Controlling heat gain on western-facing glazing?
Hi GBA,
Trying to prevent solar heat gain from cooking interior spaces through a large amount of west-facing glazing and hoping to pick the collective brain here for suggestions.
Notes:
* Two gable forms facing west, one the great room and one the primary bedroom, both connected by a glass breezeway with lift and slide doors opening on to a stone patio – diagram attached.
*All views are due west.
* CZ6, western Montana. Cold winters, hot(ish) summers, lots of sunny days, very dry, ±4,000′ elevation.
* 1′-6″ overhangs currently. I ran some daylight simulations, and you don’t really start getting appreciable shading till the overhang gets beyond 6′ – so simply blocking the light before it’s a problem doesn’t seem like an option.
* Recessed, pocketed, automated shades throughout. Obviously this is problematic/not possible at the triangular gable glazing.
* Not opposed to losing that upper glazing at the gables.
* Pushing hard for triple pane windows. I have a good local rep for guidance on coatings, etc but any suggestions welcome. Seems like triple pane + a good glass spec might be the only options for really controlling heat gain here?
* There will be a mechanical engineer designing all the systems.
* Still in design, plenty of time to pivot.
(As an aside: this is a lot of glazing, and it’s a vacation home. Not exactly “green” but I am trying to make decisions about assemblies and materials that will meet the client’s goals while doing the least harm)
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Replies
Shades aren't going to help with the heat gain. Once the light has crossed the glass the heat is trapped in the room.
There are really only two solutions. Have less light get through the glass -- less transmission, lower SHGC. Or have less of the glass exposed to the sunlight.
Big walls of glass like that create a lot of problems. Where do you put things like outlets? It may not be what the clients think they want, but I would argue you can get a lot of the same effect with less glass.
I know you don't want to hear 'less glass' but
Less glass
There are ways to get the look you want with a lot less glass.
Part of the problem is the though process
WE need these gable ends to put a bunch of glass in to get the view
then we need to have glass to the floor for dramatic effect
Baloney
You will spend little time in the room admiring the view because it will not be comfortable
Glass below the outside deck rail is useless, you are just looking at the deck rail
Full width of the room, what you need to look at the fence and the garden shed?
A more direct version of what I was hinting at in my response.
The designer's challenge is to get that "all glass" feel with a reasonable amount of glass.
DC,
It's so site and climate dependent. I can get away with huge amounts of south facing glass close to the ocean here in the PNW. This one never overheats, and I can't think of what I'd remove to lower the amount of glazing.
Why not do 6 or 7' roof extension? look at nordic designs. Idk how much an overhang will help on a western aspect as you get the setting sun but if your model shows gains, covered outdoor space is always a plus and a wall of glass protected by 6' of roof can only benefit.
Paul,
Along the same lines freyr_design suggested, what about a Brise soleil over the lower windows?
I have a largish 8x10 patio door that I was initially looking at putting a transom over. Cost and complexity nixed the idea and a lot of years down the road, I don't regret it. The extra windows up top would not have added anything but cost, the view is still great and I don't have to get on ladders to clean it.
As others have said above. Figure out how to get the most out of smaller windows. A bedroom with a wall of west facing glass (even low SHGC) will be an oven unless on its own HVAC, that is not cheap.
I do also have some larger west facing windows and get a lot of evening glare when the sun angle is wrong. I have seriously considered exterior slats to reduce it but can't figure out how to get the look right.
The one benefit of the west facing glass is a fair bit of sensible heat gain even with triple pane low E. This bit extra load really increases the runtime on my cooling which is great for humidity control, I can keep the house at 76F and RH never goes above 50% even in our hot and humid summers.
Agree with akos here
What benefit are the gable windows offering?
They *might increase the visibility of the mountains from the back of the room, but come to think of it, if you were that close, you wouldn't have a solar gain problem.
They will technically increase daylighting, but that often is practically neutralized by glare.
I just don't know what those windows are doing for the space. They do make the house look nice from the outside, but practically they're a problem that creates more problems. Lose lose
What am I missing?