Energy Star & High Altitude Markets
Approximately 1% of the population of the U.S. lives at an elevation at or greater than 5,000 feet. This is far too small of a sliver for manufacturers to build for, or regulators to consider, when writing codes.
Thus, when Energy Star 2010 levels were determined for windows, or the window efficiency required to achieve the federal tax credits was written into law, high altitude markets were ignored.
The problem is that a majority of window manufacturers are located at elevations of 1,000 feet or less and use an inert gas, mostly argon, to improve the energy efficiency (lower U-Values) in order to reach the tax credit or Energy Star values. Argon, in dual pane glass units, requires the units be sealed to preserve the gas. This seal is accomplished by deleting the capillary tube found in air-filled glass units. Seal units are not able to equalize pressure so as the windows are shipped to our Front Range location, the gas expands with the altitude gain and without the breather tube, bow outwards at the center. The higher the altitude gain, the greater the pressure – to the point that the seal between the panes can weaken and/or fail, or the glass can break.
Those of us who serve high altitude markets in the new construction and replacement window business are left with four, compromised alternatives.
- 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.
- Secondarily, we can sell the windows with capillary tubes or air-filled. These units will not qualify for the tax credit and will not meet Energy Star – Northern Region. The difference in heating cost will be negligible from a modeled energy consumption point of view.
- We can specify tri-pane glass that qualifies, but will cost significantly more than what can be recouped by the tax credit and the payback in energy savings will not be measurable for decades.
- We, or you, can buy from the vinyl and fiberglass manufacturers who fabricate windows local and thus don’t face the described altitude problems
If you are a Front Range resident or business, fear not. One of the leading float glass manufacturers is planning a late 2010 introduction of glass that while helpful in all markets, will provide the performance of argon-filed or tri-pane units without the potential side effects. Ask the window companies you are interacting with what they think is best for your home and why.
have a comment on which float glass manufacturer to contact for the late 2010 introduction of glass that will answer the risk problem of argon filled sealed windows at high altitude? Have several windows at 9,300 feet elevation I’d like to replace with argon filled low e glass units but realise the risk.
The glass in the windows we specify is provided by Cardinal (www.cardinalcorp.com).. The argon-filed, insulated glazing units are made at about 1,000 ft in elevation. Cardinal’s warranty on these units extends to approximately 6,000 ft.
The only option to argon fill at 9,300 feet is to find a window manufacture that argon fills within 2,500 to 5,000 depending on the manufacturer’s perspective on how much elevation gain in a sealed unit is acceptable.
Note, the issue with sealed, argon-filled units as they are taken higher in elevation is that the glass will bow outwards due to pressure. The greater the angle of deflection, the great the risk of compromised seals or worse case cracked glass.