Greenhouses have many requirements in order to be successful, and heating is a main component. Depending on your region and the size of your greenhouse, you may need to use heating from fall to winter. Keep in consideration the temperature your plants need and the total exposed outside area. A wide range of heating options for greenhouses is available, from central heating for a smaller space, to bottled gas units for larger spaces. Most commonly, a greenhouse heating system is fueled by electricity, oil, gas or wood and can be distributed by way of radiant heat, hot air, hot water or steam.
Electricity is probably the most popular option for clean and easy-to-control greenhouse heating, but it is also the most expensive. Many electrical heating units have thermostats and safety controls for extra protection. For beginners or start-ups, fan-heaters are ideal because they just need to be plugged in. They provide inexpensive well-circulated heat that will help prevent disease or mold in the beginning growth stages. Consider small low-wattage tubular heaters that can be installed in layers to conserve space.
Soil Warming Cables and Pads
Plastic propagating trays have soil warming cables in their base run by electricity. These can help warm the soil easily and inexpensively. Usually a thermostat is also built-in to enable various temperatures to be kept constant. These cables sit a couple inches below the soil and lightly warm it up for the plants. Warming pads are controlled in the same way, but the pad sits underneath the seedling trays. These are ideal for smaller greenhouses but can become expensive for larger units. Both of these products can also speed up germination and ensure heat is even.
Bottled Gas Heaters
A gas heater is common in greenhouses, but has more considerations to consider over electric. A gas heater that uses bottled gas is cost efficient and easy to obtain. On the other side, you need a very good ventilation system and an adequate location where the fumes or smoke can be let out through ventilation before the plants are affected. These can accommodate small to large greenhouses (they are most popular for larger greenhouses) and can be set up in a corner of the structure. The most common size is four by six feet.
A hot water or steam system is hooked up to an automatic ventilation system to create an even layer of heat through the entire greenhouse. Coal or natural gas is used to heat the water, which makes this choice the second most economical (gas is the first) and the steam sterilizes the soil as well, preventing disease and harmful bacteria. Steam and hot water greenhouse heaters can be used to maintain warm temperatures in both small and large greenhouses.
Forced Air Heater
Forced air greenhouse heaters work with a fan that creates artificial air movement and are low-cost, particularly for large greenhouses. This heater forces hot air over large distances and can be run by electric, solar powered or gas. Mounted on the wall with the ducts placed on the roof, a thermostat can help ensure constant and even temperature control.