1. Greenhouse Structures, Covering Materials, and Climate Controls
By: Heather Dixon

2. Bell Work
What is media?

3. Today’s Objectives: Identify types of greenhouse structures
Define greenhouse covering (glazing) materials.
Explain environmental controls.
Describe methods of heating and cooling greenhouses.

4. Types of Greenhouse Structures
There are four basic styles of greenhouse structures:
Lean-To
Even Span
Uneven Span
Ridge-and-Furrow

5. Lean-To Greenhouses Lean-To Greenhouse: Attached to building
Roof support from attached building
Growing Crops
South Side

6. Even Span Greenhouses Roof has even pitch and even width Single Houses
Hoop Houses

7. Uneven Span Greenhouses
Roofs have unequal pitch and width
Limited to hillsides
Disadvantages
Few Built Today

8. Ridge-and-Furrow Greenhouses
Number of greenhouses connected along the length of the houses
No side walls
Lower heating costs
Snow is a concern

9. Headhouses Structure attached to the greenhouse Work area Storage Area
Office Space

10. Covering (Glazing) Materials
Glazing is the covering of a greenhouse
Considerations:
Durability
Light Transmission
Cost of materials
Heat Loss

11. Polyethylene (poly) Film
Most widely used
6-milin thickness
Flexible Sheets
Double Layered
Heating cost 1/3 less than glass covered greenhouse
Inexpensive

12. Structured Sheets Very Popular Constructed of three materials:
Polycarbonates
Acrylic
Fiberglass

13. Polycarbonate Structured Sheets
Most widely used structured sheets
Manufactured with a “Twin Wall” held together by ribs
Insulating
Reduces heat costs
Guaranteed for 10 years
Good light transmission 80%

14. Acrylic Structured Sheets
Twin Walls much like Polycarbonate Sheets
Good insulation
High light transmission – 86%
Last 8 to 10 years
Less flexible

15. Fiberglass Widely used in 1960’s and 1970’s
Light transmission good in the beginning but discolors after 7-10 years.
Susceptible to hail damage
Flammable

16. Glass Best material for plant production
High light transmission-90-92%
Air exchange
Initial cost = expensive
Long lasting if it doesn’t break
Breakable
Insurance
Heat loss with larger panes

17. Environmental Controls
Devices used to automatically turn greenhouse systems on or off
Four types:
Thermostats
Analog Controls
Computer Controls
Computerized Environmental Management

18. Thermostats
Low Cost
Easy to install
2 types:
On-off
Proportioning

19. Analog Controls Use proportioning thermostats or electronic sensors
Integrate the operations of heating and cooling equipment
Better performance than just thermostats

20. Computer Controls Utilize microprocessors
Gathers information with sensors such as:
Temperature
Relative humidity
sunlight

21. Computerized Environmental Management
Expensive
Accurate
Greatest range of uses
All automated equipment can be controlled together
Programmable

22. Heating Systems Hot Water Systems: Small and efficient
Water heated in boilers and pumped through pipes in greenhouse
Low maintenance
Heat delivered evenly
Infrared Heat: produce heat that is absorbed by plants, media, and benches
Heat transfers to air space surrounding them

23. Steam and Unit Heaters
Steam Heat: standard heat for cut flower operations
Larger boilers produce steam
Steam distributed trough pipes
Can sterilize medium
Unit Heat: hot air heaters
Heated within unit and blown by fans throughout greenhouse

24. Cooling and Ventilation System
Fan and pad cooling systems:
Based on evaporation of water
Fog systems:
An atomizer produces water vapor
“Mist” system

25. Today we learned: What types of greenhouse structures?
What four types of environmental controls?
What is the most widely used covering material?
What is a headhouse used for?
What system uses an atomizer that produces water vapor?