The minimum temperature a cold weather greenhouse can handle depends on its insulation, heating methods, and the plants being grown. A well-designed structure with double-layered glazing, insulated walls, and thermal mass can maintain temperatures well above freezing, even in harsh winter conditions.
Some unheated greenhouses, known as cold frames or high tunnels, may drop to near outdoor temperatures at night but still provide protection from frost. In climates with extreme cold, supplemental heating may be necessary to keep temperatures above 32°F to prevent freezing. Hardy crops like kale, spinach, and carrots can tolerate lower temperatures, while more sensitive plants require a consistently warmer environment.
