Greenhouse Ventilation and Exhaust Circulation Fans


Exhaust fans play a pivotal role in greenhouse ventilation, helping ensure stable temperatures, reduce humidity fluctuations, and ensure an adequate supply of carbon dioxide for plant health. Select the best Greenhouse Ventilation Exhaust Circulation Fans.

Greenhouse fans can help to increase ventilation efficiency and enable easier climate control. They are typically connected to a thermostat which automatically activates them once your desired temperature has been set.


Greenhouses provide gardeners and growers with an ideal environment to cultivate plants in controlled conditions but are only truly effective with proper ventilation systems to reduce hot, humid airflow while keeping temperatures even.

Proper ventilation in a greenhouse is crucial to controlling temperature, avoiding fungal disease and pest infestation, and protecting plant health. A properly sized ventilation fan is key for success – greenhouse fans come in various sizes and styles that will fit your requirements perfectly.

Ventilation fans should be strategically located at one end of a greenhouse and elevated above bench level for maximum effectiveness. They move stale air out, replacing it with fresh outside air and providing fresh oxygen to plants while dispelling heat from the greenhouse environment. Ventilation serves two important functions in a greenhouse: 1) to deliver fresh oxygen directly into plants’ bodies and 2) to dispel heat.

Greenhouse exhaust fans are typically measured by how much air they can move per unit of time – usually expressed as cubic feet per minute (CFM). A higher CFM number demonstrates more power and capacity to remove moisture from a greenhouse environment. When selecting your fan, be mindful of both the volume of air you wish to move as well as static pressure requirements.

Destratification fans are another type of greenhouse ventilation fan designed to mix temperature and humidity levels evenly throughout your greenhouse, helping avoid localized pockets of warm, moist air that become ideal breeding grounds for fungal diseases such as Botrytis.

To maximize the efficiency of your greenhouse fan, make sure it is installed and maintained regularly. Cleaning fan filters and checking belt tension are crucial steps towards optimizing fan performance while using a manometer (usually $25 from greenhouse equipment suppliers) for monitoring the air pressure inside will provide users with insight into whether their ventilation system is operating optimally – assuring fans are producing intended results and users know when their ventilation systems are functioning at peak capacity. An inclined manometer can easily be placed into vents within your greenhouse while its hose can then be connected through plastic tubing to another location outside where readings can be taken each time the fan comes on.

Temperature Control

Summer temperatures in a greenhouse can easily surpass 100degF, creating stress that harms plant quality and growth while increasing energy use. Ventilation systems with exhaust and circulation fans work to push hot air out, creating negative pressure that pulls cool fresh air in through louvers and open doors – creating the best way to regulate greenhouse temperatures.

Fans should ideally be placed in greenhouses near the roof and in front of any louvered openings or shutters to help keep them open and allow air to flow in. Fans should be of sufficient size for the intended use and ventilation system as a whole; their intake area should at least equal one-half the maximum air flow rate at static pressure of 1/8 inch water column (cfm).

Greenhouse ventilation fans should be placed slightly above bench level to ensure maximum cooling air reaches plants, making maintenance tasks such as belt cleaning and wiping blades more practical. A well-functioning fan should be given regular care to maintain peak performance; its bearings must be checked for excessive wear or damage; belt drives must remain tight to avoid slipperiness; dust accumulation on blades, housings, and shutters should be cleared away twice annually to reduce energy costs.

Greenhouse fans should be reviewed regularly, particularly during periods of high humidity and dustiness, to ensure optimal performance. Inspection for corrosion bearings stretched or slipping belts, fan blades with no grip, and other signs that the system needs repair is the best way to identify issues and ensure the efficiency of the greenhouse ventilation system. In addition, periodic replacement or cleaning of filter elements on greenhouse fan motors helps remove accumulated moisture that could shorten their lifespan and prolong motor lifespan.

Humidity Control

If your greenhouse feels stagnant and humid or is experiencing issues due to a lack of ventilation, an exhaust fan could help circulate fresh air to maintain plant health while also decreasing pest and disease risks by continuously refreshing the air.

Fans are an effective way to create a slight vacuum that draws cooler outside air through vents, open doors, and cracks. Most fans run on electricity, powering up automatically when temperatures increase, and require periodic maintenance checks to ensure all louvers and fans are operating as intended.

Natural ventilation systems rely on the buoyancy of air and wind speed to exchange fresh inside and outside air, making energy savings an attractive factor in new construction. Their success relies on having large vent openings sized appropriately. To maximize air exchange efficiency it is suggested that their total opening size equal or exceed 20 percent of the greenhouse floor area.

Natural ventilation systems should include a manometer to monitor the air pressure in your greenhouse. This will enable you to know if the system is functioning efficiently by measuring differences in pressure between inside and outside structures, providing insight into its efficiency. A successful ventilation system must move two times the floor area of its structure per minute – and must include regular maintenance checks.

Destratification fans are frequently used in greenhouses to help equalize temperature and air circulation, disrupting stratified layers of hot air that accumulate near the ceiling and decreasing summer cooling loads through evaporative cooling from plant transpiration.

When selecting greenhouse fans, look for those that comply with AMCA standards. This will ensure the fan can effectively handle the air it is expected to move and can operate at an estimated static pressure. Greenhouse fans should be regularly maintained, including cleaning blades, clearing louvers of debris or grass/weeds as necessary, adjusting fan belts, or replacing fans altogether if they become worn down.

Dust Control

Enhancing ventilation can prevent condensation that breeds disease-harboring organisms such as fungi, molds, and mildew. Air circulation is one of the key aspects of greenhouse ventilation to ensure plants receive fresh air from all directions, with any stale air being expelled through vents. Ventilation also aids humidity regulation to maintain ideal plant growing conditions while decreasing risks such as diseases or pests that thrive in dampness.

A typical greenhouse ventilation system typically consists of exhaust fans on one end to push hot stale air away and intake louvers at the other to draw in fresh air. Both should be properly sized to ensure efficient operation; for instance, 14 percent of the fan area should be allocated for intake louvers to allow an even airflow without drafts; motorized louvers offer greater efficiency than manual ones and are easier to operate.

Not only should fans and shutters be of appropriate sizes, but it is essential to maximize openings in greenhouse walls to promote more even temperatures throughout the greenhouse and facilitate efficient environmental control. An optimal number of openings should comprise 15-20% of the greenhouse floor area.

Regular maintenance on both exhaust and circulation fans should be performed to keep them operating at peak performance, including cleaning the fan blades of dust that reduces their efficiency, checking motor temperature for excessive heating, calibrating thermostats and humidistats to respond properly to environmental conditions in a greenhouse, and calibrating humidistats to respond correctly to environmental changes in the greenhouse.

Be sure to remove weeds and shrubs that have grown near a fan; these could be blocking airflow out of the greenhouse and hindering its escape. Furthermore, ensure nothing obstructs it within two blade diameters to ensure its maximum efficiency while simultaneously minimizing noise pollution.