Dwayne writes from Dwight, Kansas: "I own a 16 X 80 mobile home. Field rats got under the trailer and tore out the insulation including the moisture barrier. I want to replace it with R-19 rolled insulation with a backing on it. Does the backing itself form a moisture barrier? If not, what would one run to cover the 16 X 80 area?"

Answer: If the backing you are writing about is a Kraft-paper facing, then yes, that is a vapor retarder. Install the insulation so the Kraft vapor retarder is up toward the warm-in-winter side of the home's underside.