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Earlier this spring we started excavating a big hole next to our house to serve as a root cellar. We live without electricity and with about 3/4 of the year here in the High Desert having cool, refrigeratory nights a root cellar seemed like a great idea.
Digging a Root Cellar
We are also a fossil-fuel-free urban homestead so digging our roughly 11-by 9-foot hole was done completely by hand. About half of the wonderful clay in the hole was used for our “One-Day Cob House” workshop in May and harvested by workshop participants during that weekend (we’re especially proud of that stacking of functions). The rest we dug piecemeal over several months. While I enjoy digging I never do it for more than an hour at a time unless we’ve created some sort of deadline. We also had an intern with us for a few months this past summer and she got to develop her digging skills in the root cellar quite regularly. In fact, she also dug most of our driveway Hugelkultur beds and several holes in our backyard for tree guilds. Lucky girl!
When we got to about 3 and a half feet deep I called it quits. I’m optimistic that will be deep enough to make good use of the constant coolness of the Earth. We went with earthbags for the walls until above grade and then used Balecob to the roof. Earthbags seemed the perfect fit for several reasons:
• I like working with them
• We had a ton of clay, stone, sand from our recently dug up driveway beds. Really an ideal mix for earthbags. We also added about 48 oz. of Portland cement to each bag to harden them up.
• They are inexpensive. I bought 200 of the 14-inch by 26-inch variety for about $80 and used them all.
• They partner nicely with cob and strawbales
I laid several inches of gravel on the bottom (including under the bags) and went round and round and up and up filling and tamping until reaching grade. In total we laid 9 rows of these bags. From there I added one more row of big bags (leftover feed bags from Feed World in Reno). These were heavy, but they got me about 8 inches above grade in most spots and are wide enough to hold a bale set on edge nicely. A bale is about 17 inches wide at its narrowest dimension (on edge) - the one I’ll be using above the bags. From what I recollect a strawbale set this way has an R-value of about 30. In addition to its insulative value, we chose to use bales because we want to cover their exteriors with luscious earthen plaster which we’ll get to put on and look at every day.
Other Root Cellar Features
I also set in "deadmen" of leftover redwood 4-inch by 4-inch scraps so I can attach shelving and tie in the roof beams with the shelves and walls. You'll also notice some vent pipes (black 4-inch ABS pipe) that stand up outside the wall and enter between the earthbags towards the floor on the inside. These will be cut shorter above grade and serve to improve air flow in conjunction with a high 6-inch vent on the door side of the cellar. Two low and one high on opposite sides of the cellar will bring cool air down and flush warm air out and provide needed ventilation for our future crops. Root cellars need three components to function well: cool temps, high humidity, and good ventilation.
More to come as we finish and use our earthbag root cellar.
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