1. H&CS 521 Greenhouse Crop Production
Lecture 1
Greenhouse Structure Overview
PowerPoint Lecture Developed In Part by Jennifer Leopold and Lindsay Paul

2. Greenhouse Structures: Styles, Construction, and Materials

3. Greenhouse Styles American (high profile) Dutch (low profile)
Different ridge to eave distances
Heating differences
Light interception differences

4. Greenhouse Styles Single-ridged Multi-ridged American or high profile
Dutch or low profile

5. Greenhouse Styles Multi-ridged or gutter-connected
Fewer exterior walls - save energy and materials, less construction
More room to maneuver inside (more suitable for automation)
Can have different temperature zones
Snow loads in the gutters can be a problem

6. Greenhouse Styles Quonset
2 layers of polyethylene with air in the middle
Cheap to build
Expensive to maintain
“Temporary” structures
Also used for overwintering of landscape materials

7. Double-layer polyethylene greenhouse
Fans are needed to keep the two layers of plastic inflated. These are often referred to as “squirrel cage” fans.

8. Greenhouse Styles Retractable roof greenhouses Shade structure
Flexible plastic roof and walls
To cool, just retract roof

9. Greenhouse Styles Unusual greenhouse designs
U. S. Botanic Garden in Washington D.C.

10. Greenhouse Styles Shade Structures
Generally used in southern U.S. for foliage and bedding plant production
Inexpensive
Provide protection from solar radiation
Provide some frost protection

11. Shade Structures Heaters in Shade House in Florida
Mesh roof-covering holds in heat.

12. Shade Structures
Greatest risk is with hurricanes and severe weather produced by storms.
In 1992 Hurricane Andrew destroyed much of south Florida's floral production.
Devastating hurricanes in 2004 and 2005 have also had a large impact on southern floral production.

13. Where to locate a greenhouse?
Water Supply
Quality****
Quantity
Climate
Light availability
Temperature
Labor
Available and low-cost
Transportation
Interstate highways
Airport
Accessible location for retail customers
Room for expansion
Room for support structures
4:1 ft2 greenhouse to support structures
Headhouse, storage, etc.
Zoning
Topography

14. Greenhouse Design Loads = Forces on the greenhouse Dead Load Live Load
National Greenhouse Manufacturer Association (NGMA) standards
Dead Load
Weight of permanent structure (frame, glazing materials, heaters, lights, etc.)
Live Load
Weight of temporary structures (repairmen, hanging baskets)
> 30 days, no more than 15 lbs/ft2

15. Greenhouse Design Snow Load Wind Load Ps=Ce Ctg Cs I Pg
Ps = snow pressure
Ce = exposure factor
Ctg = thermal factor
Cs = slope factor (roof)
I = importance factor
Pg = ground snow load
Wind Load
70-80 mph = lbs/ft2
Lateral and lifting forces

16. Greenhouse Design Wind Speeds

17. Greenhouse Design Unusual Loads For more information: Hurricane Load
Seismic or Earthquake Load
For more information:
National Greenhouse Manufacturers Association
American Society of Agricultural Engineers

18. Greenhouse Design Foundation Concrete foundation below frost line
No shifting with freezing and thawing
Permanent foundation
Columbus = 4 ft, Fargo, ND = 6-9 ft
Resist wind loads especially
Special soil testing for appropriate soil pressure
Depend on type of structure (polyhouse vs glass or rigid plastic structure)

19. Ridge and Eave Greenhouse Design

20. Quonset Greenhouse Design

21. Superstructure Materials Qualities Wood Strength Weight Durability
Cheap but not durable
Standard in the past
Steel
Durable & cheap
Heavy & rusts
**Aluminum**
Light & strong
More $ than steel
Reflective
Qualities
Strength
Weight
Durability
Maintenance
Costs
(initial & long term)

22. Glazing Materials--Qualities
Cost
initial & replacement
Life expectancy
Photoxidation
Oxidation
Surface erosion
Thermal degradation
Light transmission
Thermal Proportion
Strength
Mechanical shocks & shattering (hail)
Tensile strength
Weight of Material
Ease of installation and maintenance
Insurance - some materials are flammable