Attic fan options.
 

I bought a two-level townhouse in Miami that has no attic fan. As you can imagine, during the day, my AC struggles to keep the temperatures down. I will be adding more insulation in the attic, but I also want to install an attic fan to draw all that hot air out.

Problem is there is no roof vent for an attic fan to be installed, nor are are any vertical gables. The only existing vent in the roof is the one for the clothes dryer, which is connected to a 4" duct.

Before I hire a contractor to install a roof vent by cutting a new hole in the roof, I was wonsdering if I could somehow use this vent as an interim attic exhaust by attaching a fan to it. Problem is that I went to home depot and the only attic fans they have there are 15" in diameter.

My question is, can I use a bathroom fan in the attic instead of the larger attic fan? I am aware that the flow will be much less, but any venting at this point will be better than what I have now, which is zero. Can bathroom fans stand the higher temperatures and more continuous use in an attic environment?

Another alternative is a 6" booster fan that I found on ebay, which says can operate in temperatures of up to 266 degrees. I could use this along with a thermostat to vent hot air out of the attic through the existing 4" vent.




Will any of the above options work until I save enough money to hire someone to do the job of installing the large attic fan on the roof?

Thanks in advance.

Do you have soffit vents and a ridge vent? If so, an attic fan might not be your best bet.

The primary thing to do is seal off any holes where air can be coming thru, saulk or spray foam around any pipe, wire, vent, etc. Then insulate well.

At that point the higher temperature of the attic shouldn't make that much of an impact on your house. I've read studies saying that the extra power an attic fan uses will cost you more in electricity because it's not having that big of an effect on the run time of the AC.

I do have soffit vents but no ridge vents.

When you say "air coming through" you mean from the attic down into the living areas?

Odd that there is no other vent on the roof. If I were you, I would talk to the association about having a ridge vent put on the building.
Yes, exactly.

When I replace people's ceiling fixtures/fans, I can't tell you how much air I feel coming thru the box. That air (and dust and insects) comes right into your home.

You need to seal around electrical boxes. Recessed fixtures need to be air tight, any hole needs to be filled.

Going around your attic with a can of spray foam and a caulk gun pulling up the insulation and filling holes will help you, both in the Summer and Winter.

I know, that's why I need something to vent out the hot air. But I will see about sealing any openings next time I go up in the attic (have to go in the early morning hours because it's literally like a sauna up there).

You do need some way to vent the air out. A fan may be overkill. This company sells large passive roof vents:
http://roofvents.com/ventdata.html

In the meantime, make sure your current insulation is not blocking the soffit vents. All you need is a rake to do this. Baffles may be needed, but they are fairly cheap and easy to install.

Also consider a foil barrier like this:
http://www.atticfoil.com/
or this:
http://www.savenrg.com/1rbschip.htm
Again, this is something you can do yourself, cheaply.

Posting in the roofing section of this site might get you some other suggestions.

Good luck,
RST

Thanks. I really like the foil barrier idea. Once I open up a vent I'll look into that.