Thursday, June 9, 2011

Solar cooling

Several years ago, I went on a kick of reading all the solar energy books our local library had.  I was trying to find a way to heat our old home with solar energy during the winters.  To my surprise, the parts of these books that I found most useful was just the opposite:  how to keep our home cool during the summer.

We don't have central air conditioning.  We don't even have window units.  Our house does have a couple of things that have proved to be really invaluable:  a large tree on the east side and another on the west side of our home.  We also have a "whole house fan" in the attic.

Any tips you read about saving money air conditioning tell you to close curtains in sunny windows.  The greenhouse effect is a huge one, as you can tell by getting into your car on a sunny day.  We now take this advice even more seriously.  I followed the instructions in my books to make "pop-ins" for my southern windows -- essentially, styrofoam board inserts.

During the day, we cover windows and we close up the entire house.  Then at night, we open windows and turn on the whole house fan.  It helps that our bedroom window is low on the west side, and the fan is high on the east side -- the prevailing winds help blow the cooler night winds into the house; the hot air rises within the house and is blown out by the fan.  We pretty consistently keep our home temperatures about 10 degrees cooler than the outside daytime temperatures.

It's not perfect.   This works better toward the beginning of the summer, when the difference between the day's heat and the night's coolness is larger.   10 degrees cooler than 97 degrees is 87 degrees, so usually in August's really hot days, it can still get fairly warm in the house.  And the fan doesn't deal with humidity.  But it's worked out to be good enough for us.  Most of our summer guests who know we don't have air conditioning are surprised at how cool our house turns out to be.

Making a "pop-in" is really easy -- even easier than making curtains, I think.  Hardware stores sell large styrofoam sheets.  I measured our windows and cut rectangles that would fit.  I "finished" the edges with white duct tape, adding a little extra piece of tape as a tab that I could use to pull the pop-in back out of the window.  Instead of leaving the sheet plain, I decorated the fronts -- spray paint worked on one.  I taped fabric on another.  In my boys' room, I used blue painter's tape to attach a large spiderman poster to the pop-in.  During the winter when the pop-in isn't in use, it hangs on the wall as decoration.

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