Point of clarification:

-Obviously you would want to contact and contract with Andersen if the unit is still covered under warranty.

When you say don't drill the interior pane, are you saying that the opposite (i.e. exterior pane) is correct or that partially drilling the spacer is correct (as you mention in the 4th paragraph).

Is the theory/application behind that approach that the penetration of that percentage of the spacer allows the air to diffuse back into the IGU? Not questioning just asking.

How do you plan to do this on picture window IGUs? Is a picture window retrofit covered by the same $15 per sash?

The theory behind drilling the a hole in the top and the bottom is to allow convection to take place and keep the air circulating and therefore dry.

    Bookmark   January 22, 2013 at 8:24PM
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Yes, the outside pane on a non-tempered unit. The interior pane is not treated like the exterior, & tends to break after being drilled. Fortunately, I didn't find that out the hard way, but a colleague did. ;)

The spacer has twin rows of holes on the older aluminum band that can be repaired this way, and the holes are big enough to let air in without a lot of moisture. I've gone all the way through by accident, though-and it's not the end of the world.
Drilling through the glass is ok on a picture window, unless it's tempered. If it is, you can either take the sash out if it's a casement picture & repair as if it was a crank out, or take the glass out of a DH picture & drill through the spacer. If removal of sash or glass is required, the labor cost does go up, you're right. And patio doors, depending on application, are slightly more as well, but not a whole lot...

I understand that theory, I've never tried that but it's interesting. Are you able to get the 2nd hole drilled before the spacing is almost back to normal anyway after the first one? I would almost think it may make it worse-give the dry air a place to rush out while moist air rushes in, but I don't know since I've never tried it... According to what I've been told-Andersen's position is that moisture may get in, in small amounts, but the dessiccant will take care of it within a day. I've noticed sometimes after the one hole repair, there will be some slight fogging radiating from the hole-but no one has ever called me back on one yet, even after I show them the fog & tell them to let me know if it stays. But, I may need to try the 2 hole sometime & see what happens. My main drawback, just mulling it over, is the risk of breaking the glass is doubled with two holes rather than one?

    Bookmark   January 23, 2013 at 5:07PM
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Windows on Washington Ltd

You drill the outer pane? Are you worried about moisture from rain and other sources?

    Bookmark   January 23, 2013 at 8:18PM
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I haven't had trouble with moisture yet after drilling the glass & filling the hole properly afterward. Often, the moisture content IN the house is higher than the outside anyway. But any moisture that does get in is usually taken care of within hours, couple days max on humid days, by the dessiccant.

    Bookmark   February 1, 2013 at 11:47PM
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I stumbled on this thread doing a search on how to drill insulated glass. I have a total of 25 Andersen windows in my house. I purchased these during a remodel in 9/88 with delivery in 10/88 so I think I am safe from the Argon gas issue being discussed. I am also well beyond 20 yr warranty period. Regardless I do have a few windows that are fogging, I suspect from seal failure rather than pane collapse. I ordered replacement sashes for these and will be changing them soon. Just for an experiment I thought I would drill one of my fogged windows to vent it to just to see if it improves in any way before replacing it. Nothing to lose at this point being I am replacing it anyway. My thought was to drill a 1/8" hole in the glass with a diamond bit top and bottom corner. After reading this thread I may just try to drill into the aluminum spacer. Would 1/8" be a good size for this?
Another problem I am going have to deal with someday is my stationary windows. I had 3 trapezoid units custom made by Andersen. They are fixed units about 3' x3' each. They are in a tough position very high at the top of a cathedral ceiling. They are only very slightly fogged at this point but I am sure it will get worse. If my first experiment works I would like to try drilling these. Being these are fixed I will have to drill into the glass corners. If this fails I guess I will have to remove them and have replacement glass made. It looks to me like I have to remove the inside wood stops using a very high ladder and have someone push from the outside to remove these units. Any thoughts on this?

    Bookmark   September 6, 2013 at 10:45AM
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The whole drilling into the glass to somehow vent failed insulated glass just frustrates me. Moisture has found it's way into the glass. It will still find its way there but now you have a hole in your glass to allow moisture to pass in and out. It will still get fogged. It's just an ugly bandaid on a bigger issue. -End rant.

    Bookmark   September 6, 2013 at 2:58PM
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I know that sounds about right but it's simple enough for me to try at this point before I put in the new sash which I already have. I always remember when I installed a Pella multiple casement picture window about 30 years ago. It had double glass but the way that worked on Pella back then is the window was really a single pane with another pane with a gasket and clips that held it tightly in place on the inside. After about 6 months the window was fogging. I made a call to Pella and they explained that the vent holes were most likely plugged. They were right. There were a number of vent holes through the wood in between the panes. The holes were filled with some kind of material that almost seemed like mud. Bugs maybe?? Anyway after opening up the vents my fogging was gone. Not exactly the same scenario as modern day insulated glass but close enough to make it worth a try.

    Bookmark   September 6, 2013 at 5:03PM
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Windows on Washington Ltd

Good to hear that mnovak99.

I don't have any personal experience with this process but it appears that there is some data to support the idea that ventilation and air circulation would reduce the condensation potential and allow for drying.

    Bookmark   September 9, 2013 at 12:33PM
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Are you still around? I'd like to ask you a few questions on your method of drilling and filling. I have a house full of Anderson windows that were manufacturered in 1992. Many have failed (rainbow, oval football, circle of moisture on the house side of the inner lite) and I'd like to attempt to fix them. Two have even broken (outside pane spontaneously broke). I cannot afford to replace these windows or the glass. I am very handy and would like to attempt to fix them myself; however, I'm not quite sure of the approach (of the drill bit) to the inside seal (the angle; whether starting the hole from the horizontal and going through and through to the spacer; or other). I would certainly appreciate your help (or that of someone else who might have done this and is willing to help me).

Thank you kindly,


    Bookmark   February 3, 2014 at 10:51PM
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Windows on Washington Ltd
    Bookmark   February 4, 2014 at 12:06AM
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Hi, Windowsonwashinton,

I'd like to thank you for posting a link to that video that Mike made. Maybe you're Mike ... if so, thank you Mike. That gave me much of the info' I needed. I guess the bottom line is to drill the hole where it is least apparent. The only part I was not quite sure about is whether to add something else inside the drilled hole to help establish a firm seal. I couldn't quite understand what Mike said right before his comment on adding silicone. I believe I read something here about the pros using some sort of metal tube or plug before sealing with silicone. Maybe the plug was the desiccant, not sure. If you or someone here would care to comment on this, I'd certainly appreciate the input.

One last question: On very large windows (like a fixed slider), might it be just as effective to drill a hole at a diagonal, say 45 degrees, from either the inside or outside just below the aluminum spacer? A hole through a vertical side of a large window such as this at 90 degrees (like Mike's) would be near impossible because of the width of the wood frame. I guess it wouldn't matter how to get into that space, at an angle or directly, as long as one is careful to get there without intruding through the inside aluminum, right?

Most of my windows are double hung, some with a failed upper sash, some with a failed lower; however, I've got quite a few big ones (slider size), (eight to be exact) on the back wall, wrapping around to the side wall of the main part of the house, two each over each set of four sliders. I guess one might call them picture windows. ALL Andersons and all manufactured right before the house was built in '93. Bummer :( Fortunately, most appear okay, but I guess it's something I want to check every year. I've had two "explode" (outside lite on each), and that was scary! Fortunately, they were small bathroom DHs, one upper, one lower sash, same window but about 7 years apart. Guess I have a full-time job.

Thank you again, WOW, for your speedy reply. This forum is a great one!

Kindest regards,

    Bookmark   February 5, 2014 at 5:35PM
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Here is a great video showing the configuration of the glass, spacer, seal, etc. on a double-pane insulated window, explaining exactly how/why the seal fails:


    Bookmark   February 5, 2014 at 8:44PM
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Windows on Washington Ltd


I am not Mike but I should thank him as well. He did a nice job.

I would try to ping him via the video with your questions.

A desiccant would be ideal along with a good seal. At this point we aren't worried about gas getting out as much as we are about moisture getting in and condensing.

A good silicone should keep out the moisture just fine.

    Bookmark   February 5, 2014 at 9:36PM
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Thanks, WOW. I did ping Mike via the video on Youtube, thanks.

What have I got to lose. Will try drilling and filling w/silicone.

Again, thanks much for pointing me to Mike's video.



    Bookmark   February 5, 2014 at 10:18PM
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Windows on Washington Ltd

Good Luck!!!

May the power of the Grumpy Cat (aka Millworkman) go with you.

....inside joke...

    Bookmark   February 5, 2014 at 10:37PM
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Sorry I didn't get back earlier. I just happened to stumble back on this page by chance & saw your post. I watched a little bit of the video in the link that was posted, but not enough to know if the repair he is using will hold up over the long haul. But best of luck to ya & hope it works well in your house!

To Fenestration_Taylor,
You don't leave the hole opened up-as soon as the pressure is equalized, you fill the hole with an epoxy[something like a windshield repair epoxy] & set it up with a UV light. The only problems I've had with drilling through the glass is if they are drilled through the interior pane or the drill is not held steadily enough when drilling through & the burr bit breaks.


    Bookmark   February 11, 2014 at 4:20PM
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This post is for anyone who finds there way here after searching on how to fix these collapsed windows. Living in Wisconsin, I got tired of having puddles of ice on the bottoms of the frames each winter. With 30+ windows in our house, I wasn't about to replace all of them including six patio doors, so I came up with a rather simple fix. I guess I could have just poked a hole in the frame and let air in but why not refill them with Argon? Fortunately for me, I have a TIG welder which uses Argon. I'm guessing you can find a way to rent a bottle.

Basically it consists of drilling a 1/4" access hole through the vinyl/wood frame and then punching a small 1/16" hole into the aluminum frame. I quickly insert a tool I made that has a 14ga. syringe needle attached to a hollow tube and on the other end is a balloon filled with argon. The pressure equalizes (actually a bit on the positive side) and then I fill the hole with sealer and a small screw screwed into the hole in the aluminum frame. My tool pictured is a little elaborate but can be made much simpler. I made it to pierce the aluminum but found the needle hole was clogging, hence the need for a separate hole punch.

Any questions, drop me a note at

    Bookmark   October 7, 2014 at 10:18AM
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Windows on Washington Ltd

Pretty nifty little tool.

Necessity is the mother of all invention...

Be sure to poke the home near the top of the window as argon is heavier than air and I would fill it for longer than just one balloon worthy prior to closing the hole.

    Bookmark   October 8, 2014 at 7:10AM
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Actually, the window only 'inhales' what I assume is an equivalent amount of argon that was lost in the 'leakage'. The filled balloon is 8-10 inches in diameter, and a little more than half of that returns a 20"x50" pane to flat. I overpressured it just a wee bit so it gave me time to fill with sealer/screw/sealer.

I 'spose if the window pane was not in a state of low pressure/vacuum and had normalized with air, I would have drilled holes on top and bottom and tried to replace that air with two or three balloons worth of argon from the bottom, hopefully flushing out as much air as possible. In my case, it didn't need that.

    Bookmark   October 14, 2014 at 10:45AM
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Windows on Washington Ltd

Argon is pretty cheap and can be sourced locally usually so don't underdose.

Very cool tool and I am sure it will help quite a few folks.

    Bookmark   October 14, 2014 at 7:29PM
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Hi everyone,

I, too, have this collapsed glass problem on Andersen casements manufactured in 1990 and 91. I called Andersen a few days ago and even though they are several years out of warranty, Andersen offered 50% off brand new sashes. They told me that they no longer recommend the drilling method because it proved to be only a short term fix.

The problem is that I have 25 sashes, an eight foot slider and a French patio door. The total is about $5k, which is really beyond my budget. So I may attempt to drill them myself. I guess if I fail I can always spend the 5k!

    Bookmark   November 3, 2014 at 5:39PM
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Here's another youtube video showing how to drill a hole to correct the pressure problem.

    Bookmark   December 17, 2014 at 11:19PM
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OMG .... can't believe this thread is still active almost 8 years after my original post. Just wondering ... is Oberon is still hanging around on GW ??

    Bookmark   January 7, 2015 at 4:06PM
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Hiya Napagirl and I am still around.

How are things with you?

    Bookmark   January 7, 2015 at 4:45PM
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Hi Oberon,
Glad to see you're still posting on GW. Things are good with me. No more window problems :)

    Bookmark   January 7, 2015 at 10:36PM
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Good to hear.

Hope that you had a great holiday!!

    Bookmark   January 8, 2015 at 5:10PM
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