We are going to finish out part of our basement for an office. Part of the basement is already a family room with dry back vinyl-asbestos tile attached directly to the floor. Our basement is very dry but the floors are cold and do get damp in the humid summers we have is St. Louis if the air conditioning is not running. We do also have a dehumidifier which we run when the air is not on. We want to put sheet vinyl down. Would it be advisable to put a 6mm poly sheet down first? Can we put some type of pad under the sheet vinyl to add some cushioning and warmth to the sheet vinyl? We don't have headroom to spare for a subfloor. Would appreciate any suggestions.