A greenhouse heater may be needed during the cold winter months if freezing weather and overcast skies cause the temperatures inside the greenhouse to dip too low. One of the oldest types of auxiliary heaters is the paraffin greenhouse heater, one of the most basic heaters available on the market. While there are several benefits to using these types of heaters, such as the low cost, stable heat, and beneficial emissions, there are cons as well. It can be difficult to find fuel for them and they require ventilation. Manual control is needed to ensure the correct temperature.
Like kerosene lamps, paraffin greenhouse heaters have a wick that can be turned up or down, and they require chimneys to channel the flames. They use a crude form of petroleum which is usually fairly inexpensive to buy but can be difficult to find in stores because it is not popular. It may be necessary to shop for fuel in camping stores rather than typical home and garden centers. The fuel soaks into the wick and is burned slowly, while the heater is refilled as necessary. In addition to using an inexpensive fuel, the heaters themselves are usually inexpensive.
This type of heater is useful for greenhouses because it does not require electricity, which can be expensive and difficult to install in an auxiliary building like a greenhouse. In small greenhouse spaces, paraffin greenhouse heaters provide an even, stable heat, though it may take more than one heater to heat a larger space. There is also no automatic shut-off or thermostat for the heater, so it has to be manually turned on and off. If left on for too long, the greenhouse may become too hot and plants can be damaged. Conversely, if the paraffin burns out, the temperatures in the greenhouse will fall, so frequent monitoring is necessary.
Plants benefit from the carbon dioxide emissions put out by paraffin greenhouse heaters, but there are also carbon monoxide emissions, which can be dangerous to plants if not properly ventilated. Like other flame-producing devices, these heaters use oxygen, which is another reason that good ventilation is needed. It is also important to take care when refilling paraffin greenhouse heaters because paraffin spills on fingers can cause burns when lighting the heater.