Attic / Roof ventilattion - hip roof , ridge vent , poser vent ?

rkpattJune 3, 2011

The house has a gable roof over the garage (gable vent on driveway end) tied into a hip roof over the main part of the house.

The roofer installed a ridge vent across both the gable and hip sections of the roof . He left the power vent (near the peak of middle of the hip roofed section ) the but told me to disable it which I did. However, the attic seems to be hotter than before. I am thinking that the area opening of the relatively short length of the ridge vent at the peak of the hip roof is too small to efficiently exhaust the hot air What are my options here ( run the power vent, add some more passive vents ("turtle back") high up on the hip roof fairly near the ridge etc ?

- Thanks

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In theory, the attic temperatures are not an issue of concern. The roof ability to vent the moisture is what is the critical element.

Yes, zoned AC systems that are in the attic do have to work harder if that is the case, but speaking purely theoretically, the temp is not the issue if your envelope (air) and insulation layer of your attic floor are intact and sufficient.

You will always want to have more incoming air than you have exhaust air. If not, you run the risk of creating a negative pressure in the attic and thereby removing conditioned air from the conditioned zone below. This is what is often happening when people run attic fans and feel like they are "working" by keeping the attic cooler.

They are, but at the expense of sucking conditioned air into the attic.

I am guessing that you have soffit vents for the incoming air? Have you checked them and are they unblocked and open? If they are and you have good continuous make up air coming in, putting a couple of vents in the roof (not powered) is okay if you are concerned.

Again, it is not really a necessity if your attic insulation and envelope air tightness is good. If you are worried about a second HVAC system running in inhospitable environments, a little more exhaust to get the air moving shouldn't be too back. That being said, even a small ridge vent should flow plenty of air. Check your soffits.

    Bookmark   August 22, 2011 at 1:09AM
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