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Basements or portions of basements can be converted into root cellars with plywood walls, wooden shelves, and a few modifications in ventilation and insulation. Corners on the north side of the house (in the Northern Hemisphere) are the best location.
Refrigeration’s convenience, for the most part, has made root cellars a thing of the past, but they don’t have to be completely obsolete. Digging a hole isn’t even necessary anymore since a basement is naturally suited for the conditions of a root cellar. But you can’t just carry your goods down and leave them in the basement!
If you have a need for a space that stores your excess produce for far longer than any fridge, and you can save your precious fridge space for what you are currently using, a basement root cellar might be a great fit for you. If you are transforming a basement into a root cellar, then there is some important building information to know, and you will benefit from my detailed chart on how to achieve your favorite produce’s optimal shelf life.
Basements Are Ideal Spots for Root Cellars
Since a root cellar utilizes the earth’s properties of cooling, humidifying, and insulating, it would make perfect sense to have your root cellar in the basement since it is known for its cool and humid air. However, there is a difference between a basement and a true cellar.
Although your basement may seem like the perfect place for a root cellar, it is not perfect as-is. The temperatures needed to keep certain produce fresh for as long as possible are very specific, and the same goes for the humidity.
Each kind of produce you may store will have its own ideal temperatures and humidities. The average temperatures for a root cellar are between 32°F and 40°F (0°C to 4.5°C). The average humidity is between 85 to 95 percent.
Unless your basement falls perfectly into these parameters, which is unlikely, some modifications must be made.
These modifications that would have to be made would be adjustments to the ventilation and insulation of your basement. The magnitude of the modifications depends on the nature of your current basement, meaning, the quality of its ventilation and insulation, as well as its size. Furthermore, it would depend on the ideal conditions required for what you plan to store.
An important note: it is strongly recommended for root cellars not to be built in places that have a high water table or a septic system nearby. It is vital to evaluate whether this is the case for your basement.
Consider What You Plan to Store
Before the days of refrigeration, root cellars were used to store root vegetables (hence the name).
With refrigeration now readily available to most, root cellars are now used to protect produce from both the summer’s heat and the winter’s freezing temperatures. Shelf lives can be greatly extended by months with a root cellar, far more than any refrigerator.
Whether you’re storing your own harvest or your purchases from the local farmer’s market, a root cellar done right will ensure that they stay fresh for as long as possible and you won’t have to purchase and run another fridge or two.
Although root cellars should have a range of 32°F to 40°F and a humidity of between 85 to 95 percent, the produce you want to store might need more specific conditions.
It is important to consider what kinds of produce you’ll be storing so that you can provide the optimal temperature and humidity for each of them.
|Produce Type||Optimal Temperature (℉)||Optimal Humidity||Shelf Life|
|Brussels Sprouts||32||90-95||3-5 weeks|
|Winter Radishes||32||95-100||2-3 months|
Note: A root cellar does not just have to store fresh produce. It is also great for storing pickled items, bulbs of perennial flowers, and any homemade alcohol you might create. These have their own ideal temperatures and humidities to be stored at.
Turning Your Basement Into a Root Cellar
Before you break ground, so to speak, on your new root cellar, you should double-check that converting your basement into a root cellar does not require a building permit.
How Large Should It Be?
Most people do not use their entire basements for a root cellar.
Depending on the volume of produce you’ll be storing, a 5’ x 8’ area should hold more than enough for a single family.
With proper shelving and adequate use of all space, this area should hold up to 30 bushels of produce, which is more than 37 cubic feet of healthy and fresh fruits and vegetables.
If you need more or less space, this can be accommodated for as long as ventilation, humidity, and temperature needs can be met with this amount of space.
Using only a portion of your basement means that the rest of the basement can be used for pretty much anything you’d like.
A smaller space would also mean that the temperature and humidity can be controlled much easier and more efficiently since it is a small and confined area.
Where in Basement?
In a root cellar that only takes up a small portion of your basement, it is best to build in a corner. This would mean that two of the four walls are already insulated and built, with only two more needed to finish the enclosure.
A corner of the basement would also be beneficial for temperature reasons. In the northern hemisphere, the south side of the home gets the most direct sunlight, and the reverse is true for houses in the southern hemisphere.
The north corners of your basement would be the best for this reason. Although the basement may or may not have windows, the soil temperatures may vary based on the south or north side, which would potentially affect basement temperature.
Choosing the Best Materials
For building the walls of your root cellar, plywood would be the simplest. As long as it’s exterior-grade (moisture resistant), it is well-suited for this project.
As far as shelving material, wood is the best choice. Although metal may be tempting, its temperatures vary more. For consistency in the temperatures of your shelves, which come in direct contact with your produce, wood shelves are far more consistent.
Ventilation Is Vital
In order to get the longest shelf life possible for the produce and other potential products you are storing, proper ventilation is absolutely necessary.
It is vital to remember that ventilation involves old air being replaced with new air, not just air being purified. That being said, dehumidifiers and air purifiers do not ventilate.
Keeping the same, stale air in your root cellar would undermine efforts to control temperature and humidity, which would prove detrimental to the longevity of your stored products through the accumulation of mold and mildew. Not to mention what this does to the general quality of air in your home.
The most effective way to properly ventilate this small space is through mixed ventilation. This involves an exhaust and an air supply vent being installed.
The exhaust vent would pump the stale air from the root cellar and pump it outside of the house and the supply vent would pump in fresh, cool air from the outside.
This system is best since it is independent of the ventilation system of the rest of the house (allowing you to avoid chilling in the same environment as your carrots during the winter) and has the best results. It is more expensive than other ventilation options, but you will most likely find the other alternatives to be subpar.
For a room smaller than 8’ by 10’, 4” vents would be the biggest you’d need. For a larger space, you may want to consider installing more than two vents.
For more information involving mixed ventilation as well as other ventilation options for basements, visit our other article: Ventilating a Basement Without a Window (9 Practical Tips).
Insulation Is Important
When a cold and wet climate is made possible by properly done ventilation, all of this hard work can still go to waste if your root cellar is not insulated properly. Without proper insulation, cold can escape your root cellar, which also affects humidity (although insulation does not truly reduce humidity).
The average basement’s temperature is not likely to fall below 40 degrees Fahrenheit when it is unheated.
This means that the outside of your root cellar is likely to be warmer than the inside and that the temperatures and humidity provided by ventilation must have adequate insulation to protect your produce from the conditions on the outside.
Your basement temperature may vary more based on where you live, whether it’s finished, or other factors. To learn more about the ranges of basement temperatures, visit our other article: How Cold Will An Unheated Basement Get.
The walls, ceiling, and door of your root cellar must be insulated much like the rest of the basement, but in this case, to keep the cold in rather than out. The pipes and ducts connected to the root cellar would also have to be insulated since heat can enter through these too.
If at all possible, the outside of the basement in contact with your root cellar should not be insulated. This would prevent most of the soil’s natural cool and wet from entering your root cellar. This may be unavoidable since it is rare for builders to skip this step of basement insulation.
Root Cellar Insulation Based on Climate
The type and quality of insulation for your root cellar may depend on your local climate since some climates are more suited for root cellars than others.
In an already cool and wet climate, your basement may already support the conditions needed to preserve your produce. In that case, insulation can be laxer as long as the temperature and humidity are still checked often.
In warm or dry climates, it is even more important to have top-notch insulation, since the required conditions would be easily not be met if outside temperatures and humidity infiltrated your root cellar.
Controlling the airflow, humidity, and temperatures in a root cellar is very important as rotting produce is a breeding ground for pesky basement flies.
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