Local manufacturing — low-e windows for passive solar design in colder climate
Hello All,
I have reviewed various posts and want to clarify some points…Thank you for any time you can lend my questions. You all have a wonderful forum here and I am a first time participant.
I am currently doing renovations and replacements for select window on a passive solar and adobe brick structure in high elevation New Mexico. All windows addressed are picture windows, uncased and basically framed and caulked into fixed position. Working on a DIY budget at a non-profit commune.
I am considering having windows fabricated locally in Albuquerque at a reputable glass shop that does auto and window fabrication. Am looking at 1/4″x1/4″ with a 1/2″ spacer for 1′ overall. Clear over Low-e with glazing on surface #3 for optimized solar gain and emissivity. They don’t do gas fill, but then I am at 7200 feet and I have read that gas fill is not that viable long-term at this altitude. The spacer has what I am assuming is a quality desiccant design.
Question 1…Is this spacing proportion of “1/4″x1/4″ with a 1/2″ spacer for 1′ overall” ideal dimensions for SHGC?
Question 2…
Is there any reason I shouldn’t have a local glass shop manufacture these windows when working on a tight budget?
I understand surface #3 is the best surface for my purposes for east, west and south exposure.
Question 3…Is #2 advisable for Northern exposure in elevated spaces prone to rising heat and heat loss, or will #3 suffice?
I understand that hard coat glass is ideal for my passive solar purposes…
Question 4…In the north facing windows prone to heat loss, should i get soft coat glass for greater emissivity?
Many thanks for helping me make these improvements with sage decision making. I understand that getting windows from a pro window company would likely be your highest recommendation, however, its not in the credit cards.
Many appreciations for your clarity,
Layard
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Replies
Layard,
I see no reason you can't order IGUs from a local shop. A 1/2-inch gap between panes is fairly standard.
I don't have time to answer all of your questions right now -- I'll try to get back to this. In the meantime, you might want to read this article: All About Glazing Options.
Layard,
While you can order IGUs from a local shop, you need to be aware that the lack of argon gas represents a significant performance hit. You might want to ask around to see if any manufacturers offer argon-filled glazing for delivery to your area. Depending on the elevation of the manufacturing plant, and the number of high-altitude passes between the plant and your building site, you may still be able to get IGUs with argon.
Layard,
Ask the local manufacturer if they can estimate the SHGC and the U-factor of the different options. For north-facing glass, the SHGC isn't too important -- but you want the lowest possible U-factor.
For all but the south facing windows you may want to consider low E on surface #2 and a hard coat low-E on surface #4, which brings even air-filled units into the U0.25 range. They're still net energy gainers (even on the north side) but have a lower SGHC. Low SGHC for west facing windows can be an important summertime comfort factor in your location.
[edited to add]
Compare the SGHC & U-factors for both air and argon fill in the table labeled " Double Pane with LoĒ-i89 " on this page:
http://www.cardinalcorp.com/products/coated-glass/loe-i89/
The i89 on surface #4 is a hard coat low-E coating (probably indium tin oxide). The higher SGHC of their LoĒ-180 + LoĒ-i89 combination option probably makes it suitable for your high-gain windows too.