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Greenhouse Structures

Greenhouse Structures. GREENHOUSES. Structures covered with transparent material Allows sunlight to enter for plant growth and maintenance Artificially heated and cooled. Uses. Overwintering tender plants Starting seeds Starting cuttings Raising vegetables and flowers out of season

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Greenhouse Structures

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  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: 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

  22. http://www.b2science.org/

  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

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

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

  29. 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

  30. Sidewalls Between the footings and supports

  31. 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.

  32. 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

  33. 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.

  34. 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.

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

  36. 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

  37. 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

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

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

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

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

  42. Cooling

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

  44. 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

  45. Ventilation

  46. Ventilation Natural Fan Tube

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