9.3 Heating and Cooling Options

Heating: For small or backyard-size producers, implementing a passive heating system can help reduce heating costs during cold months. In this type of system, sunlight enters the south wall. The north wall has reflective material to trap and store heat. Black barrels filled with water absorb heat from sunlight during the day and slowly release the heat during the night. Thermal curtains can be hung on the south wall to trap heat during the night (Figure 26). While helpful to reduce heating costs, this practice would not be practical for large producers as it takes up valuable production space in the facility and is not able to maintain a consistent and reliable temperature.

Larger producers that have year-round, consistent production will need to maintain a temperature independent of what can be gained from the sun. Forced air heaters powered by natural gas, propane, or electricity are most commonly used in the U.S. These heaters control the air temperature by a thermostat. Radiant heaters such as wood or natural gas broilers control the temperature by pumping hot water through pipes located throughout the structure. Broilers are popular, as wood is a cheap source of fuel compared to oil or natural gas.

Cooling: The combination of manual and automatic ventilation is the most cost-effective way to cool down your greenhouse. Ventilation options include roll-up sides, ceiling vents, and vents along the long end of the greenhouse.

Forced air ventilation fans pull air through the length of greenhouse using thermostat-controlled vents at the opposite end. Evaporative coolers are a relatively inexpensive way to provide cooling to the structure in hot, dry climates. Evaporative coolers work by pulling in outside air through a wet wall, cooling the air as it comes in.

The wet wall is a frame that contains corrugated cardboard or synthetic material that is saturated by water dripping over its surface (Figure 27). Excess water is collected in a reservoir and pumped back over the cardboard. Evaporative cooling walls are not efficient in climates with high temperature and high humidity.

Source: Janelle Hager, Leigh Ann Bright, Josh Dusci, James Tidwell. 2021. Kentucky State University. Aquaponics Production Manual: A Practical Handbook for Growers.