Books for the greenhouse operator:
Greenhouse Operation and Management by Paul Nelson
Ball Culture Guide: the encyclopedia of seed germination
Hot Beds -- cold frames with heat source
· Originally manure pile was used as a heat source
o Can't control temperature
o Temperature starts low, goes to peak, then declines
· Pipes under bed, for fire/smokestack
· Steam or hot water
· Electricity
o Matts used will break down eventually
· Must provide for ventilation
o Manual
§ But must remember!
o Autonatic
§ But the mechanism makes it more difficult to open the lids
o Solar controlled opener
§ Usually expansion of liquid opens window
§ Significant weight limits: 30 pounds common limit
§ Normally opens at a preset temperature
· Cold frames and hot beds are usually associated with greenhouses (attached to them), often on the south side.
· In Alaska, about 3% of the greenhouse operators use hotbeds, 27% use cold frames
· Coverings: fiberglass, poly, special sheets
Bulb cellars
· Modified root cellar
· Place for forcing bulbs
· Force vernalization
· Forced chilling period
· Big, underground bunkers
o Sloped ramp
o Cold air flows down ramp at night
o Close it up in the day
Photos
Lath house ("Saran" house)
· Structure to give shade
· Often made of wood, metal, poles, etc. Often covered with saran (woven plastic, cloth, etc)
· Used to harden off plants
· Used for azaleas and other plants which do not tolerate full sun
Growth rooms
· Insulated buildings with no windows
· Artificial lighting
Greenhouse shapes
· Even span
· Uneven span
· Quonset hut
· Lean-to
· Contiguous greenhouse (gutter-connected greenhouses side by side)
· Ridge & furrow (also called a multi-span)
o Essentially a contiguous greenhouses, only with no walls separating the 'greenhouses'
[End photos}
Detached (also called 'freestanding')
· Even span is the most popular
o Easiest and most economical to build
o Uniform pieces of construction materials
o Simpler construction
· Provide for good zone heating
o Easy to program and maintain temperature
· Easier to ventilate evenly
o Especially large covered structures
· Require fewer ventilators = lower cost
· Lighting is more uniformly distributed through house
· More easily maintained
o Especially roofs
o Easier to clear snow
o Better roof access
· Requires more heat per volume of air
o More surface area of glass, etc per growing area
· More surface area exposed to winter wind
o = more heat loss
· higher initial construction cost per square foot of greenhouse area
o more glass (or whatever)
o more framing materials
· requires more land area per growing space = higher taxes
· zoning requirements
o # buildings per site
· easier to expand or contract to crop size
o just add curtains
o easy to add another house
· inconvenient for people and plants
o moving between buildings in all kinds of weather can pose a problem
· Commercial, prefab buildings are available
Ridge and furrow
· Use less land area
· Less costly to build
· Lower heating cost
· Lower labor cost
· Reduced light (due to gutters, supports)
· Difficult to apply pesticides
· Difficult disease control
· Made for mass crops--not a diversity
o Fewer zones
· Not easy to expand or shrink
· Minimum 20,000 square foot greenhouse needed for economic efficiency
Uneven span greenhouse
· Optimize winter light
· Unusual conditions (slope, against house, etc)
· Usually hobby greenhouse
· Optimal winter light
· More difficult to heat and ventilate evenly
· Usually built on hillsides
· Not as readily available commercially
Lean-to
· Reduced light
· Difficult to ventilate and light evenly
· Cheap (especially if house is a part of the structure)
· Readily available commercially
· Excellent access from building
· Mostly used as hobby (and sometimes shools) in Alaska
· Used for seed starting
· Small, new businesses often start with these
· Sometimes used for sales
Quonset Hut
· [1940's version of an Atco unit, manufactured in Quonset Poin, RI]
· most energy efficient of all structures
· very easily made
· cheap
· energy efficient--good surface to area ratio
· clear span, minimum shading
· crop height restrictions
· lots of prefab packages
Sawtooth
· connected lean-to's
· good in hot climates (California, Florida, Texas)
· easy to ventilate (face slope into prevailing wind and have openings on 'back side of tooth')
Dutchlite or Venlo greenhouses
· 2'x4' glass single pane windows
· highest % of light transmission
· main type used in Europe for vegetable production
· very tall
Modified Quonset--gothic arch (Quonset pulled up into a peak)
Barrel Vault (Quonset with the peak squished down)
Handouts
· Hotbeds for Transplant Production
· Cold Frames
· Hotbed design
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