I live in South Lousiana. Raised pier and beam (80 y/o) house, wood floors, no insulation. Refinishing wood floors, sanded with hardwax oil finish instead of occasionally problematic polyurethane finish.

It currently has plastic visqueen on the ground. Will be removing and adding pump sand to create some positive drainage (collecting water under middle of house). Will re apply 10mil plastic with gravel ballast after.

My preferred method would be 2″ rigid foil-faced insulation to bottom of joist. Lots of electrical, gas, and plumbing suspended below – cost and labor seems like too much. Supposed to be our 5-year-home (now 7 year..) Sprayfoam is out of the question – for resale, some buyers and inspectors won’t come near it and its expensive. 

We have a brand new A/C and furnace – air sealing and vapor control seem like a more viable option in terms of comfort. Any adverse effects or considerations to spraying the underside of floor with latex paint or specified fluid applied moisture barrier? I could get a couple buckets and my airless sprayer and knock the whole floor out in a weekend. 

Thanks for your help,