Here’s the dilemma. I have a boxed-out 24-ft by 2-ft overhang on a shed roof. The overhang abuts an SIP wall panel, the 2×10 end. The overhang is a series of chambers that are roughly 24″ x 24″ by 10″ (joist spacing is 24 OC). Basically the “joist bays” are boxes, closed on all six sides, that aren’t connected to each other, and they are sealed off from the building so there’s not much potential for air movement. There’s no heated or cooled surfaces, other than the atmosphere..
Do you vent something like this? I suppose temperature change and a tiny amount of air leakage could cause a small amount of condensation within these bays, but I’m thinking cutting a hole and installing a screened vent in each space could lead to more potential for condensation.
Anybody ever deal with this before? Thanks, Nick
Replies
Greetings Nick,
This post, in response to your question, will bump the thread through the 'recent discussion' listing again which will increase it's viewing.
Perhaps it will catch someone's attention that can help you with advice.
Cheers
Ideally it should probably be vented at the soffit and also at the top where the rafter bays meet the sidewall. Otherwise, it's a good idea to at least add the soffit vents. Solar energy will heat up the rafter bays. Venting will keep the heat gain to a minumum.
ironick88
It depends on where you live.. you haven't filled in any information about yourself so you are going to get answers all over the board and they could all be correct depending on where they are from and other factors..
To be safe yes you should vent it however you might get away with not venting it depending on factors which you haven't told us about..
there a study that many believe that in the very hot humid south, it be better not to vent, just let the attic bake but have enough insulation to control the heat.
brownbagg,
I've seen similar stuff supporting non vent of SIP's in the north.
I agree with mike
I won't vent it. If you install soffit vents where does the air flow to?
No interior air can access it with mositure.
It's no different than thousands of other non vented soffits on old homes.
Venting won't hurt it but I don't think it will have much impact.
Rich
I may be missing something here but I don't see why you need to vent these spaces. If as you say they are exposed on all sides to mother nature, the temp. and humidity should be the same inside and out. The problems occur when you have warm moist air colliding with a cold surface.
Just remember, the advise is usually worth what you pay for it. Good luck. oops
Hi
I think I'm responding to all the folks who offered their experience and opinions on my question about whether or not to vent the blind spaces in the overhang at the front of roof on the SIP house I'm building. If so, thanks to all of you for your replies. I hope I can return the favor some day.
Cargin and OOPS were in agreement with the local building inspector, who compared those overhang areas to the closed-in area created by the gable roof above a porch. When I went to his house, he had removed the ceiling of his front porch while doing some repairs, and there was nothing to be found in the way of water infiltration or condensation damage in an area that had been boxed in and sealed for 50 years.
So, I didn't vent, and I'm as sure as you can be in this businesss that there will be no ill effects.
Thanks again
Nick Mercurio AKA ironick1988