Do gas filled windows lose their gas?
I am hesitant to purchase any of the gas filled windows, though they do have an R-value significantly higher…reason being might be trust. Can I trust that the gas is going to stay in those windows and not dissipate out over time…Have there been studies on this? The cost difference is substantial and I don’t want to pay for windows that are filled with gas to have them be no different than non-gas-filled windows several years from now….and if the window is flawed and the gas leaves how will I know? The company can say they are warranted but if what they are warranting is invisible, how will I know if it dissipates out and is no longer there?
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According by "Understanding Energy-Efficient Windows," a Fine Homebuilding article by Paul Fisette, "Argon and krypton are safe, inert gases, and they will leak from the window over time. Studies suggest a 10% loss over the course of 20 years, but that will reduce [Editor's note: I think he meant increase] the U-factor of the unit by only a few percent."
The seals used in insulated glazing units are improving all the time. According to the new European standard (EN1279), argon leakage rates must be no more than 0.5% to 1% per year.
Are there any high-performance triple-glazed windows that are not gas filled and are more economical? ...or recommendations for people who want to be energy efficient and have a tight budget? Windows are something I don't want to be replacing and upgrading later, but the high cost is simply prohibitive...any suggestions for best value/performance windows? I would like to stay with fiberglass frames so that they can be painted. Any suggestions would be appreciated. Thanks, -Eric
Q. "Are there any high-performance triple-glazed windows that are not gas filled?"
A. Yes. You should be able to order windows with clear triple glazing if that's what you want. You'll end up with a high SHGC, but your U-factor will suffer compared to an argon-filled unit.
Q. "Are there any high-performance triple-glazed windows that are more economical?"
A. I doubt whether substituting clear triple glazing for argon-filled triple glazing will save you much money. To get an answer, though, just call up your window supplier.
Q. "Do you have any recommendations for people who want to be energy efficient and have a tight budget?"
A. Build a smaller house.
Q. "Any suggestions for best value/performance windows?"
A. You might want to build some site-built fixed windows. After buying a few operable windows, make the rest fixed. You can order the glazing and build your own frames.
Thank you Mr. Holladay for your insights
There's a nice UK study analyzing energy use/embodied energy/payback of window types which may be of interest:
This study shows that an air-argon upgrade (in new construction) pays back in 6-8 years - so even if all the gas were to dissipate in 10 years (which is far more dramatic than martin's data suggests), you'd have already paid it back. This study does not show a good payback on krypton; triple glazed argon pays off more quickly.
As with any payback, first cost, climate, and energy cost should all be considered. Coming from the UK, all of those values will differ, so your results may vary (though not likely to the point where it changes the determination - I know that I've seen other studies that put argon payback at 3-5 years as well).
A note of warning: I find this report a bit confusing - payback is calculated both in terms of finances and embodied energy without clearly separating the two. Energy pays off substantially faster, so some of the numbers that seem too good to be true (15 day payback!), are too good to be true, at least financially.
I agree with all of martin's points from his last post - smaller house, site built windows, etc.
But one note of caution on the site built windows. If your buidling department requires rescheck (DOE software residential energy check) for approval, you are substantially penalized for non-NFRC labeled windows. As I recall, I had to put 0.65 as the defult u-value for my site built windows (typically built with center of glass U=0.19) . Had I been allowed to use ashrae fundamentals ratios, I more likely would have considered those windows in the mid to low 20s.
As a result, my well insulated, passive solar cabin barely passed because of the number of site built windows and the amount of glazing. I won't knock my buidling department for requiring rescheck - I wish more did - but it's an imperfect system...
Any best sites that you know of for purchasing the materials for site-built windows? How much cheeper are these?
If you haven't done much finish carpentry or cabinet work, you probably shouldn't build your own windows. But if you are handy with shop tools, and you understand glazing stops, flashing, and sill angles, go for it.
Any local glazing shop should be able to order your IGUs in any size you want.
note: there is a tool that can scan the window (similar to an IR gun) to detect the gas inside it. i imagine getting a pro who has the thing to come out and check your window costs as much as the window though.
the books from many windows companies i look at have the option of air filled chambers, even on the triple pane models. of course if your paying for triple pane windows, they generally market the gas fill with it. i'd guess you may pay as much to request for them to not use the gas as an upcharge on a 'special order'.
if you trust the company enough to give you a proper tripple pane window, you should trust the glass unit sealing too.
probably the best way to save is to buy standard sizes or sizes that are premanufactured and stocked at the store. not so easy with triple pane models though. of course it kills your design ideas and color choices.
the other best way to save is to skip as many windows as possible. apart from some solar gain applications, they are costly to buy and install and not energy effecient.
and if your concerned about quality, building your own is probably not the best plan. once you pay for someone skilled enough to do it properly, you could have just ordered them from people who do it all day long in a specialized factory with quality control. a window rep will warranty the whole window and possibly the install/reinstall.