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Old 03-14-2017, 04:13 PM   #1
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Attic Ventilation


I used to have a roof fan to draw the air out of the attic. Got a new roof two years ago and have he ridge vent all the way across the top. I made sure that I have the proper soffit venting too so that the air flow is sufficient.

What I found is this attic is HOT HOT in the summer. That ridge vent and soffit vent combo simply does not keep the attic as cool as when I had the attic/roof fan.

So, I do have a large gable vent. Would you recommend attaching a fan to that blowing air INTO the attic from the outside?

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Old 03-14-2017, 04:19 PM   #2
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Re: Attic Ventilation


Attic temperatures, in theory, are irrelevant.

As long as you have sufficient insulation and air sealing across the attic / living space plane, it can be as hot as it wants to be in the attic as long as the soffits and ridge are working (i.e. flowing air and unobstructed).

The reason it was cooler with the attic fan is that is was probably sucking some of the conditioned air out of the living space below in the process. In effect, you were conditioning the attic.
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Old 03-19-2017, 07:52 PM   #3
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Re: Attic Ventilation


The gable fan may be closer to ridge and just pull exterior air from ridge vent. Check your total supply vent NFVA to see if it matches the exhaust ridge vent NFVA; https://www.google.com/url?sa=t&rct=...KPOT6w&cad=rja

Fiberglass insulation? that loses R-value when hot; up to code (minimums); http://energycode.pnl.gov/EnergyCodeReqs/index.jsp

Correctly sized attic baffles, if not, could get hotter ceiling flux?

FG, blown-in loose-fill of low density- loss due to conduction- may need a FG batts or cellulose layer (3") over it to stop that?

Need more info...

Gary
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Old 03-19-2017, 09:34 PM   #4
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Re: Attic Ventilation


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Originally Posted by Gary in WA View Post
The gable fan may be closer to ridge and just pull exterior air from ridge vent. Check your total supply vent NFVA to see if it matches the exhaust ridge vent NFVA; https://www.google.com/url?sa=t&rct=...KPOT6w&cad=rja

Fiberglass insulation? that loses R-value when hot; up to code (minimums); http://energycode.pnl.gov/EnergyCodeReqs/index.jsp

Correctly sized attic baffles, if not, could get hotter ceiling flux?

FG, blown-in loose-fill of low density- loss due to conduction- may need a FG batts or cellulose layer (3") over it to stop that?

Need more info...

Gary
My thought was not to pull the air out of the attic with a fan but instead to suck air into the attic from the outside forcing the flow through the attic and then out of the ridge vents.
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Old 03-20-2017, 09:40 PM   #5
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Re: Attic Ventilation


I doubt a gable mounted fan would do that, unless you closed the ridge vent and opened another gable at other end- with a ventilated tube from one to other- Venturi effect. Even then, big "if". It would need to be at every supply inlet vent (at same time) to wash the whole attic/roof. Did you check all things mentioned in my #3? You could add a RB, but I doubt it would pay for itself per your location.

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Old 03-20-2017, 09:59 PM   #6
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Re: Attic Ventilation


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Originally Posted by Gary in WA View Post
I doubt a gable mounted fan would do that, unless you closed the ridge vent and opened another gable at other end- with a ventilated tube from one to other- Venturi effect. Even then, big "if". It would need to be at every supply inlet vent (at same time) to wash the whole attic/roof. Did you check all things mentioned in my #3? You could add a RB, but I doubt it would pay for itself per your location.

Gary
Thanks Gary.. yes I checked out your earlier suggestions. AT this point I do not see myself investing in additional attic insulation only because I will most likely sell this house in the next two years and would not get the return on the investment.

I appreciate your feedback

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attic ventilation , gable vent , hot attic , ridge vent , roof vent


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