Roof Vents

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Old 09-19-12, 08:15 AM
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Roof Vents

I had a roofing contractor look at my roof yesterday to give me an estimate on replacing the shingles. He wants to put vents in just below the peak of the roof for the length of the roof, about 52 feet long. Currently, the attic has two large (about 24x16-inch vents) at both ends of the attic and about a 1 Ĺ-inch space for ventilation all along the roof just above the gutters. When I was up on a ladder painting the fascia boards recently, we could feel the heat pouring out of those vents, so they do work.

My question. Is it worth putting the roof vents in? I have a difficult time thinking about cutting holes in the roof if itís not necessary.

This is on the Pacific Northwest about a mile in from the beach.
 
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Old 09-19-12, 08:39 AM
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If you're cutting in new vents with a new roof, I'd be looking at ridge vent.
 
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Old 09-19-12, 09:26 AM
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I agree with Mitch that a ridge vent should be considered, but a question. was the warm air exiting the 24 x 16 gable vents or the vents by the gutters. The fascia I'm assuming would be the vents by the gutters. If so, was there a breeze?

The primary purpose for ventilation is to remove moisture from the attic. With sufficient insulation and a well sealed ceiling/attic floor, it doesn't take a ton of vent area to be good. If you have a prevailing wind, maybe even less, as long as it isn't ocean spray. As you said, extra holes should be avoided.

Bud
 
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Old 09-19-12, 10:29 AM
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Holes in roofs should be avoided!
The problem is the passing wind causes an uplift and an area of low pressure above the home and downwind.
This pulls the air from the home adding to the heating and cooling loads.
If you want holes in the roof, then make sure the living area is completely sealed off airtight from the roof.
 
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Old 09-20-12, 09:19 AM
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Thanks for the replies. Iím a little hesitant to cut holes in the roof, hence asking this question here. I had another contractor look at the roof yesterday, and he agrees that cutting more holes in the roof probably isnít a good idea, and I trust him as he has done work for me before, so I have decided to not do the roof vents.

The house had a 1:1 pitch roof on it when I bought the house. I put a steep roof over it leaving the old roof in tact in 1991. I wanted nothing flatter than 4:1, so I ended up with 3 different pitches on the house. 4:1, 6:1, and 7:1 on the south side, the part Iím replacing as it gets damage every year from the strong winter storms we get. Blown insulation lays on top of the old roof. The gable vents along with the vents above the fascia boards should give it plenty of ventilation.
 
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Old 09-20-12, 10:03 AM
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I'm concerned about the extra layers of roof structure. Example, when they foam the bottom of a roof to insulate right under the shingles they do not recommend a lot of insulation down at the ceiling level. The purpose is to allow some heat up into the attic so the bottom of the insulated roof will stay above the dew point. If we follow that logic, when you insulate above that interior roof, you would want to be sure the space below gets some heat, all-be-it without inside air and its moisture.

I can't say for sure how this applies as I am here and you are there, it is hard to be sure I have the full picture.

Bud
 
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Old 09-20-12, 11:58 AM
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There is no foam insulation or any insulation attached to the roof at all. The blown fibre insulation lays on top of the old roof.

I guess photos will tell more than I can put into words.

First photo shows about 2/3 of the roof which is 52 feet long. The south side, or the right side of the roof in the photo is what I am going to have re-roofed. Photo was taken last year just before I patched the missing shingles you see. Iím tired of doing that 2 or 3 times every year, and since the roof has been there since 1991, Iíve decided to replace.



The second photo shows the attic. The yellow insulation you see towards the back and on the right is insulation for skylights.

 
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Old 09-20-12, 12:22 PM
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You said:
<I put a steep roof over it leaving the old roof in tact in 1991.......
Blown insulation lays on top of the old roof.>

I realize this has already been done, but my concern was for the space under the rood under all of that insulation. I'm assuming there is an attic below the attic we are seeing and the question is, is there more insulation on the floor of the lower attic?

Probably not a concern. My mention of foam was just an illustration.

Bud
 
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Old 09-20-12, 01:13 PM
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The old, or original roof was a 1:1 pitch roof that leaked when we bought the house and again within 2 years of replacing the roll roofing that was on it. The roof is made from 2x4 stringers and poorly insulated. The old roof is now the attic floor.
 
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Old 09-21-12, 03:09 PM
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I think a ridge vent is still in order. The heat and moisture that builds up in your attic needs to get out and at the top is the place to do it. Hot air is going to want to rise so getting it to run up one side of the house and then back down the other side to escape is hard to do. I realize you have gable end vents but a good ridge vent will do a better job of this and should be able to cut down on the heat build-up in your attic in the summer months.

I would emphasize GOOD ridge vent. do not use a ridge vent that comes on a roll. It will crush, it will allow wind blown rain, it will disappoint you in a number of ways. A rigid plastic one like an AirVent, Inc. product will cost more but it will preform better, last longer and give you fewer headaches. If you have a roofer who thinks ridge vents are a bad idea you probably have a roofer who has installed cheap ridge vents and then regretted the call backs.
 
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