Basement root cellar
Traditionally, this cold room was an underground space built under or near the home, insulated by the ground and vented so cold air could flow in and warm air out in the fall. Then when winter temperatures arrived, the vents were closed, and the cellar stayed cold but not freezing.
Most modern basements are too warm for long-term winter storage, but you can create an indoor version of the cellars that have long served homesteaders well by walling off a basement corner and adding the vents, as shown in the drawing above. The two vents create a siphon effect that lets you regulate the flow of cold outside air into the insulated cellar room, allowing the temperature to remain near freezing through the winter months.
That’s why you’ll want to choose a corner location for your installation if you can. This offers maximum exposure to exterior walls while minimizing the need to build and insulate interior walls. And if you’ve got a choice, select a spot with the highest soil height outside. Does one of your possible options include northern exposure? Terrific! That’s great if you can get it.
Insulation is your next challenge, and good reasons exist to consider using rigid sheets of foam instead of traditional fiberglass batts. The most important is moisture resistance. Any basement is likely to get damp from time to time, and fiberglass has almost no ability to resist mold growth and deterioration when water is present. Foam, on the other hand, tolerates moisture much better. It’s also easier to use than fiberglass, and it’s non-irritating. Extruded polystyrene is especially good in this regard. It’s also a highly effective thermal insulator. Just be aware that some jurisdictions require foam to be covered with a fire-resistant sheet to meet code specifications. As you plan your insulation strategy, be sure to include the ceiling of your cellar. Warmth coming down from heated areas above could raise cellar temperatures too high for the food.
To function optimally, space the interior ends of the intake and exhaust pipes as far apart as possible. Also, you’ll need to plan your shelf layout to allow as much top-to-bottom air movement as you can achieve. This is where ceiling-mounted shelves can really help. The best idea is to use hanging metal wire frames that support shelves made of 2-by-12-inch lumber you cut yourself. Cover the vent openings with screen to keep out insects and mice, and if you want to really cool the room down quickly, add a little exhaust fan to supplement the natural flow of cool air down into the room.