Chris writes from Chicago, Illinois: "We are replacing a flat roof/deck on the 3rd floor with EPDM. Below the roof is a 2nd floor bedroom with pink insulation fiberglass insulation with R-11 between the rafters. There is Kraft-paper vapor barrier to the inside of the room.

My question is that when we tore the old roof off, there was a layer of plastic sheeting between the roof/felts/plywood top layers above and the subfloor boards below. With the fiberglass insulation that is in the bedroom ceiling below, is having the moisture barrier above also a good idea? Seems like a double moisture/vapor barrier to me. What do you think?"

Answer: A vapor retarder on the top side is not recommended in your situation. The Kraft facing on the product acts as the vapor retarder and is facing the interior of the room. Two vapor retarders on both sides of the insulation could lead to moisture problems.