Although not fully researched, reports by growers suggest radiant systems may save 30 to 50 percent on fuel bills. Convection heaters are an option for hobby and small commercial greenhouses. Although not as automated as more sophisticated systems, their relatively low price is attractive to some growers. These heaters use many types of fuel, including wood, coal, oil, or gas combusted in a firebox. The heater is usually at one end of the house and exhaust exits are at the opposite end.
Heat passes through an exhaust pipe along the ground between ground beds or beneath benches.
It is important that the exhaust not contact the crop, because incomplete combustion or impurities in fuels may injure greenhouse plants. Not yet in widespread use, advances in technology may make solar heat more attractive as a heat source for greenhouses. With solar heating systems, a backup unit is usually required to provide supplemental heat when solar heating is not enough to meet plant needs. Other Considerations When evaluating heating methods and fuel choices, consider many factors in addition to cost. For example, although wood or oil-fired convection heaters may be cheaper than natural gas or propane units, make sure the heater adequately protects plants overnight or at other times when the greenhouse may be unoccupied.