Please proof this new article about double-paned windows. John McKenna mentioned.


You might wanna grab one of the many IR images around of a gas filled window where the seal has failed. It makes a very distinct bullet pattern in the middle of the glass with an infrared camera. When the seal goes it sucks the two panes of the window together. Providing there is a Delta T there will be a temp difference from the outter edge of the window to the middle.

Just thought it might be a good image for your article.

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Nice image…

This is not exactly the case! Windows can, of course, lose their seal and you will then find moisture between the panes.

For argon filled window units, however, the issue is actually the result of pressure equalization between the high concentration in the window and the lower concentration in the atmosphere: they want to equalize and will if at all possible. Over time, argon escapes, even through a “normal " seal or window and the panes collapse; if the window is smaller than about 20"x20” it will often implode! Larger windows simply flex but will, ultimately, end up touching each other. You can see this with IR long before you can see the condensation (which occurs on the exterior of the panes). I’ll attach in next posting.

My partner, Rob Spring, PE, and I authored a paper, A Unique Thermal Problem Found in Certain Double-Glazed Windows, a number of years ago on this. Along with many others, it is available as a free download (we only ask for your contact information) at our website:

This is a great find, especially before they go out of warranty!!!

Thermally yours,

John Snell
ASNT NDT Thermal/Infrared Level III #48166
Snell Infrared

Found these gems today during a hot inspection.
I could not believe my eyes but the ice cube trick was a cool thing to try.
The final tally was nine windows.
What a day.




Nice find and great looking images!! Just out of curiosity, are you using a T Series Flir with a wide angle lens? I’m asking because I notice a small shadow (upper left corner) in your digital images.

When I first started using my T400 with a wide angle lens, I got the same shadow in the upper left corner. I thought at first it was a defect with my camera and actually sent it in for repair. The Flir tech decided that nothing was wrong with my camera and came to the conclusion that the shadow was produced by the rubber gasket installed at the end of the wide angle lens. If you remove the rubber gasket, you will see that the shadow goes away.

Because the wide angle lens is longer than the standard lens, it slightly blocks the field of view of the digital camera (with the gasket installed). I have to remove the gasket everytime I take an image. Flir reps still do not consider this a defect with the camera, but I do!! The rubber gasket is there to provide protection for the end of the lens. My argument was that the Thermographer should not have to remove the gasket in order to get a clear image.

Try taking the gasket off and take an image. Sorry for the slight thread drift.


Here is good IR shot of a busted seal.

Oppps,just my regular eyes.

Hey Kevin, you nailed it. It’s a FLIR T400. I said the same thing to flir. what idiot designed this? By the way, the windows are Andersons. I couldn’t resist the ice cube test either. Nine windows, which may not be under warranty… ouch. The visible image was re-touched as the t400 visible is too dark. (time for service)
The wide angle is the cat’s meow. I only use that, period.
This house has significant air leakage at the envelope. It has a whole house fan that I cranked up. All five bedrooms, and three bathrooms, have insulation faults, major ones. I am talking about 4-6 images per room.
Sorry for the significant drift.

Many Andersen windows manufactured between 1990 & 1993 have a seal issue that allows the glass panes to collapse near the center. I recently had several of these defective windows repaired and two replaced by Andersen. The window manufacturing date is etched at a corner of the window. The attached images taken at my home are now used at a Andersen training center.





1992 Andersen window image taken this week.


Amen to that. I now use my wide angle exclusively, except for electrical. I think we need to be more precise on electrical surveys and the wide angle “stretches” the FOV.

I brought my FLIR w/ a wide angle to a training class and I was envy of all the other students. It’s one of those things that you wonder how you got along without it.

FWIW, FLIR slashed the price of the wide angle lens near the beginning of this year. Before the price cut, they were absurdly expensive. Now they are just overpriced. Thanks Fluke!

I never noticed the wide angle gasket interfering with the visible image (but you’re right, it does) because I never use the visual camera on my FLIR.
My Stylus Tough (thanks for the recommendation, Mr Pope) takes much better pics and the LED illuminator on the FLIR just doesn’t put out the light or throw needed -but it does drain the battery quickly. But I have the older 1.3MP camera. If I had the new 3.0MP visual camera I might use it.

In the tradition of veering off subject. . . One of the best improvements on the Stylus series cameras is the change from XD to SD cards. So now one type card fits my IR and photo cameras and plugs right into my laptop - BRILLIANT!


Would someone explain the ice cube trick to a slow guy like me?

I see the ice cube and cold spot it left . . . are we looking for condensation inside the window?

Does it prove anything?

Thanks for any info!


Does it apply to skylites too? This is from today.


First sentence,

*“Condensation is the accumulation of liquid water on relatively cold surfaces.” *

I would change liquid water to water or moisture.

Here’s a couple I got from a brand new building in Vegas last week.

These windows gotta still be under warranty. I have several more pictures of them where you can see that there all starting to go bad. I’m interested in seeing how they’ll look next year at InfraMation.






Wouldn’t this be the result of “partial pressures” equalization? Simple pressure equalization between the interior of the sealed panes and the atmosphere would not cause the glass to go concave and collapse towards each other.

I’ve always thought it was because the gas molecules that escape from the thermal seal are smaller than air molecules, so when the gas escapes the air can’t take it’s place causing the windows to pull together?