Share Facebook Twitter Google + LinkedIn Pinterest Soon it will be time to heat the greenhouse. The heating system may have been working when it was last used this past spring, but those systems have had several warm and humid summer months to degrade.A heater or boiler out of tune will use more fuel than necessary and could produce harmful exhaust inside the greenhouse. In addition, new cracks or other air gaps in the structure will quickly leak heat. Checking over the greenhouse structure and heating systems as fall approaches will save your heating costs.HeatersService space heaters or boiler serviced once a year. Check with your natural gas or propane provider to see if heater inspection is a service offered. Hire a qualified service technician to perform regular maintenance. Gains in efficiency can more than pay for a professional tune-up.There is some basic maintenance for a gas space heater, but only perform as much self-service as you feel comfortable with. Before the heating season check heaters, air inlets, and chimneys for bird nests and other debris. Clean gas burners with a bristle brush and compressed air. Inspect the heat exchanger and exhaust pipe for cracks. A cracked heat exchanger or vent pipe will allow harmful gasses such as carbon monoxide and ethylene into the greenhouse. Electrical connections should be tight. If fuel oil is used, replace the fuel filter. Check pilot or spark ignition for proper operation.Turn on gas burners and inspect gas flames. The burner flame should be blue. A yellow flame indicates incomplete combustion and could be caused by a dirty or misaligned orifice. An unstable flame may be an indication of drafts from a cracked heat exchanger or other air leaks. Check gas supply lines for leaks with a soap solution while the gas is on. Make sure propane tanks have adequate pressure or that fuel oil tank is full.Regular heating system maintenance results in a 2% increase in efficiency. For a 30-foot by 100-foot greenhouse 2% can save: 285 therms of natural gas, 330 gallons of propane, or 200 gallons of fuel oil. The savings should more than pay for the service. Seal air leaksExpandable foam, weather stripping, and caulking can be used to seal air leaks in the greenhouse structure where heat can escape. Check for air gaps around doors, ventilation fans, and other equipment mounted through the glazing. Plastic film can become cut, punctured, or torn with regular use throughout the year. It is very easy to accidently poke a long handled tool through polyethylene film. Inspect the film and use an appropriate tape to seal any holes.Keep photosynthesis in mind when sealing the greenhouse. Plants require carbon dioxide for photosynthesis. If the greenhouse is too well sealed, carbon dioxide levels will drop and photosynthesis will decrease. Monitoring carbon dioxide levels in the greenhouse will help to determine if there is enough ventilation for plants to grow. An air exchange rate of 0.1 to 0.3 exchanges per hour is necessary to ensure sufficient carbon dioxide. An alternative option to ventilation is the installation of a carbon dioxide burner.In addition to using up carbon dioxide, plants in an air-tight greenhouse will raise relative humidity. It is therefore necessary to actively remove moisture from a well-sealed greenhouse. To maintain acceptable humidity levels, a greenhouse will require between 0.3 and 1 air exchanges per hour. The exact air exchange rate required is dependent on outside humidity level. Measuring relative humidity in the greenhouse will be necessary to ensure proper humidity levels for plant transpiration and disease control.Louvers are designed to seal when ventilation fans are not operating. If ventilation fans will be needed for dehumidification during the winter, lubricate louvers so they can easily shut when fans are turned off. If fans will not be used during the winter, consider sealing them with plastic or Styrofoam insulation inside and out. Any other openings in the greenhouse structure that will not be used during winter such as cooling pads should be well sealed.Light LevelLimited light in the winter due to low solar angle and short daytime can be made worse by dirty glazing. Glazing should be cleaned prior to the winter season. Double layer plastic film should be inflated with outside air for higher light transmission. If high humidity greenhouse air is used to inflate double layer plastic covering, condensation will form between the layers and reduce light transmission. Inflation to the proper static pressure is important for maximizing the insulating properties of the glazing. Double layer plastic film greenhouses naturally have lower light transmission than single layer films, so make sure you are taking full advantage of the heat savings by keeping the film properly inflated. Also in preparation for the low light levels associated with the winter, check the operation of supplemental lighting. Prevent freezingAny water lines that may be subjected to freezing temperatures should be blown out or otherwise winterized. Make sure equipment, such as pressure washers, are winterized so freezing water does not cause damage. Cooling systems for internal combustion motors must have antifreeze in the coolant. Dr. Peter Ling is an Associate Professor and Extension Specialist in the area of controlled environment plant production. He can be reached at 330-263-3857 or [email protected] This column is provided by the OSU Department of Food, Agricultural and Biological Engineering, OSU Extension, Ohio Agricultural Research and development Center, and the College of Food, Agricultural, and Environmental Sciences. Luke Power is a Research Associate with Dr. Ling.