Eliminating ridge vent, concerned about exhaust from fan


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Old 06-20-24, 05:52 PM
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Eliminating ridge vent, concerned about exhaust from fan

We’re getting a new roof put on my mom’s house. The roof is a hip roof, only has 1 soffit vent, has a ridge vent, and a power vent.

The roofing contractor says we have to eliminate the ridge vent to make the power roof fan work properly, I see his point. They are going to add shingle over roof vents a few feet up from the edge of the roof.

My mom has a 36” whole house fan in her hallway that she uses on mild days. My concern is once the roof vent is eliminated, I’ll only have these shingle over vents plus a hole in the roof for the power fan. I’m hoping that there’s enough square area of vent that the whole house fan doesn’t just pressurize the attic and cut down on exhausted air from the home.

Any advice?
 
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Old 06-21-24, 05:08 AM
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Is the whole house fan, in the hallway, also in the ceiling to the attic? If yes, don't agree with the roofing contractor. What was his reasons?
 
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Old 06-21-24, 05:32 AM
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The fan is centrally located in the hallway blowing up into the attic.

The thought on eliminating the ridge vent, and 3 roofing companies told me the same thing, was that the power vent wouldn’t work properly because there was too much free exhaust area with the ridge vent, and the fan couldn’t draw properly. There was only 1 vent in the soffit, therefore eliminating the ridge vent required them to install shingle over vents lower on the roof, about 3’ up from the edge.
 
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Old 06-21-24, 08:03 AM
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Why is there a power vent as well as a whole house fan? Can you be more specific about what fan blowing up into the attic means? Is the whole house fan in the ceiling of the hallway?
 
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Old 06-21-24, 08:04 AM
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The fan draws from the house and exhausts through any vents in the roof. I think you need new contractors.
 
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Old 06-21-24, 09:59 AM
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As far as I'm aware, roof fans have been largely replaced by passive venting (soffit/ridge vents).

While I agree the power vent won't work properly with the ridge vent, my preference would be to remove the power vent and add additional soffit vent options. If there isn't space for soffit vents, similar venting can be accomplished with a low-profile vent near the base of the roof.

What area/climate are you in?
 
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Old 06-21-24, 01:33 PM
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We’re located south of Pittsburgh. They are installing the low shingle over vents, but my contract doesn’t say how much or how many.

As near as I can figure, this 2 speed Sears belt drive whole house fan can move about 7000 cfm. One formula that I saw said that you take the cfm divided by 300 to get the required free air space for the inlet, I guess that would be the same for the exhaust, but 23.33 square feet sounds like a lot!
 
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Old 06-21-24, 02:02 PM
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I have a 40" whole house fan but it's in a sidewall. I use it to draw primarily from the whole house and discharge outside. I don't have a lot of soffit venting. I also have a rooftop venter and it draws enough from the existing soffit venting.

In your case your fan discharges into the attic. You must have a ridge vent or increase the soffit venting.
Additional soffit venting is always a plus with any system.
It's not always the easiest to add/install though.
 
 

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