Al Gore vent fans

[Kenneth E. Sitzes]

I got my buck knife, too. I found the 2hr course to be full if great in formation, I would tell ever one who can attend to take the time.

[Christopher Currins]

Stay away from solar attic fans.




POST #5
"Power vents and ridge vents would fight each other. Power vent would suck easiest flow of air. Power vent would suck high from the ridge vent instead of where it is supposed to suck low from the soffitt vents. This would be wasting your time."

[Joe Funderburk, CMI]

Originally Posted by ccurrins

Stay away from solar attic fans.

POST #5
"Power vents and ridge vents would fight each other. Power vent would suck easiest flow of air. Power vent would suck high from the ridge vent instead of where it is supposed to suck low from the soffitt vents. This would be wasting your time."

Still waiting on an authoritative source, such as the Energy Dept. or a scientific study. Anyone got that?

P.S. Seminars by folks selling ridge vents do not count as authoritative.

[Christopher Currins]

Originally Posted by jfunderburk

Still waiting on an authoritative source, such as the Energy Dept. or a scientific study. Anyone got that?

P.S. Seminars by folks selling ridge vents do not count as authoritative.

All I got is other opinions mixed with common sense.

[Bruce A. King]

I have first hand experience with this.


I have soffit vents, ridge vents and two power vents near the top of different sections of the attic. The attic is very large, about 4900sf with a 10/12 hip roof. I built the house and designed the attic ventilation this way on purpose. The ridge venting is simply there for exterior architectural effect and backup venting purposes in case the fans quit or it is not hot enough for them to come on.


To summarize a lot of "testing" and experience with the fans on/off or in one case a broken fan on hot days I know very well how this works.

Its one of those things that, yes, there is interaction between having the ridge and power fans both but it is a small percentage. A small fact that can be easily blown out of proportion in building science discussions.


The fact is this, when you have just soffit/ridge venting it meets code but barely vents the attic. (Think about all of those hot attics you go in) When you turn on a power roof fan or two, that hot air is sucked right out!

Since heat rises, all of that really hot air gets sucked right out and the lower attic area is very warm but not hot! I even have a black roof. With good soffit venting very little air is pulled from the living space, again a small percentage.

[James H. Bushart]

"Hot air rising" is really not the best way to describe the full effect of the ridge vent pulling air through the soffits, IMO.

The concept is much like an airplane wing...where the air blowing over it creates a negative pressure that lifts the plane....the wind blowing over a ridge vent also creates a negative pressure which pulls the air from the attic through the ridge vent, with that air being replaced through the soffit vent.

When there is a gable vent or some other source closer to the ridge vent, the negative pressure will draw air into the attic through that source which is closest to the ridge vent.

[Joe Funderburk, CMI]

Originally Posted by bking

...Its one of those things that, yes, there is interaction between having the ridge and power fans both but it is a small percentage. A small fact that can be easily blown out of proportion in building science discussions...

I'm with you Bruce.

[Bruce A. King]

Originally Posted by jbushart

"Hot air rising" is really not the best way to describe the full effect of the ridge vent pulling air through the soffits, IMO.

The concept is much like an airplane wing...where the air blowing over it creates a negative pressure that lifts the plane....the wind blowing over a ridge vent also creates a negative pressure which pulls the air from the attic through the ridge vent, with that air being replaced through the soffit vent.

When there is a gable vent or some other source closer to the ridge vent, the negative pressure will draw air into the attic through that source which is closest to the ridge vent.

I was not referring to the ridge vents.

In my attic, the warm/heated air rises to replace the hot air that was sucked out by the power fans. After it runs awhile it has warm air rising to a hotter area as it gets sucked out.

The ridge vents have very little effect on anything while the fans are running.

If the ridge vents "ruined" my setup then it would stay hot at the standing level and that is not at all true.

The entire attic (top to bottom and left to right) is actually very much cooler than with only soffit/ridge venting.

[Kenton H. Shepard, CMI]

On a warm day, a little testing with a smoke pencil might go a long way in resolving these arguments, most of which seem to based on theory. I've seen arguments one way or another from some pretty credible sources (Certainteed Shingle Applicator's manual, which I like a lot) but I never see any studies cited. I'd be inclined to believe Building Science Corp. if they have a good article.

[Kenton H. Shepard, CMI]

... and besides... Al Gore gives us all a chance to vent about something... him! Good 'ol Al... invented the internet and reduces our stress levels.

[Kenton H. Shepard, CMI]

If Al Gore were from Texas, what would he have invented?

[Gerry Pallotta]

Joe
Here's something done by Building Research Council at the University of Illinois.
http://www.oikos.com/esb/30/atticvent.html

Some more stuff.
http://www.cmhc-schl.gc.ca/publicati...ech/93-201.pdf
http://apps1.eere.energy.gov/buildin...rica/26450.pdf
http://www.airvent.com/pdf/RMETherma...ecSumJan09.pdf
http://www.airvent.com/pdf/AVBalUnba...aseStudy08.pdf

The guys from Air Vent also said that all roofs are not candidates for ridge venting but emphasized that those that do have it, venting should not be mixed unless attic space is separated (blocked off) due to different heights, shapes etc.. It's about finding the right balance for your attic. By the way air vent used to be a part of Certainteed