Attic Fans

[MuleyFever]

I had to spend some time in my attic this weekend and holy cow was it hot up there, and its only March. The roof has at least 6 vents. This got me thinking about an attic fan. Are they worth it? Things to watch out for? Is there a temperature that I can watch for in the attic that would tell me it is getting abnormally hot? Other opinions on the subject?

 

[strousek]

Get you a QuietCool whole house fan. When the temp outside drops below the temp inside your house you simply open some windows up and turn on the fan. It will draw in outside air through the house and then exhaust into the attic. The positive pressure in the attic then pushes all that hot air out through the attic vents.

Cooling your attic off at nigh drastically reduces the heat blanket and keeps your house cooler inside longer the following day saving on AC cost.

Super easy to install and wire up. We run ours every evening and morning when it gets hot, like it has already. As long as you don't have bad allergies and can sleep with the windows open these things are great.

Whole House Fans

Classic & Energy Saver Whole House Fans for the best ventilation and cooling

store.quietcoolsystems.com

 

[Nine Banger]

Force draft attic fans are set to 95 degrees and typically only installed on hip roofs with no ridge vent/soffit here in my AO. It's salty here and they only work for a couple years before they seize up but that may not be a factor where you are. It wouldn't be a huge priority for me to run a wire and cut a hole in my roof.

Spray foam in the rafters is where the entire industry is going. Here we would install a dehu in the attic after foam but I doubt you need that where you are given presumed atmospheric conditions there.

 

[veganhunter]

Do you have enough intake ventilation on your soffits/eaves? The 6 turtle vents are there to exhaust warm air but often times the intake vents are covered up with insulation or are painted shut.

 

[MuleyFever]

Do you have enough intake ventilation on your soffits/eaves? The 6 turtle vents are there to exhaust warm air but often times the intake vents are covered up with insulation or are painted shut.

Hadn't thought about the intakes being covered.

 

[Silver Wings]

Whole house fans and attic fans are 2 different things. Whole house is great when you want outside air streaming through the house and out the attic. When outside conditions are optimal they are really nice…I have one and it works great for that. I installed it myself and it wasn’t particularly difficult, other than having to work in the attic. However, when temperatures are hot and the attic is super heated and radiating heat back down into the living space you can’t use the whole house fan or you pull hot outside air through the living space when you likely have the AC running. That is the case for an attic fan which can be mounted at a large vent exit and it will pull outside air from all the other vents, exhausting the super heated attic air. I think ideally you would have both. I currently do not have an attic fan but am considering adding one.

 

[Beendare]

Venting a whole house fan into the attic is usually a bad idea.

A quality attic vent with a thermostat is usually a great idea

 

[strousek]

Venting a whole house fan into the attic is usually a bad idea.

A quality attic vent with a thermostat is usually a great idea

Why would you say that venting a whole house fan into the attic being a bad idea? These products are literally desinged to be installed venting into the attic. Wondering why you would advise otherwise...


I should have looked at your location too I guess. Here in Colorado there are only maybe 3 or 4 days a year that we don't get below 70 degrees at night so we can run our whole house fan every night we want to. I could see if you lived in an area where the nights stay hot a humid where you run AC all night where it would not be feasible.

 

[Brewski]

Put a temperature sensor in the attic, the Bluetooth ones work well for this, and see how hot the attic really gets. If the temp is over 140 F, or around 130 F if your hvac blower is in the attic, add more vents. You want more intake vents than exhaust vents. The easiest time to add more exhaust venting is when reroofing.
If your house happens to have two layers of shingles (new roof built on top of old) then adding vents won't help much or at all.

 

[Silver Wings]

Why would you say that venting a whole house fan into the attic being a bad idea? These products are literally desinged to be installed venting into the attic. Wondering why you would advise otherwise...


I should have looked at your location too I guess. Here in Colorado there are only maybe 3 or 4 days a year that we don't get below 70 degrees at night so we can run our whole house fan every night we want to. I could see if you lived in an area where the nights stay hot a humid where you run AC all night where it would not be feasible.

Agree with you on this and would add…
With the whole house fan you are essentially saying I want the living space to feel like it does outside right now. After changing the air in the living space you will have the same temperature as outside.
By venting through the attic you get the benefit of not only removing the hot air but as the hours go by the heat that has sunk into every structure member, insulation material and HVAC equipment is pulled away. In the morning you start off with an attic that has cooled to ambient and will take longer to re heat as the day goes on.
As you pointed out, you have to have a climate that is amenable to letting the fan run at night.
As a side benefit the fan can be run all day to change out the air in the house many times over, as I’m doing today. This is helpful when your dog comes running back into the house after be sprayed by a skunk