solar attic fan opinions please

17 years ago

We have a modest new home which is very well insulated and has been situated for simple passive solar. This has worked well for winter heating help. What can I say? We have lots more heating days here in WI than we have cooling days. :-) We did a lot of research before designing this house and have 3 ft. overhangs on the south side to shade the windows in summer. We did not install air conditioning. It is a 50 ft. long ranch with 6/12 pitch, which one long expanse of roof is directly south. Shingles medium-dark. No trees shading, yet. We would like to exhaust some excess heat from our attic, to assist with summer comfort.

There is NO QUESTION that the exhaust fan we choose will be solar. I would like some of your opiniions on the solar attic fans that exhaust out the gable vent, rather than install through the roof. Obviously it is a much easier installation (handy hubby can do either way). But will having one fan, sized to suit the 1400 sq. ft. of attic, installed on one end do as well as one that can be installed centrally through the roof?

We do have adequate passive venting for the air to come in to replace what the fan draws out--50% of the 3 ft. soffits are full vents (not just little round "pucks") and the ridge vent runs the entire length of the roof and the gable ends have 18" X 24" vents.

Any experience greatly appreciated!

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Comments (8)

solargary
17 years ago
oops!
My brain slipped a cog on the calculation above.
The 230 BTU/hr less heat flow from attic to living area is OK, but this would be in the summer, and it would effect your electricity use for AC, not your heating bill.
Since you don't use AC, it would not save you any money, but would make the living area more comfortable.

I never thought about it before, but a solar attic fan would also run on sunny days in the winter. It would (I think) on average make the attic colder by bringing in more outside air. I would guess this might slightly increase your winter heating bills? Anyone have any thoughts on this?

Gary

Gary
JXBrown (Sunset 24, N San Diego County)
17 years ago
Wouldn't you want to run it at night to vent warm air and cool the house down in the summer?
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sweatin_in_texas
17 years ago
Here's MY experience.We dont have to worry about "winter" conditions here in Houston.Its that simple. We do fight heat and humidity.I had over 30" of insulation blown into my attic,and then added one solar fan that is capable of handling 1600 sq.ft. My home is just over 2500 sq.ft. My solar fan installer agreed to install my second fan,BUT with a thermostat on it.It runs at 80 degrees and above but will not run at 65 degrees and under.The first fan will run as long as it is daylight,which is OK. I have ridge vents as well as gable vents,my entire West wall soffitt is a continous vent underneath it.This attic BREATHES!!! My elec. bill hasnt exceeded 207.00 yet and our AC thermostat is set at 77 during the day and 73 all night. Sat and Sundays are at 73 day and night. I think the three main ingredients in keeping a home cool in the summer are as follows, inusulation,insulation and insulation. I have never heard of having "too much". I also have storm windows and doors. I did spend additional on my AC system "plenium" and vent work to "balance" the house.In the end,i think it has paid off for ME. Good Luck......
rockwater
14 years ago
my brother put in a Solatube solar fan early this year and so far he loves it. This is where he got it..
http://www.houseneeds.com/shop/vent/solartube/solarstarattickfans.asp he lives in california
srercrcr
14 years ago
Good insulation, attic vapor barrier, ridge and soffit vents are quite adequate. Beyond that there's a poor benefit to cost ratio. I hear solar fans aren;t durable and I had a powered attic fan in the 70sand 80s. It did have an adj tstat, could hear it run, and they are fire hazards (extreme temps/aging motor). I read that its crazy to pay for electricity to run the fan to reduce the attic temp slightly to save electricty.
Billl
14 years ago
Just as a basic physics premise, hot air rises. The most efficient way to cool a space is to pump hot air out the top and draw in cool air from the bottom.
garymunson
14 years ago
My personal experience in a hot climate (cent FL) is that the best return on investment for cooling is to install radiant barrier insulation. Easy DIY if you have room to get around in the attic and not too costly. A number of sellers online if you Google for them.
skrdtoask
14 years ago
If you are properly insulated in your ceiling, the transfer of heat DOWN to the living space is going to be modest. You do need proper natural ventalation in the attic to keep moisture at bay though. An attic fan can help this, but don't expect much of a difference over a properly vented attic.