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Old 04-21-2011, 06:31 AM   #1
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Roof Venting

I recently had a ridge vent installed on my roof that was never properly vented, but there are no sofit vents. I'm considering installing round aluminum vents in sofit, but would like to know if that is adequate. Also, do I use a special hole saw to cut the openings in the plywood sofits?


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Old 04-21-2011, 06:40 AM   #2
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The ridge vent lets out hot air, but without inlets, it is not a venting system. Yes, install soffit vents. The soffit vents should equal the ridge vent in area, but a small area(even a 4" hole) in each rafter bay at the soffit will improve things greatly. In the summer, this provides flow through ventilation. In the winter, it allows cold air to flow under the roof sheathing, reducing or eliminating ice dams.


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Old 04-21-2011, 09:32 AM   #3
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There are a variety of soffit vents you can install. As Bill stated, it's a system. The number and type of vents you install will depend on the soffit construction you have. If each rafter bay is isolated, you would install a vent in each bay so the hot air would not be trapped. If the soffits are a common area around the houses perimeter, you could evenly space the vents. In some construction, they install a continuous soffit vent all around the house.
There is a formula for the total size of the soffit vents. Figure this out before you start so you get the correct size and number of vents.
You can't put too many.
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Old 04-23-2011, 10:24 PM   #4
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If using the 3-1/2" vents, they would need to be continuous to get the required 9NFVA per ft. at each soffit of a gable roof to match the 18NFVA at ridge;

The math;

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