Frank writes from Attleboro, Massachusetts: "I have a 16' x 14' unheated porch about 5' off the ground. I want to insulate the floor w/ 6" faced insulation. Should I put foam backer board on the bottom of the floor joist to hold up the insulation and keep it from getting wet?"

Answer: You won't see much benefit in terms of energy saving if the porch is unheated but if you really want the floor insulated you can install Kraft-faced insulation with the facing toward the warm air.

Building codes require that you cover foam products like FOAMULAR® extruded foam insulation so they are not left exposed. You can enclose the insulation with plywood.