Notes for 2/8/00

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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