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Triple pane IGU question

chuck77 | Posted in General Questions on

I’m looking at two manufacturers of uPVC windows. They use different frame profiles that are nearly identical, the colored foils are from the same supplier, the spacers and glass are slightly different but overall the specs are nearly identical. The price quotes are very close but structured differently so it’s difficult to compare apples to apples. The biggest difference is their approach for higher alltitude installations. One uses a pressure release tube that is pinched at the final destination and only the units requireing it are tempered SG. The other uses a pre-pressurized system at the factory to set the internal pressure for final destination and then it’s sealed. All panes are tempered SG. So is one or the other significantly better to choose between the two?

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  1. davidmeiland | | #1

    I would only want tempered glass where required by code.

  2. [email protected] | | #2


    Care to share who are the manufacturers and a few of the differences?

    The "pressure release tube" that you describe is usually just called a breather tube. Breather tubes are typically installed in the IG during manufacture and are then crimped at the final destination. Not sure why they require tempered glass with breather tubes though.

    I am very curious about the "pre pressurized" system though.


  3. jackofalltrades777 | | #3

    Knowing the manufacturer will help us answer your questions.

  4. chuck77 | | #4

    Greg, that was a poorly worded sentence. All the IGUs have breather tubes and only the units that need to be SG per code hade tempered panes. These are the Intus eForte. The other "altimeter sealed" IGUs are all tempered to withstand pressure changes enroute to the installation site. These are the Zola ThermoUPVC units.

  5. jackofalltrades777 | | #5

    Typically if all three units are tempered, the costs of the entire window unit will be more, since tempered glass is more expensive than just regular glass. It is common practice to use breather tubes and it has been done so for many years. Intus' use of breather tubes is a common practice. The use of tempered glazing on all three panes of glass and the "altimeter sealed" is something that is not common practice. I'm not saying it can't work but it is not common to use such a sealed system because the stress on the window glass and seals during transport to the site will be tremendous. Hence the reason why they use tempered glass because the forces on that glass and the seals from sea level to say 7,000 feet will be pretty insane. Three panes of tempered glass will cost you more, there is no getting around that.

    Both Intus and Zola are great quality windows but I believe you are better off going with the Intus and using the breather tubes. Whatever Argon/Krypton gas that escapes is not going to make a significant difference in your final R-Value for the window. We are talking decimal points that you will never see and would not play a calculable role in the homes efficiency. Paying attention to air sealing will bring a true ROI.

    Another thing to remember is that if the windows are factory sealed at say 1,000 feet elevation and then will reside in a home at say 6,5000 feet elevation. That glass will be subject to constant pressure differences for the life of the window or until it leaks. While a window with breather tubes will actually equalize the pressure whatever elevation it finally resides at. Remember also, all window units will leak over time, so even in the altimeter sealed units, 5-10 years later, the argon/krypton gas WILL leak out, no getting around that.

    I would go with the Intus Windows and the tried & true breather tubes but the choice of course is up to you....

  6. chuck77 | | #6

    I'll check with the Zola project manager but if I understood correctly the IGUs are put under vacuum at the factory and actually appear concave until they arrive at destination and then appear normal. Zola requires tempered glass on all IGUs on projects over 5000' elevation due to the pressure stress at the factory and during shipping but they would be equalized at the installation. I was pretty set on getting Zola windows but am leaning a bit more toward Intus's tried and true breather tube to avoid the higher cost of tempered glass. Another company I plan to get a quote from and see how they handle higher altitudes is Energate. Thanks for your reply.

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