objective: students will be able to know and understand what they need to have when choosing a...

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.