Passive Solar Heating

I have a passive solar house that is not heating enough, probably due to energy efficient, low e windows. In thinking about additional passive solar heating, my science geek husband warned me that they wouldn't work if placed in front of windows as "energy is neither created nor destroyed, so I would only be blocking the heat that was coming in and creating alternative heat." Adding passive solar heaters to a small section of the house that didn't have windows has always bothered me, as I couldn't figure out how to shut them down in the summer without taking them down so they wouldn't overheat. Then I was in the car the other day, thinking about how the slant on the windshield was so efficient in bringing in heat. I was thinking about using a storm window with a hinge at the top attached to my window, having hinged pieces on the sides that came in to hold it up, that could open to screening in the summer. I would basically be creating a greenhouse in the winter so I could open my windows a little at the top and a little at the bottom so convection could move the heat in during the day, and closing the window at night. During the summer, I could add a UV film to the underside of the storm window and use it as an awning with the screen sides. I would not have to take anything down and store it. I could use some kind of weather stripping where it all fits together for a seal and put something on the bottom with a hinge to seal in the last side.

Would this work or would it be too complicated for what it was worth?

Hi Sherri,

"Energy efficient" low e windows are the enemy of good solar design in my experience. My dad used them for the clear story windows in his shop and they barely let in any heat at all. For northern facing windows I can see using them (if there is a need for view or something similar) but overall they seem like a net negative for a well designed house. Blinds work much better for increasing the insulation of windows, as they can be opened during the day to allow for heat gain within the structure.

What your describing sounds an awful lot like a french tromb wall, I think it would certainly work. If I were in your shoes I would try to minimize moving parts, as they are points for something to break, but other than that it sounds like a great idea. If you are keeping the low e window couldn't you have a permanent installation (without moving parts) and just keep the window closed during the summer?

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I'm not sure what you are describing is worth it. Maybe a plan for an actual greenhouse on the southern side of the house is a better idea. It doesn't have to be large. I'd like to do this myself even though I have great solar heating. A sunny day in winter will raise the temps inside at least 5 degrees.

For me, I'd like it for a double entry. Our main entry is a sliding glass door and after 18 years it wants to pop back open a half an inch. Not a big deal except when it's less than freezing. at 10 or less it can really cool down the house over night!

Last thing, honeycomb blinds are great for keeping the heat in.

As I am working on window quilts, sounds like the only other thing I should do is get rid of the low e windows. plain double Glazed?