In my previous article, we looked at how root cellars work and how we can best use them for winter storage of root vegetables. Now, it’s time to turn our attention to different kinds of root cellar designs.
Conditions for Storage
I like to say that it is better to have your cellar be at a slightly less than ideal temperature for carrot storage (say 39 degrees F, as opposed to 33.5 degrees F), then to have it fluctuate between those temperatures throughout the storage period.
For most roots, the ideal conditions are like those found in the soil over the winter—very cold, very humid and dark. Carrots and beets store best at around 33 degrees F, 95 percent relative humidity and dark.
Take these conditions into consideration. And understand the need to avoid fluctuations of these conditions. Then we can design low-cost root cellars that provide these conditions.
A root cellar that uses a compressor or other means of managing cold evenly can do this. However, the trade-off is a cost and a reliance on electricity.
On the other hand, an in-ground root cellar can do this by maximizing the exchange between the earth’s ambient temperature. It will balance it against the outdoor conditions. Furthermore, you can improve the cellar through the addition of some ice made in-situ in January and February.
The design I use provides great conditions for storing root vegetables right through winter and into the summer. The basic design is as follows.
- Build a concrete (or other) root cellar into the side of the hill.
- Use the earth as both a source of geothermal heat and insulation on all sides.
- Create a well-insulated façade and airlock (if you have the space).
You do need additional insulation on the front façade and the roof (as well as a waterproof membrane) to ensure the cellar is well protected against both summer heat and winter extremes.
Concrete provides a thermal mass for the cellar, so the temperature doesn’t fluctuate readily in the fall and spring, or freeze easily in winter. The larger the cellar, the more thermal buffer is available to prevent freezing in winter extremes.
I store vegetables in new feed bags that allows them to breathe. They hold humidity as well. This prevents mold from growing and ensures they don’t dehydrate.
I never store anything directly in front of the door. This is the one place where cold or warm air can seep, especially when opened.
Instead the cellar is divided into a few bays with cinderblock partitions. These act as both thermal buffers and dividers for organizing different crops. When I want to get a bag of carrots or beets, I just bring it to a wash area and process it.
Discovering Your Passive Cellar Conditions
Passive root cellars are like living entities. Each is unique, and you need to use them to find their balance. Observe and ask yourself questions such as:
- Do you need to add more soil on top to keep the temperature up in winter?
- Would more insulation help if added to the front wall?
- Will an overhang keep sun off the face to provide better conditions in spring?
Taking records and having a temperature humidity gauge in the cellar is key to understanding how the cellar is functioning and what is needed to improve it. Remember, unlike a “cold storage,” this is a passive entity that uses the earth’s natural conditions and the weather outside to strike a balance that serves your vegetables.
Root cellars are cold, dark and humid. They are also, by nature of being buried in the ground, very stable in their conditions.
When I used to store tens of thousands of pounds of roots in the winter for sale at farmers markets, people would sometimes ask me how I could stand packing and sorting vegetables in a cold cellar (mine keeps at 37.4 degrees F).
The fact is, because the cellar temperatures are so stable, free of winter effects and variation, I found it quite comfortable. When you have the right gear, a root cellar can feel far more comfortable than anywhere with a cold breeze.