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Old 05-08-2011, 10:41 PM   #1
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Venting a "hot roof"


I have a 1 1/2 style cape cod house. I have a problem with Ice dams. The primary culprit is that the top section of the roof is considered "hot" (no venting is going on. Only 4 inches of insulation (4" trusses) between the outside and inside of the house. I'm going to reroof the house with asphalt shingles. Someone recommended to remove the turtle vents and use a ridge vent. In order to get complete circulation of the roof (especially over the "hot" section, add 1" x 4"'s from top to bottom, and add on another layer of decking, thus allowing air to move all the way to the top of the ridge. My question is whether or not a 1" space will be sufficient to get the air to circulate?

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Old 05-09-2011, 04:17 PM   #2
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Venting a "hot roof"


A 1" space is the Minimal amount recommended, and most insulation Baffle Vent Manufacturers have 1 1/2" depths extruded in their products.

Without adding 100% continuous eave edge Intake Ventilation, you will not be doing much good.

I like to use the Smart Vent from DCI Products Inc.

http://www.dciproducts.com/html/smartvent.htm

By adding on another layer of decking, you will also have to consider in the weight factor, which should be okay, as long as there is only one layer of shingles installed on top.

But, additionally, custom made gable/rake edge flashings and gutter apron drip edge flashings will have to be created to cover the new height and gaps.

Ed

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Old 05-09-2011, 05:02 PM   #3
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Venting a "hot roof"


A few pictures of the flashing Ed is talking about; http://danperkinsroof.com/1108_JCL_Perkins_A.pdf

Can you add furring to the inside rafters (with foam board) to reach the minimum recommended R-value? Where are you located?

Then the sloped area would be non-vented, adding gable end vents for the side-wall attic and the peak attic.
http://www.buildingscience.com/docum...d-roof-systems

Gary
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