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Old 09-18-2012, 01:11 PM   #1
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roof ventilation quandary

I am having an issue with ventilation in my shop building.
The taller building is 48x72 with a 12 foot ceiling and is insulated with blown in cellulose which is a little lite as my inspection shows.
Less than 4" in some spots and lite at the outside edges. So I am planning to put another 4" of blown in fiberglass.
As far as i can calculate not knowing exact brands the roof seems to have required ventilation with the ridge vent and the ventilated soffit running full length.
The shorter building is 30x50 with a 10 ft ceiling that somewhere along its lifespan has lost its roof vents which will be corrected, it has vented soffit full length.
I have been having issues with ice dams and and you can see have ripped off my gutters and fascia trim and soffits on one side.
Luckily i had 2 rows of ice guard when we had the building built so no evident sheathing damage from the underside inspection. This is the only addition that has any issues at all.
I was going to install a powered gable vent but as i researched more that seems to be inadvisable .

Anyone here have any suggestions other than the ones i mentioned?


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Old 09-18-2012, 01:23 PM   #2
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Use a ridge vent not a powered vent.
Those foam baffels are needed in every bay.


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Old 09-18-2012, 02:33 PM   #3
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The baffles are in every bay (sorry bad picture) and open and it has an existing ridge vent about 68 feet.
This building should be venting but evidently is not.
Thanks for the reply
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Old 09-18-2012, 05:35 PM   #4
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4" is not enough and regardless of the baffles, if you are leaking radiant heat and a bunch of air, you are going to ice dam.

Seal up the top plates and blow in 14" of cellulose. The roof will never ice dam a gain.

Google Air Sealing and get some foam.
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