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HCS 521Greenhouse Crop Production

• Lecture 1
• Greenhouse Structure Overview

PowerPoint Lecture Developed In Part by Jennifer
Leopold and Lindsay Paul
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Greenhouse Structures Styles, Construction, and
Materials
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Greenhouse Styles

• American (high profile)
• Dutch (low profile)
• Different ridge to eave distances
• Heating differences
• Light interception differences

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

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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

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

• Retractable roof greenhouses
• Shade structure
• Flexible plastic roof and walls
• To cool, just retract roof

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Greenhouse Styles

• Unusual greenhouse designs
• U. S. Botanic Garden in Washington D.C.

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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

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Shade Structures

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

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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.

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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
• 41 ft2 greenhouse to support structures
• Headhouse, storage, etc.
• Zoning
• Topography

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Greenhouse Design

• Loads Forces on the greenhouse
• 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)
• gt 30 days, no more than 15 lbs/ft2

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Greenhouse Design

• Snow Load
• PsCe 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 16-20 lbs/ft2
• Lateral and lifting forces

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Greenhouse DesignWind Speeds
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Greenhouse Design

• Unusual Loads
• Hurricane Load
• Seismic or Earthquake Load
• For more information
• National Greenhouse Manufacturers Association
• http//www.ngma.com
• American Society of Agricultural Engineers
• http//www.asae.org

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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)

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Ridge and Eave Greenhouse Design
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Quonset Greenhouse Design
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Superstructure

• Materials
• Wood
• 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)

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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