Circulation fans in use. Photo courtesy of Forever Flowering Greenhouses.
Circulation fans in use. Photo courtesy of Forever Flowering Greenhouses.

Sponsored article by Eric Brandstad of Forever Flowering Greenhouses, a Silver sponsor of the Ganjier Spring Kickoff!

Evaporative greenhouse cooling systems are like swamp coolers — water runs over a thick pad at one end of the greenhouse while exhaust fans pull air from the other end through the wall of cool water. These tend to work well in moderate temperatures and dry areas but can cause humidity levels to rise, not to mention your electric bill.

Circulation fans are another very important part of a greenhouse. Some growers find themselves near the coast or in a foggy mountain area that gets higher humidity in the morning or evening. Take Florida for instance — they have pretty good humidity even on a warm day so you can’t fire up a heater to dry out the air.

Horizontal airflow (HAF) fans are the key to drying out the air in these situations because the air is moved in a specific direction rather than just scattering it like an oscillating fan. The air will dry out faster and more efficiently if moved in a specific direction. Some greenhouse companies recommend fewer fans, but there is a benefit to adding more circulation in this department for dryer, fresher air.

Cooling Options for Light Dep Growing

Adding a light deprivation or blackout capability to a greenhouse can be another important factor in increasing productivity. Normally when growing outdoors or in a greenhouse you have to wait until fall for the harvest season. With a blackout cover, though, you can force flowering as early as July. A light deprivation cover can be manually pulled over the garden or greenhouse and as long as you create the correct light cycle every day, you should be able to start your harvest long before Mother Nature intended. Internal and external systems for light control are both options.

For internal systems I recommend a breathable blackout material—this helps avoid any condensation drips that can occur after the curtain is pulled. Remember, the fans and intakes will be restricted because of light leaks. You’ll obviously see a bit of a heat and humidity spike since the sun is still out and you are covering your crop.

For external systems, I recommend a non-breathable blackout material. If you have a greenhouse cover and you try to pull the breathable cover over the outside of it, it won’t breathe and you’ll still have the same issues with ventilation. The next step would be to use underground ventilation since you can’t go through the walls of the blackout and you are cut off from the exhaust fans you might use throughout the day. Going underground would mean a bit more work when building your greenhouse, though—and if you already have a greenhouse, underground ventilation might be a real pain to install.

There is another solution. Forever Flowering Greenhouses has unveiled a new product called The Breathable Wall. The Breathable Wall was created to allow full airflow through your exhaust and intake without any light getting through—the designers basically created a baffle that breaks up the light and not the air. Even indoor growers can find a use for The Breathable Wall for covering holes in walls for vent and air conditioning systems.

More info to come in upcoming articles on the best way to get your greenhouse setup to meet your needs and your budget.


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