H&CS 521Greenhouse Crop

Production

Lecture 1Greenhouse Structure

OverviewPowerPoint Lecture Developed In Part by Jennifer Leopold and Lindsay Paul

Greenhouse Structures: Styles, Construction, and

Materials

Greenhouse Styles

American (high profile)Dutch (low profile)

Different ridge to eave distances Heating differences Light interception differences

Greenhouse Styles

Dutch or low profile

American or high profile

Single-ridged

Multi-ridged

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

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

Fans are needed to keep the two layers of plastic inflated. These are often referred to as “squirrel cage” fans.

Double-layer polyethylene greenhouse

Greenhouse Styles

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

Greenhouse Styles Unusual

greenhouse designs U. S. Botanic

Garden in Washington D.C.

Greenhouse StylesShade Structures

Generally used in southern U.S. for foliage and bedding plant production

Inexpensive Provide protection from solar radiation Provide some frost protection

Shade Structures

Heaters in Shade House in Florida

Mesh roof-covering holds in heat.

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.

Where to locate a greenhouse?

Room for expansion Room for support

structures 4:1 ft2 greenhouse to

support structures Headhouse, storage,

etc. Zoning Topography

Water Supply Quality**** Quantity

Climate Light availability Temperature

Labor Available and low-cost

Transportation Interstate highways Airport Accessible location for

retail customers

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)

> 30 days, no more than 15 lbs/ft2

Greenhouse Design Snow 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 = 16-20

lbs/ft2

Lateral and lifting forces

Greenhouse DesignWind Speeds

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

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)

Ridge and Eave Greenhouse Design

Quonset Greenhouse Design

Superstructure Qualities

Strength Weight Durability Maintenance Costs

(initial & long term)

Materials Wood

Cheap but not durable

Standard in the past Steel

Durable & cheap Heavy & rusts

**Aluminum** Light & strong More $ than steel Reflective

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