Exhaust fans are an essential component of greenhouse ventilation. By pushing stale air out, they create negative pressure that draws in cool, fresh air through vents, louvers, and cracks in the greenhouse roof. The best guide to finding Greenhouse Ventilation Exhaust Circulation Fans.
Greenhouse exhaust fans help maintain an environment less welcoming to pests and diseases by creating an even supply of carbon dioxide and decreasing humidity variations.
Air Circulation
Air circulation is at the core of greenhouse exhaust fans’ functionality, helping ensure plants have optimal conditions and minimizing potential disease risks. Movement of fresh air breaks up stratification in a greenhouse where hot air rises while cold air sinks – without fans to circulate air, these layers could remain stagnant, restricting plant growth.
Greenhouses naturally vent through roof and sidewall vents, but an exhaust fan can enhance active ventilation even further. By creating a pressure difference between the inside and outside of the greenhouse, an exhaust fan creates airflow that pulls heated air out through roof vents while drawing cooler replacement air through shutters or open doors into the greenhouse – helping eliminate hot, humid pockets of air that could otherwise lead to fungal diseases like botrytis.
Temperature regulation capabilities of an exhaust fan enable greenhouse operators to more easily manage crop production. Unventilated greenhouses can quickly heat up, leading to overstressed and even deadened plants within. An exhaust fan helps regulate internal temperatures by forcing out hot, moist air while simultaneously drawing in cooler air into the space, helping create optimal conditions for healthful plant development and growth.
Ventilation is essential to controlling humidity levels in greenhouses. While plants produce moisture via transpiration, too much humidity can lead to mold and mildew growth that compromises crop quality. An exhaust fan can help balance humidity by expelling moist air while simultaneously drawing in dry air from outside.
If you use a fan to actively ventilate your greenhouse, its capacity should at least two times that of its floor area. This is particularly crucial if you grow tall crops or employ hanging baskets; an efficient fan with higher capacity will be able to overcome additional turbulence caused by these features and ensure your plants receive enough fresh air for proper growth.
For optimal results, your exhaust fan should be linked to a thermostat so it will only come on once the desired temperature has been met. This enables you to automate the ventilation of your greenhouse, freeing you to focus on cultivating plants inside.
Humidity Control
A greenhouse without proper ventilation can quickly reach high humidity levels that will stress plants and reduce performance. An exhaust fan creates a vacuum effect to pull in air from outside and help regulate temperatures and humidity levels more evenly across its entirety.
Greenhouse exhaust fans come in various sizes and designs. For maximum efficiency, look for those that feature shutters to prevent backdrafts and come equipped with built-in thermostat controls – these allow users to activate them whenever the temperature inside their greenhouse reaches an undesirable threshold, then shut them off once back to normal again. They are particularly well suited to large greenhouses as well as growing rooms, providing temperature regulation.
No matter the type of exhaust fan used, it must be properly sized and placed for effective air movement. Fans should direct air towards the opposite end wall of the greenhouse to optimize ventilation effectiveness. Furthermore, regular maintenance must take place to ensure optimal functioning.
Exhaust fans should be designed to produce one volume of air change per minute at 8 feet for summer ventilation, taking into account greenhouse size (length, width, and average height), desired ventilation rate, and exhaust fan volume requirements.
Vents should be strategically positioned to draw in fresh air from around the greenhouse. This can be achieved either by adjusting louvers to match the direction of wind blowing through or installing a fan-jet system where air is forced through a perforated tube mounted under the greenhouse roof and drawn in through open doors and vents.
Circulation fans can further improve the greenhouse’s ventilation capabilities. When used together with exhaust fans, these can increase overall efficiency while helping even out temperature distribution within the greenhouse and decrease hot spots or moisture pockets.
Pest Control
Lack of ventilation in greenhouses can create stagnant air that provides ideal breeding grounds for pests. Installing an exhaust fan helps circulate fresh air while also maintaining optimal humidity and temperature levels, thus helping prevent internal temperatures from skyrocketing in warmer climates and potentially stunting or killing plants.
As well as an exhaust fan, a greenhouse should contain many passive and active vents – both passive and active – throughout its structure, which should be opened or closed depending on weather conditions. Some vents should be located near the base or roof; others on the sides or perimeter; still others are best placed elsewhere within its interior structure for cross ventilation, forcing warm stale air out through exhaust fans while drawing cooler fresher air in via other vents. This allows optimal cross ventilation results in forcing warm stale air out while drawing cool fresher air in through other vents to exchange the warm stale air out with cooler fresher air entering from other vents in return through the exhaust fan.
Ventilation systems that include both exhaust and circulation fans can be integrated with a thermostat to form an automated greenhouse control system. The thermostat monitors greenhouse temperature and turns on fans when either is too high or too low; providing your plants with a custom growing environment that ensures their well-being and success.
An exhaust fan can be installed in the ridge of one end wall to provide air intake that is powered by both an external motor and a perforated tube. When activated, this tube inflates and draws air in through its louvers; then shut off via a motorized shutter. Similar to fan-jet systems but using lower-cost power units (relays, contactors, or simple contactor switches).
Greenhouse fans should ideally be installed at the highest point possible within the structure, to draw air in from above or from other parts of the greenhouse structure. Furthermore, fans should be selected according to size and type of greenhouse and regularly cleaned to ensure efficient operation while clearing any dust that might hinder energy efficiency.
Temperature Control
Exhaust fans are an effective way of rapidly venting greenhouses with excess heat, helping excess to dissipate more quickly than would otherwise be the case. Pushing out stale air creates a negative pressure that draws in cool, fresh air through louvers, open doors, and cracks into the greenhouse and helps create an even flow of air throughout. This constant circulation of air helps ensure more stable temperatures for plant health during bright, sunny days when high temperatures can cause thermal shock leading to thinner stems and buds, delayed flowering, blight, canker, and poor fruit set.
Greenhouse exhaust fans can work hand in hand with your heating system to control the climate of your facility. As temperatures cool off, fans can help even out temperatures and create an uninterrupted supply of fresh, warm air through vents.
Destratification is another function that greenhouse fans can perform. By redistributing the warm, stratified layers that tend to accumulate near the ceiling and keeping them mixed, destratification improves air circulation, and temperature regulation and can even reduce humidity pockets.
Fans play an invaluable role in maintaining humidity levels below damaging levels during winter. Without proper exhaustion of humid air, fungal diseases could rapidly spread through the plant canopy and increase heating costs; greenhouse owners must find an optimal balance between moisture removal needs and heating capacity to ensure healthy, strong plants.
General guidelines recommend selecting fans that deliver an air volume of about 1/2 cubic foot per minute per square foot of floor area in the greenhouse, which provides up to two or three complete air changes per hour. When choosing a fan, look for one rated according to AMCA (Air Moving and Conditioning Association) standards which provide information on its ability to move air against static resistance measured in inches of water pressure.
Exhaust fans should be strategically installed so they work in sync with your greenhouse’s summer wind direction, typically installing fans at one end of a single-span greenhouse and placing louvers at the other to draw in fresh air. For larger greenhouses with longer sidewalls and fan installations on both ends of each structure. For optimal results, exhaust fans should be situated accordingly for best results.
