100 year raised old house in hot humid south louisiana. Following several local publication, my preference would be to install 2” foil faced poly iso to bottom of joist. Cost + time = not going to happen at this stage of ownership.

I refinished all my wood floors with vapor permeable (oil) finish, not film polyurethane which I’ve seen so many problems with when coupled with spray foam.

I’m not planning on insulating the floor, but can I spray just an air barrier (exterior) to underside of decking? No plywood, all solid-sawn wood decking. 

I’m trying to understand the potential risk of spraying paint or a dedicated air barrier with respect to dewpoint WITHOUT insulating the floor.  All my windows and door I retrofit weather-stripping at time of restoration – My goal is to seal up the subfloor. 

Thanks in advance