Passive Solar Glazing
Good morning! I’m currently in the process of designing my own home in Massachusetts, and I’m wondering about the 9-12% glazing rule on the south facing wall. I currently have a little under 1,800SF of finished living space, and I’m hoping to heat and cool with a minisplit on each floor. Currently I have 13% glazing on the south wall, which I worry will be too much in terms of overheating, and I’m wondering if anyone has dealt with this in the past? Windows are Pella Impervia triple glaze, and walls are double stud with roughly R-40 dense-pack cellulose. Site is decently shaded but not so much so that I’m worried about not getting enough sunlight, and the first floor windows have a large overhang above them for blocking out summer sun. I will attach a floorplan and southern elevation if anyone can help me decide if I should make the windows a touch smaller? Thanks, and have a great day!
GBA Detail Library
A collection of one thousand construction details organized by climate and house part
Replies
While I would always bias my windows southward, that does not mean add excessive glass
Glass to the floor in bedrooms? You will end up with the curtains drawn day and night, so what is the point? Additionally that bottom 2+ feet of glass is difficult to shade.
Agree on the glass to the floor. Windows that go lower than table height are impractical in a lot of ways -- placing furniture, placing electrical outlets -- and you can't see anything out of that part of the window unless you're on the edge of a cliff looking down.
That does make sense, maybe I'll raise the height on those so I'm not dealing with tempered windows as well. Thanks for the input!
Your title for the post makes me think you drank the passive solar Kool-Aid but you question no so much. The way I see passive solar is it is a great idea on paper but totally fails in the real world but not for the lack of time effort and money wasted.
The wall of windows could ne nice if you have a great view but without a view it is pretty pointless.
Note windows are almost always the single biggest line item in every construction budget. If one can control the window area and the square feet of the building magically the budget seems to work out.
When I made a computer (BEopt) model of my house and spun it in every direction it made almost zero difference. What I gained in the winter I lost in the summer.
Tripple pain windows and R40 walls sound great but are very expensive in fact they may never recover their high costs.
Have you considers the “pretty good house” idea?
https://www.greenbuildingadvisor.com/collection/the-pretty-good-house
Walta
It's not so much that I'm going for a "passive-solar" home, but that I'm trying to gain some benefits of solar gain on the southern side of the home without necessarily overheating the first floor, or possibly overworking the cooling system. I have read the Pretty Good House book and done extensive research as well. I am lucky enough that I can get a pretty good deal on triple glazed windows and the dense-pack cellulose insulation will end up being roughly the same cost as R-30 walls and an R-60 roof with closed/open sprayfoam if I were to build to code for my area, which is the Massachusetts Stretch Energy code, so I figured I might as well go a touch heavy on the insulation. However, this is not carved in stone, and why I'm looking for some input.
Passive solar works in sunny areas, I don't think Massachusetts qualifies as sunny. Overheating won't be a problem with the proper overhang unless its hot in October
My opinion randomly adding south facing windows and calling them a passive solar designed features is an insult to the people who poured lives into making it work.
I have that wall of window for the view, it gets me out of bed at sun rise to pull the shades from May to October.
Since the house is still just a plan build a BEopt model try it with more and less windows spin it 360° and listen to the numbers.
The software is free to use be sure to watch the training videos.
https://www.nrel.gov/buildings/beopt.html
https://www.youtube.com/playlist?list=PLHC0xDtkdjgec8QhVt7exJY3tpSLEFk-d
Walta