1. Greenhouse Structures

2. GREENHOUSES Structures covered with transparent material
Allows sunlight to enter for plant growth and maintenance
Artificially heated and cooled

3. Uses Overwintering tender plants Starting seeds Starting cuttings
Raising vegetables and flowers out of season
Growing specialty plants

4. Designed to local weather extremes
Minimum yearly temp.
Max. wind speeds
Max. snow loads
Best light transmission

5. Environmental considerations for plants
Light
Temperature
Humidity

6. Headhouse
Office, storage, and work space from which greenhouses are located

7. Types of Greenhouses
Attached
Freestanding

8. Attached Greenhouse Connected to building Floral shop Garden center
Office
Home

9. Attached Greenhouses Advantages: Disadvantages
Less construction material needed
Can be utilized to heat homes in winter, cool in summer through heat and humidity change
Disadvantages
Existing building can shade the greenhouse, limiting light needed for plants
Ventilation and temperature are difficult to control.

10. Lean-To Attached to building, usually on the south-facing side
Ridge to the roof is attached to the building side

11. Attached Even-Span End wall is attached to a building
Rafters are equal length

12. Attached Even-Span Advantage More available space Disadvantage
More expensive to build and heat than a lean-To

13. Window mounted Attached to windows as a pre-fabricated unit.
Disadvantage
Limited space
Plant environment is difficult to control

14. Freestanding Greenhouse
Even Span
Uneven- span
Quonset
Gothic Arch

15. Even-Span Rafters of equal length
Usually clears spans w/ truss supports
ADVANTAGE: Allows more freedom of space/ movement and equipment

16. Uneven-Span Rafters of unequal length
Usually used for hillside placement
ADVANTAGES: maximizes sun light
DISAVANTAGES: internal orientation of greenhouse can make working in it difficult

17. Quonset Curved roofs; military hut-style
May or may not include sidewalls

18. Gothic Arch Cathedral arch-forward style Eliminates truss supports
Adds a double layer of polyethylene covering

19. Gothic Arch Advantages Less construction material
Less land needed for spacing
Heat conservative due to less exposure
Workers and equipment can move through the buildings rather than between buildings

20. Gothic Arch Disadvantages
Creating different environmental conditions for crops is more difficult
Connected houses do not distribute snowfall weight well and can collapse
Require heating cables to melt snow to prevent collapse
Difficult to ventilate, requires fans to circulate

21. Types of Connected Greenhouses
Gutter-connected – made up of even span greenhouses
Venlo or Dutch – twice as many ridges as gutter connected
Barrel Vault – quonset style with walls joined
Sawtooth – lean to style joined together

23. Review What is a greenhouse?
What are the four types of freestanding green houses?

24. Review
Three environmental considerations for Plants?

25. Objectives for the day
What are the structural components of a greenhouse?
What are five different ways of heating a greenhouse?
What are three ways of cooling a greenhouse?
What is a forcing structure?

26. Components of Greenhouse Structure
Frame
Foundation
Concrete Footings
Sidewalls

28. Frame Pressure-treated wood Aluminum Galvanized steel
NOTE: glass greenhouses require more structural support than polyethylene

29. Foundation Continuous concrete bed upon which greenhouse is built
Water and electrical lines are placed before concrete is poured

30. Concrete Footings
Non-continuous supports located below the frost line (cannot be affected by frost heaves)
Take the place of foundations.
Spaced at intervals according to placement of support anchor posts

31. Sidewalls
Between the footings and supports

32. Greenhouse Coverings Glass Provides excellent light transmission.
Long-lasting.
Double-strength, grade B weight used for greenhouses except in cold areas, where thermopane (with a ¼ to ½ inch layer of trapped air between panes) is used.
Expensive installation and heating.
Requires good structural support of aluminum or steel.
Sash bars
Frame glass panes; held by glazing compound.
Bar caps
Attached to outside of panes to hold glass in place.

33. Greenhouse Coverings Polycarbonate Lightweight Ease of installation.
Good heat insulation.
Good light transmission.
Available in clear, corrugated single layer panels.
Good replacement for corrugated fiberglass-reinforced plastic.
Disadvantage: Flammable

35. Greenhouse Coverings Corrugated Fiberglass-Reinforced Plastic
Low in cost.
Ease of installation.
Tensile strength.
Longer lifespan.
Good light penetration.
Can degrade over time from ultraviolet damage, dust, and pollutants.
Flammable and may increase insurance costs.

36. Greenhouse Coverings Polyethylene Inexpensive installation.
Low heating cost.
Short-lived.
UV inhibitors increase its lifespan.
Produces condensation which increases wet plant foliage and disease possibilities.
Light reduction compared to glass.

37. Greenhouse Coverings Acrylic Lightweight Easy to install
Good heat insulation.
Good light transmission.
Long lifespan.
Flammable.

38. HEATING Steam -produced in a boiler
-Circulated by pipes in sidewalls and overhead
-Used mostly when several greenhouses are attached
-this steam can also be used to sterilize media

39. Heating (cont.) Hot water -similar to steam but used in smaller houses
Forced-Air
-Local Units force hot air into houses
-Can be moved through plastic overhead tubing

41. Heating Infrared Radiant -Individual unit heaters
-Directly warms the plants in the greenhouse
-Conserves energy but is generally cooler than other types of heat.

42. Heating Con’t Solar Restricted to passive designs
Crops require little additional heat

43. Unit Heaters Fired by natural gas, propane, fuel oil, coal, or wood.
Electricity not recommended, due to reliability.

44. Determining size HVAC Climate Area of exposed greenhouse surface
Type of construction and materials
= # of BTU’s need maintain inside temp.

46. Cooling

47. Fan and Pad Exhaust fan draws air through moist cellulose pad.
Air is cooled through evaporation
For low humidity conditions

48. Fog evaporative Fog is generated within the greenhouse
Heat is absorbed by the water droplets and evaporated, cooling the greenhouse environment.
Used in propagation houses

49. Ventilation

50. Ventilation
Natural
Fan Tube

51. Natural
Air exchange is fostered through open ridge and side venting, under thermostatic control.
Not advised for winter cooling due to possible plant injury

52. Fan-Tube
Fans bring in cool air which is mixed with warm air and distributed though holes in plastic tubing running the length of the greenhouse
May be used in conjunction with heating systems

53. Shading
Fabric
Compound

54. Fabric
Black polyethylene pulled over the greenhouse to reduce light intensity and temperature.
Comes in a range of shade percentages.

55. Compound
Liquid compounds applied to glass or polyethylene covered greenhouses to reduce light intensity and temperature

56. Forcing Structures Used in Raising Plants

57. Lath House/ Shade House
Provides some shade and wind protection for plants
Allows moisture and air to permeate structure
Used as an outdoor setting for plants with some protection

58. Cont’d Much smaller than a greenhouse
For plant establishment, acclimatization, or plants requiring shade
Weatherproofed wood or galvanized steel
Frame is three sided: roof, back, two sides

59. Con’t
Covering
Wooden roof is slatted to permit weather and light, but not full sunlight
Plastic net fabric is commonly used, in a range of shade percentages

60. Overwintering Structures
Cold Frame
Hotbed

61. Cold Frame Unheated Structures
Wind protection and moderated temp. control
Placed partially below ground level
Frame is wood W/ hinged or sliding glass top opening or covering of plastic film
Backs are higher and tops slanted down for weather protection
Insulation can be used on tops of plants or containers

62. Hotbed
Similar to a cold frame in structure, but with and underlying heat source
Used to start seedlings or cutlings
Heat from pipe (steam or hot water), heat coils (electricity), or natural sources are used (manure)
Hotbeds have brick or concrete sides and back with a glass top slide or hinged covering

63. Review What are the structural components of a greenhouse?
What are five different ways of heating a greenhouse?
What are three ways of cooling a greenhouse?
What is a forcing structure?