What are the best brand windows to use in Zone 6a?
tmossy
| Posted in Green Products and Materials on
What would be the best type, brand, style, windows to use for the money?
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That's a bit like asking, "What would be the best type, brand, style, cars to use for the money in zone 6a.", isn't it? I'm thinkin' pale green framed windows with rose-tinted glass might just be the ticket... :-)
In general, it's worth paying a bit for low air leakage windows, especially if you live in a windy area, so compare specs. In general, casement, awning, and hopper windows seal tighter than double-hungs, since the total weatherstripping length per unit open (egress & ventilation) area is less, and holds up better since it is compressed while closing rather than abraded by sliding sashes. Fixed (inoperable) windows are of course tighter still, and often a preferable solution in places where egress and natural ventilation aren't required. Not all windows will have an air leakage spec on the label, but better windows usually do. (eg: http://yourgenerals.com/nfrc_label_clip_image002.jpg http://integrityrbd.com/wp-content/uploads/2012/11/Blog-Topic_Selecting-New-Efficient-Replacement-Windows_Segment-Three_112812.gif )
While lower U-factors are generally better, at any given U-factor a higher solar heat gain coefficient (SGHC) is going to provide a lower annual energy use in a zone 6a location (even on the north facing windows) and that sometimes trumps going with ever lower U-factors. Downloading the RESFEN modeling tool developed at the Lawrence Berkeley National Laboratories can help you out with the specifics- try to be realistic about the shading factors and pay attention to which cardinal direction it faces.
http://windows.lbl.gov/software/resfen/resfen.html
IIRC 2012 code max for U-factors in zone 6 is U0.32, but there will be situations where a high-SHGC and a U0.35 solution is better from an annualized energy use point of view, even in zone 6a.
Avoiding high SHGC windows may be important for both comfort & peak cooling loads on west facing unshaded windows. While the solar gains from east facing windows are the same as from west facing windows, the gain occurs at a cooler time of day, and in zone 6a the early AM wintertime gains may be more important than the air-conditioning load it presents in the summer. Think about it before specifying a high SHGC window on the east side though.