[PonchoV8]

I'm checking my temps in the attic and thinking about an attic fan. I see some that have adjustable temps and some that are set at 90. We've had a cool summer so far, but temps here are usually above 90 in the summer and high humidity. A 90 degree setting is not going to help if it's 95 outside.

What attic temps would be required to make my decision for me to buy an attic fan? At 1:00 pm my attic is 94 degrees and it's 86 or 87 outside--partly cloudy. Almost half of my ceiling surface is vaulted, so there's no way to add insulation without a roof tear off (sheathing and all). That's planned down the road if/when the economy stabilizes on an upward trend.

[PonchoV8]

At 1:22 pm it's 96 attic temp and about 88 outside.

[mike nixon]

Ours probably wouldn't work well in your situation. It's an 18" squirrelcage unit with a 1/2 hp motor that is belt driven. We set it up to suck air out of the house and push it out thru the attic killing two birds with one stone. In 10 minutes of run time it'll drop the house temp 10 degrees on a normal summer eve.

IMO I'd set something up on your attic that was t/stat controlled to keep the attic temps below 100 degrees. You should be able to install this economically an I think I'd wire in a manual over ride switch in to the living area.

Mike

[PonchoV8]

That's a whole house fan in the attic that you're talking about, Mike. And yeah, they're great in the evening. I was thinking of just using an attic-only fan that ventilates the attic--like the turbines do. But a powered unit, maybe mounted to the gable or a disc in the middle of the roof.

My max temp in the attic was 114 degrees this afternoon. It probably didn't get above 87 today according to the weather station.

[David Holmberg]

Doug, first you need to make sure the vents already there, in the eves are working and not blocked.

Lowe's and Home depot both have powered vents, even powered turbine style vents.
Depending on the style of roof, there are some good choices.

The best really isn't a DIY'er project, where they cut the very top of the roof off and install a vented cap. But anything that gets the air moving up there will help.

[fyrffytr1]

I have the vented ridge cap but am thinking about removing it and installing two roof fans.
Mine is a hip roof and therfore I have only about 40' of ridge vent. The attic is 2800 sqft. and the roof has a 6/12 or 7/12 pitch.

[Cammer-6]

make sure you install a firestat

[PonchoV8]

That must turn it off in case of fire.

Right now it's not bad up there. It's 79.3 in this room and 80 flat in the attic, but that's right at the hatch too. It could be a little higher back up in there.

[GT182]

Best I've had was a MaxiVent they make up in Canada. No power needed and you can see the heat coming rolling out. Looks just like a chimney. Only thng is, you must have vented soffits..... NO gable end vents.

Attic fans are a waste of electricity.

[PonchoV8]

I've got ridge vents on another house that we lived in, but it still seemed to get really hot up there. I installed that and vinyl soffit venting. I never tested for temp though.
If it costs less to run an attic ventilator than to run the ac non-stop when it's 90 plus outside, it makes sense to buy a fan.

It's about 86 outside now and 112.5 degrees up in the attic--no ridge vents. Just gable with a 64 little 1.75 inch holes for soffit vents. There are 28 in front and 36 in the back. They sure seem small.

[Blackwood Goat]

Doug

Never had any luck with attic fans. Had roof replaced two years ago and added Ridge,Soffit and static vents. Better air flow now.

[PonchoV8]

I'll have the roof done next year hopefully, with a metal roof. We're thru the biggest part of the hot summer now anyway.

Thanks,

[PonchoV8]

Guess what? I have a ridge vent. I realized it just now when I stuck my head in the attic to look for a gable vent, a vent that was never installed. So I'm not too 'up' on the ridge vent idea.

Attic temp today hit 118.2 with an outside temp of mid to upper 80s--full sun though.

[mechanickeith]

Doug, When the humidity is down, I run the evaporative cooler in the house. When I run the cooler, I have a box fan I put up in the attic crawl space access door. I have the fan blowing up into the attic. That way all the excess air from the cooler vents into the attic & out the gable vents. It dropped the attic tempurature more than 25* in the summer & the house inside temp even more.

[PonchoV8]

What's an evaporative cooler? Something that cools humidity and blows it in the air?

[grnmnstr]

I have an attic that gets very hot. It is fully insulated. I have a gable vent on each end that allows cool outside air in the attic with a thermostatically controlled attic fan (electric). The mfg set the stat at about 105. I left it there. It usually comes on about noon and goes off about 10 pm.

[JLHarper]

Thats about the way ours operated on our first house we built. Pitch roof mounted though. Kind of noisey too, and not sure it saved much.

You could about set your watch by the time it would go off, if not raining or weather change.

House faced South / Sout East and ranch style picking up hot Southern summer sun on a large roof expanse.
Jeff

[george kujanski]

An evaporative cooler is a device that essentially evaporates water with warmer, dry air, making the air cooler but adding humidity in the process. works in dry areas like Az. but not in areas where the humidity gets up to 90+ RH like the midwest or Florida.

George

[PB]

Doug-
I put in a ridge vent last fall when I put on a new roof. There is a math equation to figure air flow in your attic based upon your square footage. I think I got it from roofing.com...something like that. Anyway, I had to add more soffit vents around the perimeter of my house. I also had to install those soffit to attic dividers so the insulation in the attic doesn't block air flow from the soffits and up to the ridge vent. Check to make sure your soffit air space isn't blocked by your attic insulation. I still have a few more vent's to cut in on my house....maybe tomorrow

[David Jones]

My gable fan is set for 105. It runs until just before dark on a 90plus degree day.