Greenhouse Structures What are the elements of a greenhouse structure?

Key Questions  What is a greenhouse structure?  What are the various design styles of greenhouses?  What are the structural parts of a greenhouse?  What are the differences between the transparent coverings used for greenhouses?  What factors are involved in locating a greenhouse?  What are the different types of benches and bench arrangements used in greenhouses?  What are the different methods used in controlling greenhouse temperature?

What is a greenhouse structure?  Greenhouse-  structure covered with a transparent material, which allows sufficient sunlight to enter for the purpose of growing and maintaining plants  Greenhouse range-  two or more greenhouses located together  Headhouse-  a central building attached to a greenhouse and used for office, storage, and work space

What are the various design styles of greenhouses?  Attached greenhouse- connected to a building  1. Lean-to greenhouse  2. Attached even-space greenhouse  3. Window-mounted greenhouse

 Freestanding greenhouse- separate from other buildings or greenhouses  Need more land or space  More exposed surface area, therefore, require more heat

Four types of Freestanding Greenhouses 1.Even span- rafters of even length 2.Uneven span- rafters of unequal length 3.Gothic arch- styled in the shape of a pointed arch 4.Quonset- curved roofs with or without side walls

Even Span/Gothic Arch

Uneven Span

Quonset

Four types of connected greenhouses 1.Gutter-connected- several even-span greenhouses attached together 2.Venlo- different from gutter-connected in that they are normally wider and have twice as many ridges between supports 3.Barrel vault- Quonset-style structure with attached sides 4.Sawtooth- lean-to structures joined together

Gutter-connected

What are the structural parts of a greenhouse? 1.foundation- support for the framework 2.Footings- concrete support for foundation; located below the frost line 3.Sidewalls or curtain walls- wall on which the framework sits 4.Ridge- top of the greenhouse 5.Anchor support posts- provide main structural support for the greenhouse

6. Trusses- provide structural strength 7. Purlins- run length of greenhouse connecting trusses 8. Ventilators- moveable units that allow for natural ventilation. They can be located on the top or sides.

What is the difference between the transparent coverings used for greenhouses?  Glass  Usually expensive and hard to heat  Double strength; grade B is usually used  Sometimes, thermopane- a double of layer of glass with ¼ to ½ inch dead air space between panes- is used  Sash bars used with bar caps keep glass in place

Glass

 Polyethylene- flexible plastic film  Initial cost of installation is cheaper  Fuel cost to heat is cheaper  Life span is short, usually three years  Coverings are 4 mil or 6 mil thick  Condensation can be a problem

Poly

 Fiberglass- reinforced plastic  Corrugated polycarbonate  Less expensive than glass  Easy to install  Longer life span than polyethylene  Highly flammable  Susceptible to ultraviolet, dust, and pollution degradation

Fiberglass

 Acrylic and polycarbonate  Replaced the use of fiberglass  Lightweight and easy to install  Excellent heat insulating and light transmission  Life of 15 years  Flammable  Generally used on the ends or side walls

Polycarbonate

What are the factors involved in locating a greenhouse range?  Market  Accessibility  Climate conditions  Topography and drainage  Water and other utilities  Zoning regulations  Labor supply  Expansion

Greenhouse range  Should be oriented to present the least amount of shadows and achieve light intensity  Most important in N latitudes of N.A.  Prevailing winds are also an important consideration  Also consider entrances and drives that are accessible for large trucks and sufficient parking  Location of headhouse and storage facility is important to consider also

What are the different types of benches and bench arrangements used in greenhouses?  3 types of bench arrangements  Longitudinal- runs entire length of the greenhouse  Cross-benching- runs the width of the greenhouse  Peninsular- similar to cross-benching but has a middle aisle

 Types of benches  Wood bench fabrics- lath or snow fencing  Welded wire- 14-gauge galvanized wire coated with a plastic  Prefabricated plastic- lightweight, strong vinyl material  Moveable benches- 14-gauge galvanized expanded wire on frames with steel rollers

What are the different methods used in controlling greenhouses temperature?  Generally night temps should be degree F and day temps should be degree F  Ways to control temp  Heaters  Ventilation and evaporation cooling systems  Shading material

 Types of heating systems  Steam  Hot water  Forced air heaters  Infrared radiant heaters  Types of cooling systems  Natural ventilation  Fan ventilation  Fan-tube or fan-jet ventilation  Fan-pad cooling system  Fog-evaporation  Shading Materials  Liquid  Black polypropylene shade fabric