1. VIII. AIR CIRCULATION
Definition - movement of air within greenhouse

2. Circulation importance
1. Uniform air movement
2. Prevent temperature layering

3. 3. better air exchange around plant
Leaf
CO2
H2O
Heat
3. better air exchange around plant
a. replace CO2 depleted air
b. remove high humidity
c. reduce temperature of leaf surfaces

4. C. Circulation requirements
40 ft/min minimum up to 100 ft/min
Slight movement of leaf

5. Circulation: Photosynthesis vs rate of air movement around leaves
Low
High
Circulation: Photosynthesis vs rate of air movement around leaves
High turbulence
Low turbulence

6. D. When to Circulate When Night: Day: continuous all year winter
only when min. ventilation off
during medium or
max ventilation
summer - usually off

7. E. Problems
Uniform air movement
Moving air through plants

8. a. Description b. Requirements c. Better than poly tube
Types of Systems
1. Horizontal Air Flow (HAF)
a. Description
b. Requirements
Fan capacity: 1/4 vol.
Placement:
25' x 100' four fans
20’ x 50’ two fans
c. Better than poly tube

9. Circulation: HAF
HAF

10. 2. Plastic (poly) tube system
a. Description
b. Requirements
fan capacity = 1/4 house volume
cross sectional area of tube = 1 sq ft/100 cuft/min, capacity of fan
total area of all holes = 1.5 to 2 times cross sectional area
30' wide house: two fans
' long: two fans

11. Circulation: Polytube- minimum ventilation and heating

12. Circulation: Polytube

13. Circulation: Polytube
air

15. Circulation: Horizontal Air Flow (HAF) Fan Placement

17. Polytube circulation