1. Greenhouse Ventilation and Cooling
Greenhouse Management

2. Ventilation vs. Cooling
Ventilation: bringing outside air into the greenhouse to lower the temperature.
Cooling: reducing the temperature of the greenhouse by:
lowering the temperature of the air being brought into the greenhouse
cooling the air inside the greenhouse using fog cooling
shading

3. Reasons for Ventilation/Cooling
Greenhouse temperatures greater than 95 degrees F. stress plants.
Exchange air and renew the supply of carbon dioxide inside the greenhouse.
Exchange hot, humid air with cooler, drier air thus reducing the relative humidity of the air inside the greenhouse. Lower humidity levels help control disease problems.

4. Air flow during ventilation using a ridge vent and side wall vent
How Ventilation Systems Work
Air flow during ventilation using a ridge vent and side wall vent

5. Ridge vents on barrel-vault and quonset style greenhouses

6. Even span greenhouse with ridge vent open
Ridge Vents
Even span greenhouse with ridge vent open

7. Wall Vents
End wall vent

8. Louvered vent (end wall) on quonset greenhouse
Wall Vents
Louvered vent (end wall) on quonset greenhouse

9. Wall Vents
Side wall vent

10. Exhaust Fans

11. Exhaust Fans
Greenhouse manufacturers recommend that there be a complete change of air every minute during the summer.
Fans are rated on the basis of how many cubic feet of air they can move in one minute (cfm).
The number and size of required fans can be calculated by determining the volume of the greenhouse.
Fans should be spaced a maximum of 25 feet apart.

12. Fan-jet with Convection Tube

13. Open vs. Retractable Roof
As the technology has developed, an “open-roof” house has come to be defined as a rigid roof panel that hinges open. It can be glazed with poly film, twin-wall sheeting or glass.
“Retractable” describes a fabric roof that’s suspended over the crop, like a curtain. The curtain can be flat, angled or in a traditional peaked shape.

14. Retractable Roof

15. Retractable Roof

16. Open Roof

17. Retractable Sides

18. Cooling Systems
Fan and pad cooling
Fog cooling
Shading

19. Fan and Pad Cooling Basic parts: Exhaust fans Cooling pad Sump Pump
Water distribution pipe and baffle

20. Evaporative Cooling Pad (Inside Greenhouse)

21. Fan and Pad Cooling System

22. Fog Cooling
Water is forced through small orifices at high pressure (1,000 psi) creating tiny droplets of water which remain suspended in the air.
Exhaust fans and open vents circulate the fog throughout the greenhouse.
The fog quickly evaporates, cooling the air in the process.

23. Mee Fogging System You Tube Video
Fog Cooling
Mee Fogging System You Tube Video

24. Greenhouse Shading Spray-on shade (whitewash) Saran (shade cloth)
Woven, synthetic fabric
The tighter the weave, the less light is able to pass through it.
Available in 25%, 30%, 35%, 50%, 75%, etc. shade

25. Shade Cloth (Saran)

26. Spray-on Shading Compound

27. Controls Aspirated thermometers are connected to step controllers.
Step controllers heat and cool the greenhouse in “steps” or stages.

28. Aspirated Thermometer

29. The End