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venting a valley rafter?
- To: seaint(--nospam--at)seaint.org
- Subject: venting a valley rafter?
- From: Jim Wilson <wilsonengineers(--nospam--at)yahoo.com>
- Date: Thu, 27 Mar 2008 18:39:13 -0700 (PDT)
Is anyone aware of any verifiable ways to add venting to a large valley condition on a wood framed residence? The condition is a double 18" LVL valley with 2x12 rafters on an 8:12 pitch roof. The valley has a horizontal projection of 25ft. Currently, there are no holes drilled in the rafters and the top of the valley is tight to the roof sheathing. The roof was constructed a few months ago and is fully shingled, but not yet insulated.
The inspector is scrupulous and adheres to the letter of the code. (That's something of a relief in these parts.) Only that which is proven by testing or calculation is acceptable. He generally does not allow hole drilling in the rafters and it is not enough that I could validate the capacity of the members with the holes. I think there is something more about the air flow and the way the insulation is installed that tends to prevent
proper flow. If I could find some literature that explains the hole concept better, that might be adequate, if appropriate.
I searched the internet and found a patent issued to someone a few years ago for a valley venting device, but I couldn't find anything more about it. The inspector did suggest a product that can be installed prior to setting the sheathing. I am interested in what that product is if any of you are in the know.
Thanks in advance,