Attic fans

[Oregonhunter5]

Guys I'm getting my roof Done right now. It has a attic fan that's dead. Do you guys have attic fans? Do you think there needed? Warmer weather here. I heard if you had enough vents that's fine.

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[oknow]

You can cool down the whole house in a matter of a few min. With a attic fan.

 

[deadeye]

I have one at each end of my house they are temperature controlled for on and off. They help extend the life of the composite type shingles, keep the house cooler in summer and make air conditioning more efficient.

 

[RicInOR]

What do you mean by Attic Fan?

I had one growing up in the midwest, which pulled cool air thru the house from the basement.

I have one in my house which vents just my attic area - draws outside air into the attic.

This second kind I recommend here in the PNW.

 

[The B]

As a roofing contractor here in the PNW......

Aside from some specific applications, fans are gonna be completely useless in your typical residential roof. If you have standard attic airspace ventilators installed, the fans will just draw air through these, which can and probably will interfere with proper convective airflow. You want intake at the bottom and exhaust at the top and nothing interfering with that cross-ventilating system - if your upper exhaust units are busy sucking IN fresh air because of the fan, your roof will actually stay overall hotter than it would without the fan.

There's some really good applications for electric fans, but they need to be engineered specific applications. Just throwing one up without any consideration for cross ventilation isn't gonna do you any good.

 

[Member 5605]

http://www.energyvanguard.com/blog-...e-1-Reason-Power-Attic-Ventilators-Don-t-Help

I agree with this, even if nobody else does.

Researchers at the Florida Solar Energy Center (FSEC) have reached similar conclusions to those reached by Tooley, Davis, and Katz. In an FSEC publication called "Fans to Reduce Cooling Costs in the Southeast," researcher Subrato Chandra wrote, "Data measured at FSEC and elsewhere show that attics with nominal natural ventilation and R-19 ceiling insulation do not need powered vent fans. Such fans cost more to operate than they save in reduced cooling costs, so they are not recommended." Of course, if your ceiling insulation is deeper than R-19 — as it should be — there's even less reason to worry about your attic temperatures.

 

[308]

One can ventilate the ceiling space but there needs to be a correct balance of the space pressure. Too negative and we pull air from below through the bathroom exhaust fans which have crappy backdraft dampers. Too positive in the attic and the same thing happens in reverse.
An attic fan with a speed controller pulling outside air set to a neutral attic space pressure would be best in my not so humble opinion

 

[308]

Perhaps a Greenheck direct drive inline fan ducted from an appropriately sized OSA louver....shouldn't be too hard to sort out.

 

[albin25]

Look for a "whole house fan" if you want to cool the house interior. they create a nice breeze through every open window and can cool a house down in minutes.
Don't vent it into your attic though, do a through the wall installation. They're pretty big though, so it may be hard to find a spot to locate it.

 

[The B]

Perhaps a Greenheck direct drive inline fan ducted from an appropriately sized OSA louver....shouldn't be too hard to sort out.

Sure, there's all kinds of ways you can do it. But it must be designed specifically for the attic in question. No one-size-fits-all. Gable vents are generally heat exhaust, not intake, because you don't get any airflow across the underside of the roof deck, which is what you need to actually cool the shingles down, as well as keep that radiant heat from penetrating the interior living space.

In any attic airspace ventilation system, your goal is to drag fresh air across the underside of your roof deck on it's way to exhaust.

 

[Oregonhunter5]

Topics like this interest me. Would that said, I have no gabel ends. Is t that when there's a peak? My roof slopes down on all sides. I thought my fan was to pull the hot air out of the attic?

 

[308]

Sure, there's all kinds of ways you can do it. But it must be designed specifically for the attic in question. No one-size-fits-all. Gable vents are generally heat exhaust, not intake, because you don't get any airflow across the underside of the roof deck, which is what you need to actually cool the shingles down, as well as keep that radiant heat from penetrating the interior living space.

In any attic airspace ventilation system, your goal is to drag fresh air across the underside of your roof deck on it's way to exhaust.

I'm visualizing my own roof with vents at the top and vents around the perimeter. In the case of my attic which is vaulted, any size fan pulling OSA would tend to push out pretty well. I do these things for a living on a much larger scale fwiw.