I’ve been asked to insulate a porch that is now a part of the living space of the house. It was converted to living space a long time ago. The insulation there now is fiberglass batts that have fallen onto the ground. The joist are not 16″ on center – looks like an old farmer used what he had. I’m thinking about spraying the floor with two part expanding foam. Do I have to cover this with fire retardent paint? The space under the porch varies from 16″ to 36″. The closed cell foam would keep moisture out. The porch is on piers over earth with lattice on three sides.