Most people say to use open cell foam for attic roof leaks. Could I spray closed cell foam over baffles from soffit to ridge vent?

Asked by Greg Childress
Charlotte, NC

If I put baffling between the rafters next to the roof sheathing, then spray 3" of closed cell foam, would this eliminate water issues and a hot roof? It seems like a good idea that I had never heard of before from other closed cell contractors. This would in theory create an airspace for molecule movement as well. I just want to know if this is a viable solution for NC climate.


Danny Kelly

Answered by Danny Kelly

Charlotte, NC

Kelly McArdle Construction

October 11, 2010

Greg --

That is a fine option and should work very well.

  • Your solution addresses the majority of the concerns of a "hot deck" or unvented attic.
  • If you are going to install home foam insulation over the baffles, I would build my own baffles rather than use the cheap foam ones you typically see with fiberglass. The cheap baffles are not rigid enough to withstand the expansion of the foam and you risk closing off your ventilation channel.

I would build my own baffles with either rigid foam or plywood. The rigid foam will also give you some additional R-value. Even better, use a foil-faced rigid foam with a minimum 1" airspace and you have a radiant barrier in your assembly as well.


For more information:

Check our best attic insulation Q&A to see what other homeowners and contractors are saying about attic ventilation, open cell vs closed cell, etc.

Tagged In: spray foam, attic insulation, attic ventilation

Do you have a question about greening your home? GreenHomeGuide invites you to Ask A Pro. Let our network of experienced green building professionals – architects, designers, contractors, electricians, energy experts, landscapers, tile & stone specialists, and more – help you find the right solution.