*CUSTOM DESIGNED WINE ROOM
Floor, ceiling and all walls of the enclosure must be insulated to minimum R-20 rating, although R-30 is recommended. Best material is foil-backed urethane foam, sealed at all joints with thermal tape. Build a proper sub-floor with vapor barrier, and insulate to at least R-20, especially if floor is concrete.
All surfaces of the enclosure must be protected by a proper vapor barrier, ideally on both cold and warm sides.
Seal corners, joints, gaps, vents, electrical outlets and switches, and especially around door and frame, to achieve airtight seal. Pack larger gaps with insulation. Seal all with silicone caulking. Seal drywall with odorless waterproof paint.