Ventilation Tips in the Winter Greenhouse

While this may seem reasonable to novice greenhouse growers, experienced growers know this is a recipe for disaster.Get more news about Greenhouse Exhaust Fan,you can vist our website!

Winter greenhouses require a minimum ventilation rate to discharge solar heat gain, provide carbon dioxide for plant growth, and reduce humidity (without losing too much heat energy) in the greenhouse structure. A greenhouse typically requires 20 to 30 percent of the summer ventilation requirement in the winter. This translates to 1.5 to 2.5 cubic feet per minute per square foot of greenhouse floor space.

When cool air is introduced into the greenhouse, it must be introduced at a slow rate and must be mixed with warm air before contacting the growing crops. Natural airflow can meet this ventilation requirement, or growers can use a low-speed fan to pull cooler air into the greenhouse environment.

Horizontal Air Flow (HAF) fans are used in most modern greenhouses to circulate air and to wick moisture away from the crop canopy to minimize diseases like Botrytis (Gray mold). In the fall and winter, cool air enters through a motorized inlet or louver and is mixed into the air by the HAF fans. A low-flow rate exhaust fan opposite the motorized inlet or louver removes warm moist air.

Fan-perforated tube systems are still used in some greenhouses and are very effective for cooling and reducing the humidity in the fall and winter greenhouse. Fan-perforated tube systems are designed to pull cool air through a motorized inlet behind the circulation fan. The cool outside air is mixed thoroughly with the warm interior air through the distribution tube. A low-flow rate exhaust fan is positioned in the opposite greenhouse endwall. The first stage of exhaust ventilation should be less than 10 to 20 percent of the fan-perforated tube system capacity to prevent cold air from being pulled directly onto the crops below.