Greenhouse temperatures can generally be controlled using ventilation during the day to keep the greenhouse from overheating. In very cold climates a heat source is necessary to keep the temperature close to the ideal range, particularly at night.

Small Greenhouse Heater For For Winter

Monitoring and controlling greenhouse temperature is very important to overwintering success. Usually a small greenhouse heater is sufficient, even in a cold climate. Plants in the greenhouse require ideal temperatures of 45°-55°F in winter. The higher the temperatures above this range, the more likely the plants will produce weak growth out of season. This causes the plants to be susceptible to various infestations.


With the small greenhouse heater in place, it is necessary to build plastic structures around the greenhouse to maintain insulation needed to hold the heat through the late cold spell. The plastic structure should have two layers with air between them. A small greenhouse heater will be good enough to keep the hot air inside and the cold outside if the plastic is airtight.

Sizing Of Small Greenhouse Heater

The sizing of small greenhouse heater is based on local climate, desired greenhouse temperature and greenhouse covering. Small greenhouse heater is usually rated by energy input requirements. By multiplying input value with heater’s efficiency factor, the output values can be obtained. To ensure that the small greenhouse heater is installed with right output sizing, several sizing factors must be considered:

• Surface Area, in square feet, of walls, ends and roof
• Lowest expected outdoor temperature
• Minimum desired temperature in the greenhouse
• Estimated heat loss