A warm-air oil-fired heater with a 100,000 BTU output is available. This is large enough to heat a 25-foot-long greenhouse. The heater is 23 inches high, 72 inches long and 22 inches deep, and is designed to fit underneath a greenhouse bench. The gun-type oil burner comes equipped with all controls, and a special thermostat with sunshade. The built-in blower has a rating of 900 cubic feet per minute, to assure good air circulation. A masonry chimney 12 to 24 inches above the ridge, or a metal smoke pipe with rotary cap to help provide adequate draft, should be provided.
Standard household fuel oil can be used. If the heater is installed in an attached workroom, a return air duct is required.
With the continually rising costs of all forms of energy, be sure to do a cost-analysis to be sure that at least for the foreseeable short-term that choosing oil will result in optimal costs for you. There are in addition, many low cost ways to enhance the heating in your greenhouse, and we will post some links to these shortly.