Temperature and humidity play a critical role in long-term food storage in a root cellar, with ideal conditions falling just above freezing at 32-35 degrees Fahrenheit with high humidity of 90-95%.
Food typically keeps at its best under optimal temperatures and humidity conditions; however, even in climates where this is possible it will still require an effective cooling and ventilation system to avoid spoilage or rot.
An effective root cellar design involves four essential elements: insulation, ventilation, moisture control and darkness. Insulation helps ensure optimal temperatures remain constant, ventilation systems control ethylene gas from ripening fruit while moisture controls protect against mold growth and prevent rot and mildew growth.
Underground locations provide optimal temperature stability. Fully subterranean root cellars require excavation but provide the ultimate cooling environment, while partially-buried options such as hillside root cellars combine accessibility with efficient cooling for many homeowners.
Insulation is key to creating an ideal cellar environment, keeping out heat during summer and regulating temperatures during winter. A thick layer of insulation crafted from natural materials like straw bales, earth or recycled foam boards should be placed around the entire perimeter to reduce air leakage; strategically-placed vents allow cool outdoor air to enter during summer while colder indoor air can circulate.
Humidity is also an integral factor of optimal storage conditions, as too little moisture leads to vegetables withering away and too much dampness leads to spoilage. Moisture levels are managed through ventilation systems which have intake vents near the floor and exhaust vents near the ceiling to create a chimney effect; these passive ventilation systems also help reduce condensation.
Darkness is also key, preventing root vegetables from sprouting and maintaining nutritional values in other foods. While total darkness in an underground root cellar may be challenging to achieve, total darkness can still be achieved with simple measures like covering its door with plastic sheet or using an old ice chest or refrigerator as an insulated container.
As with any structure, root cellars require routine maintenance to ensure their longevity and functionality. Regular cleaning, repairs to any cracks or holes and pest control measures such as sealing entry points with screens or hardware cloth and creating rodent barriers underground may all help ensure its longevity and functionality. A yearly inspection should also take place so as to identify any maintenance needs that arise in time.