West-facing thermopane windows with insufficient overhang – film, storm window, low e replacement?
I have a contemporary house with a 20′ wide x 22′ high west facing window wall and 12-12 pitch roof. There are four modules across, 5′ wide each. There are four 5′ x 5′ windows 2′ off the floor, two in the center above that, and four trapezoid shaped windows roughly 6′ high on the long side and 1′ long on the short side, with the top at a 45 degree angle to match the roof.
Believe it or not, the one thing I did not consider when designing the house was the consequence of the sun in the room facing west. There were a lot of trees shading the house, which are now dying.
I have white roller blinds on the rectangular windows, and a half-height bronze film attached to wood “sashes” I made in the trapezoid shaped windows. So, I get some areas with no shading at the top of the trapezoidal windows, a pretty strong glare of the sun through the bronze film – but very reduced heating on surfaces and skin, and the blinds are very warm to the touch – meaning each blind is a very warm 25 sq ft radiator into the room when the sun is shining on them.
I should have had a 3′ overhang when the house was built if the sun had been considered but I have only 14″. I also should have used low-E glass but did not. One issue service wise is I do have bird strikes multiple times a year.
I have dreamed up possible options of a custom awning, replacing the 10 glass units with low-E units, exterior or interior storm windows made of acrylic (low E appears to be an option), window film on exterior or interior (low E appears to be an option).
My main two concerns are the heating of the space from the sun, and the strong glare through the current film. On the windows with roller blinds, the 2″ space between the blinds and the window is getting very warm, the same as the blind material. In the area of the window below the bottom of the blind, the window is just above room temperature. I am wondering if this is infrared heating, even though the blind is white. Would a film on the inside of the window reflect a large amount of such energy back outside?
I would appreciate any and all comments. I don’t know that custom awnings could be created that would work and be structurally sound. It would have to be a large triangular affair on each side that sits under the eaves and juts out 4′ at the top I would guess. Replacing all the windows would be extremely expensive and what would the result be? Would there still be significant glare? If I have indoor storms, the roller blinds I currently use would have to go away, and I may find the glare from the storms unacceptable. Would an inside storm window suffer the same effect I currently have of becoming a radiator?
I prided myself for years at how I envisioned the house from all different angles. Ha ha the joke is now on me, 28 years later. I now have a hotbox. The house is on a slope, so the floor of this room is 10′ above grade to the downslope side. Trees would take another 28 years to help.
Don
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Replies
Don,
Consider installing horizontal metal Brise Soleil over the windows. The advantage of over other options is that while they stop direct sunlight, they don't collect snow or debris, interfere with wind, and let in diffuse light when not directly in sun. They also work well architecturally with modern designs.
Right now your most economical fix would be to install an aftermarket film with low solar heat gain LowE option as well as a dark tint to block solar glare.
Ideally your best performance option would be to install the film on the exterior glass surface, and there are films that are designed for exterior application, but life expectancy could be dependent on your local climate.
Since your current windows don't have a LowE coating there isn't a huge concern about trapping heat between the lites if you were to install the film on the interior glass surface, but ideally blocking the heat and glare on the exterior is preferable since your interior glass wouldn't get as hot as it would if the film was applied to the interior.
Hi Don,
If you haven't done so, you might consider doing simple solar modeling using 3D software to see what size and orientation of shading devices will be effective (if any). You don't say where your house is located; where I live, late afternoon sun though west-facing windows is indeed oppressive, and can be difficult to block with external horizontal shading or roof overhangs, because of the low angle of the sun.
Solar Screens are used a lot in the SW desert climates, especially on the west side. They are pretty effective as they mount on the outside of your windows.
The unfortunate thing about window walls like this is that the upper windows aren't really there for "view" (other than looking at the sky) but are really there for light and when there's way too much light there isn't much you can do to shade them properly. Even if you extended the overhang to 3 or 4 feet it wouldn't do much good since the sun is lower in the sky in the west.
Adding a pergola to the west side (with the top at the height of the beam that runs between the lower and upper sections of the window wall would shade the lower windows but do nothing for the upper windows. Therefore, since the upper windows are only producing glare at this point I would add outside privacy screens over the upper windows.
Here's some examples from a company in Australia just to show you what is possible.
https://environmdesigns.com.au/metal-privacy-screens/
I think they look quite good and would probably work quite well for your contemporary house.