Greenhouse HVAC

By Mark Watola on 11/03/2020

Photo by Emily Hopper

Plants need light, soil, and water. But if plants are too hot or too cold, they cannot flourish. Greenhouse HVAC helps regulate temperatures in greenhouses to help maximize plant growth. Depending on the plant, keep the temperature generally around 70 to 80 degrees Fahrenheit.

Ventilation and Cooling

Fresh air brings in carbon dioxide, an essential ingredient for plants to create glucose. Proper greenhouse ventilation circulates air using shutters or vents on the walls or roof of the enclosure.

Passive, or natural greenhouse ventilation, requires shutters that allow air to flow freely in and out of the greenhouse. Using air conditioning in greenhouses is expensive and unnecessary with proper greenhouse ventilation, which provides enough cooling for plants in warmer months.

Mechanical ventilation provides more control and reliability than natural ventilation, leading to more consistent growth results. Ventilate a greenhouse with several options. An exhaust fan actively pulls stale air out of a greenhouse, so air remains fresh. A circulation fan directs the fresh air throughout the greenhouse.

Having good greenhouse ventilation mitigates risks such as:

  • High humidity: leads to excessive condensation and in turn, fungus
  • Excessive heat: damages plants and decreases production

Heating

Cold temperatures also create adverse effects on plants. Temperatures drop in at night and in winter, but greenhouse heating keeps plants warm. Even in hotter states in the summer months, greenhouses require heating at night to maintain steady temperatures. Greenhouse heating works by capturing the sun’s heat radiation, although not always possible in inclement weather or colder months.

To supplement the sun’s heat, record the temperatures of your greenhouse and determine if a heater is necessary. If required, calculate 10 watts per square foot. A 4,000 watt heater heats approximately 400 square feet.

Stelpro offers an agricultural unit heater with a disconnect switch and an agricultural unit heater with a built-in thermostat and disconnect switch.

Both models mount to the ceiling or wall with included universal mounting bracket and can also act as a circulation fan when heat is turned off.

For a residential indoor garden or greenhouse use space heaters.

Other considerations

Geographic location affects climate, and, in turn, flora. This affects greenhouses too, despite their controlled environment. Some plants flourish in cooler temperatures. Others prefer the heat. Adjust heating and ventilation accordingly.

The size of the greenhouse dictates how much ventilation or heating you may require. A larger operation requires more vents and shutters or unit heaters.

Construction material, like glass and polycarbonate, will absorb and hold the sun ray’s differently.

Mind windows and doors and their proximity to heating or cooling elements. If placed too close to an entrance or exit, the heat or air produced can escape the greenhouse faster, leading to wasted energy and resources.

Properly seal and caulk edges so heat does not escape from small crevices.

If you have any other tips or tricks about greenhouse HVAC, let us know in the comments below!

Sources:

https://www.gardenandgreenhouse.net/articles/greenhouse-articles/the-basics-of-greenhouse-ventilation/

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