Whether the prized possession of a dedicated amateur gardener or a facility owned by a large commercial grower, many greenhouse operators equip their facilities with heaters to prevent damage to plants in a sudden cold snap. Greenhouse heaters carry BTU (British Thermal Unit) ratings as well as guidelines for the amount of square footage they can heat. The heaters may be powered by a variety of fuel or energy sources, including electricity, propane, natural gas or kerosene. Some models have forced air capabilities, while others circulate heat through normal convection.
Portable Electrical Heater
For small greenhouses lacking access to either propane or natural gas, a small electric heater may be the solution to cold weather heating needs. Units of this type will heat a space of approximately 150 square feet. The units may be equipped with multi-speed fans, a thermostat and protection against overheating. The advantage of this type of heater is that it takes up minimal floor space and may be stored away when not in use.
In a location which lacks electric power, a kerosene greenhouse heater may be an alternative. The units come equipped with a fuel reservoir capable of providing steady heat for many hours. Units of this type can heat spaces of approximately 150 square feet. The advantage of this type of unit is that it can provide heat during any type of emergency.
Non-vented Propane Heater
For use in a free-standing greenhouse, a non-vented propane heater is yet another equipment option. The units require the installation of a fresh air intake pipe, meaning they are usually installed along the wall. In a small greenhouse, one unit may provide adequate heating. In a larger structure, multiple heaters can be installed a regular intervals. The advantage of this type of unit is that it can be fueled by any propane source, including small portable propane cylinders. Using propane cylinders eliminates the need for permanent gas lines to be installed.
Natural Gas Heaters
For larger greenhouses or outbuildings, an economical option is to install a vented natural gas heater. Available models can produce as much as 400,000 BTU of heat. Most feature pilot-less ignition, automatic timers, thermostats and blower fans to provide even air circulation. While heaters of this type require air intakes and exhaust venting, their advantage over propane is that natural gas is generally a less-expensive fuel source.
If the greenhouse is located in an area not served by natural gas lines, an oil-fired heater might be a practical heating alternative. These units also require permanent air intake and exhaust ducts. Most feature automatic ignition systems. A fuel oil tank. must be installed with these units. Oil-fired heaters can provide as much as 185,000 BTU of steady reliable warmth.