We are building a new home this summer in Central MO with a sunroom to actually help heat the house. Should I forego low-e and settle for plain insulated glass (only on the south wall), or sacrifice some of the incoming sun by using low-e to help me out with the A/C? I am afraid the solar heat gain coefficent of Andersen and Marvin low-e would kill the solar input. I will be using Window Quilts to help with night-time heat loss in the winter and will have overhangs to keep out summer sun. Anybody still into solar?
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Our 1909 foursquare had the front porch converted to a sunroom in the 80's. Unlike alot of 70's and 80's solar projects, this one still works great. Since we face a city sidewalk and street, polycarbonate translucent panels are the glazing. Even with those, that allow significantly less light than low-e or low-solar-gain glass, the heat gain on a clear winter day is significant. If anything, I'd be afraid of overheating with any clear glass. A key will be sizing the overhang, and perhaps making it adjustable (what feels great on March 21st would cook you on Sept. 21st)
The best feature of ours is 3 ft. deep of river rock under the room, a column at the ceiling with thermostat & fan, & vent in the floor on the opposite corner - set it to 75 degrees or so and the mass really helps temper heating needs. (and even helps cool a bit in summer)
Thanks for your input. Your polycarbonate experience steers me toward low-e.
bob, it was my understanding that low e coating reflects out the rays when coming in at a higher angle, allowing them in when at a low angle. Perfect (if my understanding is correct) for your situation. Shade it in the summer, allow it in in the winter.Remodeling Contractor just outside the Glass City.
Quittin' Time
Calvin
Low-e does not depend on sun angle. It depends on wavelength. And my by which type of coat (or separate sheet) and on which surface they can be tweaked to allow more gain in one direction than the other.
There is a product that has a number of very fine layers of light blocking material sandwiched between clear layers that will only allow light from certain angles. That is what is used on some traffic lights so that you can only see the one in your lane.
When this first came out they where touting it for sun control, but I don't think that ever got of the ground. I suspect that it is too expensive for that.
Here are a couple of links on windows, the first was working the other day, but is done at the moment.
http://www.efficientwindows.org/
http://windows.lbl.gov/
Calvin-
I remember low-e being described to us that way when it came out. I had that same thought re: my situation. I haven't seen low-e described like you mentioned in recent literature. I will inquire and hope it still works that way. Manufacturers publish their solar heat gain coefficient (SHGC) and low-e really knocks that way back. I don't know if they factor angle in or not. Thanks
Manufacturers publish their solar heat gain coefficient (SHGC) and low-e really knocks that way back.
Last time I posted from this chart I screwed up. One more try:
Reading carefully, comparing dual glazed and dual with low e, low e loses SHGC by .72 to .78 (8%). U value, however, goes from .49 to .35. In your area, as here, I'd certainly go for low e. Added benefit is greatly reduced fading/degradation of everything inside. With argon, the U difference is even greater.
If you intend to use good window covers carefully, you'd probably make up the difference. We don't bother with any window covers for our 300 sq ft of glass and like living this way.PAHS Designer/Builder- Bury it!
Are you talking about the double or triple layer polycarb like is used on greenhouses?
Ours is almost 20 years old, but it is double layer, with channels about 3/4" wide - similar to Lexan Thermoclear http://www.solar-components.com/sun.htm#polycarb or by Duo-Gard http://www.duo-gard.com/index.html
Yes, that is what I was thinking about.
Thanks. I have a project in the back of my mine for using those.