If you’ve ever popped your head up into an attic on a remotely sunny day you know it can be incredibly warm up there. So, this idea got me thinking about how I could use that heat in a what useful manner. Often the more simple you can do things the more efficient they are. So, I thought about blowing the hot attic air right down into the house to heat it up in spring and fall.
The first test was done in the fall of last year (2010). I had put a thermometer up in the attic to watch the temperatures. I saw it was more than 90F/32C up there and I have my heat set to 68F/20C. So, I decided to just try and throw a fan into the attic opening. This blew air for a while and warmed up the immediate area quite a bit. It was quite warm by the end of the night, and the amazing thing was the attic was still quite warm even a while after the sun had gone down and that was with the fan blowing. After seeing this, I was hooked and knew that there was a sizable amount of heat ready for the taking. The best part is its clean energy (no fuels burnt) and it is virtually free!
I used the first setup a couple times and then started improving upon it. I knew a lot of the air blowing down was probably going right back up into the attic. The fan wasn’t even covering half of the attic access opening. So, I found a piece of foam insulation that just happened to fit quite well and laid it in the opening. This improved the setup quite a bit. The heat was able to spread around the house much better and it warmed up the rooms around it a couple degrees F.
So, I was quite happy with the improved setup, but there was still a lot of room for improvement. If I wanted to do this every day in spring and fall I’d have to go upstairs, open the attic hatch, get the fan, put it up there, put the piece of insulation in place and manually turn the fan on. If the attic wasn’t really warm I’d have to watch the temperature to make sure the fan wasn’t in fact cooling the house off. It worked great, but it needed some automation. That was the next step.
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Be careful. What is the insulation in your attic? Blowing it into your house could adversely affect air quality. Sealing the ladder when you are not using the fan is very important. The attic hatch is one of the biggest gaps that can let your winter heated house air escape into the attic, so make it a very tight fit. You could put a filter on the fan to make a poor man’s hepa filter from Univ. of Mich. http://www.youtube.com/watch?v=kH5APw_SLUU
Thanks for the warnings David.
I have cellulose in the attic. Despite what some people may think, its not dusty at all up there. I have used my current automated system (next week’s blog covers it) for over 3 months now. There is no build up of dust on the fan blades. That said, a filter isn’t a bad idea at all and I may eventually add one.
The ladder door does have weather stripping all around it and seals quite well.
Love the concept and have thought about something similar for years, but wondering how to maybe just run the air through tubes so the air recirculates with the indoor air. Can’t beat your simplicity. You might love a http://www.wattvision.com I have one and love it.
So it’s like a whole house fan in reverse.
Since you already use a ground source heat pump you might look into these two companies:
http://www.nuenergyalternatives.com & http://www.dawnsolar.com
Both companies make additions to fluid heat systems that capture heat lost through the attic. Nuenergy has a product called “Greenward Ridge Vent” that captures heat exhausted through the ridge vent. And Dawn Solar uses the roof itself as a heat absorber. (using components like those use in radiant heat flooring but in reverse)
Both systems are relatively easy to reproduce at a diy level.
This might negate the need for the fan idea or just boost the available heat for your ground source heat pump in the end.
Yep, it is essentially an attic fan in reverse.
I’m not the one who has the heat pump. AC Hacker, who is a member on our forum, is the one who has been doing all the DIY heat pump stuff.
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