“More Than Anything, - KSRE Bookstore

9Greenhouse orientation.A greenhouse must be free fromwinter and summer tree shadows.Make sure you have enough spacefor expansion of greenhouse andsupport areas. When possible,orient connected greenhousesnorth to south to provide evenlight coverage within the housesthroughout the day. Constructfreestanding houses with thelength running east to west. Placecooling exhaust fans so that theywill not be required to blowagainst prevailing summer winds.Roadways. Your greenhousesmust be accessible for deliveryof supplies and pickup of finishedplants. Retail operations shouldseparate customer and serviceentrances and provide sufficientparking. However, locating thegreenhouse near parking areaswith night lighting may limit thetypes of crops you can grow.Topography. Natural topography is important. Choose a sitewhere a minimal amount of dirtwill have to be moved to provide alevel construction and parkingsite. The slope of the land shouldnot be more than 5 percent.Greater slopes drain workerenergy, affect product movement,and generally reduce labor efficiency. Avoid flood plains, frostpockets and hilltops.Windbreaks. A windbreak oftrees will reduce heat loss fromgreenhouse surfaces during thewinter. This may have a dramaticeffect on heating costs.

10SiteSelectionYour greenhouse should beengineered for your location andclimate. Climatologically, Kansasis in a transition zone, a locationwhere it “enjoys” the worst ofboth the cold north and the hotsouth; often, on consecutive days.Greenhouses must be designed toprovide an appropriate environment for plant growth under theseclimatic extremes.Greenhouse CoveringsThe greenhouse covering is theprimary decision when choosinga greenhouse design. The differenttypes of greenhouse coverings, orglazings, can be used on thebowed, quonset-style greenhouseor the A-frame, peaked-roofgreenhouse. When either style ofgreenhouse is connected at theeaves or gutters, the greenhousesare known as gutter-connectedhouses. The connected A-framegreenhouses will also be called aridge-and-furrow greenhouse. Therigid types of glazing materials areused on A-frame greenhouses.Some of the rigid, structuredplastics (polycarbonates andacrylics) and non-structuredplastics (fiberglass and polycarbonates) have enough flexibility tospan a quonset-style greenhouse.Polyethylene film plastics are mostcommonly used on quonset-stylegreenhouses (poly-houses). Thedifferent glazing materials havedifferent characteristics, associatedcosts, and require different sup-port structures. Therefore, selection of the glazing material needsto be made before selection of thestructure.Polyethylene Films. The majoradvantage of polyethylene filmplastics is cost, which is why newgrowers often choose a poly-housedesign. The greenhouse structureitself, and the polyethylene plasticcovering, are considerably lessexpensive to purchase and install.When using two layers of polyethylene, with an insulating air spacebetween them, there is a 40 percent savings in heating costs oversingle-layer polyethylene, glass, orfiberglass. Double-layer polyethylene also tends to resist hail damage (Table 1).The polyethylene plastics havea UV inhibitor which has extended useable life to three yearsdepending upon thickness of theplastic and the manufacturer.Some newer materials are beingintroduced which reportedlyextends the life up to four years.However, the polyethylene filmstill needs frequent replacement,a major disadvantage over time.There are problems near the endof the life of the plastic. As it ages,it becomes brittle, increasing therisk of tears.Most poly-houses are built withextruded aluminum or galvanizedsteel. Depending upon span andintended use, there may or maynot be a truss or horizontalsupport members. Because of thestructure and short-term natureof the polyethylene film, insurance costs can be greater thanin comparison to other materials.Rigid Plastic. The rigid plasticsare corrugated and flat fiberglass(fiberglass reinforced plastic),structured acrylics, and corrugatedand structured polycarbonates.Corrugated fiberglass sheets areused for their greater strength.However, the major drawbackis that corrugated sheets have agreater surface area than flat sheetsallowing for greater heat transfer.The outer layer needs to be coatedwith a UV inhibitor to minimizeyellowing of the acrylic resins usedin the manufacture of the sheets.If this coating is damaged fromhail, other abrasives, or air pollutants, dust and dirt will collect onthe surface and light transmissionwill be reduced. Most fiberglasscoverings are warranted to maintain 80 percent light transmissionfor the first 10 years and structuralintegrity for up to 20 years. Amajor problem with fiberglassis it is highly flammable andsupports rapid combustionbecause of the acrylic resin. Thisincreases insurance costs, and maynot be an acceptable covering(building codes) for school systemteaching greenhouses.The structured acrylic andpolycarbonates are very similarin characteristics. The structuredrigid plastics are double-layeredand ribbed for strength, creating

11an air pocket reducing heat loss.Panels come in thicknesses from6 to 16 millimeters thick withgrowers gaining up to a 50 percentheat savings with the 16-millimeter panels; up to 30 percent withthe 6-millimeter panels. Thepolycarbonate panels are moreresistant to hail damage than theacrylic panels; some are warrantedagainst hail damage for five years.The acrylic panels are flammable;the polycarbonate sheets are not.The acrylic and polycarbonateplastics are also available in bronzecolored panels which reduces lightintensity. These can be used wherereduced light is an advantage suchas retail display areas to make theenvironment more comfortablefor the customer.The polycarbonate rigid plasticis also available in a corrugatedsheet (Dynaglas ). This providesgreater light transmission than thestructured polycarbonate panels,however, heat loss is comparableto corrugated fiberglass. Thethinner structured acrylic andpolycarbonate panels, and thecorrugated polycarbonate sheets,are flexible and can conform tothe shape of a quonset greenhouse. They are also used onA-frame greenhouses. Becausethese come in widths from 48 to72 inches, fewer structural members are needed in greenhouseroofs and side walls than if glassconstruction is used, helping toreduce the cost of the structure.However, these materials are veryexpensive in comparison todouble-layer polyethylene. Priceis comparable to glass.Glass. The major advantagesof the glasshouse are the highinterior light level and its long life.The stability of a glasshouseprovides good crop protectionunder bad weather conditions. Forexample, extremely wet snow maycause a double-layer polyethylenehouse to collapse. A properlydesigned glasshouse may losesome panes, but would notcollapse. Tempered glass is strongenough to withstand most hail.The major drawbacks to glass areheat loss and high initial capitalinvestment resulting from a moreexpensive structure, the glassitself, and greater installationcosts. Glass panes come up to39 inches wide and up to65 inches long. Since the panesare more narrow than the rigidplastic panels or sheets, andbecause glass weighs more thanthe plastics, more support members are needed. The greenhousestructure will be more costly.area of the greenhouse exposedto the outside air. By covering theroof with polyethylene, the costfor covering the greenhouse canbe reduced and a savings onheating costs can be gained.End and side walls. The endand side walls can easily becovered with one of the rigidplastics. The structured acrylicsand polycarbonates will providebetter insulation and securityagainst theft or vandalism, but atgreater initial costs, than fiberglass. Since the structured plasticscome in 8- or 10-foot panellengths, less cutting and splicingwill be needed in comparison topolyethylene which comes in aminimum of 20-foot wide rolls.Also, the side and end walls rungreater risk of being damaged byequipment movement. Thestructured plastics will be moreresistant to this type of damagethan polyethylene.Growers who decide to cutexpenses with used materials orto build a greenhouse themselvesshould be careful to weigh structural soundness along with cost.Greenhouse structures are designed with the glazing materialin mind. Some structures, whenrecovered with a different materialthan what it was originally engineered for, may loose structuralintegrity after glazing and be moresusceptible to wind or snow-loadA common compromisein greenhouse coveringsRoof. Cover the roof withdouble-layered polyethylene. Theroof represents the largest surfaceTable 1. Influence of hailstone diameter and velocity on damage to four classesof greenhouse glazing materials.Class of materialDiameter of hailstone (mm)10Float 840 50 1123020102510 35225622 788207 3040184516 677 105 1016 2211 22* Velocity of hailstone in meters per second (m/s) when damage (holes or dents) is first observed.† Velocity of hailstone in miles per hour (mph) when damage (holes or dents) is first observed.

12damage. Homemade woodenstructures are bulky and canadversely affect light distributionand/or restrict air circulationwithin the structure.Greenhouse Structure. Severalitems need to be taken intoconsideration when deciding onthe greenhouse structure. First,of course, is the glazing material.The weight and flexibility of thematerial will influence design ofthe structure. Climate factors suchas snow-load, wind, and theamount of sunlight, will alsoinfluence the needed strength ofthe glazing material, structure andmembers. The weight of equipment such as thermal curtains,overhead racks for hangingbaskets, and high-intensitydischarge lights, needs to bedistributed to the load bearingmembers of the frame. Finally, thewidth of the greenhouse will alsoinfluence the truss size and design.Each manufacturer will specify theappropriate thickness of steelmembers or aluminum extrusions.Trusses, and gutter and side postsare spaced 6, 10, or 12 feet apartdepending upon the manufacturer. Roof and side bars arespaced between the trusses depending upon the width of theglazing material being used. Forglass, the bars will be much closerthan for the rigid plastics.Other factors to consider beforeselecting a greenhouse manufacturer are the thickness of thegalvanization coating on steel,free-standing versus gutterconnected greenhouses, andgutter height. If hanging basketswill be produced or if overheadequipment, such as shade clothor thermal curtain systems, will beused, the gutter height should beincreased.Climate Control Systems.Greenhouses need to be heated,cooled, or ventilated dependingupon the time of the year. Thesesystems need to be integrated toobtain maximum efficiency.Heat can be provided by centralboilers generating hot water orsteam, or by individual unitheaters hung in the greenhouse.Fuels used to fire the heaters orboilers are natural gas or liquidpropane. Electric heat is prohibitively expensive. If boilers areused, smaller multiple boilers arepreferred over one large boilercapable of heating the entirerange. Multiple units allow forzoning and can provide minimalheat requirements in case oneboiler fails. Steam or hot wateris distributed through the greenhouses in a radiant heat pipesystem.Unit heaters are gas-fired, oroperate from steam or hot watergenerated in a central boiler room.Unit heaters are located at gutterheight in the greenhouses.Warmed air from the unit heatersor radiant pipes is distributed bymeans of horizontal air flow fansor polyethylene tube systems.Regardless of the heating systemutilized, thermal curtains can beinstalled to insulate the greenhouse from extremely low nighttime winter temperatures. Theseare normally installed at gutterheight and span across the greenhouse. Installation of thermal orheat retention systems will havean influence on the selection ofthe greenhouse structure.The horizontal air flow fans orpolyethylene tube (fan-jet) systems are also used to recirculate airwhen no additional heating orcooling is needed. Air circulationthroughout the greenhouse isimportant to prevent hot or coldspots, and to minimize diseaseproblems resulting from highhumidity pockets developingabout the plant canopy.Greenhouses need to beequipped with exhaust fans toexchange inside and outside air,and to equalize temperatureswithin the greenhouse. To reducegreenhouse temperatures onsunny winter days, an inlet louveris installed adjacent to the fan-jetsystem. This inlet louver will opento draw in fresh, cool outside airand is circulated through the fanjet system. To reduce summergreenhouse temperatures, exhaustfans used in conjunction withevaporative cooling pads (madefrom corrugated cellulose) arenecessary. The energy requiredto evaporate water from the padscools the air drawn across the padshelping to reduce the interiorgreenhouse temperatures.Floor. Growers may choosefrom a range of floor surfaces:bare ground to concrete. Theactual floor design will be dependent upon the type of productionbeing planned and the availablecapital. Bare ground will createmanagement problems: insectand disease control and a muddywork environment. Where capitalis limited, heavy plastic or specialwoven, weed barrier cloths can beinstalled between gravel aisles. Ifthere is a need to have carts andother wheeled-equipment, concrete aisles are preferred. Entireconcrete floors will help minimizeweed growth under benches,reduce insect and disease hosthabitats, and allow for capture ofrun-off into holding ponds. Runoff capture and recycling havebecome critical concerns sincegreenhouses can contribute toground and water contamination.Holding and settling ponds aredesigned so that water fromgreenhouse run-off (roofs andinterior irrigation systems) can bereused in production or purifiedbefore introduction to the groundwater.Benches. Although plants canbe grown on the ground, accurateand uniform temperature controlis difficult to achieve. Whengrown on the ground, there is agreater risk of spreading certaindiseases among plants. Most

13potted greenhouse crops aregrown on benches that are 32 to36 inches tall. Width varies withlocation in the greenhouse: 3 feetwide against a wall, up to 6 feetwide, if accessible from both sides,with 18 inch aisles. Center aislesand/or traffic aisles should be from3 to 12 feet wide to be able toaccommodate movement ofequipment such as carts andsprayers. On fixed bench arrangements, a 60 to 70 percent benchefficiency can be expected. Thiscan be improved by utilizingpeninsular benching, when smallbench surfaces are installedadjacent to the endwalls betweenbenches. Movable aisle benchingcan increase bench efficiency tonear 90 percent, however, theseare expensive systems to install.In greenhouse retail sales area,bench efficiency will be reducedto allow for easy traffic flow.Additionally, with new construction of retail space, benching aisledimensions need to conform withthe Americans with DisabilitiesAct in order to provide access toall customers.Benching materials should allowfor air circulation around theplants and drainage from thecontainers. This is to minimizedisease problems and to allow forcomplete coverage by fumigantand fogged pesticides. Commonbench surface materials are: redwood lath in woven wire, redwood boards with ¼- to ½-inchspaces, l-inch square 14-gaugewelded-wire fabric, and expandedsteel mesh. These materials aresupported on frames made fromwood, pipe, or extruded aluminum supported by concrete blockor aluminum pipe-frames.Bench efficiency can be increased for some crops. It is notuncommon to produce beddingplants directly on the floor toallow for greater use of greenhousespace—fewer aisles will be used.It is also common to producehanging baskets suspended fromsupports hung over aisles andunder gutters.Root-zone Heating System.Some form of a root-zone heatingsystem will be needed if plantpropagation is planned. For seedgermination and rooting ofcuttings, an area should beequipped with a hot-water distribution system. Root-zone heatingcan be installed as part of aconcrete or gravel floor. Heatresistant polybutylene pipe,recirculating pump, thermostatcontrols, and commercial-sizedhot-water heaters are required.Simpler hot-water systems utilizing residential hot water heatersand on-bench tubing are available.Storage and Work SpaceWarehouse storage and workspace is often overlooked indesigning a new business. Without storage and work space,material costs increase and laborbecomes inefficient. Bales of peatmoss and pre-mixed pottingmedia should both be stored outof the sun and weather, becausethe plastic packaging may splitwith exposure to ultraviolet raysfrom the sun. Cardboard boxesdisintegrate in the rain. Fertilizerforms hard clumps from moisture.A separate space for chemicalstorage is needed, and it must beconstructed to meet currentgovernmental requirements.Consult your local county extension agent for more information.Work space is required to mixpotting media, fill pots, pottingand transplanting activities, placeplants sold and waiting to bedelivered, and to load or unloadtrucks out of the weather. A mostefficient space design is one wherestorage is located adjacent to thework space, reducing the distancematerials must be transported.

14SitePlanProduction. The primary factorin all site and building arrangement considerations is materialflow and how it affects laborutilization—how will materialscome in, move through theproduction process, move out, andbe delivered to customers.lWhere will each input(material) be delivered?lHow will it be unloaded?lWhere will it be stored untilneeded?lWhere will labor activitiestake place?- mixing potting mediaSite Plan Examples.-potting and transplantingfertilizer mixing and injectionpesticide mixing and storagemoving plants into and outof the greenhouse- packing plants for deliveryto customer- staging orders for delivery- loading trucks both inthe cold of winter and heatof summerThe site must be designed fora material flow which optimizeslabor utilization. Labor is thelargest single expense in a greenhouse business. Whether youwill be paying an employee ordoing the work yourself, theinefficient use of labor is a costto be avoided.Retail. Material flow andcustomer access to products is alsocritical within a retail operation.A retail greenhouse facility mustbe designed for ease of productmovement through the operation.How will products for sale movefrom the delivery truck to the salesdisplay area, from the display tothe check-out register, and fromcheck-out to the customersvehicle?

15CropsWhat crops should you grow?The simplest answer is to growwhat you can sell. Marketingshould drive production. Don’tgrow it if you can’t sell it. A morecomplex answer is to only growwhat you can sell profitably—onlygrow what you can grow at a coststructure low enough and sell at aprice high enough to make aprofit.The critical side of the profitability equation is the cost side.Competition sets price. It isdifficult to charge more than thecompetition and it may not beprofitable

The greenhouse covering is the primary decision when choosing a greenhouse design. The different types of greenhouse coverings, or glazings, can be used on the bowed, quonset-style greenhouse or the A-frame, peaked-roof greenhouse. When either style of greenhouse is connected at the eaves or gutters, the greenhouses are known as gutter-connected