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 connected 2. Free standing Quonset 3. 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:  Glass  Fiberglass  Polyethelene (PE) film

Glass  Best light transmission  Costly structural supports  High initial cost  High maintenance costs  Limited use Photo © 2009 Nancy Crombie, UBP

Fiberglass  Rigid  Extremely durable  Less 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 efficiently  Toxic fumes must be vented  Heat often distributed through polyethylene (PE) vent tubes  Heating 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.