Using Your Attic to Heat Your Home – Part 3: Results

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by Tim Fulton on July 25, 2011

Over these couple of articles, you’ve learned a simple way to use your attic’s heat to warm up a house. But, how well does it really work? Lets take a look at some data I collected.

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To try to get an idea of we can do with the heat, I did some data logging. I started the fans manually on a sunny day in fall after getting home from work. Every 15 minutes or so I would check the attic and kitchen temperature (note: the time periods toward the end are not every 15 minutes). For the first couple of hours, the room was steadily increasing temperature at the rate of about 2 degrees and hour. The sudden dip around 7:00 shows the sun going down. Until then, the attic slowly drops in temperature as we pull the new cold/fresh air through it. Of course, as the attic decreases in temperature, the fans are turned off and then the room starts to cool.

Over the course of using the attic fan for the spring season, I noticed the fans would be on when I got home from work on any remotely sunny day. It really didn’t take a lot to turn them on. If it was sunny, I would find I normally came home to a room about 72F/22C versus about 65F/18C. To me, this is totally worth it.

Moving forward and as tips to others who might want to make their own system I have a few recommendations. I would suggest a larger fan. My fans would still be running when I went to sleep some nights when it was very sunny out. If you can move the heat faster, you can capture more of it before it escapes into the afternoon sky. Next, I would try to figure out a way to better distribute the heat through the house. With my small setup, the kitchen gets plenty warm and I wouldn’t mind that being spread around the house a bit. Unfortunately, it doesn’t seem to do this very well naturally.

So, thats it. That is my “free heat” setup. I love how it works and will probably tweak it here and there. For now it works nicely. For more information on the progression of things you can check out the forum thread. It also contains some other good ideas on what to do with the attic heat.


1 Mark O October 15, 2011 at 6:13 pm

This is very clever. However, there might be a risk of increased exposure to fiberglass particles…perhaps an air filter would help?

2 Tim Fulton October 19, 2011 at 9:28 am

Well, I don’t have fiberglass in the attic. I have cellulose insulation up there. I’ve also inspected the outlet down in the kitchen and the fans in the attic and I have found virtually no dust build up. Filters were initially in the plan and definitely aren’t a bad idea. However, I really don’t think its a necessity.

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