Converting a new chest freezer into a climate controlled "root cellar".

Last edited Sat Dec 8, 2018, 10:39 PM - Edit history (1)

Relative humidity and temperature play an important role in long term storage of certain vegetables and fruits. provide optimum consideration and one may be able to store produce such as potatoes, onions carrots, parsnips, apples and others for months.

Now many of us don't have a root cellar out in the back yard or have a damp basement or accessible crawl space that stays quite cool in warmer weather but well above freezing in winter. I've been doing a lot of reading on the internet about storing produce long term and and idea that I had was to convert a new freezer into a root cellar. A root cellar that could be located anywhere in the home where it could fit and had access to a properly sized electrical outlet. I had seen numerous videos in the past where people converted a new chest freezer into a refrigerator because they claim that a chest type fridge is more efficient because when one opens the door, the cold air will remain in the chest rather then flow out like it would with a normal fridge and thus the unit will run less and thus cost less to operate. And some say that a chest freezer is cheaper then a comparable sized refrigerator even when one factors in the cost of a control need to do this conversion and that appears to be true when looking at Home Depot, Lowes and Best Buy websites.

First I'll talk about capacity. Chest freezers are measured in cubic feet an dry produce is often measured in bushels. It's easy to convert one to the other and below are the bushel equivalents of common chest freezer sizes:

3.5 cubic feet = 2.8 bushels
5 cubic feet = 4 bushels
7 cubic feet = 5.6 bushels
10.2 cubic feet = 8 bushels
15.7 cubic feet = 12.6 bushels
21.7 cubic feet = 17.4 bushels

Here is one bushel of common produce and their weight:

54 pounds onions = 1 bushel
45 pounds parsnips = 1 bushel
60 pounds potatoes = 1 bushel
50 pounds sweet potatoes = 1 bushel
48 pounds of apples = 1 bushel *(apples may not work well in this as they give off a lot of ethylene gas and should be stored alone)

Optimum temperatures and relative humidity (RH) for long term storage of produce:

potatoes - 38°F to 40°F at 95% RH
carrots - 32°F to 40°F at 98% RH
onions - 32°F to 35°F at 65%-70% RH
apples - 32°F to 40°F at 90%-95% RH
parsnips - 32°F to 40°F at 90%-95% RH
turnips - 32°F to 40°F at 90%-95% RH
rutabaga - 32°F to 40°F at 90%-95% RH

Potatoes, parsnips, carrots, turnips, and rutabagas can be stored together and based on the above info, this method may work best for the aforementioned produce. Onions should not be stored with other produce other then garlic and leeks but one may consider purchasing a $99 3.5 cu. ft. freezer just for onions.

Modifying a chest freezer to maintain a higher then freezing internal temperature is a simple process. One can purchase a temperature control such as this one which is listed at $62.21:

https://www.amazon.com/gp/product/B0002EAL58/ref=as_li_ss_tl?ie=UTF8&linkCode=ll1&tag=nloah-20&linkId=c4a1f00d6df86ed7164fbc0f183f2a50

Installing the above freezer temperature controller is simple and there are numerous videos on Youtube that one can watch to see how it's done. You should also purchase a stand alone freezer/refrigerator thermometer to put in the chest freezer.

To keep an eye on humidity, one will also need to purchase a good quality hygrometer to also place in the chest freezer.

To maintain proper humidity levels, one can achieve that by storing produce such as carrots and parsnips in plastic totes that contain clean, damp sand and rutabagas and turnips in totes that contain damp peat moss. Just make sure to keep checking the sand and peat moss and add water if needed to keep the medium damp. If that isn't enough to maintain a desired RH in the chest freezer, one may take a bowl, line the inside with a properly sized towel and add an inch or two of water to the bottom of the bowl. The towel will act as a wick and the moisture will then evaporate off the large surface area of the towel. If humidity gets too high, remove the bowl if there is one or leave the door open till the humidity level drops to where you want it. By trial and error, one should find how to best reach and maintain the proper humidity level.

Now for the part I'm not sure about and am still researching. Ventilation. Food storage areas, be they root cellars or indoor cold rooms, require proper ventilation lest the food spoil. Adequate ventilation for a chest freezer may take place by simply opening the top door for a few minutes every few days while removing food for consumption or checking the quality of food contained therein but I can't vouch for that. A better method is to buy a chest freezer that has an exterior drain plug. Then every so often remove the plug and open the top door. The heavy, cold air will flow out the plug and be replaced by fresh air coming in the top. You don't have to leave the drain plug open very long. Maybe a minute every few days as the cubic feet of the inside of the freezer isn't much and you certainly don't want to lose all your cold air and high humidity. Just make sure you don't block the inside of the drain plug so that little to no air can flow. And this is going to be another trail and error thing until you find by experience how often and how long you should do this.

In summary, while I've watched lots of videos of people who converted their chest freezer into a fridge or kegerator, I have not found a single video or article about converting a chest freezer into a cold unit for long term storage of vegetables. To me, it does look to be doable and requires just three things: Temperature control (already been done with a proven method), humidity control (looks to be simple) and adequate ventilation (trial and error).