Open cell vs. closed cell for hot roof in Florida
I just bought a 25 year old home in Jacksonville. 2 Story framed home off grade. We are considering replacing the fiberglass insulation in the attic with spray foam on the underside of the roof sheathing. My goal is to move make the attic more of conditioned space because 1) the air handler and all the A/C ducts are in the attic 2) We’re just finishing install a number of recessed cans in second floor ceiling.
I’ve been reading the recent articles that show open cell can lead to roof decking deterioration from humidify coming up through the attic. Locally the spray foam installers all recommend open-cell. Their arguments are that when the roof leaks you can tell with open cell. Some even claim 5.5″ of open cell is a air/vapor barrier but I don’t think that’s true.
I should say also that this house had a high humidify problem. When we moved in November with no A/C or heat on (yes it can happen in FL) we measured indoor humidify of 70-80%. We’ve tackled that with re-grading certain areas, gutters, french drains, whole house dehumidifier and finally 2″ of closed cell under the first floor decking.
What would you recommend for my goals in the attic?
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