Elevation change and argon gas (3,100 feet)
How much should elevation play into choosing a window manufacturer with regard to argon gas? I see that Colorado is a completely different ballgame, with elevations seeming to start at 4,000 feet and only going up. But I am sitting at 3,100 feet elevation, and I found one site that suggested that manufacturers start to become cautious between 2,000 to 4,000 feet in elevation gain from the manufacturing point to the point of installation. I am sitting roughly 2,300 ft above several manufacturers that we had considered using. Is this something that I should be worried about? They were certainly willing to sell to me. I would hate for expanding argon gas to cause seal failures. And is it just the final installation point, or do I need to worry about transport elevation, as well, which seems to max out at around 4,800 feet? This might be a question for the manufacturers, but this site is such a wealth of information, I had to ask.
Thanks,
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Replies
The Denver airport is just over a mile above sea level. Quite a change when I watch GPS stats flying from Detroit (under 900 feet) and landing in Denver :-)
Alpen Windows is out in Colorado I believe. I know there have been reports on here in the past that they are quite willing to work with customers at high elevations. You might try reaching out to them.
Bill
Hi Todd,
According to a report by Peter Yost and Alex Wilson:
If a sealed insulated-glass window is manufactured at sea level and installed at 5,000 feet, where the air is less dense, the window glass will bow out. Even when the windows are installed at the same elevation where they were made, if they were shipped over a high-elevation pass (across the Rockies to the West Coast, for example), the glass could break or the seals fail en route.
Randi Ernst, president of FDR Design, Inc. (a producer of equipment for gas-filling IG units) and a recognized expert on glazing performance, says that “manufacturers generally get concerned with elevation gains of 2,000 feet (610 m) or more and elevation losses of as little as a 1,000 feet (305 m).”
The susceptibility of an IG unit to glass deflection, seal failure, and breakage from pressure differences also depends on the unit’s characteristics. Thicker glass that is less flexible is more likely to break or cause the seals to blow out. Long, narrow glazing units are more likely to fail than ones that are closer to square. Tempered glass is far less prone to breakage. And seal quality determines how well the seal will hold.
Many window manufacturers install some type of breather tube in windows to allow for pressure equalization. At one time, short, fairly thick breather tubes with 1⁄8” (3 mm) openings were installed. These are seldom used today because they were difficult to install and had to be crimped shut to prevent the IG unit from fogging (the most common evidence of seal failure). Today, most tubes are much longer (12”—300 mm) and thinner (0.021”—0.53 mm) and usually called capillary tubes. Because capillary tubes are so thin, gases flow through very slowly, and some experts argue that they can be left open without resulting in fogging.
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. It is also likely that water vapor will gradually enter the IG unit, resulting in fogging if enough moisture gets in. . . . Just how long the IG unit can survive before fogging depends on the amount of water vapor in the outside air and the quantity of desiccant in the glazing spacer. (Desiccants are commonly put in glazing spacers to absorb water vapor that leaks into IG units.)
Although there are a number of large national window manufacturers distributing to higher elevation areas or transporting product over high elevations, there are many smaller companies for which elevation change may not be an issue.
Recommendations:
First, insist on the highest performance windows within your budget. In most cases, these will be low-e, gas-filled windows. Second, avoid breather tubes or capillary tubes. If you are building or designing in areas where elevation is a concern for sealed insulated-glass windows, choose a window company that deals responsibly with this issue and—if at all possible—uses a solution other than tubes. And third, if you must select windows with capillary tubes, do not attempt to crimp the tubes shut during installation unless such action is specifically called for by the manufacturer. The tubes are generally hidden in the sash and inaccessible. Even if you could get to the tubes, they are not designed for site modification and doing so would risk damaging the tubes or the seals or both (and almost certainly void the warranty). If the windows have capillary tubes, the length of the warranty against seal failure (fogging) is particularly important. Look for at least a 15-year warranty.
Resources:
National Fenestration Rating Council
American Architectural Manufacturers Association
Andersen Window Care Solutions Andersen® Window and Patio Door Altitude Limits