Ray writes from Thunder Bay, Ontario: "I am building a cottage on sono tubes. The area underneath the cottage will have plenty of ventilation as I plan on only using a lattice skirt. My question is whether or not I should be applying a vapor barrier over the insulation and under the 3/4 inch OSB flooring. Using a vapor barrier will not allow me to use construction adhesive when screwing down the OSB. I am also concerned about water seeping down through the OSB and laying on the vapor barrier prior to getting the roof on. If I silicone the OSB joints will the OSB serve as a vapor barrier. The cottage will only be used seasonally."

Answer: I do not recommend installing insulation unless the building is dried in. Three-quarter-inch floor decking will act as a vapor retarder with or without caulking the seams, meaning an unfaced insulation can be used. Only your local code can dictate what should be used. If you want to caulk the seams to minimize the amount of water getting in then you can do that. Even with the seams caulked we do not recommend installing the insulation until the building is dried in.