I wanted to get input from some of the experenced members of the forum on the topic of at what altitude difference between manufacturing and installation a window needs a capillary tube.
Most of the windows sold in the mountain west are manufactured in other sates at elevations of 500-1000 feet. Meaning the installation altitude is about 4000' different. Some manufacturers claim this is no problem, they do it all the time. Others say, can't be done and they always use capillary tubes above 2000' difference. Sometime I get different answers from different people at the same companies. I've talked with cardinal IG who supplies these glass unit to many of the manufacturers, and they shurg it off as not an issue.
However, as an engineer it seems to me this is putting a lot of stress on the window and is bound to lead to early failure. At 0.5 PSI per 1000' raise, thats 2 PSI at 4000'. That adds up to a few thousand pounds of outward pressure on a medium sized window. That bowing can't be good for the edge seal.
Is there any research on durability and altitude?
thanks
Argon, IG units and Altitude
Re: Argon, IG units and Altitude
". . . At what altitude difference between manufacturing and installation a window needs a capillary tube."
When standard insulating glass manufactured at one altitude is shipped to a higher altitude, the decreased air pressure can cause the glass to deflect. This deflection can lead to seal failure of the IG unit. The amount of glass deflection depends upon many factors, such as glass thickness, air space width, difference in altitude, and size of the piece of glass.
A way to avoid glass deflection in high altitudes is through the use of capillary tubes that serve as "breathers" - allowing the air between the two pieces of glass to equalize with outside air in high altitudes. You can use the following guidelines to determine when to use capillary tubes.
Additional comments. The 5/8" to 3/4" IG is assuming heat strengthened 2.5mm glass or 3.0mm annealed double strength glass. Argon gas would not be included in high altitude glass with capillary tubes. The values for 1" IG are different than the values for 5/8" to 3/4". Sorry it took so long to respond - I tried to post this more than once but the website was stating error messages when I would try to post the chart. I finally figured out a way around the error messages!
When standard insulating glass manufactured at one altitude is shipped to a higher altitude, the decreased air pressure can cause the glass to deflect. This deflection can lead to seal failure of the IG unit. The amount of glass deflection depends upon many factors, such as glass thickness, air space width, difference in altitude, and size of the piece of glass.
A way to avoid glass deflection in high altitudes is through the use of capillary tubes that serve as "breathers" - allowing the air between the two pieces of glass to equalize with outside air in high altitudes. You can use the following guidelines to determine when to use capillary tubes.
Additional comments. The 5/8" to 3/4" IG is assuming heat strengthened 2.5mm glass or 3.0mm annealed double strength glass. Argon gas would not be included in high altitude glass with capillary tubes. The values for 1" IG are different than the values for 5/8" to 3/4". Sorry it took so long to respond - I tried to post this more than once but the website was stating error messages when I would try to post the chart. I finally figured out a way around the error messages!
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