Transcript H&CS 521 Greenhouse Crop Production Lecture 1 Greenhouse Structure Overview

H&CS 521
Greenhouse Crop Production
Lecture 1
Greenhouse Structure Overview
PowerPoint Lecture Developed In Part by Jennifer Leopold and Lindsay
Paul
Greenhouse Structures:
Styles, Construction, and
Materials
Greenhouse Styles
American (high profile)
Dutch (low profile)
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Different ridge to eave distances
Heating differences
Light interception differences
Single-ridged
Greenhouse Styles
Multi-ridged
American or high profile
Dutch or low profile
Greenhouse Styles
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Multi-ridged or gutter-connected
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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
Greenhouse Styles
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Quonset
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2 layers of polyethylene
with air in the middle
Cheap to build
Expensive to maintain
“Temporary” structures
Also used for overwintering
of landscape materials
Double-layer polyethylene greenhouse
Fans are needed to
keep the two layers
of plastic inflated.
These are often
referred to as
“squirrel cage”
fans.
Greenhouse Styles
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Retractable roof greenhouses
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Shade structure
Flexible plastic roof and walls
To cool, just retract roof
Greenhouse Styles
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Unusual greenhouse
designs
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U. S. Botanic Garden
in Washington D.C.
Greenhouse Styles
Shade Structures
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Generally used in southern U.S. for
foliage and bedding plant production
Inexpensive
Provide protection from solar radiation
Provide some frost protection
Shade Structures
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Heaters in Shade House
in Florida
Mesh roof-covering
holds in heat.
Shade Structures
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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.
Where to locate a
greenhouse?
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Room for expansion
Room for support
structures
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ft2
4:1
greenhouse to
support structures
Headhouse, storage, etc.
Zoning
Topography
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Water Supply
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Climate
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Light availability
Temperature
Labor
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Quality****
Quantity
Available and low-cost
Transportation
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Interstate highways
Airport
Accessible location for
retail customers
Greenhouse Design
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Loads = Forces on the greenhouse
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Dead Load
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National Greenhouse Manufacturer Association
(NGMA) standards
Weight of permanent structure (frame, glazing
materials, heaters, lights, etc.)
Live Load
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Weight of temporary structures (repairmen,
hanging baskets)
> 30 days, no more than 15 lbs/ft2
Greenhouse Design
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Snow Load
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Ps=Ce Ctg Cs I Pg
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Ps = snow pressure
Ce = exposure factor
Ctg = thermal factor
Cs = slope factor (roof)
I = importance factor
Pg = ground snow load
Wind Load
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70-80 mph = 16-20 lbs/ft2
Lateral and lifting forces
Greenhouse Design
Wind Speeds
Greenhouse Design
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Unusual Loads
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Hurricane Load
Seismic or Earthquake
Load
For more information:
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National Greenhouse
Manufacturers
Association
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http://www.ngma.com
American Society of
Agricultural Engineers
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http://www.asae.org
Greenhouse Design
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Foundation
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Concrete foundation below frost line
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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)
Ridge and Eave Greenhouse Design
Quonset Greenhouse Design
Superstructure
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Qualities
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Strength
Weight
Durability
Maintenance
Costs
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(initial & long term)
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Materials
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Wood
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Steel
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Cheap but not durable
Standard in the past
Durable & cheap
Heavy & rusts
**Aluminum**
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Light & strong
More $ than steel
Reflective
Glazing Materials--Qualities
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Cost
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initial & replacement
Strength
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Life expectancy
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Photoxidation
Oxidation
Surface erosion
Thermal degradation
Light transmission
Thermal Proportion
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Mechanical shocks &
shattering (hail)
Tensile strength
Weight of Material
Ease of installation
and maintenance
Insurance - some
materials are flammable