Remove roof vent when replacing roof on a spray foamed roof deck?
Almost 15 years ago we were one of the first people in our area to use spray foam, and used open cell foam in a cathedral ceiling. Closed cell foam was available, but at that point it was hard to find information about the pros and cons. At that time, the County where I live required us to put in a ridge vent despite me telling them that it was not necessary. Now we need to replace our roof and I am curious to see how the roof and insulation performed, especially since we have a solar system installed on top of it with a bunch of penetrations. My question is, do you think that we should remove the ridge vent while re-roofing, or if it the roof seems solid in that area, would it be better to retain the ridge vent? If we remove it, should we install some type of air barrier and insulation in that void or a vapor permeable material? Maybe rigid foam with spray foam around it?
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Replies
A roof vent where the air flow if blocked by foam on the interior side isn't doing anything for the roof.
When re-roofing it's an opportunity moment (albeit expensive) to add rigid insulation above the roof deck to raise the average wintertime temperature of the roof deck. The amount of exterior-R needed for dew point control at the roof deck is of course dependent upon local climate. Where is this house?
The PV on top of the roof deck complicates adding exterior insulation, but it's complicating the re-roofing project no matter what.
Thanks Dana. So we will plan not to reinstall the ridge vent. I will inspect it when the roof comes off to make sure there is no gap in the insulation at the ridge and that it is dry. The project is in Climate Zone 4 near Washington, D.C. Yes I would love to add rigid insulation above the roof deck on this roof and another vented shed roof with poor insulation. The issue is that we just don't have any roofing contractors or general contractors who will do this type of work in our region. If you know of any, please send them our way!
Dana has it right; most important step is using this opportunity to learn how your assembly has performed over the last 15 years, then use that info to inform what you change.
Peter
Thanks Peter. That sounds like a good plan.