Root Cellar Ventilation System

Always having had a desire to be self-sufficient, my parents had space for an under-the-porch root cellar included in the home they had built in the mid 1990s. The cellar is 6' x 6' with a 10' ceiling, a dirt floor, and concrete walls on all sides (the wall against the basement has a doorway for entrance from the basement). For years this space sat vacant as no one in the family understood the purpose of a root cellar and the principles that allow storage of root vegetables through the cold months of winter. Fifteen years later, as my parents are working to finish the basement to make room for grandchildren, the question of "what to do with the root cellar" has arisen again. Having always been curious about how root cellars work, when home for Christmas in December I volunteered to research root cellaring and determine how to turn the "shed attached to the basement" into a storage room for the vegetables harvested from the family garden each fall.

I jumped on the internet and within an hour learned the basic principles of root cellar operation. I learned that the ideal temperature for the root cellar is 32 - 40 F. I learned the importance of having vents to allow cool air to fall into the cellar and warm air to escape. I learned how building custom shelving allows you to store different vegetables at heights that correspond to their ideal storage temperature within the cellar. I learned that keeping the humidity as high as possible (90-95%) prevents vegetables from shriveling. And I was fascinated to find out how an ideal root cellar utilizes natural processes to keep temperature and humidity at their optimum values.

For example, warm air rises and cool air falls. Thus, having a cool-air intake vent at the bottom of your cellar and an exhaust vent for warm air at the top of your cellar facilitates a ventilation cycle as cool outside air falls into the cellar and warm air escapes through the exhaust vent. Opening these vents when it's cool outside and closing them when it's warm is an additional measure that keeps the cellar as cold as possible. For humidity, the ideal cellar has a dirt floor which allows the moisture in the ground to regulate cellar humidity. Additional measures such as misting the walls of the cellar or leaving out a pan of water help keep humidity high.

I truly appreciate these natural processes and the way they've allowed people to store vegetables for hundreds of years. But as an engineer by training, however, my initial thought was that root cellar performance could be improved by the installation of a simple control system. For example, an automated system that opens and closes the intake and exhaust vents and turns on and off a ventilation fan depending and outside temperature would improve performance. Adding a humidification system to maximize relative humidity would be an additional benefit.

If a traditional root cellar allows the storage of vegetables from November through March, how long could root crops be stored in a cellar with a ventilation/humidification control system? September through April?

The purpose of this blog is to document (1) the construction of my parents' under-the-porch root celler, (2) the performance of the root cellar utilizing natural process climate control, and (3) any improvement in performance afforded by a ventilation control system.