Running a greenhouse during the winter is much like running it throughout warmer months. The protective environment of a greenhouse shields plants from most of the outdoor elements. Although the greenhouse environment strives to maintain the same inside year-round, some outdoor elements do affect it. Cloudy winter months provide less sunlight, and the greenhouse struggles to maintain consistent warmer temperatures during these cold months. Keep these factors in mind when running your greenhouse in the winter.
Install a 200-volt circuit electric heater with a preset thermostat, recommends the West Virginia University Extension. Keep the heater set to about 70 degrees Fahrenheit during the day, turning it up to this temperature first thing in the morning. Turn the heater down to 50 degrees Fahrenheit at sunset and maintain this temperature throughout the night.
Install small ceiling mounted fans throughout the greenhouse to circulate heat down to the floor level.
Install smoke and carbon monoxide detectors in the greenhouse to alert you of potential dangers. Keep a weather station with a remote sensor in the greenhouse with an ice alert setting to notify you if the heat systems fail and temperatures fall below freezing.
Place plants on shelves to protect them from the cold floor. Build shelves only wide enough that you can easily reach the plants from each side.
Suspend grow lights 2 to 6 inches above sun-loving plants. Keep the glass in the greenhouse clean to take advantage of as much sunlight as possible.