How to Build a Wine Cellar: Cooling Unit Size, Racks and the Parts That Seal the Room

A cellar sits colder than the rooms around it, so warm, humid air pushes toward it and condenses inside the walls. Staple 6 mil polyethylene to the warm side of the studs (the outside of the cellar walls and above the ceiling), tape every seam and penetration, then insulate: at least R-13 in the walls and R-19 in the ceiling, and many makers prefer R-19 walls and an R-30 ceiling.

The door is the biggest leak. Use an exterior grade or solid core door, a compression weatherstrip on the jamb and a door bottom that seals to the floor. A hollow interior door with a gap under it will undo the rest.

Measure the finished inside length, width and ceiling height and multiply: an 8 x 6 ft closet with an 8 ft ceiling is 384 cu ft. Self-contained cooling units are sold by the largest insulated cellar they hold at 55 F. Pick one rated at or above your volume.

Then add margin. Glass walls or a glass door let in far more heat than an insulated wall; we size up by half for them. A cellar inside a 70 F house, or next to a warm garage, also loads more than one in a cool basement. Vendors suggest 15 to 50% extra for weaker rooms.

Through-wall units blow their heat into the room behind them. That room has to stay below the unit's rated maximum and should be at least as large as the cellar, or the unit breathes its own exhaust. Mount it high, since cold air sinks.

Amazon does not sell through-wall cellar units, so these come from dealers. Prices below are dealer prices on the date shown; these links are not paid links.

Single-deep racking on 4 in cells holds about 9 bottles per square foot of wall, so about 60 bottles per foot of wall at 7 ft tall. Leave 3 ft for the door. Stackable floor racks are the cheapest way to fill a wall; label-forward wall racks show off the bottles you want to see.

Store bottles on their sides so the corks stay wet, and keep heavy racks anchored to the wall.

Keep the cellar at about 55 F and 50 to 70% humidity. A cooling unit failing in August can push a closet cellar to 80 F in a day, and you will not notice from upstairs. A WiFi sensor sends the alert to your phone.

A 24 in column fridge holds 150 or more bottles at cellar temperature with no construction, and front-venting models build into cabinetry.