High-solar-gain windows only on the south side?
user-2812795
| Posted in PassivHaus on
HI
zone 4/5 border. southern exposure faces ocean.
do we need high solar gain (.47 SHGC – ALMOST qualifies for Canada zone C, even) in all windows or just the south facing ones? Low E 180 glass…
THX
PATRICK
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One usually does not want high SHGC windows on the east and west sides because they are difficult to shade during the summer and it can lead to overheating. Passive House (PH) have a rule of thumb that the homes square footage should equal 8-12% of the south elevation glazing. So on a 3,000 ft² home, that would equal to 240-360 ft² of south facing glazing. The north side doesn't really matter because it will never really see direct sunlight (although water reflecting onto the glass can possibly radiate heat?).
Patrick,
The classic approach to choosing orientation-specific glazing calls for high-solar-gain glazing on the south side of your house (and, if you live in a cold climate, the east side) and low-solar-gain glazing on the west (and sometimes east) side of your house.
Every house is different, however. If one of your orientations has a very large area of glazing, the risk of overheating increases compared to a house with moderate glazing.
A good energy modeling program will show you the effects of different glazing choices. An online tool that is imperfect, but gives you an idea of various options, is available at the Efficient Windows Collaborative web site.
For more information on these topics, see All About Glazing Options.