How to insulate a screened porch floor
I am looking to insulate the floor of a 3-season porch that is outfitted with removable sashes that will be removed for the entire summer season, thus exposing the floor to some blown-in rain. The sashes will be reinstalled in the fall so that the porch can be used in the fall and spring and will be opened up to the main house to benefit from the heating system in the house.
Is it safe to insulate beneath the porch floor, knowing that the wood floor (tongue and groove garapa) may get wet when the window sashes are not installed? I was thinking about using closed cell spray foam, but not sure if that will trap moisture at the underside of the flooring or if the moisture will eventually evaporate back up through the wood. I also thought about providing an air space below the flooring, with closed cell foam sprayed onto pressure-treated plywood run beneath the floor joists, but there really isn’t any conditioned area to vent the airspace to, and venting it to the exterior would defeat the purpose of insulating.
Any ideas would be appreciated!
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