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Ghm2 ppt Ghm2 ppt Document Transcript

  • Greenhouse • greenキhouse   [green-hous] noun, Greenhouse Construction plural greenキhousキes a building, room, or area, usually chiefly of glass, in which the temperature is maintained within a desired range, used for cultivating tender plants or growing plants out of season. Greenhouse Components• Refers to a structure covered with a clear material • Frame- be mindful of load bearing requirements, to allow in natural light for the purpose of growing the closer the bow spacing the greater the strength plants but more expensive• It is usually artificially heated • Glazing- different types, usually double layer • End walls• 2 or more greenhouses in the same location is usually referred to as a greenhouse range • Cooling and ventilation systems • Floor type- ranges from bare to concrete• A building associated with the greenhouse not for growing plants, usually for storage or potting is • Benches referred to as a head-house or service building. Location Topography• Location should be the first consideration • It is best to chose a level site to reduce the cost of grading• Allow for room for expansion if possible • The site should be well drained, where drainage• Non greenhouse space needs should be issues exist drainage tiles should be installed considered such as service buildings, under the surface prior to construction parking lots, storage. • It is advised to chose a site with a natural windbreak, such as a row of trees or hills on the north and windward sides. • In areas that receive significant show fall trees should be 100 feet from the greenhouse to keep drifts back from the greenhouses. 1
  • Climate Water• The primary limiting factor to greenhouse • Water is frequently overlooked when crop production is adequate light in winter establishing a greenhouse thought it is one• Areas with frequent fog, inclimate weather of the most important factors and shadows from tall mountains are not • Before a site is purchased the water should ideal for plants with high light be tested, cost of removing ions is requirements. expensive• Areas in high altitudes with high light levels • Well water is usually desired because is not best for plants with low light municipal water is often expensive and can requirements, such as bedding plants. contain harmful fluoride Orientation Orientation• The magnitude of the shadows cast by the greenhouse depends on the angle of the sun • Single greenhouses located above 40˚N and season of the year. latitude in the northern hemisphere should be built with the ridge running E to W• The effect is most seen in the winter when the sun remains closer to the horizon and • Below 40˚N latitude, the ridge should be shadows are longer oriented N to S • All ridge and furrow and gutter connected greenhouses should be oriented N to S. Styles of Greenhouses Glass • Only glass greenhouses existed prior to 1950s • They have greater light intensity due to single glass covering • Tend to have higher air infiltration rate, leads to lower interior humidity- good for disease prevention • Glass greenhouses have a higher initial cost than film plastic greenhouses- cost of glass plus structure to support the weight of glass • Breakage is a major disadvantage • Tempered glass is much more durable 2
  • Glass Film Plastic Greenhouses• Light transmission of up to 90% • Polyethylene is what is most used today• Heat, UV and wind resistant • Other materials include polyester and polyvinyl chloride (PVC)• Has low heat retention • Popular because it costs less than glass and the• Not flexible cost of heating is aprox 40% less than single layer• In 2000 13% of greenhouses built used glass greenhouses. glass • Light transmission is lower than single later glass • Material coverings are shorter lived than glass Types of film plastic Polyethylene • Principal film of choice for greenhouse covering in the world • Almost always have 2 layers, outer layer is typically 0.15mm thick, inner later only needs to be about 0.1mm thick • Double layer helps retain heat and extends life • Has a UV protection additive • Lasts up to 4 years • Light transmission 87% single layer, 78% for double layer PVC ETEF• Lasts 4-5 years, was an advantage until 4 • Ethylene tetrafluoroethylene year polyethylene was invented • Most recent category of greenhouse film• The cost is aprox 3 times polyethylene • Anticipated life expectance is over 10 years• Vinyl films hold a charge which attracts • Light transmission of over 90% dust which reduces light transmission • Much more expensive than polyethylene in• PVC is seldom used in the US but is used the US primarily in Japan 3
  • Film Plastic Greenhouse Polyester Designs• Was used because of durability and price, lasted 4 years• Free of charge so it does not attract dust• Light transmission equal to glass• When other industrial uses were found the price went up making it not practical for use in greenhouses• Still used in heat retention screens Wood Frame Greenhouse• Polyethylene made it affordable for growers • Wood requires frequent painting to prevent to enter the industry rotting• People who did not have funds for glass • White paint was typically used to increase were able to build greenhouses interior light intensity• Inexpensive frames were also sought • Only treat wood with approved treatments,• Pinewood was used some can cause plant death or deformed• A-Frame was very popular growth• Scissor-truss frame is very strong Quonset Greenhouse• Today wood is rarely used in established • Price of wood is high compared to metal and greenhouse because of the cost of upkeep metal does not have the burden of painting and low levels of interior light • In the 1970s many greenhouses were Quonset style• Single layer plastic film was usually used • They can be purchased prefabricated or until the 1960s constructed on site• Due to fuel costs double layer plastic • Less expensive than gutter connected greenhouses coverings were used after 1960s so are popular for those on a limited budget• This gives about 40% fuel savings • Good when small isolated area is need such as cold treatment 4
  • Gutter-Connected Greenhouses• Trusses are often constructed from water • Most efficient film covered greenhouse design pipes bent to 180° arc • Cheaper and easier to automate because it is a single consolidated space• Quonset greenhouses are either freestanding • Management is more efficient when they are in the or arranged in a interlocking ridge-and- same building instead of scattered among many furrow manner buildings• Single large interior is better adapted to • Cost to build and heat a single space instead of multiple buildings is much less because of less movement of labor and automation surface area to lose heat from • Gutter-connected costs about $1.25-1.50/sq ft, Quonset is as high as $3.00/ sq ft Options • Height• New houses can be connected to existing houses  Height has been increasing in recent years to• Many owners of gutter-connected and Quonset accommodate elevation of climate control equipment, automation devices and hanging baskets greenhouses use double layer polycarbonate (sometimes acrylic) panels on the ends these can • Distance between gutter rows last over 20 years  Ranges from 10.5-40 ft, wider spaces between rows are weaker and need extra strong trusses• Side walls are usually covered with double layer of polyethylene film • Contour of the roof  Traditionally were relatively flat, Quonset arch shape,• Polycarbonate and acrylic are becoming more today can have gothic-arch or peaked roof popular for side walls for passively cooled greenhouses using side-wall ventilators • Active or passive cooling  Passive cooling is offered with roll up side curtains, roof and side ventilators, hinged and retractable roofs Double-Layer Covering Rigid panels• Dead-air space provides the best and • Today 16% of greenhouses are covered with cheapest insulation for greenhouses rigid panels• Space should be 0.5-4 inches• More than 4” air currents can form in air space which reduces insulation• Almost all film plastic covered greenhouses use double covering 5
  • PVC Fiberglass reinforced Plastic• For the most part PVC is not used anymore • Was very popular in the past but is declining in popularity and rarely used today for rigid panel greenhouses • Today twin wall polycarbonate panels are used in• Life expectancy was much lower than was place of fiberglass reinforced plastic because it once believed, as little as 2 years reduced heating cost by almost half• Cost was 4-5 times of polyethylene film • Corrugated sheets are preferred because they have greater strength • FRP offered advantages over glass, more resistant to breakage , uniform light intensity • Disadvantages are that it is subject to etching and pitting by abrasion and pollution Acrylic and Polycarbonate• Light transmission • Has been available for about 25 years  FRP is roughly equivalent to glass • Acrylic is particularly popular with research institutions because of high light transmission and• Heat transmission longer life, 83-90% light transmission  Easier to cool than glass • Acrylic is preferred by growers of plug seedlings,• Fire hazard cut flowers and vegetables because of their high light requirements.  Fire is a concern in FRP greenhouses • Polycarbonate tends to be used for bedding plants and perennials , reduces fuel costs lasts 10 years 81% light transmission• The main deterrent to acrylic is the price • Polycarbonate is available in flat and• Risk of fire corrugated single-layer sheets• Advantage of acrylic over polycarbonate is • Trend is moving to twin-wall panels to has about 2.5x longer life expectancy, reduce heating costs higher light transmission, lower heat • Triple layer is now becoming available for 2 transmission and greater resistance to hail layers of deal air space damage 6
  • Types of Greenhouses Venlo • Low profile, known as the Venlo Greenhouse, originated in The Netherlands • Eves are 10.5 feet apart • Lower profile slightly reduced the exposed surface area, reducing the heating costs Lean-to Even Span Greenhouse• This is where a greenhouse is places up • Two roof slopes of equal pitch and width. against the side of building.• Minimizes the need for roof support• Mostly used in the retail industry Ridge and furrow Uneven span greenhouse• Not used much because it is not adaptable to • Uses one or more A frame greenhouse connected to each other along the legnth of the eave automation • The eave serve as a furow to carry rain or melted snow• Has roofs of unequal width away • The side wall is eliminated between greenhouses • Reduces the cost of automation and labor • Less cost to heat because there is less exposed wall area 7
  • Quonset Structure• Metal frame • Wood• Less expensive than wood and does not require • Need to be painted to prevent rotting painting to prevent rotting • Rarley used today• Popular among people entering the industry on a low budget • Metal• Trusses are often built from water pipes bent to • Long lasting 180 degree arc • Aluminum usually used• Free standing or ridge and furrow • High stregnth• Curved surface so flexable covering is needed • Low maintence Benches and Beds Cut Flowers • Cut flowers can be grown in raised benches or in ground beds. • Plants that get tall such as roses that are grown for 5 years or more are usually grown in ground beds. • If crop is moderate height (snapdragon, chrysanthemum) if raised benches are used, they should be located close to the ground so plant is at a practical height for maintenance • In ground beds should be raised so the substrate is separate from the external soil to allow for sterilization of the substrate on a routine schedule Cut Flowers Cut Flowers• Most roses used a cut flowers are grown in in- • In recent years some crops including roses ground beds because of their height and gerbera have been grown in rows of• Walls of in-ground beds can be treated wood or individual containers filled with substrate cement blocks • Containers are placed in a trough and• Walls should be at least 8” deep and beds should watered with a nutrient solution via plastic extend down into a well drained foundation tube on top of each container substance, such as gravel • Excess solution leaches out the bottom into• If foundation substance is not well drained, a the trough and is captured, pasteurized and drainage tile should be placed under each bed reused 8
  • Potted-Plants Floor Options• Raised benches are typically used for pot plants• A height of 32-36” is best for working.• They should not be wider than 6 feet if not next to a wall or 3 feet if next to a wall to allow access from both sides.• Benches used for ebb and flow irrigation are water tight• Movable benches can increase production space by up to 90% of the floor space• Some greenhouses use a porous concrete flooring and grow plants in pots directly on the floor. This system makes it possible to use up to 90% of floor space Considerations Considerations• Drainage- crucial in a wet environment like • Heat- heat retention is important in colder climates a greenhouse. With a solid floor drains must materials such as brick and flagstaff retain heat, be installed to keep mold away this can help reduce heating costs in colder month• Decomposition- organic materials like • Comfort- standing on a hard floor like concrete wood, bark, sawdust etc will decompose can be hard on your feet and back over time and will need to be removed and • Traction- consider that the floor may be wet so replaced consider traction• Price- one of the most important • Weeds- be sure to put down weed blocking considerations material under flooring material Materials Materials• Standard concrete- no drainage, should be avoided • Stone- durable, easily cleaned, individual in growing areas stones so it can drain in the cracks.• Porous concrete- allows for drainage, avoid using Expensive and may not be level in seeding and propagation area because over time particles will clog holes • Wood- planks across greenhouse floor, attractive, cracks provide drainage but can• Gravel/dirt- inexpensive but can not be properly disinfected or cleaned, harbor more pests, plants be expensive can not touch floors, not good for retail operation • Bark chips, wood chips, sawdust- because can be hazardous and not wheelchair inexpensive but will need to be replaced accessible when they decompose 9
  • Flood Floor Videos• The flood floor is a non porous floor that slopes • http://www.greenhousegrower.com/video/c:99/str form the sides to the center of each bay. A drain is uctures-equipment/ at the low point. When water or fertilization is required the floor is flooded for approximately 10 • http://www.greenhousegrower.com/video/c:99/str minutes and then the floor is drained. uctures-equipment/772/• Water moves into the pots by capillary action• Heat pipes under the floor allow for speedy drying • http://www.greenhousegrower.com/video/c:99/str uctures-equipment/1170/ 10