How to Build a Passive Walk-in Cooler
- 1). Find a good location for your passive walk-in cooler. Ideally, your cooler should be close to your house and in a shady spot, such as under a large tree. For a family of four or five people, plan on building a cooler that is about 12 by 12 feet and 8 feet tall. Make sure your chosen space can accommodate the size of cooler you want to build.
- 2). Pour footings for your cooler. Footings extend below the frost line so the structure won't move or heave as the ground thaws and freezes during seasonal changes. Call your local county extension or county building department to find out your region's frost depth. In Minnesota, the frost depth is 42 inches, but it's only 12 inches in Missouri. Dig a hole in each corner of your site that is at least as deep as the frost depth for your area. Insert the cardboard concrete form tubes into the holes and pour pre-mixed concrete into the tubes. Allow the concrete to cure for a week.
- 3). Install a plank floor that slants slightly toward one corner. Make a square frame with treated 2-by-6-inch boards and lay your floor planks along the top of the frame. In the lower corner of the floor, install a drain to catch water from melting ice throughout the summer. Ice melts more quickly if it's sitting in standing water.
- 4). Build the outside walls of the walk-in cooler using standard 2-by-4-inch stud construction. Frame out a door but don't add windows. After the frame is in place, install siding on the outside walls. For the roof, install a simple shed roof that slants to the north. Install a vent in the peak of the roof under the eaves.
- 5). Construct a rectangular framework of 2-by-4-inch boards inside the cooler. This framework should be 10 to 20 inches in from the outside walls. Make sure it's wide enough for you to walk through. Board up the inside walls with plywood, and frame out a door that lines up with the exterior door. Install plywood to make a ceiling between the inner and outer walls. The space between the outer framework and inner framework will be filled with material to keep the building cool.
- 6). Pack the space between the interior and exterior walls with sawdust, hay, wood shavings or rock wool. Also, pack the space above the ceiling with this material.
- 7). Install a heavy outside door, and use spray insulation to fill in the areas around the door to keep cool air from escaping. Also, install wooden or metal shelves in the inner room for holding food.
- 8). Fill the space between the outer and inner walls with ice. If you live near a frozen lake, cut chunks of ice from the lake and stack them up between the walls. If you don't live near a frozen lake, buy blocks of ice or fill empty 2-liter water bottles with water and add 200 grams of salt to each bottle to give you a 10 percent salt water solution. The salt water solution lowers the freezing point of water and helps to keep the plastic bottles from being damaged.