It is plausible and without confirmation of any exterior damage (i.e. rock, foreign object, etc.) the pressure differential certainly can do that if it is extreme enough.

Should be a covered warranty item if it is not from an impact.

Thanks, Windowsonwashington. I appreciate your input. Nick

Does a window with integral blinds even have gas infill?

Yes. It ends up being 3 layers of glass. One removable, the other two fixed.

+1

Sealed IGU with removable interior panel for the blinds.

"My theory is that the gas in the window was never equalized and the heat from the morning sun, that much greater because the blind was drawn behind it, increased the pressure between the panes such that the exterior pane broke."

More like working hypothesis, but you hit that nail right on the head...that is exactly what happened.

At 8000ft installation, your IG units needed to to be either a) manufactured at a comparable altitude or, b) manufactured using either breather or capilary tubes to equalize pressure between the lites if they weren't produced at a comparable altitude.

In this case your IG units were put together in Iowa, which is a long way from 8300'.

Although up to this point the units were able to withstand the altitude change without failing, you are correct that closing the blinds helped to trap sufficient heat between the lites of the IGU resulting in gas expansion enough to break the glass.

The break pattern in your picture is an absolute text book example of a high internal pressure break.

You are absolutely correct that you need to equalize pressure in the other windows before you see more of this type of breakage.

You need to contact the window supplier or the Pella rep and find out if the IGU's are factory sealed, or if they have tubes that were somehow crimped or plugged. In either case someone needs to make arrangements to get those windows checked and if there is over pressure then get it fixed before you lose anymore of them.

If you do have factory sealed IGU's, then in my opinion it appears that someone, somewhere, may have made an error in sending them to your altitude...

Thank you for adding your detailed analysis, Oberon. I sincerely appreciate it. We obviously have quite a bit invested in these windows, and it sounds like we need to take a close look at what accommodations were made by the manufacturer for altitude.

Oberon is the man when it comes to glass.

Oberon is spot on. IGUs need capillary tubes at this altitude. No doubt the sales rep knew this. The tube may be plugged or the factory may have forgotten to install it. The bulging other IGU is a good indication that this is the issue.

On the other hand, glass plates have significant internal stresses built in and edge strength varies. It's a statistical thing, but a certain percentage of glass plates will break in the first year of service due to thermal stress (either from the sun or room-side infrared radiation). The unit could have failed for this reason even if it had a properly functioning cap tube.

Thanks, Trapper. I appreciate your added comments.

Thanks Busterlode and thanks WoW.

Trapper,

Good comments on thermal breakage and edge flaws, but this one isnt a thermal break.

In this instance the glass failed because there was too much gas in it for the altitude. If it was thermal-induced the break pattern would be very different.

This is a very high stress break and in this case the IG popped like an overinflated balloon.

Oberon, yeah, looking at the break pattern again, I think you're right. It certainly doesn't look like any thermal stress crack I've seen.

Missing or plugged cap tube.

Although Pella took care of this issue without a squabble, my problems appear to be far from over. The fact remains that we have a lot of bulging IGUs that seem to break at the slightest provocation. We just had one side of a sliding patio door go on us. This time, there was an external factor involved (a pebble kicked up by a weed eater) so we may not be able to make an airtight (haha!) case that this particular window broke because it was under excessive pressure.

However, since these units were not manufactured with capillary tubes and are very obviously under pressure, I feel that most of the windows installed in our house are unusually brittle. One window shattered during a strong wind, another window broke from interior pressure, another round window has failed and we have moisture between the panes. The way I see it, whether it’s particularly strong sunlight heating the gas between the panes, a small external impact, or spontaneous failure, these windows seem ready to pop at the slightest provocation. For the sliding glass door, I’ve submitted a complaint to the dealer and they are going to appeal to Pella Corporation. However, if Pella denies our claim, I want to figure out what my next steps are going to be.

Based on the assessment provided by Oberon, "At 8000ft installation, your IG units needed to to be either a) manufactured at a comparable altitude or, b) manufactured using either breather or capillary tubes to equalize pressure between the lites if they weren't produced at a comparable altitude." They were not manufactured at comparable altitude and no capillary tube were installed in the vast majority of units. We have a lot invested in these windows and we’ve just about lost all faith in them. My sense is that we should ask Pella to replace all the windows in the house that are not equalized. Is there a precedent for such a request? It would be great if there was a way to equalize the pressure after the fact. Is there a way to do this? Microscopic holes drilled into the glass and then sealed? If not, should my first step be to hire someone who can come out and give me a professional assessment? We have too much at stake to take a passive approach to this.

Thanks for any input on our situation.

All the best,

Nick

There are ways to drill the IGU but I would make Pella own the fault first before going that route. This is, what I would consider, a manufacturer defect as of right now.

This is Busterlode posting using my Houzz ID.

Windows on Washington, thanks for your comments. I'm interested to know more about drilling, as it makes sense to me.

Update on my situation: Several months after requesting it, I just received a quote from Pella for >$12K to replace all the non-high altitude IGUs in the house. Yikes!

They are covering the cost of the glass, so this is just labor, disposal and parts. And after spending the $12K, I'd have a lot of painting to do.

Has anyone run into a situation like this before? Right now, all the glass in the house is in tact, but I don't know how long that will last. The windows that broke spontaneously are some of the smallest in the house. Intuitively, it seems that small windows would be less elastic and hence break sooner.

Anyway, my questions are

1. What am I likely to see happen in the future? Are the IGUs more likely to fail and develop condensation? Is wait and see a reasonably sensible option?
2. Or should I push harder and try to get Pella to pay for full replacement costs? This creates quite a bit of disruption and will probably require some legal fees, but we've got a very solid case in my opinion.

Thanks for your comments, thoughts and suggestions.

All the best,

Nick

Google around for Andersen windows negative pressure. They had issues with gas leaking out and creating a negative pressure issue, the the fix would roughly be the same. Drilling the IGUs on the exterior surface (should be ultra low humidity in the winter and in the mountains) should keep any condensation in the IGU to nil. Equalizing the pressure for your altitude should keep it from happening again and fill the hole with silicone. Drilling the top side would keep the argon intact as well.

Interesting. Drilling seems like a much less invasive approach to the problem. So long as it can be unobtrusive, this may offer a compromise solution for the non-tempered panes. I saw on one post that the hole was filled with epoxy. Can one can achieve a near invisible plug using epoxy?

Windows on Washington, I really appreciate your response and expertise. Thank you. Until now, I had always imagined that IGUs are two pieces of class precisely molded and stuck together, and where they actually come together is glass on glass. But from what you are saying (and from some research I just did) there's a spacer between the glass panes around the edges. So all I need to do is drill in from the side. Easily done for operable windows. A little trickier for large picture windows etc. Hmmm... Would this invalidate my (20-year) warranty?

I'm wondering what you or others would do in my situation? Almost two years has elapsed since I first posted this comment. I need to respond to their offer to supply windows at no charge.

"Would this invalidate my (20-year) warranty?"

Glass fogged warranty? Yes, consider that voided if you drill. If they give you the glass or sash at no charge you still need to have it or them installed.

Are they offering new windows at no charge, or is it new sashes, or just IGU's?