1 &1/2 Story House Attic Ventilation

 
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Old 02-03-2010, 11:56 PM   #1
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1 &1/2 Story House Attic Ventilation


Client as a house that Ice dams and drips inside the house. The slanted ceiling is fully insulated so there is no air flow.
Wondering about putting vents at the top of the lower attic area, so air comes in the eave and out the middle of the roof.
And vents at the bottom line of the upper attic area so air comes in and out the ridge.

The middle area will still have no air flow.

Will this help? Who do you go to for such information. Not really structural. So not an engineer.

Thanks for any help.
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Old 02-04-2010, 12:19 AM   #2
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Re: 1 &1/2 Story House Attic Ventilation


Hard to tell without seeing the house, but if you can get air flow where the eaves are, that should help. When there's no cold outside air flowing through the eves, the roof surface gets too warm and melts the snow. Then you have water, then ice, then ice dams, then leaks.

In the past I've torn off a whole roof and put three-tab shingles on top of the insulation to push it down a couple inches. Enough to get some air flow through the whole roof. Hard to fix though without doing a lot of demolitioning.

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Old 02-04-2010, 12:30 AM   #3
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Re: 1 &1/2 Story House Attic Ventilation


What I would like to do is remove shingles and sheeting and insulation. Fix/install poly, fiberglass insulation, 2-4" styrofoam on top of rafters, 2 by 2's on top of insulation to provide air flow, then sheeting and new shingles.

This would give proper vapor barrier. Better insulation (R40 is considered minimum here) and proper attic ventilation. T
his is a costly remedy and was wondering if any good ideas out there on a less expensive way.
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Old 02-04-2010, 03:08 AM   #4
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Re: 1 &1/2 Story House Attic Ventilation


How about just strip first 3 ft of roof edge, I&W shield REROOF, worth a try, if that does not work, strip rock from int, add baffles and soffet vents, GMOD.
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Old 02-04-2010, 01:15 PM   #5
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Re: 1 &1/2 Story House Attic Ventilation


The ice & water may help with the ice build up at the bottom, but there is frost on the underside of the sheeting up as far as I can see which is about 1/2 way.
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Old 02-04-2010, 02:15 PM   #6
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Re: 1 &1/2 Story House Attic Ventilation


ridge vent, soffit vent, and RAFT-R-MATE baffles in the bays before re-insulating.
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Old 02-04-2010, 06:02 PM   #7
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Re: 1 &1/2 Story House Attic Ventilation


Ok so no easy way, either roof comes off, or drywall does.
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Old 02-04-2010, 06:04 PM   #8
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Re: 1 &1/2 Story House Attic Ventilation


Quote:
Originally Posted by Cjeff View Post
Ok so no easy way, either roof comes off, or drywall does.
Yes, but do it in steps, i would first I and W shield the first 3' see if that works, if it does not, then go for the baffles and the venting, GMOD
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Old 02-04-2010, 06:38 PM   #9
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Re: 1 &1/2 Story House Attic Ventilation


a few years ago we had the same problem with a spray foamed cathedral.

We stripped the shingles, stacked 2x purlins on the rafters (over the sheathing), then re-sheeted and shingled....I can't remember the actual detail, but we added to the facia and re-wrapped with coil to provide the ventilation.

The only real PITA was replacing the skylights and trim.
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Last edited by WNYcarpenter; 02-04-2010 at 06:47 PM.
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Old 02-04-2010, 08:00 PM   #10
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Re: 1 &1/2 Story House Attic Ventilation


During cold temperatures outside, the frost that you see in the attic can be associated with attic bypasses, i,e when warm air from inside the house escapes in to the attic (through light fixtures, attic access panels are not being closed evenly,etc) especially during freezing digits weather, the moisture condenses in the attic on the roof boards and rafters, where the frost can form.
Installing mechanical ventilation could cause other problems, because by adding more attic ventilation, it will allow more air to escape from the attic and by doing that, it will pulls more warm moist air from the house into the attic. I would start by finding the source of humidity and try to bring it down.
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Old 02-04-2010, 08:08 PM   #11
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Re: 1 &1/2 Story House Attic Ventilation


More ventilation is needed above the insulation. No other cure. You need cold roof above the existing cathedral.

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