I’ve got an old house with no ridge vents and gable vents. I currently have a powered gable vent. It works but I hate the noise and constant use (here in the DC area).
I’m thinking about installing two solar powered attic fans. I’m lucky that the back of my roof faces due South.
Are these fans legit? Do they work or am I better off with good ole wired power?
Thanks,
JNF
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Replies
check the Florida Solar Energy Council's site, http://www.fsec.org, I think. They did some research on solar powered fans recently. Check also http://www.buildingscience.com.
Andy
"Never try to teach a pig to sing. It wastes your time and annoys the pig." Robert A. Heinlein
"Get off your dead #### and on your dying feet." Mom
The Felician School for Exceptional Children?
If Tyranny and Oppression come to this land, it will be in the guise of fighting a foreign enemy. --James Madison
check the Florida Solar Energy Council's
Did you mean the Florida Solar Energy Center?
http://www.fsec.ucf.edu/
Because that link you provided has nothing to do with Florida solar energy.
jt8
"A tree is known by its fruit; a man by his deeds. A good deed is never lost; he who sows courtesy reaps friendship, and he who plants kindness gathers love." -- Saint Basil
This is probably what he was referring to: http://www.fsec.ucf.edu/bldg/pubs/pvfan/There is a modest savings in cooling cost.But note that the house had no ridge vents. It's not clear that adding passive ridge vents wouldn't have produced an eqivalent effect.
If Tyranny and Oppression come to this land, it will be in the guise of fighting a foreign enemy. --James Madison
Passive ridge vents are great. I can go on the roof in the evening, hold my had over the vent, and feel the hot air coming up.
-- J.S.
Hey - I did it from memory. Be glad I didn't say the Phonecian Solar Enigma Castinet.
Yes, that's what I meant. Thanks.Andy
"Never try to teach a pig to sing. It wastes your time and annoys the pig." Robert A. Heinlein
"Get off your dead #### and on your dying feet." Mom
Solar powered fans are great IF you don't already have a wire run for an attic fan. The only area where you would save money with a solar fan vs an AC powered fan is the cost of the electrician you won't have to hire (or time saved jacking around running a wire yourself).
Solar fans cost $250+, while thermostaticly controlled AC units start aroung $70+. I think it takes longer than the lifespan of the solar unit to recoup the difference in electricity usage.
BTW, I have two solar units myself... and realized my poor math skills after I installed them. They work fine though.
Rebuilding my home in Cypress, CA
Also a CRX fanatic!
How do you know when you need more attic ventilation? Is there a specific temperature above which problems occur? The house I'm about to buy has ridge venting and vents below the eaves on the gable ends, but no vents in the soffits (near Asheville, NC). Thanks,
Erich
[email protected]
Almost certainly it needs soffit vents, and the gable end vents should be blocked (since they tend to "short-circuit" airflow between eaves and ridge.Current code generally requires about one-half square inch of ventillation for each square foot of roof, divided more or less evenly between soffit and ridge (or rooftop) vents. But a lot of folks recommend about twice that amount (and a one inch per foot rule is easy to remember).If there are decent size enclosed eaves it's usually easy to retrofit eave vents -- just cut holes, push back any insulation blocking airflow, and install vent grilles. Harder if the eaves are open on the bottom, or there's no eave overhang.
If Tyranny and Oppression come to this land, it will be in the guise of fighting a foreign enemy. --James Madison
I wondered about the short circuiting thing. Seems like the air would be entering close to the top of the roof where it wouldn't be as helpful. I could retrofit some soffit vents, but the roof pitch is fairly low and its going to be a real pain putting in the foam thingies to keep insulation from blocking the air path.Erich
Let the insulation guys put in the foam thingies -- I'm sure they have tricks to do it. (Just be sure that you specify that they're to be correctly installed and the vents not blocked when you sign the insulation contract, and don't pay them until the job's done correctly.) All you need to do, when installing the vents, is push back any fiberglass that's in the way.
If Tyranny and Oppression come to this land, it will be in the guise of fighting a foreign enemy. --James Madison
A ridge vent needs to have an equivalent open at the bottom as the top. So if the continuous ridge vent is .5" high x 20' long, you will need 240sq" of total opening along the bottom, or 120sq" opening per side. If you have a ridge vent, you sould insure that there is a path for the air to flow - it's not unusual for insulation to be installed up to and blocking the air intakes.
If you already have a ridge vent, you already have the best most efficient method for attic ventelation... just make sure that it can operate efficiently.
If you still are feeling the heat from the attic, then you just need to add more insulation to the attic.Rebuilding my home in Cypress, CA
Also a CRX fanatic!
Thanks for the advice, makes sense, volume in equals volume out etc. I won't know until I actually take possession of the house whether the heat will be an issue, but I already plan on adding blown in insulation to the bats already present (truss system, would be hard to roll out addtional bats, and I think Andy Engel recommended blown in in another thread somewhere.Erich