Making a new penetration in Sealed Crawlspace?? Help
I am working on a kitchen remodel that will require the addtion of a MUA system to accomodate a High Power Range Hood.
The best opportunity to add the outside air intake is through one of the crawlspace vent holes. The vents are no longer functional as the crawl has been sealed using a 20mil vapor barrier and closed cell sprayfoam on the inner walls.
The idea is to fix a duct to one of the old vents (16"x8") to feed the MUA. Unfortunately this will require cutting away the foam around the vent. I can break away the mortar holding in the vent grate from the outside to remove it. Then I will carefully try to cut a rectangular hole in the foam to fit the duct. I feel like I will need to seal the duct to the foundation wall somehow on the inside, but that would require me to remove a wider section of foam to access the masonary on the inner wall.
Either way, how can I reestablish the integrity of the seal around the duct once it is installed??
I also need to add a few penetrations for some electrical conduits (1.5" - 2") they would need resealing too.
Only Idea I have is to use a can of Great Stuff or one of the higher end Great Stuff type kits that uses a gun. Is there potential that Great Stuff, or the like, would react with the existing closed cell foam in a damaging way?
I do not have a way to take the MUA intake through the ceiling/roof for acess reasons over the kitchen (2nd story). The attic and roof deck is sealed with foam too, so the same challenge would apply.
Thanks for support!