Doesn't look like many are interested in a very useful mod.... it is a lot of work, but work, I think will pay off in the long run.
Hi Arpipeliner. I've insulated my 29HFS Toy Hauler in the cargo area (under bed) tanks, water lines/pipes, and the entire floor, as well as sealing up holes better than the factory. I really should have bought the winter package (Extreme Pkg), but seldom get caught in cold weather. I know it makes a difference with heat as well, but I don't have data to back it the claim.
I really like Reflectix, but found an excellent insulation / sound proofing material at HD. Its the bottom link. I am also redoing a 66 Mustang and am in the process of covering surfaces under floor and truck (behind rear seat, etc) with it. It isn't 'itchy' like fiberglass, which is nice. The Frost King product doesn't stick to plastic (poly tanks) as well as I would have liked, but by cleaning the tanks well with a degreaser; it is better. Strange that the aluminum duct tape that sticks incredibly, doesn't stick to it either (Frost King)... tried degreaser, alcohol, lacquer thinner, even enamel reducer, no luck. It sticks incredibly to metal, such as it as designed to do, but I think it will stay on the tanks. I'm going to find a picture or two to attach.
Shop Frost King 1-in x 12-in x 15-ft Plumbing Duct Insulation at Lowes.com
Shop Reflectix 25-ft x 48-in Double Reflective Insulation at Lowes.com
Radiant Barrier - Insulation - Building Materials¬*at The Home Depot