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    http://www.envirocept.com/gh_guide/index.html

    TYPES OF GREENHOUSESThere are two basic types: attached and free-standing. An attached structure may beeven-span, lean-to, or window-mounted. A free-standing type is usually even-span(symmetrical roof).

    Attached Lean-ToA lean-to is built against a building, using the existing structure for one or more of itssides. It is usually attached to a house, but may be attached to other buildings. Thelean-to is limited to single or double-row plant benches with a total width of 7 to 12feet. It can be as long as the building it is attached to. The advantage of the lean-tois that it usually is close to available electricity, water, and heat.

    The lean-to has the following disadvantages: Limited space. Limited light.

    Limited ventilation and temperature control.

    http://www.envirocept.com/gh_guide/index.htmlhttp://www.envirocept.com/gh_guide/index.htmlhttp://www.envirocept.com/gh_guide/index.html
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    Attached Even-Span

    The even-span is the standard type - the one people generally visualize when theythink about greenhouses. The even-span is similar to a freestanding structure except

    that it is attached to a house at one gable end. It can accommodate 2 or 3 rows ofplant benches. The cost of an even-span is more than the cost of a lean-to type, butit has greater flexibility in design and provides for more plants. Because of its sizeand greater amount of exposed glass area, the even-span will cost more to heat.

    Attached Window-Mounted: A window-mounted type will allow space to grow a fewplants at relatively low cost for heating and cooling. This reach-in is available inmany standard sizes, either in single units or in tandem arrangements for largewindows. Only simple tools are needed to remove the regular window from the frameand fasten the pre-fabricated window type in its place. See your favorite gardencatalog or visit your local building center for styles and availability.

    Free-StandingThe free-standing is a separate structure and consists of side walls, end walls, andgable roof. It is like an even-span except that a free-standing is set apart from other

    buildings to get the most sun. It can be made as large or small as desired.

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    $ COST $

    The lowest cost per square foot of growing space is available in the even-span 17 to

    18 feet wide. It will house 2 side benches, 2 walks, and a wide center bench. Thelowest total cost is the lean-to house 7 to 12 feet wide with double-row benches anda central walk.A separate heating system is necessary unless the structure is very close to aheated building. The free-standing structure is more easily adapted to the builder'sideas of location, size, and shape than an attached type. It also provides more light,but requires more heat at night due to the additional glass.

    STYLE OF GREENHOUSE CONSTRUCTIONWhether you build a glass, fiberglass, or plastic type, shopping around for ideas iswise. Greenhouses have supporting framework made of wood, aluminum, iron, orgalvanized pipe. Some have curved eaves; others have flat eaves. Some are glassor plastic from the ground up. All structures have advantages and disadvantages.If you build your own, have the plumbing and electrical work done by professionals inaccordance with local codes. Most local governments require a building permit toerect a building of this type.Glass Type: Glass is the traditional covering. It is available in many designs to blendwith almost any style or architecture. Glass greenhouses may have slanted sides,straight sides and eaves, or curved eaves. Aluminum, maintenance-free glassbuilding has very pleasing lines and will provide a large growing area. It assures youof a weather-tight structure, which minimizes heat costs and retains humidity. Foramateur gardeners, small prefabricated glass kits are available for do-it-yourselfinstallation. They are sold in different models, to fit available space and to fit yourpocketbook. The disadvantages of glass are that it is easily broken, expensive, andrequires a much better type of building structure than fiberglass and plastic.Fiberglass Type: Fiberglass is lightweight, strong, and practically hail proof.Corrugated panels 8 to 12-feet long and flat fiberglass in rolls are available in 24 to48-inch widths. Thickness ranges from 3/64 to 3/32 of an inch. Poor grades offiberglass will discolor and the discoloring reduces light penetration. Using a goodgrade, on the other hand, may make your fiberglass as expensive to build as a glassone. If you select fiberglass, choose the clearest grade. Do not use coloredfiberglass.Plastic Type:Plastic is increasing in popularity for these reasons: Building cost per square foot is generally one-sixth to one-tenth the cost of glass

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    Plastic can be heated as satisfactorily as glass greenhouses. Crops grown under plastic are of equal quality to those grown under glass. Plastic styles are considered temporary structures and usually carry a low

    assessment rate for tax purposes, or may not be taxed at all.Plastic structures can be made of polyethylene (PE), polyvinyl chloride (PVC),copolymers of these materials, and other readily available clear films.Polyethylene - The advantages of polyethylene are that it is low in cost andlightweight. It also stands well in fall, winter, and spring weather, and lets throughplenty of light for good plant growth. However, polyethylene constantly exposed tothe sun deteriorates during the summer and must be replaced each year. Ultravioletlight energy causes polyethylene to break down. This first deterioration occurs along(or over) the rafters and along the creases where the film is folded. Ultraviolet-

    inhibited polyethylene lasts longer than regular polyethylene. It has an inhibitor thatprevents the rapid breakdown caused by ultraviolet light. UV-inhibited polyethylene isavailable in 2- and 6-mil thickness up to 40 feet wide and 100 feet long.Polyethylene permits passage of much of the reradiated heat energy given off by thesoil and plants inside the structure. Therefore, a polyethylene type loses heat morequickly than glass both during sunny periods and after sunset. This is an advantageduring the day and a disadvantage at night. Polyvinyl chloride (PVC or Vinyl) - Vinyl'sfrom 3 to 12 mils thick are available for covering your structure. Like polyethylene,vinyl's are soft and pliable; some are transparent, others translucent. They areusually available in 4- to 6-foot widths only; larger widths can be made byelectronically sealing several smaller widths together. Vinyl's cost from 2 to 5 timesas much as polyethylene. When carefully installed, 8 or 12-mil vinyl holds up for aslong as 5 years. Vinyl attracts dust and dirt from the air and has to be washedoccasionally.

    Environmental Conceptsprovides UV inhibited corrugated plastic panels that arestrong, durable, and lightweight. These panels can be used in many applicationsincluding cold frames, propagation chambers, or custom designed greenhouses.These translucent panels transmit 70-75% soft diffused light, encouraging lush greenplant growth. The strength of the corrugates provides maximum wind and snowprotection. The trapped air space in the panels provides optimal solar heat collectionwith a 2.5 R insulation factor in the 3.5 mm panels and a 3.0 R insulation factor in the5.0 mm panels.These UV protected, double-walled high density polyethylene panels are mildew,water, and chemical resistant and will not yellow. A double ultraviolet treatment filters

    out harmful rays and extends the panel life. All paneling has a 6 year limitedwarranty against ultraviolet breakdown. These panels measure about 4'-1" x 8'-1"

    http://www.greenhouses-etc.net/glazing
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    and 4'-1" x 12'-2" and are available in 3.5 mm and 5.0 mm thickness. The panels arelonger to enable overlapping. These panels, like most plastics, expand and contractdepending on the temperature. The panels fill the structure with soft diffused light,ideal for plant growth. Use 5.0 mm paneling for more rigidity, a higher insulationfactor and softer light. Galvanized, self-tapping screws with neoprene washers are

    used with this paneling to easily attach the lightweight, flexible, corrugated panels tothe structure frame.

    TYPES OF FRAMESPlastic structures range from crude wooden frameworks to air-supported houses. Ifyou plan to build a plastic structure, carefully consider economy of size and futureexpansion. Because plastic is available in large widths and is lighter in weight, raftersand supporting members can be widely spaced to permit maximum light penetration.

    Common structures of frames are as follows:

    A-FrameIn building an A-frame structure, consideration must be given to the placement ofcross rafters (supporting members). Cross rafters should be placed at least one-thirdof the distance down from the ridge on the outer rafters. Otherwise, working around

    the cross rafters to apply an insulating layer of plastic will be difficult. When thecross-rafter support is high in the peak of the building - especially in narrowstructures - an essentially clear-span type of structure permits easy application of aninner layer of plastic. The inner layer can be applied under the cross-rafter supports,leaving a small triangular air space in the peak of the house. Diagonal bracing wiresprovide added strength to an A-frame structure. This type is among the least difficultto build.

    Rigid Frame

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    Rigid-frame structures have been designed in widths up to 40 feet. This clear spanstructure has no columns to hold up the roof section. The best available rigid-frametype has a 6-foot sidewall and is designed from 30, 36, or 40-foot widths. Aprefabricated unit built with curved laminated wood rafters is commercially available.It has very low sidewalls (low head room), and to grow tall plants the structure must

    be raised higher on the foundation sidewalls.

    Panel FramePanel-frame types are a modification of the sash house (a small plastic style used forgrowing plants for later transplanting). This structure requires accurate carpentry,and building costs are higher than for other frames because of the added lumber andlabor needed to build the panels. Advantages of panels are that they can be quicklyinstalled and taken down and stored during the summer; this will increase the life of

    the plastic panels. Panel styles can be easily ventilated because you can easilyplace a vent.

    Round TopRound Top styles have the same general shape as the Round Top huts of WorldWar II. Some have been constructed of wood, but usually the frames are metal. The

    half-circle frames are covered with one piece of wide plastic and the houses are upto 20 feet wide. The advantage of this house is the ease of building and covering.Ventilation is by exhaust fans at the ends of the houses.

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    Pipe Frame (Galvanized Steel or Polypipe)

    A pipe structure can be used to frame an air inflated style. Air is introduced into achamber formed by 2 layers of 4- or 6-mil film. The effect of the air under slight

    pressure is to force the inner layer of film over the circular pipe frames. The outerlayer assumes a circular shape over the frame and rides on a cushion of air. Theouter layer lifts 3 to 4 inches from the frame at the top and 1 to 2 inches from theframe at the foundation sill. Air enters the chamber through 6- inch plastic tubing. Amanometer is used to measure static air pressure between the layers of film.

    PLANNING YOUR GREENHOUSE LOCATIONAfter you have decided which kind of greenhouse you want, you will need todetermine where you are going to put it. The first choice for a site should be on thesouth or southeast side of the house in a sunny location. The east side is the secondbest location. That's where it will capture the most November to February sunlight.The next best locations are the southwest and west. The north side is the leastdesirable location. You can place your structure where it will be partly shaded duringthe summer when light reduction is not serious and may be desirable. Be sure totake into account the possibility of falling limbs that can damage the structure. Some plants will grow in a greenhouse in any location. African violets and orchids,for example, will grow with northern exposure - but heating costs will be high. Youwill limit the types of plants you can grow if you don't put your structure in the bestpossible location. Sometimes you can place a structure against a door, window, orbasement entrance of your house. This will let you use heat from your house to growplants, make your structure more accessible, and save on construction costs. Yourhome heating bill, however, will increase significantly. If you have an L-shapedhouse, you can save the cost of 2 walls by building in the "L".Whether your structure runs north and south or east and west is not so important aswind protection. Protect your building from winds by locating it so existing buildings

    will shield it, or by providing it with a windbreak hedge or fence.

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    NoteAn ideal site would be one that is well-drained, nearly level, and has full southern exposure to

    sunlight. It would slope slightly to the south and have a windbreak on the side of the prevailingwind.

    BASIC GREENHOUSE DESIGNYou will need to determine the exact dimensions before you start to build. Width isthe most important dimension; it will not be changed during the life of the structure.Length can be increased if more space is desired.Structure Width:Determine the width by adding the widths of the plant benches and the walks. Allowapproximately 6 inches for an air-circulation space between the side walls and thebenches. Side benches are serviced from only one side and should be no wider thanyou can reach across. For some people this will be 2 feet, for others perhaps asmuch as 3 feet. Center benches are serviced from both sides and can be as wide as6 feet. They should be no wider than to permit you to work comfortably.Determine the width of the walks inside the structure by how they are to be used. Ifthe walks will be used only as a place to stand while servicing the benches, an 18- or19-inch walk is sufficiently wide; if a wheelbarrow will be brought into the building,the width must be greater. Wide walks - 24 to 30 inches - will allow easy passage for

    visitors who may not be used to walking between rows of plants.Structure Length:Determine the length by multiplying the number of plants you can grow across thebenches by the number of plants you want to grow. Then round off the measurementso that no glass will need to be cut to fill odd sash bar spacing. (A sash bar is ashaped wooden or metal bar used in the construction of a sash or frame anddesigned to hold and support the glass secure to it.)Standard glass sizes are 16 x 24, 18 x 20, and 20 x 20 inches. (Larger glass sizes

    means few sash bars and less shadow inside the structure.) Most plastics areavailable in 100-foot lengths. When you figure the length of a glass structure, allowfor the width of the projecting part of each sash bar plus a fraction of an inchclearance. For plastic, allow an extra 24 inches to fasten the plastic properly.Structure Height:The height depends on the desired height to the eave. An eave height of 5 feet issatisfactory for side benches with low-growing plants. If you want to grow tall plants,however, you will want an eave height of 6 or 7 feet. The pitch of the roof should be6 in 12 (approximately 27 degrees). The eave height, the distance from the side wallto the center of the structure, and the roof pitch will determine the height of your

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    structure at the center. The height of the structure should be equal to the eave heightplus one-fourth the width.For instance, in an even-span unit 18 feet wide, the distance from the side wall to thecenter of the structure is 9 feet. The difference in height between the center of the

    structure and the eave will be one half of 9 feet, or 4 feet. If the eave is 5 feet high,the structure should be 9 feet at the center.

    LIGHTING AND TEMPERATUREPlants respond to the relative lengths to light and dark periods as well as to theintensity and quality of light. Artificial light has been used extensively to control plantgrowth processes under various conditions. Plants differ in the need for light; somethrive on sunshine, others grow best in the shade. Most plants will grow in either

    natural or artificial light. Artificial light can be used in the following ways:To provide high intensity light when increased plant growth is desired.To extend the hours of natural daylight or to provide a night interruption to maintainthe plants on long-day conditions.Proper lighting not only extends the gardening day by enabling the gardener to workin the greenhouse during the dark evenings of winter and early spring, but it aidsplant growth. Three basic types of lamps used in greenhouse lighting are:Fluorescent lamps- These have the advantage of higher light efficiency with lowheat. This type of lamp is the most widely used for supplemental light. It is availablein a variety of colors but cool-white lamps are the most common. High intensity(1500 ma) fluorescent tubes that require higher wattage are also commonly used toreach 2000 foot candles. - These have the advantage of higher light efficiency withlow heat. This type of lamp is the most widely used for supplemental light. It isavailable in a variety of colors but cool-white lamps are the most common. Highintensity (1500 ma) fluorescent tubes that require higher wattage are also commonlyused to reach 2000 foot candles.Incandescent lamps -These vary in size from 60 watts to 500 watts. They are usedto extend day- length in greenhouses. The grower can vary foot- candle levels byadjusting the spacing and mounting height above the plants. These vary in size from60 watts to 500 watts. They are used to extend day- length in greenhouses. Thegrower can vary foot- candle levels by adjusting the spacing and mounting heightabove the plants.High-intensity discharge (HID) lamps - These have a long life (5000 hours ormore). With improvements made possible by the addition of sodium and metal-halides, the lamp has a high emission of light in the regions utilized by plants. Thesehave a long life (5000 hours or more). With improvements made possible by the

    addition of sodium and metal-halides, the lamp has a high emission of l ight in theregions utilized by plants.

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    Light Meters - Inexpensive light meters are available for measuring the lightintensity. The most common light meters are calibrated in foot candles (1 ft cd=10.76 lux). Foot candles should be measured at the growing level of the plants.Research your particular type of plant and find out what the optimum foot candlesare for growth or propagation. Adjust your light height accordingly so that the the foot

    candles are correct at the growing level when measured with the light meter.

    LIGHT INTENSITY METERMeasure the number of foot-candles from sunlight or grow lights to create the optimum growing

    conditions for your plants.Information booklet with recommendations included. No batteries required. GS-775

    Temperature - As a gardener you will be concerned with 2 temperatures - the airtemperature required in the greenhouse and the minimum outside temperature thatyour heating equipment must overcome. For most plants, a night temperature of 60to 65 degrees F in the greenhouse is adequate. The general rule, however, is not tohave a higher temperature than is necessary. If you grow some plants that require ahigher temperature than is provided in the greenhouse, use a propagating case or awarmed bench with thermostatically controlled warming cables to warm the airsurrounding the plants. This can be done at a fraction of the cost that would be

    necessary to heat the whole greenhouse to provide the same temperature. As agardener you will be concerned with 2 temperatures - the air temperature required inthe greenhouse and the minimum outside temperature that your heating equipmentmust overcome. For most plants, a night temperature of 60 to 65 degrees F in thegreenhouse is adequate. The general rule, however, is not to have a highertemperature than is necessary. If you grow some plants that require a highertemperature than is provided in the greenhouse, use a propagating case or awarmed bench with thermostatically controlled warming cables to warm the airsurrounding the plants. This can be done at a fraction of the cost that would benecessary to heat the whole greenhouse to provide the same temperature.If you want a temperature of 60 degrees F, install heaters that will provide thattemperature. If you want no more than frost protection, set the thermostat at 40degrees F. Space heaters can maintain a minimum of 60 degrees F in thegreenhouse. Higher temperatures on plant benches can be provided with soil-warming equipment.Remember that heat is lost from a greenhouse by radiation, conduction, andconvection through: Glass. Walls and other non-glass parts of the structure.

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    Floor or soil. Ventilation, door openings, and cracks. Choose your greenhouse covering carefully.

    CO2 ControlCarbon dioxide (CO2) and light are needed for plant growth. Closed greenhousesoften have too little carbon dioxide during the day to effectively utilize available light.Therefore, plants grow poorly when air vents are closed. By enriching theatmosphere with CO2, plant growth can be accelerated. Because light and carbondioxide complement each other in plant growth, additional electric lights forgreenhouses combined with good carbon dioxide control will increase yields of

    lettuce, tomatoes, orchids, chrysanthemums, carnations, snapdragons, geraniums,and other crops.CO2 equipment utilizing infrared sensors is available for greenhouse owners whowant to benefit from carbon dioxide enrichment with supplementary lighting. Theequipment will measure and control CO2 levels from 0 to 2,000 parts per millionwhich will satisfy most of the production needs of greenhouse growers. Thisequipment is fairly expensive and requires frequent calibration. Inexpensive colormetric kits are also available for determining the CO2levels in your greenhouse.Forms of CO

    2

    Forms of CO2 for enriching greenhouse atmospheres follow:Bottled CO2, which has been liquefied from a burning process. This liquid carbondioxide is kept under pressure and is controlled by means of a solenoid or meteringdevice.Dry ice, which may be placed in a greenhouse or growth chamber in block form orplaced in a converter (a pressure bottle) and stored until needed.Burned sulfur-free gaseous fuels such as natural gas, LP gas, or a liquid carbon fuelsuch as kerosene.

    "EnviroCept R-Value Paneling Compared To Other Popular GreenhouseCoverings"

    Compared Materials Cost PerSquare Foot LightTransmission ImpactStrength

    Double-walled 8' Wide Roll (4.0 mm) approx $.84 75% diffused ExcellentSolexx Double-walled Panels (3.5 mm) approx $.84 75% diffused ExcellentSolexx Double-walled Panels (5.0 mm) approx $1.09 70% diffused ExcellentFiberglass approx $.67-.79 86% diffused Excellent

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    Single Layer Glass (1/4") approx $3.48 90% direct PoorPolycarbonate (6 mm thru 18 mm) approx $1.57 to $3.75 82-92% direct ExcellentPoly Film (1 layer, 6 mil) approx $.08-.16 91% diffused Very Poor*Standard greenhouse covering with all our kits Comparisons Based on 2001 Retail Prices

    Accelerates plant growth, +Insulation of 2.5R 3R, +Transmits 70-75% diffused tight,+Strong, durable, and flexible, +Chemical and mildew resistant, +Extends growingseasons, +Easy to handle and apply, +Not affected by temperature extremes, +High

    quality paneling at an affordable price!

    ***Control Units:

    Automatic controls are important. Without them, switching lights, fans, pumps,heaters, and misters on an off at a prescribed time would be a complicated andlaborious task. Many time clocks, photo cells, thermostats, and other controls areavailable commercially. When used individually or in combination they will provideany time interval or control desired.

    How Many BTU Do You Need? Here Is A Tip!Multiply the width x the length of your greenhouse, this equals the sq/ft. Multiply the sq/ft by

    77.The result is approximately how many BTU you need to operate your greenhouse.

    HEATING GREENHOUSESMany types of heaters and heating systems are satisfactory for greenhouses. You

    must decide which system best suits your greenhouse operation. Consider the initialcost, economy of operation, and available fuel. You can heat your greenhouseefficiently with coal, electricity, gas, and oil. Heating equipment can be a spaceheater, a forced air heater, a hot-water or steam system, or electric heaters. Radiantheat lamps over plants and soil cables under plants can also be used.The capacity of your system will depend on the size of your greenhouse, whether itis covered with a single layer or a double layer of plastic or glass, and the maximumdifference between inside and out- side temperatures. Heat systems are rated inBritish thermal units (BTU) per hour. The firm from which you buy your greenhousecan tell you what size of heater you will need; or you can estimate the size as

    follows:

    http://www.greenhouses-etc.net/glazing
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    First, find the temperature difference. This is the difference in degrees Fahrenheitbetween the lowest outside temperature and the temperature you want to maintaininside your greenhouse. For instance, if you want to maintain a minimum insidetemperature of 60 degrees and the coldest night temperature you expect is -10degrees, your temperature difference is 70 degreesNext, find the number of square feet of exposed glass or plastic in your greenhouse.Don't forget to add the areas of the sides and ends to the area of the roof.Multiply the temperature difference by the number of square feet. For example,suppose you have a 20 x 100 foot greenhouse with a total of 3,400 square feet ofexposed plastic. You would multiply 3,400 by 70 (the temperature difference). Thiswould give you 238,000.Now, if your greenhouse is covered with 2 layers of plastic or glass, multiply the238,000 by 0.8. If it is covered with only 1 layer, multiply by 1.2. This will give you the

    required BTU per hour capacity of your heater.In the example, a 2-layer greenhouse would be: 238,000 x 0.8 = 190,400 BTU perhour. The 1-layer greenhouse would be: 238,000 x 1.2 = 285,600 BTU per hour.

    BTU Quick GridTemp Rise Greenhouse size

    4x8 6x4 6x8 6x12 8x12 8x165 682.5 710.5 952 1228.5 1379 1648.5

    10 1365 1421 1904 2457 2758 329715 2047.52131.52856 3685.5 4137 4945.520 2730 2842 3808 4914 5516 659425 3412.53552.54760 6142.5 6895 8242.530 4095 4263 5712 7371 8274 989135 4777.54973.56664 8599.5 9653 11539.540 5460 5684 7616 9828 11032 1318845 6142.56394.5856811056.51241114836.550 6825 7105 9520 12285 13790 1648555 7507.57815.51047213513.51516918133.560 8190 8526 11424 14742 1978265 8872.59236.51237615970.51792721430.570

    9555

    9947

    13328

    17199

    19306

    23079

    The type of system you choose will depend on how much you want to spend.

    The four types are:Space heaters - For low-cost heating for small greenhouses, use one or moreordinary space heaters.WARNING: If you use a gas, oil or coal heater, be sure to have a fresh airsupply to avoid carbon monoxide buildup due to restricted oxygen supply.

    Fans are also needed to improve circulation. Use high grade (low sulfur)

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    kerosene to avoid sulfur dioxide damage; high ignition temperature to avoidcarbon monoxide and ethylene buildup is important.Forced-air heater - The best system for heating a small greenhouse is a forced-airfurnace with a duct or plastic tube system to distribute heat. You can use a

    thermostat to control the temperature in the greenhouse.Hot-water or steam heater - A hot-water system with circulator or a steam systemlinked with automatic ventilation will give adequate temperature control. In someareas, coal or natural gas is readily available at low cost. This fuel is ideal for hot-water or a central steam system. Steam has an advantage in that it can be used tosterilize growing beds and potting soils.Electric heaters - Overhead infrared heating equipment combined with soil cableheat provides a localized plant environment, which allows plants to thrive eventhough the surrounding air is at a lower than normal temperature. Electric resistance-

    type heaters are used as space heaters or in a forced air system.

    GREENHOUSE HVAC CONTROLEven during cold weather a greenhouse can get too warm on bright, sunny days. Soventilation equipment should be built into your structure to control temperatures in allseasons. If you use hand- operated roof vents, they will require frequent temperaturechecks. As outdoor weather changes, sashes must be opened and closed manually

    to keep plants from getting too hot or cold. Automatic ventilation eliminates themanual work and is the best way to cool a greenhouse. As an example, if yourstructure has roof vents, a special electric motor and thermostat will open and closethe vents. Fresh outside air is brought in through the roof vents. Warm air flows outthrough escape vents. Besides reducing heat, the change of air improves growingconditions.Responding to this air transfer, the thermostat will turn off and on to keeptemperatures right for plants. Fans provide good ventilation and are needed in bothlarge and small greenhouses. Exhaust fans should be large enough to change theair within the structure every minute. To accomplish this, the capacity of the fan in

    cubic feet per minute at 1/8-inch static pressure should equal the volume of thestructure. The volume can be calculated by multiplying the floor area by 7.If the structure is high enough, place the exhaust fan and the motorized intakelouvers above the doors at opposite end-walls. This will exhaust the hottest, mosthumid air, and prevent a direct draft on the plants near the intake. Fan and ductHVAC can also be used for automatic HVAC. Plastic ducts are suspended by wiresor straps from the roof of the structure. The fan-heater-louver unit gives positive airflow and the polyethylene duct distributes the incoming air evenly throughout thehouse.

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    SHADINGWhen protection from the sun is needed, use roll-up screens of wood or aluminum,vinyl plastic shading, or paint-on materials. Roll-up screens are available with pulleysand rot-resistant nylon ropes. These screens can be easily adjusted from outside, asweather and sunlight vary. Vinyl plastic shading is made of a flexible film thatreduces light from 55 to 65 percent. The material comes in rolls and installs easilyagainst the glass inside your structure. To apply, just wash the glass with a wet

    sponge, then smooth the plastic onto the wet glass. When smoothed into position itadheres to the glass. It can be pulled off and used again. Shading compound canalso be applied on the outside of the glass. It can be thinned with paint solvents. Itusually comes in choices of white or green. Shading compound which mixes withwater can also be used.

    EVAPORATIVE COOLINGAn evaporative cooler (or fan and pad system) eliminates excessive heat and addsbeneficial humidity to the structure atmosphere. With an evaporative cooler, moistcool air is circulated throughout the structure. Warm air flows out through roof ventsor exhaust fans. Temperature is lowered, humidity is increased, and watering needsare reduced. You can select a cooler of the right size as follows: First, calculate the cubic feet of your structure by multiplying the length by the widthby the average height. Next, add 50 percent to the total cubic space, then select a cooler which has atleast this CFM (cubic feet/minute) air capacity rating.The cooler must be installed outside the structure. If it is inside, it can only humidifyand cannot cool. A properly sized cooler will reduce the structure temperatureapproximately 80 percent of the difference between the outside wet-bulb and dry-bulb thermometer readings. In hot, dry areas this system can reduce the temperature

    from 30 to 40 degrees. In wet, humid areas the heat reduction will be less. It is mosteffective during the hottest part of the day.

    http://www.greenhouses-etc.net/equipment/custom_shade_cloth.htmhttp://www.greenhouses-etc.net/equipmenthttp://www.greenhouses-etc.net/equipment/custom_shade_cloth.htmhttp://www.greenhouses-etc.net/equipment
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    MIST PROPAGATION CONTROLSMist sprays are used in propagating to keep the atmosphere humid. The most

    popular of 2 types of mist propagation controls is by means of time clocks. The othersystem controls the cycles by evaporation from a mechanical or electronic leaf orscreen.Time Clock System:This system of automatic watering includes: A dual-time clock consisting of a 24-hour clock and a 6-minute clock. An electric water valve with strainer. Hose bibbs. A toggle switch to give you a choice of manual or automatic operations.

    ***Evaporation System

    This system provides a special unit that operates within the mist spray from the

    nozzles. When the stainless steel or ceramic screen and the plants becomesaturated, the screen tilts to a downward position, which switches off the water. Thewater evaporates both on the mesh screen and on the cuttings. When the screenloses weight, the screen raises and actuates the switch. This opens the solenoidvalve and starts the misting cycle again, according to the needs of the cuttings.Because this control is activated by the weight of the water, it is fully automated andoperates continuously day and night.

    EXHAUST FAN CALCULATORS

    In order use an exhaust fan calculator to figure out the appropriate type and sizeexhaust fan for you, you must consider the size of your garden area first. Thegeneral rule is to have an exhaust fan that will completely exhaust the garden area inless than 5 minutes. This is how...

    Let's figure out the cubic feet of your garden area. Measure the floor of the area(example 3 feet by 4 feet), and multiply this by how tall the area is (example 8 feet).In this example, you would have 3 times 4 times 8, which equals 96 cubic feet.

    Naturally, if you buy a 96 cubic foot per minute (CFM) fan, you would be able toexhaust the whole room in one minute.

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    If you divide this number by 5, you get the smallest CFM (cubic foot per minute) thatyou would want to go with. In this example, 96 divided by 5 = 18.24 CFM. An 18.24cubic foot per minute fan is the smallest fan you would want to consider.

    Now, to get a better idea of your fan needs, you need to look at your whole exhaust

    setup. Your light, your fan, and the way you move the air through the garden areaare known together as your exhaust setup.

    Other Things to Consider

    In reality, there are a number of things to consider that will affect the actual cubic feetthat your garden exhaust fan will move each minute. These things fall into threecategories...

    your air exhaust duct runs your light reflector options the addition of a carbon filter

    The exhaust fan is designed to move air FROM your garden area TO another area.In order to do that, you normally need to move the air through air ducts.

    The minute you connect an air duct to your exhaust fan, the amount of air you canmove (your CFM) drops. This is because it takes more energy to blow air through tenfeet of air ducts than to just blow the air straight out the fan.

    The longer the air duct run, the more your CFM will drop, especially if there arebends/turns. Try to keep it under 20 feet.

    Your grow light reflector can block your airflow and reduce your CFM. This is criticalinformation for anyone who wants to get started in the right direction.The above are all good reasons to get an over-sized fan (one larger than indicatedon the exhaust fan calculator).

    There are only two types of fan that are appropriate to use as exhaust fans... theyare squirrel cage fans and centrifugal fans. Everything you have read up to this pointcan be accomplished with a squirrel cage fan.Exhaust Fan Options With a Carbon Filter

    If you decide to add a carbon filter, than a squirrel cage fan is not quite powerfulenough to do the job well. You need the kind of air pressure only one kind of fan candeliver. You need a centrifugal fan. Your centrifugal fan will both filter your air, coolyou lights, AND exhaust your garden area.

    In addition, a centrifugal fan will maintain it's CFM in many situations where a squirrelcage fan will not, so it is not necessary to get an "over-sized" fan. Simply followwhatever CFM the exhaust fan calculator indicates.

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    Watering Kits for Potted PlantsWatering kits for potted plants can also be used. Water is supplied directly to eachplant through hollow plastic tubes, which are permanently attached. One tube can beused for each small pot and 2 or more for larger pots. Water tubes are weighted at

    the outlet end; each tube is approximately 5 feet long, and can be cut to shorterlength if necessary.

    High Quality Shade Cloth, Designed to your specifications...Greenhouse covers, Hail protection, Livestock shading, Vegetable crops,Temporary fencing, Windbreaks, Bird netting, Truck tarps, Tennis courts.

    Shade Cloth with a quality knitted appearance provides crop protection forUV and heat sensitive plants. This material provides better ventilation andwater permeability because of its open lockstitch design which reduceswind speed and heat buildup in structures. The material is lightweight,being 20-25% lighter than other woven materials and dramatically morestrength. It is easy to install and can be cut on site and will not unravel.Shade Cloth material will reduce soil loss by helping lessen evaporation.

    The tough lockstitch knitted construction resists rips, tears and fraying.Applied levels remain constant during product life. All standard widths canbe seamed together for even wider dimensions than standard widths.Material can be ordered in black (8 year UV protection), white (4 year UVprotection), green (5 year UV protection), violet (4 year UV protection) andAluminet Reflective (4 year UV protection).