Greenhouses are often heated passively, through solar energy in the form of sunlight that enters through clear windows and stays trapped in the building. However, some greenhouses, including those used over the winter, require extra sources and methods of heating to remain productive and warm. While central heating systems for greenhouses are expensive, there are less costly systems that keep the price of heating a greenhouse low.
Small, portable heaters are useful for raising the temperature of a greenhouse, especially at night when outside temperatures drop. Space heaters help keep smaller greenhouses warm although they are not a cost-effective or energy-efficient option for large or commercial greenhouses. Combining a space heater with other forms of greenhouse heating systems is one way to keep the greenhouse warm throughout the year without paying for a central heating system in the building.
Insulating the inside of the greenhouse is one effective way to raise the temperature inside the greenhouse. Apply a silver or reflective sheet of greenhouse insulation along the north wall of the greenhouse; the reflective sheet acts as a mirror and stops sunlight from escaping through the back wall. This adds more light and heat to the greenhouse. Additionally, using clear greenhouse insulation to cover the other walls prevents extra heat from escaping, which raises the temperature of the greenhouse, even in winter.
Insulating around the base of the greenhouse helps keep the ground around the building warmer, which helps keep the interior of the greenhouse warm. Dig trenches around the base of the greenhouse that are about 2 feet deep and place polystyrene or insulation sheets into the trenches before filling them back in. The presence of insulation stops heat from escaping through the ground around the greenhouse. Combine ground insulation with other methods of heating.
Grow lamps are spotlights that shine heat and light directly onto an individual plant or a specific area of the greenhouse. The light emitted from a grow lamp is in the same spectrum as natural light, which keeps the plants healthy and growing, even during winter when there is less natural light available. Grow lamps also produce heat, which keeps the greenhouse temperature higher. However, grow lamps alone are not enough to keep the greenhouse productive during winter. Combine them with other heating methods.