I'm not going to use Styrofoam around water heater. Was putting some bat insulation around it and installing a piece of plywood to box it in then Styrofoam on the outer wall of the plywood as well as the outer wall under the bench seat.
Have started under the bed. Nothings square, found a big hole in the floor area that was never sealed as well. Also discovered a leak in the back wall when I removed a light fixture that has a lot of rust on it. The fresh water fill line and overflow line are full of mold where the lines drooped down. They should have strapped them up to keep them drained. Guess that would be expecting too much.
I've put down some Styrofoam and put hangers above the fresh water to hold Styrofoam pieces in place. Will use some spray foam in areas that it's not feasible to cut and glue Styrofoam pieces. Will put down heat and noise mat over entire area when Styrofoam installation and batting is completed.
In Pensacola so didn't accomplish as much as I wanted due to tropical storm Gordon. Gonna try to post a few pics starting after removal of plywood then progression of installing Styrofoam board.