What are Greenhouse Structures

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What are Greenhouse Structures?

• By Jay Holcomb

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Greenhouse Structure

• Foundation
• Floor
• Frame
• Greenhouse Types

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Greenhouse Foundation

• This is the link between the greenhouse and the
  ground
• Footing should be below the frost line--at least
  24 inches
• Piers spaced about 4 feet apart can be the
  footing
• A 2-3 foot curtain wall may be used as part of
  the foundation.

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Greenhouse Foundation-2

• Some greenhouses need little foundation
• Pipes driven into the ground may be the only
  foundation

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Greenhouse Floors

• A natural soil floor is generally a poor choice
• Gravel is used most often. Drains well and
  generally weeds dont grow too well
• Porous concrete is a good choice. Water will
  drain through, but carts can move on it
• Solid concrete. Must plan to drain water from
  the floor.

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Greenhouse Frame

• Wood--paint to maintain and improve light
  reflection--pressure treated, redwood,
  cypress--Do not use creosote and penta
• Steel--strong, use hot-dipped galvanized or black
  pipe with rust inhibiting paints--paint at
  intervals
• Aluminum--few corrosion problems--no need to
  paint--heat loss through aluminum

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Greenhouse Types

• Lean-to
• Single span gable
• Quonset
• Ridge and furrow
• Moveable roof

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Lean-to Greenhouse

• One wall in common and ridge attached to another
  building
• Roof slants in one direction so maximum width is
  about 14 feet
• Difficult to mechanize because of small size

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Single Span Gable Greenhouse

• Detached structure except at end.
• Can be even-span, or uneven span.
• Any covering including glass
• Maximum width about 50 feet

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Single Span Gable Greenhouse-2

• Optimum environment for specific crops
• Easier pest control
• Higher construction costs

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Single Span Gable Greenhouse-3

• Generally trussed for open interior space
• Snow slides off
• Generally good light in winter

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Quonset Greenhouse

• Generally detached
• Most frequently built structure in industry
• Maximum width about 30 feet
• Surface curved so cover must be flexible
• Some need minimal foundation

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Quonset Greenhouse-2

• Optimum environment for specific crops
• Easier pest control
• Higher construction costs than for equal area
  under ridge and furrow
• May be harder to move plants between houses in
  winter

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Quonset Greenhouse-3

• Open interior--little or no truss work
• Very good light penetration in winter

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Ridge and Furrow

• Connected at gutter
• Can be gable or curved roof
• Any covering including glass
• Low profile (Venlo) or high profile roof

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Ridge and Furrow-2

• Prone to snow accumulation on roof
• Burn less fuel than equal area of separate houses
• Cost effective to build
• Increase in these being built

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Ridge and Furrow-3

• Very large interior space
• Easy to supervise employees since all are in one
  place
• More difficult for pest control

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Movable Roof

• Substantial portion of roof will open up
• Must have adequate side vents
• Covering can be glass or any other material
• Increased interest in Natural ventilation

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Movable Roof-2

• Advantages
• Plant more compact
• Reduced insect infestations
• Reduced disease development
• Potentially reduction in water use.
• Potentially reduction in labor
• Quieter to work in

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Angle of Incidence

• This is defined as the angle between a line
  perpendicular to the surface and the ray.

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Angle of Incidence-2

• As the angle of incidence increases the light
  transmission decreases.
• A high angle of incidence means less light is
  transmitted.

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Angle of Incidence-3

• Because of the low sun angle in winter, to obtain
  maximum light in the greenhouse you need a steep
  greenhouse roof.

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Greenhouse Spacing

• Tangent A H/Y
• A angle of sun
• H height of structure
• Y distance from highest point to where shadow is
  cast