BuildingBuilding HobHobbbyy GrGreenhouseseenhouses

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Louisiana State University Agricultural Center William B. Richardson, Chancellor Louisiana Cooperative Extension Service Jack L. Bagent, Vice Chancellor and Director Pub. 1794 (2M) 4/2001 Rep. Issued in furtherance of Cooperative Extension work, Acts of Congress of May 8 and June 30, 1914, in cooperation with the United States Department of Agriculture. The Louisiana Cooperative Extension Service provides equal opportunities in programs and employment. Space heaters can maintain any time interval or control a minimum of 60 degrees F in the desired. BuildingBuilding HobHobbbyy greenhouse. Higher temperatures on plant benches can be provided Before Building Your with soil-warming equipment. Greenhouse Remember that heat is lost GrGreenhouseseenhouses from a greenhouse by radiation, Almost every gardener conduction and convection eventually reaches a point of through glass; walls and other wanting a greenhouse. Before non-glass parts of the structure; buying or building one, you floor or soil; ventilation, door So you’ve finally decided to should-- You can get the most openings and cracks. get that hobby greenhouse you’ve greenhouse for your money by •Give careful thought to the always wanted. The first thing doing some of the construction Control Units size, style and kind of control you have to do is make a couple of work yourself. How much work desired. decisions: How much money do you do depends on how handy you •Contact your county Automatic controls are you want to spend? How much are with tools. Be honest with agricultural agent to help you work do you want to do? yourself; don’t take on a job that’s important in greenhouses. With- out them, switching lights, fans, locate and visit a few of your A hobby greenhouse can too big to handle. neighbors who have garden range from a simple polyethylene If you are good with tools, pumps, heaters and misters on and off at a prescribed time would be greenhouses. Learn about their covered framework that you can you can put up any plastic covered problems so you can choose the put together in an afternoon for greenhouse and almost any a complicated and laborious task. Many time clocks, photo- best greenhouse for you. less than $125 to a $6000 fully prefabricated glass greenhouse. •Check local building codes automated conservatory. cells, thermostats and other You may have to hire a qualified and zoning laws before you start No matter which greenhouse controls are available commer- electrician and plumber. construction. you choose, consider how much cially. When used individually or in combination they will provide time you’ll have to spend in it Types of Greenhouses after it’s built. Don’t be overly enthusiastic; some new green- house owners find they don’t have There are two basic types of Information for this publication was furnished by William A. Bailey, as much time as they thought for greenhouses: attached and free Robert C. Liu and Herschel H. Klueter, agricultural engineers, gardening. standing. An attached greenhouse Northeastern Region, Agricultural Research Service. On the other hand, there is a may be even-span, lean-to or misconception that greenhouses window-mounted. A free-standing require constant attention. By greenhouse is usually even-span combining automatic controls and (symmetrical roof). easy-care plants, maintenance can be kept low. Automatic controls Attached Lean-to are ideal for providing proper A lean-to greenhouse is built growing temperature, artificial against a building, using the light, watering, humidity and existing structure for one or more ventilation. Or if you have time, of its sides. It is usually attached you can save a lot of money by to a house, but may be attached to not using automatic controls. other buildings. 2 19 single units or in tandem arrange- very close to a heated building. directly to each plant requires frequent calibration. ments for large windows. Only The free-standing greenhouse is through hollow plastic tubes, Inexpensive color metric kits simple tools are needed to remove more easily adapted to the builder’s which are permanently attached. are also available for determining the regular window from the ideas of location, size and shape One tube can be used for each the CO2 levels in your greenhouse. frame and fasten the prefabricated than attached greenhouses. It also small pot and two or more for window greenhouse in its place. provides more light, but requires larger pots. Water tubes are Forms of CO2 more heat at night because of the weighted at the outlet end; each Free-standing additional glass. tube is approximately 5 feet long, Free-standing Forms of CO2 for enriching and can be cut to shorter length if greenhouse atmospheres follow: The free-standing green- Cost necessary. •Bottled CO2, which has been house is a separate structure and liquified from a burning process. consists of side walls, end walls The lowest cost per square CO and Light Control 2 This liquid CO2 is kept under and gable roof. It is like an even- foot of growing space is available pressure and is controlled by a span except that a free-standing in the even-span greenhouse 17 to Carbon dioxide (CO2) and solenoid or metering device. greenhouse is set apart from other 18 feet wide. It will house two side light are needed for plant growth. •Dry ice, which may be buildings to get the most sun. It benches, two walks and a wide Closed greenhouses often have too placed in a greenhouse or growth can be made as large or small as center bench. The lowest total cost little carbon dioxide during the chamber in block form or placed in desired. greenhouse is the lean-to house 7 to day to use available light effec- a converter (a pressure bottle) and A separate heating system is 12 feet wide with double-row tively. Therefore, plants grow stored until needed. necessary unless the greenhouse is benches and a central walk. poorly when air vents are closed. •Burned sulfur-free gaseous By enriching the atmosphere with fuels such as natural gas, LP gas or CO you can accelerate plant 2, a liquid carbon fuel such as growth. kerosene. Because light and carbon dioxide complement each other in plant growth, additional electric lights in greenhouses combined Lighting, Temperature with good carbon dioxide control and Control Units will increase yields of lettuce, tomatoes, orchids, chrysanthe- Plants respond to the relative mums, carnations, snapdragons, lengths of light and dark periods as geraniums and other crops. well as to the intensity and quality

CO2 equipment using red of light. Artificial light has been sensors are available for green- used extensively to control plant house owners who want to benefit growth processes under various from carbon dioxide enrichment conditions. with supplementary lighting. The Plants differ in the need for equipment will measure and light; some thrive on sunshine,

control CO2 levels from 0 to 2,000 others grow best in the shade. parts per million which will satisfy Most plants will grow in natural or most of the production needs of artificial light. This 10-foot-wide lean-to has ample room for two 36-inch-wide benches along each greenhouse owners. This equip- Artificial light in greenhouses wall. Glass shelves and hanging baskets may also be installed. ment is fairly expensive and can be used: 4 17 If you have an L-shaped for an air-circulation space house, you can save the cost of between the side walls and the two greenhouse walls by building benches. the greenhouse in the “L.” Side benches are serviced Whether your greenhouse from only one side and should be runs north and south or east and no wider than you can reach west is not as important as wind across. For some people this will protection. Protect your green- be 2 feet, for others as much as 3 house from winds by locating it so feet. existing buildings will shield it, or Center benches are serviced by providing it with a windbreak from both sides and can be as Fan and tube ventilation give positive air flow while polyethylene ducts distribute the hedge or fence. wide as 6 feet. They should be no incoming air evenly throughout the greenhouse. The plastic ducts are suspended by wires or wider than to permit you to work straps from the roof of the greenhouse. Location comfortably. Determine the width of the endwalls. This will exhaust Vinyl plastic shading is An ideal site for your walks in your greenhouse by how the hottest, most humid air, and made of a flexible film that greenhouse is well drained, nearly they are to be used. If the walks prevent a direct draft on the plants reduces light from 55 percent to 65 level and has full exposure to will be used only as a place to near the intake. percent. The material comes in sunlight. It slopes slightly to the stand while servicing the benches, Fan and duct ventilation can rolls and installs easily against the south and has a windbreak on the an 18- or 19-inch walk is suffi- also be used for automatic glass inside your greenhouse. To side of the prevailing wind. cient; if a wheelbarrow will be brought into the greenhouse, the greenhouse heating and ventila- apply, just wash the glass with a width must be greater. Wide tion. Plastic ducts are suspended wet sponge, then smooth the walks -- 24 to 30 inches -- will by wires or straps from the roof of plastic onto the wet glass. When Designing Your allow easy passage for visitors the greenhouse. The fan-heater smoothed into position, it adheres Greenhouse who may not be used to walking louver unit gives positive air flow, to the glass. It can be pulled off between rows of plants. and the polyethylene duct distrib- and used again. utes the incoming air evenly Shading compound can also Determine the exact dimen- Greenhouse Length throughout the house. be applied on the outside of glass sions for your greenhouse before greenhouses. It can be thinned you start to build. Width is the Shading Your with paint solvents. It usually most important dimension; it will Determine the length of your comes in white or green. Shading not be changed during the life of greenhouse by multiplying the Greenhouse compound which mixes with water the greenhouse. Length can be number of plants you can grow can also be used. increased if more space is desired. across the benches by the number When protection from the of plants you want to grow. Then sun is needed, use roll-up screens Evaporative Cooling round off the measurement so that of wood or aluminum, vinyl Greenhouse Width no glass will need to be cut to fill plastic shading or paint-on An evaporative cooler (or odd sash bar spacings. (A sash bar materials. fan and pad system) eliminates is a shaped wooden or metal bar Roll-up screens are avail- Determine the width of your excessive heat and adds beneficial used in the construction of a sash able with pulleys and rot-resistant greenhouse by adding the widths humidity. With an evaporative or frame and designed to hold and nylon ropes. These screens can be of the plant benches and the cooler, moist cool air is circulated support the glass secure to it). easily adjustable from outside as walks. Allow about 6 inches for throughout the greenhouse. Warm walls at either side and 2 inches weather and sunlight vary. 6 15 For amateur gardeners, under plastic are of equal quality to Heating temperature you expect is -10 small prefabricated glass green- those grown under glass. degrees, your temperature differ- houses are available for do-it- •Plastic greenhouses are Many types of heaters and ence is 70 degrees. yourself installation. They are considered temporary structures heating systems are satisfactory for •Next, find the number of sold in different models, to fit and usually carry a low assessment greenhouses. You must decide square feet of exposed glass or available space and to fit your rate for tax purposes, or may not be which heating system best suits plastic in your greenhouse. Don’t pocketbook. taxed at all. your greenhouse operation. forget to add the areas of the sides The disadvantages of glass •Plastic greenhouses can be Consider the initial cost, economy and ends to the area of the roof. are that it is easily broken, made of polyethylene (PE), of operation and available fuel. •Multiply the temperature expensive and requires a much polyvinyl chloride (PVC), copoly- You can heat a greenhouse effi- difference by the number of square better type of construction than mers of these materials and other ciently with coal, electricity, gas feet. For example, suppose you fiberglass and plastic. readily available clear films. and oil. have a 20 by 100 foot greenhouse Polyethylene must be replaced each Heating equipment can be a with a total of 3,400 square feet of Fiberglass Greenhouses year; it deteriorates rapidly in the space heater, a forced-air heater, a exposed plastic. You would strong sunlight of summer. Other hot-water heater or steam system or multiply 3,400 by 70 (the tempera- Fiberglass is lightweight, films such as PVC or copolymers electric heaters. Radiant heat ture difference). This would give strong and practically hailproof. with ultraviolet (UV) inhibitors last lamps over plants and soil heating you 238,000. Corrugated panels 8- to 12-feet longer. Descriptions of plastics cable under plants can also be used. •Now, if your greenhouse is long and flat fiberglass in rolls are available are provided. The capacity of your heating covered with two layers of plastic available in 24- to 48-inch widths. system will depend on the size of or glass, multiply the 238,000 by Thicknesses range from 3/64 to 3/ Polyethylene your greenhouse, whether it is 0.8. If it is covered with only one 32 of an inch. Poor grades of covered with a single layer or a layer, multiply by 1.2. This will fiberglass will discolor, and the The advantages of polyethyl- double layer of plastic or glass, and give you the required Btu per hour discoloring reduces light penetra- ene are that it is low in cost and the maximum difference between capacity of your heater. tion. Using a good grade, on the lightweight. It also stands up well inside and outside temperatures. In the example, a two-layer other hand, may make your in fall, winter and spring weather, Heating systems are rated in greenhouse would be: 238,000 x fiberglass greenhouse as expen- and lets through plenty of light for British thermal units (Btu) per 0.8 - 190,400 Btu per hour. sive to build as a glass one. If you good plant growth. However, hour. The firm from which you The one-layer greenhouse select fiberglass, choose the polyethylene constantly exposed to buy your greenhouse can tell you would be: 238,000 x 1.2 = 285,600 clearest grade. Do not use colored the sun deteriorates during the what size of heater you will need; Btu per hour. fiberglass. summer and must be replaced each or you can estimate the size as The type of heating system year. follows: you choose will depend on how Plastic Greenhouses Ultraviolet light energy •First, find the temperature much you want to spend. The four causes polyethylene to break down. difference. This is the difference in types are: Plastic greenhouses are This first deterioration occurs along degrees Fahrenheit between the •Space heaters. For low- increasing in popularity. The (or over) the rafters and along the lowest outside temperature and the cost heating for small greenhouses, reasons are: creases where the film is folded. temperature you want to maintain use one or more ordinary space •Construction cost per Ultraviolet-inhibited polyeth- inside your greenhouse. For heaters. WARNING: If you use a square foot is generally one-sixth ylene lasts longer than regular instance, if you want to maintain a gas, oil or coal heater, be sure to to one-tenth the cost of glass polyethylene. It has an inhibitor minimum inside temperature of 60 have a fresh air supply to avoid greenhouses. Plastic greenhouses that prevents the rapid breakdown degrees and the lowest night carbon monoxide buildup caused can be heated as satisfactorily as caused by ultraviolet light. UV- glass greenhouses. Crops grown inhibited polyethylene is available 8 13 A-frame structure must be raised higher on house. Air is introduced into a weeks before outdoor planting. the foundation sidewalls. chamber formed by two layers of Often, you will gain sufficient In building an A-frame 4- or 6-mil film. The effect of the time to grow an extra crop. You structure, consider the placement Panel Frame air under slight pressure is to force can start vegetables, annual of cross rafters (supporting the inner layer of film over the flowers for fall and winter, and members). Cross rafters should be Panel-frame greenhouses are circular greenhouse pipe frames. perennials for next year’s bloom. placed at least one-third of the a modification of the sash house (a The outer layer assumes a circular Plants are protected from distance down from the ridge on small plastic greenhouse used for shape over the frame and rides on harsh weather and will grow to the outer rafters. Otherwise, it growing plants for later transplant- a cushion of air. The outer layer transplant size quickly. You can will be difficult to work around ing). This structure requires lifts 3 to 4 inches from the frame root cuttings of deciduous and the cross rafters in applying an accurate carpentry, and construc- at the top and 1 to 2 inches from evergreen shrubs and trees. insulating layer of plastic. tion costs are higher than for other the frame at the foundation sill. Softwood cuttings of chrysanthe- When the cross-rafter frames because of the added Air enters the chamber through 6- mums, geraniums and fuchsia, leaf support is high in the peak of the lumber and labor needed to build inch plastic tubing. cuttings of rex begonias, African greenhouse, especially in narrow the panels. violets, and succulent and foliage greenhouses, an essentially clear- Advantages of panels are A manometer is used to plants take root faster in a span type of structure permits easy that they can be quickly installed measure static air pressure coldframe, particularly during application of an inner layer of and taken down and stored during between the two layers of film. warmer months. plastic. The inner layer can be the summer; this will increase the You can also grow your own applied under the cross-rafter life of the plastic panels. Panel Beds for Growing lettuce, chives, endives, parsley supports, leaving a small triangu- greenhouses can be easily venti- Small Plants and green onions right through the lar air space in the peak of the lated. winter by converting your house. coldframe to a hotbed. Diagonal bracing wires Quonset Coldframes Portable coldframes can be provide added strength to an A- built in your workshop from frame structure. This type of Quonset greenhouses have A coldframe is a bottomless surplus materials you may have on greenhouse is among the easiest to the same general shape as the box with a removable top. It is hand. build. quonset huts of World War II. used to protect small plants from Rigid Frame Some have been constructed of wind and low temperatures. No wood, but usually the frames are artificial heat or manure is used Rigid-frame structures have metal. The half-circle frames are inside a coldframe. been designed in widths up to 40 covered with one piece of wide Coldframes use the sun’s feet. This clear span structure has plastic, and the houses are up to heat. The soil inside the box is no columns to hold up the roof 20 feet wide. The advantage of heated during the day and gives section. The best available rigid- this house is the ease of construc- off its heat at night to keep the frame greenhouse has a 6-foot tion and covering. Ventilation is plants warm. The frame may be sidewall and is designed for 30, by exhaust fans at the ends of the banked with straw or strawy 36, or 40 foot widths. houses. manure to insulate it from the Prefabricated greenhouses outside air and to retain heat. are commercially available. They Pipe Frame With a coldframe, you can do many of the same things you An aluminum coldframe glazed with have very low sidewalls (low head corrugated fiberglass panels. Lightweight do in a greenhouse. You can sow room), and to grow tall plants the A pipe structure can be used sash covers lift or slide for ventilation summer flowers and vegetables control. to frame an air inflated green- 10 11 Coldframes are constructed per square foot should be adequate. Vinyls cost from two to five from sections of 3- by 4-foot or 3- Lining the side walls with mois- times as much as polyethylene. by 6-foot millwork sash or plastic tureproof insulation is desirable. When carefully installed, 8- or 12- covered panels. Most coldframes For localities with severe winters, a mil vinyl holds up for as long as can be converted to hotbeds for higher heat capacity is needed. five years. Vinyl attracts dust and use in all seasons by installing Fifteen watts per square foot is dirt from the air and has to be electric heat and automatic clock recommended. washed occasionally. controlled misting or watering. Tape or wire screening, 1/4- or 1/2-inch mesh, should be placed Plans and Drawings Hotbeds over the heating tape or cable to prevent possible damage by Greenhouses come in many types, Plans and drawings for A hotbed is a bed of soil cultivating tools. styles and sizes. A plastic tri-penta plastic greenhouses and propagat- enclosed in a glass or plastic Do not place hotbed cables of greenhouse can provide do-it-yourself ing frames are available free from satisfaction. USDA Plan. No. 6097, “Tri- frame. It is heated by manure, any type directly in peat. When your state agricultural experiment peat dries out, it acts as an insulator Penta Greenhouse,” is available from your electricity, steam or hot-water Extension Service. station, county agricultural agent, pipes. Hotbeds are used for and may cause the cable to over- extension agricultural engineer at forcing plants or for raising early heat. Use a thermostat to control in 2- and 6-mil thicknesses up to your state university or are for sale seedlings. Instead of relying on temperature automatically and 40 feet wide and 100 feet long. by the Superintendent of Docu- outside sources of supply for make more efficient use of electric- Polyethylene permits ments, U.S. Government Printing seedlings, you can grow veg- ity. passage of much of the reradiated Office, Washington, D.C. 20402. etables and flowers best suited to Because accurate temperature heat energy given off by the soil If you do not know the location of your own garden. control is possible with a thermo- and plants inside the greenhouse. your state university, send your Seeds may be started in a stat, you can grow better plants at Therefore, a polyethylene green- request to Agricultural Engineer, heated bed weeks or months lower costs by separating plants house loses heat more quickly than Louisiana Cooperative Extension before they can be sown out of requiring different temperatures in a glass greenhouse both during Service, P. O. Box 25100, Baton doors. At the proper time the different beds. Temperatures from sunny periods and after sunset. Rouge, Louisiana 70803-5100. hotbeds can be converted into a 50 to 70 degrees Fahrenheit are best This is an advantage during the coldframe for hardening. Then for hotbeds. On very cold nights day and a disadvantage at night. the plants may be moved to the cover the beds with mats, burlap, Types of Frames garden when outdoor conditions straw or boards. are favorable. Polyvinyl chloride (PVC or Plastic greenhouse structures Between 10 and 15 watts of Weatherproof Wire Vinyl) range from crude wooden frame- electric heat should be provided works to air-supported houses. If for every square foot of growing Use weatherproof wire for all Vinyls from 3 to 12 mils you plan to build a plastic green- area in a hotbed. Soil-heating outside wiring. Wire size depends thick are available for greenhouse house, carefully consider economy tape or cable is available in on the distance to be covered and covering. Like polyethylene, of size and future expansion. several lengths, which give a the number of hotbeds to a circuit. vinyls are soft and pliable; some Because plastic is available choice of wattages. Use approved terminal equipment, are transparent, others translucent. in large widths and is lighter in If the bed is in a sunny, and follow safe wiring practices. They are usually available in 4- to weight, greenhouse rafters and well-sheltered location, and the All wiring must conform to local 6-foot widths only; larger widths supporting members can be widely climate not too severe, 10 watts wiring codes. by oxygen supply. can be made by electronically spaced to permit maximum light sealing several smaller widths penetration. Common types of together. greenhouse frames follow.

12 9 Fans are also needed to improve bright, sunny days. So ventilation Standard glass sizes are 16 feet. If the eave is 5 feet high, the circulation. Use high grade (low equipment should be built into by 24, 18 by 20, and 20 by 20 greenhouse should be 9 1/2 feet at sulfur) kerosene to avoid sulfur your greenhouse to control inches. (Larger glass sizes mean the center. dioxide damage; the need for high temperatures in all seasons. If you few sash bars and less shadow ignition temperature to avoid use hand-operated roof vents, they inside the greenhouse.) Most Types of Construction carbon monoxide and ethylene will require frequent temperature plastics are available in 100-foot buildup is important. checks. As outdoor weather lengths. Whether you build a glass, •Forced-air heater. The changes, sashes must be opened When you figure the length fiberglass or plastic greenhouse, it best system for heating a small and closed manually to keep of a glass greenhouse, allow for will pay you to shop around for greenhouse is a forced air furnace plants from getting too hot or cold. the width of the projecting part of ideas. with a duct or plastic tube system Automatic ventilation each sash bar plus a fraction of an Greenhouses have supporting to distribute heat. You can use a eliminates the manual work and is inch clearance. For plastic, allow framework made of wood, plastic thermostat to control the tempera- the best way to cool a greenhouse. an extra 24 inches to fasten the pipe, aluminum, iron or galvanized ture in the greenhouse. As an example, if your plastic properly. pipe. Some have curved eaves; •Hot-water or steam greenhouse has roof vents, a others have flat eaves. Some are heater. A hot-water system with special electric motor and thermo- Greenhouse Height glass or plastic from the ground circulator or a steam system linked stat will open and close the vents. up. All types have advantages and with automatic ventilation will Fresh outside air is brought in The height of the green- disadvantages. give adequate temperature control. through the roof vents. Warm air house depends on the desired If you build your own In some areas, coal or natural gas flows out through escape vents. height to the eave. An eave greenhouse, have the plumbing is readily available at low cost. Besides cooling the greenhouse, height of 5 feet is satisfactory for and electrical work done by This fuel is ideal for hot-water or a the change of air improves side benches with low-growing professionals in accordance with central steam system. Steam has growing conditions. plants. If you want to grow tall local codes. Most local govern- an advantage; it can be used to Responding to this air plants, however, you will want an ments require a building permit to sterilize growing beds and potting transfer, the thermostat will turn eave height of 6 or 7 feet. erect a greenhouse. soils. off and on to keep temperatures The pitch of the roof should right for plants. Fans provide •Electric heaters. Over- be 6 in 12 (about 27 degrees). Glass Greenhouse good ventilation and are needed in head infrared heating equipment The eave height, the distance from both large and small greenhouses. the side wall to the center of the combined with soil cable heat Exhaust fans should be large Glass is the traditional provides a localized plant environ- greenhouse and the roof pitch will greenhouse covering. It is avail- enough to change the air in the determine the height of your ment, which allows plants to greenhouse once very minute. To able in many designs to blend with thrive even though the surround- greenhouse at the center. almost any style of architecture. accomplish this, the capacity of The height of the green- ing air is at a lower than normal the fan in cubic feet per minute at Glass greenhouses may have temperature. Electric resistance house should be equal to the eave slanted sides, straight sides and 1/8-inch static pressure should height plus one-fourth the width heaters are used as space heaters equal the volume of the green- eaves, or curved eaves. or in a forced air system. of the greenhouse. For instance, Aluminum frame and glass house. The volume can be in an even-span greenhouse 18 calculated by multiplying the floor construction has pleasing lines and feet wide, the distance from the will provide a large growing area area by 7. side wall to the center of the If the greenhouse is high as well as being maintenance-free. Ventilation greenhouse is 9 feet. The differ- It assures you of a weather-tight enough, place the exhaust fan and ence in height between the center the motorized intake louvers structure, which minimizes heat of the greenhouse and the eave costs and retains humidity. Even during cold weather, a above the doors at opposite air will be one-half of 9 feet, or 4 1/2 greenhouse can get too warm on 14 7 flows out through roof vents or Time Clock System exhaust fans. Temperature is lowered, humidity is increased This system of automatic and watering needs are reduced. watering includes - You can select a cooler of •A dual-time clock consisting the right size as follows: of a 24-hour clock and a 6-minute •First, calculate the cubic clock. feet of your greenhouse by •An electric water valve with multiplying the length by the strainer. width by the average height. •Hose bibbs. •Next, add 50 percent to the •A toggle switch to give you total cubic space, then select a cooler which has at least this CFM a choice of manual or automatic (cubic feet per minute) air operations. capacity rating. The cooler must be installed Evaporation System outside the greenhouse. If it is This system provides a inside, it can only humidify and A free-standing greenhouse is set apart from other buildings, with a door at one end (or cannot cool. A properly sized special unit that operates within the a door in both ends for long units). cooler will reduce the greenhouse mist spray from the nozzles. When temperature about 80 percent of the stainless steel or ceramic screen the difference between the outside and the plants become saturated, Locating Your may be desirable. Be sure to take the screen tilts downward, which into account the possibility of wet-bulb and dry-bulb thermom- Greenhouse eter readings. switches off the water. falling limbs that can damage the In hot, dry areas this system The water evaporates both on greenhouse. can reduce the temperature from the mesh screen and on the cut- After you decide which kind Some plants will grow in a 30 to 40 degrees. In wet, humid tings. When the screen loses of greenhouse you want, you need greenhouse in any location. areas the cooling will be less. It is weight, the screen raises and to determine where to put it. African violets and orchids, for most effective during the hottest actuates the switch. This opens the The first choice for a example, will grow with northern part of the day. solenoid valve and starts the greenhouse site should be on the exposure, but heating costs will be misting cycle again, according to south or southeast side of the high. You’ll limit the types of Mist Propagation the needs of the cuttings. house in a sunny location. The plants you can grow if you don’t Because this control is east side is the second best put your greenhouse in the best Controls activated by the weight of the location. That’s where it will possible location. water, it is fully automated and capture the most November to Sometimes you can place a Mist sprays are used to keep operates continuously day and February sunlight. The next best greenhouse against a door, window the atmosphere humid. There are night. locations are the southwest and or basement entrance of your two types of mist propagation west. The north side is the least house. This will let you use heat controls. The most popular is Watering Kits for Pot desirable location. from your house to grow plants, time clocks. The other system Plants You can place your green- make your greenhouse more controls the cycles by evaporation house where it will be partly accessible and save on construction shaded during the summer when costs. Your home heating bill, from a mechanical or electronic Watering kits for pot plants light reduction is not serious and however, will increase signifi- leaf or screen. can also be used. Water is supplied cantly. 16 5 •To provide high intensity light when increased plant growth Light Meters is desired. •To extend the hours of Inexpensive light meters are natural daylight or to provide a available for measuring the light night interruption to maintain the intensity in greenhouses. The plants on long-day conditions. most common light meters are Proper lighting not only calibrated in foot candles or lux extends the gardening day by (10.76 foot candles). enabling the gardener to work in the greenhouse during the dark Temperature evenings of winter and early spring, but it aids plant growth. As a gardener you will be concerned with two temperatures Three basic types of lamps -- the air temperature required in are used in greenhouse lighting. the greenhouse and the minimum They are: Fluorescent lamps, outside temperature that your which have the advantage of heating equipment must over- The glass-to-ground even span can be built free-standing or attached to your home. This “all glass” greenhouse can accommodate 3 full-sized benches plus shelves. higher light efficiency with low come. heat. This type of lamp is the For most plants, a night most widely used for supplemental temperature of 60-65 degrees F in light. It comes in a variety of the greenhouse is adequate. The The lean-to is limited to even-span greenhouse is similar to colors but cool-white lamps are general rule is not to have a higher single or double-row plant a free-standing structure except the most commonly used. High temperature than is necessary. benches with a total width of 7 to that it is attached to a house at one intensity (1500 ma) fluorescent If you grow some plants that 12 feet. It can be as long as the gable end. It can accommodate tubes that require higher wattage require a higher temperature than building it is attached to. The two or three rows of plant benches. are also commonly used to reach is provided in the greenhouse, use advantage of the lean-to green- An even-span greenhouse 2000 foot candles. a propagating case or a warmed house is that it usually is close to costs more than a lean-to, but it Incandescent lamps, which bench with thermostatically available electricity, water and has greater flexibility in design vary in size from 60 watts to 500 controlled warming cables to heat. and provides for more plants. watts. They are used to extend warm the air surrounding the The lean-to has these Because of its size and greater day length in greenhouses. The plants. This can be done at a disadvantages: amount of exposed glass area, the grower can vary footcandle levels fraction of the cost that would be Limited space. even-span greenhouse will cost by adjusting the spacing and necessary to heat the whole Limited light. more to heat. mounting height above the plants. greenhouse to provide the same Limited ventilation and High-intensity discharge temperature. temperature control. Attached Window-mounted (HID) lamps, which have a long If you want a temperature of life (5000 hours or more). With 60 degrees F, install heaters that Attached Even-span A window-mounted green- improvements made possible by will provide that temperature. If house will allow space to grow a the addition of sodium and metal you want no more than frost The even-span greenhouse is few plants at relatively low cost halides the lamp has a high protection, set the thermostat at 40 the standard type -- the one people for heating and cooling. This emission of light in the regions degrees F. generally visualize when they reach-in greenhouse is available in used by plants. think about a greenhouse. The many standard sizes, either in 18 3