objective: students will be able to know and understand what they need to have when choosing a...
DESCRIPTION
Greenhouse Types and Designs Type of structure influences efficiency and productivity Understand the advantages and disadvantages of each type There are also choices of frame type, covering, heating system and more.TRANSCRIPT
Objective:Students will be able to know and
understand what they need to have when choosing a greenhouse.
This will be accomplished by students designing their own greenhouse.
Greenhouse Types and Designs
• Type of structure influences efficiency and productivity
• Understand the advantages and disadvantages of each type
• There are also choices of frame type, covering, heating system and more.
Selecting the type of greenhouse you want….
3 Main Structure Types
1. Gutter connected2. Free standing Quonset3. Single gable structures
Some lean-to structures are also used, primarily for home gardens and hobby use.
1. Gutter Connected May or may not be an
internal wall below the gutter
Structure without internal walls is more efficient.
May have gabled roof or curved arch.
Photo courtesy Atlas Manufacturing Inc.
2. Quonset Most common type of detached
greenhouse. Arched rafters and solid end walls Restricted growing area near side
walls reduces efficiency and productivity.
Photo courtesy Atlas Manufacturing Inc.
3. Single Gable or Free Standing
Staff photo/Nancy Crombie
Even span roofs Solid walls
Key parts of a greenhouse structure
Key Parts
Rafters – primary roof support Purlins – horizontal supports between
rafters Side posts/columns – vertical supports End walls and side walls – enclose the
structure, may be vented
Framing Materials
Materials used for Greenhouse Support System Aluminum:
Most economical and longest lasting; extruded in various shapes and thickness
Wood: Deteriorates quickly in moist
environment; pressure-treated lumber resists decay.
Steel: Stronger, heavier and more costly than
aluminum; potential for rust.
Covering Materials
The Function of Greenhouse Coverings
Clear enough to provide light transmission Durability Affordability 3 most common:
GlassFiberglassPolyethelene (PE) film
GlassBest light transmissionCostly structural supportsHigh initial costHigh maintenance costsLimited use
Photo © 2009 Nancy Crombie, UBP
Fiberglass
RigidExtremely durableLess extensive structural supports than glass
Staff photo/Nancy Crombie
Polyethylene (PE) Film
Common covering: double sheets of PE film inflated with air.
Not rigid, but provides needed support for normal operation
Lasts about two years Initial low cost, but high
replacement and maintenance costs
Less costly support structures New polycarbonate and acrylic
materials are being developed. Photo courtesy Atlas Manufacturing Inc.
Heating Requirements
Heat is Needed for Year-Round Production
Solar heat is not enough for year-round production
Coal, oil, and gas are most common energy sources
Choice of energy source is based on cost and local supply and demand
Staff photo/Nancy Crombie
Heating with Gas
Burns efficientlyToxic fumes must be ventedHeat often distributed through
polyethylene (PE) vent tubesHeating tubes placed under plant
benches will improve heating efficiency.
Using Boilers with Hot Water or Steam Heating Systems
More common in northern areas than in the southern states.
Hot water for "under pot heating“ is effective and efficient. Heat radiated from tubes is absorbed by pots placed directly on them.
Media in the pot is maintained at a constant temperature, improving plant growth and reducing energy costs.
Controlling Heat Levels Place thermostats and environmental
controllers at plant level. Have an appropriate number of sensors
throughout the production area. Thermostats should out of direct
sunlight and facing north or in a protected location.