Closing hoophouses for the winter

Once the holiday plants have been shipped, there is a time period when considerable growing area may be empty before spring crops need the space.

This period is a good time to clean up, make necessary repairs and maybe schedule a much needed vacation. It can also save considerable fuel as the period from January to March is about one-third of the total heating season. Delaying the opening by having pre-planted material delivered when you are ready is convenient and can save on fuel and labor.

The procedure for closing a greenhouse is simple but should be followed so that it will weather the winter storms and be ready for crop production when the season starts.
 

Greenhouse glazing

• On poly-covered greenhouses, check to see that the covering is securely fastened and fully inflated.
• Tears and cuts should be closed with plastic mending tape, or plastic should be replaced.
• Clean the inflation blower.
• Check the pressure to see that it is operating at about ¼-inch water static pressure. Excess pressure will stretch the plastic.
• Under-inflation will allow the plastic to rippling in the wind creating excess force on the fasteners.
• Also, check to see that the inflation blower intake is free of debris and is located where it can’t be blocked by snow.
• Check the integrity of the greenhouse structure.
• Bolt connections, collar ties, truss supports and purlins should be inspected and tightened if needed.
• Diagonal bracing should be securely in place as this keeps the greenhouse frame from racking end to end in a heavy wind.
• In heavy snow areas, wood 2 x 4 (two inch thick, four inch wide) posts should be placed under the ridge at 12 feet to 16 feet spacing. This will help to support any snow loading.
• Doors should be securely fastened closed to keep the wind out.
• Clean the area around the outside of the greenhouse so that heavy snow accumulation that could crush the sidewalls can be removed with a bucket loader or snowplow.
  
   

Heating system

As most hoophouses are heated with hot air furnaces or unit heaters, these can be turned off without damage. Propane tanks should be filled so that condensation is kept to a minimum. In fuel oil tanks, the remaining oil should be treated with an additive that will absorb moisture and make it more viscous. Fill the tank so that fuel will be available for emergency use should a heavy snowfall occur.

Shutting down a hot-water boiler is more difficult. The water must be drained and blown out of the boiler and piping. Most manufacturers do not recommend turning off the boiler because the gaskets and seals may dry out and valves can corrode. It is better to fill the system with an antifreeze solution.
 

Ventilation system

• Motorized vents and shutters should be closed to keep weather from getting in.
• Non-motorized shutters should be taped shut or covered with plastic. This also allows the temperature to build up on sunny days for some solarization to control insects and disease.
• Evaporative pad cooling systems should be shut down and cleaned before cold weather. Drain pumps and tanks and clean pads and filters.
  
   

Irrigation system

• If there will be no heat in the greenhouse, the irrigation system should be turned off and drained.
• Any above ground piping should be blown out with compressed air. If there is a pressure tank, it should be drained to remove water and sediment.
• Leaks in the pipes should be repaired and filters and screens cleaned.
  
   

Maintenance

On sunny days, greenhouses will warm up to comfortable working temperatures. This is a good time to remove containers, weeds and other things found under the benches and make repairs or changes to the bench system.

Servicing should also be done on the heating system. Besides having the furnace or boiler serviced, the heat distribution ducts or radiation can be cleaned. This will pay for itself in increased efficiency. Thermostats should be cleaned and checked for accuracy.

Most storm damage can be eliminated or areduced by preparation before a storm. With weather forecasts frequently inaccurate, it pays to plan ahead.

Bartok is a regular contributor to Greenhouse Management and an agricultural engineer and emeritus extension professor at the University of Connecticut. He is an author, consultant and a certified technical service provider doing greenhouse energy audits for USDA grant programs in New England.

Have a question? You can write John at jbartok@rcn.com.