When windows are filled with a special low conductivity gas such as argon or krypton it is clear that those gases will be lost over time if capillary tubes are left open.
Argon filled windows at high altitude.
Milgard is now making windows in salt lake city and offering argon gas as an option to those of us at 6000.
Argon filled units also cannot use breather tubes for high altitude applications.
Argon permeation is greater than air for most ig sealants which can result in negative pressure in the ig air space.
When windows filled with argon are transported and installed in buildings above 5 000 ft however lower atmospheric pressure causes the argon gas to expand which in turn can lead to adverse effects.
It is also likely that water vapor will gradually enter the ig unit resulting in fogging if enough moisture gets in.
These inert gases are denser than regular air so they slow heat transfer to a crawl keeping more of the heated air inside your high altitude home.
I have a couple of concerns about the longevity of the gas fill.
These units will not qualify for the tax credit and will not meet energy star northern region.
There are also concerns about maintaining the gas fill levels over time.
We can specify argon filled units if the job site altitude and the nature of the window is such that the structural integrity and warranty can be maintained.