跳至内容 
Greenhouse Fans and Air Circulation
Greenhouses use two kinds of fans. Exhaust fans pull air out so fresh air comes in, and circulation fans keep the air inside moving evenly. FANGCHENG supplies both and matches them to your house.
What airflow does for the crop
Evens out temperature between the floor and the roof, and from one end to the other
Dries wet leaf surfaces, which lowers disease pressure
Brings fresh air with carbon dioxide to the leaves
Keeps humidity from pooling in pockets
Exhaust fans
Exhaust fans pull air out of the house and create negative pressure that draws fresh air in through vents or cooling pads.
How an exhaust-fan layout works
Exhaust fans sit on one wall and openings or cooling pads on the opposite wall. The fans create lower pressure inside, and fresh air is pulled in through the inlets and across the house. If another opening is left ajar, air takes the shortest path to it and the rest of the house is not ventilated.
Circulation fans
Circulation fans push air horizontally. They reduce dead zones and even out temperature and humidity across the crop.
How circulation fans are arranged
Circulation fans are usually placed so that together they set the whole volume of air moving in a loop, instead of blowing in random directions. This keeps warm and cold layers mixed and avoids still corners. When vents are open and air is already moving, the circulation fans may not be needed.
Choosing fan capacity
- Greenhouse floor area and height
- Required air exchange for your crop and climate
- How much cooling is done by pads or fog
- Whether the house is a single span or a large gutter-connected block
Which fan runs when
Hot weather
exhaust fans, often with pads or fog
Mild weather
natural vents, and circulation fans if the air is stagnant
Cold weather with heating
circulation fans to mix warm air, with minimum ventilation
Humid nights
circulation plus a little ventilation to move moisture out
Fan types in plain terms
Axial exhaust fans.
Move large volumes of air out of the house against low pressure.
Mixed-flow fans.
Used where more pressure is needed.
Horizontal circulation fans.
Move air sideways inside the house to mix it.
Shutters, guards and inlets
Exhaust fans work with shutters that open when the fan runs and close when it stops, so cold air and pests do not enter through a stopped fan. Guards protect people and plants. Inlets, pads or louvers must be large enough to supply what the fans remove.
Fan with shutter and guardNoise and energy
Keeping fans running
Maintenance
- Check fan belts, bearings and blades
- Keep housings and guards clean
- Inspect motors and wiring before the hot season
A simple maintenance routine
- 01Before the hot season: test every fan, shutter and control
- 02Monthly in use: clean blades and guards, listen for bearing noise
- 03After the season: inspect belts and motors, and protect the fans
What we need from you
- Greenhouse length, width and height
- Climate and the hottest months
- Whether pads or fog will be used
- Crop
- Power supply
Common fan mistakes
No inlet area, so the fans starve for air
Inlets too close to the fans, so air short-circuits
Circulation fans fighting the exhaust airflow
Fans running all the time because no controller is fitted
Blades and guards left dirty
Common questions
Straight answers. If yours is not here, ask us.
It depends on area, height, climate and crop. We size the fans after we know these details.
Exhaust fans exchange air with the outside. Circulation fans only move air inside the house.
Yes, with a plan. Fans that pull air out need controlled inlets, and circulation fans should be coordinated with open vents. Climate control handles this.
On the wall opposite the air inlets, so air crosses the whole house. The exact layout depends on the structure.
Often yes, because they prevent stratification, but they should be coordinated with open vents and the controller.
Fans use electricity every hour they run. Good sizing and automatic control keep running time down.
The inlet area may be too small, a door or vent may be open, or the fans may be undersized. We check these with you.
They mix air but do not exchange it, so they do not cool on their own. Combine them with vents or exhaust fans.
Explore other systems
Size your fans
Send your greenhouse size and location. We reply within 24 hours.
Consultation and project proposals are free.
What to include
- Location
- Crop
- Greenhouse size
