Soffit Venting in High Humidity Area
I am having a roof redone, and I asked the contractor about continuous soffit venting as I want to provide air flow between every rafter. He is installing ridge venting full length except for the very ends. We are in northeast Louisiana where the temperature and humidity are often the same (90 degrees and 90 percent!) The contractor is saying we need to go with single vents in between rafters instead of continuous because that where the continuous goes over the rafter tail the area will start rotting because of the humidity being pulled in by the venting process. I have never heard of this nor have I found any information about this process. What do you think?
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Replies
Jay,
That same 90/90 air he is worried about introducing is also all around your house, under his truck and in his dog's fur. It's the ambient air, so where exactly you introduce it makes no difference. If it's capable of rotting the rafter tails, it should also be able to rot the area in between them - or any other part of the roof structure (Whether vented roofs are a good idea in hot humid climates like yours is a separate question, and something I'm not familiar enough with to comment on).
All that said, if spot vents are sized to provide the required intake volume, there is no disadvantage to using them over a continuous strip vent. What you are aiming for is air-movement in each rafter bay from eaves to ridge. How it is introduced isn't that important. I have spot vents on my own soffits.
Malcolm is correct. Also, I would be concerned about that contractors knowledge/lack thereof...
So if I am understanding your responses, I need to have a vent in each rafter bay. He is proposing putting one in every other bay and stating that will be enough ventilation. I am thinking that the unvented bays will be missing out on the updraft flow and will hold. What should I tell the contractor?
Jay,
It can work. If the enclosed area in the eaves above the soffits is unimpeded so air can flow horizontally, and the vents are sized to provide the required volume of air, then you should get good ventilation in every bay.
That's independent of his assertion that it's "enough" ventilation, as the vents will now have to be double the size they would be if placed in each bay. And it does nothing to solve his worries about the rafter tails.
That's a crazy high dew point. Hope that's not what your experiencing right now.
Does dew form on underside of soffits there ever?