indian river environmental management in the broiler house
TRANSCRIPT
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Environmental Management in the Broiler House
Indian River Environmental Management in the Broiler House2
Indian River Environmental Management in the Broiler House3
CONTENTS03 Introduction: Economic Value of Proper EnvironmentalManagement03 Overview:EnvironmentalManagementObjectiveandMethods05 EconomicBenefitsofEnvironmentalControl
06 Climatic Factors in Housing and Ventilation Decisions06 ExtremelyColdClimate07 ColdClimate07 ModerateClimate07 HotClimate
08 How Birds Work and What They Need 08 BirdsProduceHeatandMoisture09 EffectsofTemperatureandRelativeHumidityonBirds12 HowRelativeHumidityWorks
13 Ventilation Basics 13 NaturalVentilation14 Fan-PoweredVentilation15 NeedforTightlySealedHouse15 TypesofNegative-PressureVentilationOperations16 HowMinimumVentilationWorks18 HowTransitionalVentilationWorks19 HowTunnelVentilationWorks20 HowEvaporativeCoolingWorks
22 Making Good Ventilation Decisions24 ChoosingFans26 IntegratedControlSystemDecisionFactors27 AirInletDesignConsiderations28 BenefitsofUsingStirFans29 EvaporativeCooling:FoggersorPads?29 EvaporativePadCooling:HowMuchPadisNeeded?30 NeedforBackupandFail-SafeSystems30 HouseOrientation31 InsulationRequirements
32 Keys to Managing a Modern Tunnel House32 WhichVentilationModeisNeeded?33 ImportanceofStayingonTargetTemperature34 KeystoManagingMinimumVentilation36 KeystoManagingTransitionalVentilation36 KeystoPerimeterInletManagement38 KeystoManagingTunnelVentilation40 KeystoManagingTunnelandEvaporativeCooling41 ManagementIncludesMonitoring
43 Helpful Conversion Factors
Acknowledgment
ThemaincontentofthispublicationwaswrittenbyProfessorJamesO.Donald,ofAuburnUniversity.ProfessorDonaldisanagriculturalengineerwidelyrecognisedasanauthorityonpoultryhousingandenvironmentalmanagement,andappreciationisexpressedtohimforpermissiontousethesematerials.
Contents
Indian River Environmental Management in the Broiler House2
Indian River Environmental Management in the Broiler House3
Introduction: Economic Value of Proper Environmental ManagementWhether producing meat, eggs, milk or other animal products, it is well established that effectivelymanaging environmental conditions reduces the total cost of production. In the broiler meat productionbusiness, all components of the production process from parent stock broiler breeders to broiler progenybenefit from effective environmental control. Given the economic benefits of effective environmentalcontrol it is imperative for managers and technicians to understand the basic concepts of this topic. Thispublicationhasathreefoldpurpose:
•Toclarifywhatenvironmentalcriteriaandconditionsarenecessarytoachievethegeneticpotentialofthemodernbroiler.
•Tooutlinethemostimportantfactorsinthedesignofmodernbroilerhousingtobeabletoprovideoptimumenvironmentalconditions.
•Toprovidebasicoperationalguidelinesforthishousing.
Key Point
•Itiswellestablishedthateffectivelymanagingenvironmentalconditionsreducesthecostofproduction.
Overview: Environmental Management Objective and Methods
Theobjective is toprovide an environment tomaximise flockperformance, achievingoptimumanduniformgrowthrateandfeedefficiencyinmeatyieldwhileensuringthatbirdhealthandwelfarearenotcompromised.
Supplementalheatingsystemsplayanimportantroleinenvironmentalmanagement,especiallyduringthebroodingphase.However,inmanylocationsforaportionofthegrowoutsupplementalheatingmaynotbeneeded.Ontheotherhand,properventilationisneededthroughoutagrowout,evenduringtimeswhensupplementalheatisbeingprovided,forcontrolofairqualityifnotforcooling.Ventilationisthereforethemostimportanttoolinmanagingthein-houseenvironmentforbestbirdperformance.
Ways of providing supplemental heat in poultry houses around the world vary farmore than do ventilationmethods, relyingonawidevarietyof fuels andheat-deliverymethods, including radiant andhot-air systems,direct in-house combustion and indirect heat-exchange, etc. Examination of the details of particular heatingsystemsisbeyondthescopeofthispublication,whichfocusesprimarilyonthemostwidelyapplicableprinciplesofin-houseenvironmentalmanagement.
Exceptwithveryyoungbirdsand/orinverycoldweather,temperaturecontrolistheprimarygoalofventilation.Ateachstageofabird’sdevelopment,therewillbeacertaintemperaturezoneinwhichasurplusoffeedenergyabovetherequirementsofbodymaintenanceallowsthebirdtogainweight,asshowninFigure1.Withinthisbroad“thermalcomfortzone”therewillbeanarrowtemperaturerange(within1or2°C)inwhichthebirdmakesbestuseoffeedenergyforgrowth.Thisistheoptimumperformancezone.Providingthisoptimumtemperature-alongwithadequatefeedandwater-assuresthatthebird’swelfareandeconomicperformancearemaximised.
Note that, although there is abroader temperature range inwhich thebirdswillbemoreor lesscomfortable(the“thermalcomfortzone”),thispublication,asiscommonintheindustry,uses“comfortzone”tomeanthatnarrowerrangeofmaximumcomfort,thetemperaturethatisthebull’s-eyeoftheperformancetarget.
Ifthetemperatureistoolow,birdsincreasetheirfeedintakebuthavetousemoreofthatfeedenergytokeeptheirbodieswarm.Iftemperatureistoohigh,theyreducefeedintaketolimitheatproduction.Adequateventilationpreventsheatbuildupandkeepsbirdsintheiroptimumperformancezone,firstbyexhaustingwarmairfromthehouseandreplacingitwithcooleroutsideair,andinmostwellequippedmodernhousingbyeffective(wind-chill)coolingthroughtunnelventilation,andbyloweringtheactualairtemperaturethroughevaporativecooling.
Contents Introduction
Indian River Environmental Management in the Broiler House4
Indian River Environmental Management in the Broiler House5
Thetargettemperatureforbestbroilerperformancechangesduringagrowout,typicallyfromaround30°Condayonetonear20°Corloweratharvesttime,dependingonbirdsizeandotherfactors.Ventilationthereforemustbeadjustedaccordinglytomaintainoptimumtemperature.Thetemperatureexperiencedbythebirdisdependantupondrybulbtemperatureandhumidity.IfRHisoutsidetheidealrangeof60-70%,thetemperatureofthehouseatbirdlevelshouldbeadjusted.Forexample,ifRHiscloserto50%,thedrybulbtemperatureondayonemayneedtobeincreasedto33°C.Atallstages,monitorbirdbehaviourtoensurethatthebirdisexperiencingadequatetemperatures.
Ventilationistheonlypracticalwaytolowertoohighhumidity,whichismostoftenawinterproblemandcanaffectbirdhealth.Evenwhenventilationisnotneededforheatremoval,maintainatleastaminimumrateofventilationtopreventwet,cakedlitterandammoniaproblems.
Bybreathing,birdstakeoxygenoutoftheairandbreatheoutcarbondioxide,sofreshairmustbebroughtintothehousetoreplacethatoxygenandexhausttheexcesscarbondioxide.Ventilationtoprovidefreshairisneededinallseasonsandinhotandcoldweather.
Themostcommonairqualityproblem,however,isammoniacomingfromtoowetlitter,whichleadstohealthproblemsandloweredperformance.Properventilationheadsoffbuildupofammoniabycontrollingrelativehumidity.
Alloftheabovefactorsareimportant.Fortunately,inmostsituationsbringinginfreshairandexhaustingtoxicfumesareaccomplishedbyventilationaimedprimarilyatcontrollingtemperatureandmoisture.
Important:properin-houseenvironmentmustbedistributedevenlythroughoutthehouse.Pocketsofdeadair,drafts,coldspots,orhotspotscanlowerflockperformanceandevencausemortalities.
Figure 1:Optimumperformancetemperaturezone
Ateachstageofabird’sdevelopment,thereisonenarrowtemperaturerangewheremaintenanceenergyrequirementsarelowestandthebirdcanmakemaximumuseoffeedenergyforgrowth.Iftemperaturegoesjustafewdegreesoutsidetheoptimumperformancezone,coolerorwarmer,birdswillbeusingahigherproportionoftheirfeedenergyforbodymaintenanceandlessforgrowth.
Key Points
•Ventilationisthemostimportanttoolinmanagingthein-houseenvironmentforbestbirdperformance.
•Ateachstageofabird’sdevelopment,thereisoneoptimumperformancetemperaturezoneinwhichthebirdmakesbestuseoffeedenergyforgrowth.
•Thetargettemperatureforbestbroilerperformancechangesdailyduringagrowout,ventilationmustbeadjustedaccordingly.
•In-houseenvironmentmustbeuniform:pocketsofdeadair,drafts,coldspotsorhotspotscanlowerflockperformance.
Increasing Cold Stress
Cold Cooler Warmer HotTemperature
Increasing Heat Stress
Thermal Comfort Zone
Tota
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isabl
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Maintenance Energy Requirements
Amount of Energy Deficit Amount of Energy
Surplus Available for Growth and Weight
GainAmount of
Energy DeficitOptimum Performance Zone
Energy Intake
Introduction Introduction
Indian River Environmental Management in the Broiler House4
Indian River Environmental Management in the Broiler House5
Economic Benefits of Environmental Control
Birdsmostefficientlyconvertfeedtomeatwhentheyaregivenconsistentlyoptimumenvironmentalconditions,withtemperaturebeingthemostcriticalfactor.Smalltemperaturedifferencescanhaveasignificanteffectonreturnstotheowner.Thishasbeenwellconfirmedbyresearchandbyexperienceworldwide.Figure 2belowshowsdifferencesintotalcentsperbirdvalueresultingfromon-targetvs.off-targettemperatures,basedonacomputerstudyoftemperatureeffectsonbirdperformance.Thestudyisbasedon,andfiguresgivensolelyfor,thegrowingstageafterbrooding,whenthetargettemperaturehaslevelledoffatabout22°C.Undertheseconditions,consistentlymissingtargettemperatureonthehighsidebyonly2.2°Cwouldmeanaonecentlossinvalueperbird.
Duringthebroodingphase,evenbrief chillingcanseriouslyhurtflockperformance.Forexample,universityresearchintheUnitedStatesshowedthatexposingday-oldchickstoanairtemperatureof 13°Cforonly45minutesreduced35dayweightsbyabout110grammes.Afterthebroodingphase,birdperformanceismorequicklyhurtbyhighthanbylowtemperature.Forexample,Figure 2showsthecostofbeingconsistentlytoohighby4.5°Cisabouthalfagainasmuchasthecostofbeingconsistentlytoolowbythesamenumberofdegrees.Sincemaintainingoptimumtemperatureisevenmorecriticalduringthebroodingphase,therewardforbeingconsistentlyontargetwouldbeevenhigherforanentiregrowout.
Sincecostsandsellingpricesvary,theexactrewardforon-targettemperaturecontrol(orthe“costofbeingwrong”)willalsovary.Whatresearchandon-farmexperiencedemonstrateistheprinciplethatconsistentlymaintainingtargettemperatureyieldssignificantreturns.
Figure 2: The“CostofBeingWrong”-costadvantagesofconsistenton-targettemperaturecontrol
Beingjustafewdegreesofftargettemperatureinthegrowingphasecanhurtgrowerincomesignificantly.Theabovegraphshowscentsperbirddifferencesintotalreturnsforconsistenton-targetvs.off-targettemperaturecontrolfornon-broodingphasebirds.Conditions:Broilersgrownto49days,meatsoldfor$0.89perkg,nodockagefornon-uniformity;feedcosts$278/tonneStarter,$270/tonneGrower,$258/tonneFinisher.Source: Veng, Hot climate ventilation.
Key Points
•Duringthebroodingphase,evenbriefchillingcanseriouslyhurtflockperformance.
•Consistentlymaintainingtargettemperatureyieldssignificantreturns.
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Deviation from Ideal Temperature ºC
Target Temperature
Target
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Introduction Introduction
Indian River Environmental Management in the Broiler House6
Indian River Environmental Management in the Broiler House7
Climatic Factors in Housing and Ventilation Decisions
Themajorfactorinfluencingtypeorstyleofhousingisclimate.Differentclimaticconditionscallfordifferentventilationandheatingstrategiesandaffectthepossibleordesirablebirdstockingdensity.Generally,extremeconditionsrequiremoreandmoresophisticatedinsideenvironmentalcontrolequipmentandmanagement.Whereseasonalvariationsinweatherarepronounced,ahousemayrequireventilationsystemsforhotandcoldweather.
Inagivensituation,housingandventilationchoicesmustbebasedoncalculatingthebenefitsofprovidingtechnologytocopewith:
•Prevailingweather, or prevailing seasonalweather - that is, conditionswhich generally persist over at least severalmonths;
•Weatherextremeslikelytobeencountered.
Thefollowingisanoutlineoftypicalclimaticand/orweatherconditionsandtheireffectsonventilationdecisions.Itisimpossibletogivespecificregionaladviceinthelimitedspaceavailablehere,sotheseareverygeneralrecommendations.Elementsofmorethanoneclimatemayhavetobeappliedtoagivenproductionfacility.
Key Point
•Extremeclimatesrequiremoresophisticatedinsideenvironmentalcontrolequipmentandmanagement.
Extremely Cold Climate
Inlocationsthatproducebroilerswhereextremelycoldsituationsmayexistforperiodsoftimeduringtheproductioncycle,someparticularcautionsinregardtothedesignandoperationofpoultryhousesshouldbenoted.
Inregardtodirecteffectsonbirdhealthandperformance,extremelycoldairisalsoextremelylowinmoisturecontent,sothatwhenthisairisheatedandmixedwithairinthehouseitisoftenpossibletohaveconditionsthatareextremelydryandcanaffectbirdhealth.Extremelylowrelativehumidityinwintertimeproductionmeansthatbirdswillrespiremoreheatthanthosegrowninhigherrelativehumidityconditions,thustheirheatlossisgreater.Tocompensateforthisgreaterbirdheatloss,oftenthetemperaturesetpointsmustbeincreased.Atthesametime,managersareoftentemptedtoreduceventilationtimetoreducefuelcosts.Thiscanbeaseriousmistake,sinceperformancelossescausedbyinadequatecoldweatherventilationcanoutweighadditionalfuelcosts.
Inextremelycoldconditionswemustalso take intoaccount issueswith thestructure thatarenotcommon inmoretemperate climates.When the outside air temperature is well below freezing it becomesmore important andmoredifficulttoavoidputtingcoldoutsideairdirectlyonthebirds,soapre-warmingplenumorheatingroomtoconditionairbeforeentrytothehousemaybeneeded.Also,extremelycoldoutsideair,despiteitsrelativelylowmoisturelevel,cancauseseriouscondensationproblemsandevencauseairinletdoorstofreezeup.Preventingsuchproblemsrequiresspecialattentiontoinsulationandtosealingpreventoutsideairleakageintothehouse,aswellaspossiblyinstallingpre-warmingplenumsforincomingair.
Key Points
• Inextremelycoldclimates,dryconditionsmaycausebirdstolosemoreheat;temperaturesetpoints mayneedtobehigher,butminimumventilationmustbemaintained.
•Extremelycoldconditionsmayrequireuseofapre-warmingplenumtoconditionoutsideairbeforeit entersthehouse.
Climatic Factors in Housing and Ventilation Decisions
Indian River Environmental Management in the Broiler House6
Indian River Environmental Management in the Broiler House7
Cold Climate
Inhighaltitude locationsandinhighnorthernorsouthernlatitudeswithprolongedwintertemperaturesconsistentlybelow10°Candwithmoderatesummertemperatures,tunnelventilationandevaporativecoolingarenotusuallyneededtocopewithbirdheat.
Negativepressurepoweredventilationisneededtokeepbirdscomfortableandmaintainoptimumflockperformance,especiallybypreventingexcessivemoisturefrombuildingupinsidethehouse.Housestypicallywillneeda“minimumventilation” setup augmentedwith additional fan (and air inlet) capacity to exhaust bird heat duringwarmweather.Additionalsupplementalheatingsystemsandimprovedinsulationmayalsobeneededtohandletheeffectsofextremecold.
Key Point
• Incoldclimatesventilationisneededtohelppreventexcessivemoisturebuild-upinthepoultryhouse.
Moderate Climate
Wheretemperaturesconsistentlyriseabovethe24°Crange,powerventilationwillberequiredforallbutthelowestbirdstockingdensitiesinsmall,naturallyventilatedhouses.Wheretemperaturesconsistentlyriseintoorabovethe24-30°Crange,tunnelventilationisusuallyrecommended.Tunnelventilationprovideshigh–volume,rapidhouseairexchangeandahighvelocity“wind-chill”airflowwhichgivesasomewhatlowereffectivetemperatureexperiencedbythebirds(Figure 16).Astemperaturesriseintothe35°Crange,thewind-chilleffectbeginstodisappearandevaporativecoolingmustbeaddedtoprovideactualairtemperaturereduction.
Key Point
•Eveninmoderateclimates,tunnelventilationisusuallyrecommendediftemperaturesconsistentlyriseintoorabovethe24-30°Crange.
Hot Climate
Generally,hotterweathermakesitmoredifficulttoincreasehousesizeandbirddensity.Airexchangealonecanonlykeepinsideair temperaturefromrisingmorethanafewdegreesaboveoutsideair temperature. However, ifrelativehumidity isnot toohigh,higherbirddensitiescanusuallybemaintainedreliablyeven inveryhotweatherby tunnelventilationwithevaporativecooling.
In tropicalor subtropical areaswhere temperaturesareconsistently in the35-38°Crange, highdensityhousingandopen-sided, naturally ventilatedhousing are generally not feasible. In hot climateswith lowhumidity (such as highaltitudedesertfacilities)thelowhumiditycontributestoascitesandlowersgrowthrate.
Thecombinationofhighhumidityandhightemperatureisparticularlydifficultforbirdsbecauseamajorwaytheyexpelexcessbodyheatisthroughbreathing(orpanting)whichevaporatesmoisturefromtheirlungsandairways.Thehighertheairhumidity,thelessselfcoolingtheyareabletoachieve.However,inproperlydesignedtunnelventilatedhousestheeffectsofhumidityareminimisedovernaturallyventilatedhousing.
Key Point
• Higherbirddensitiescanusuallybemaintainedreliablyeveninveryhotclimatesbytunnelventilationwithevaporativecooling.
Climatic Factors in Housing and Ventilation Decisions Climatic Factors in Housing and Ventilation Decisions
Indian River Environmental Management in the Broiler House8
Indian River Environmental Management in the Broiler House9
How Birds Work and What They Need
Veryyoungchickshave littleabilitytoregulatetheir internal temperaturesandtheyneedwarmth;anair temperaturearound30°C.Asthebirdsgrow,their“comfortzone”temperaturerangewidensabitanddropssothatatcatchtimethey’remostcomfortableataround20°C.Thismeansthatearlyinagrowout,ourmainconcernisusuallymakingsurethebirdsarewarmenough.Asthebirdsgrow,toomuchwarmth,whichcanhappeneveninwinter,isamorecommonproblem.Ourgoalinventilationistomaintainin-housetemperatureswithinthebirds’comfortzonenottoowarmandnottoocoldatalltimesduringthegrowout.Todothis,weneedtounderstandhowbirds,heatandhumidityinteract.
Key Point •Earlyinagrowout,themainconcernusuallyiskeepingbirdswarmenough.Asthebirdsgrow,toomuchwarmthisamorecommonproblem.
Birds Produce Heat and Moisture
Birdsconvertfeedandwaterintoenergytheyuseforbodymaintenance(operatingtheirorgansandmusclesandkeepingthemselveswarm)andforgrowthtoproduceweightgain.However,theyaren’t100%efficient,sotheygeneratequiteabitofexcessheatalongwithquiteabitofmoisture(infaecalmatterandbybreathing).
Typicallybirdswillproduceabout11.6kJ/hour/kg.Thismeansthatthelargerthebirdsgrow,themoreheattheyputout.Ifwehave20,000birdsat1.8kg,forexample,theywilladdaround417,600kJ/hourtothehouse,orasmuchheatastwoorthreeforcedairfurnacesrunningcontinuously.Ifwehave20,000birdsat3.6kg,theywillproduce835,200kJ/hour.Worldwidethetrendistowardbiggerbirdproduction.Theamountofmoistureproducedalsovarieswithage.Thesameflockof1.8kgbirdsmayproduce3,785litresofwaterperday,dependingonthetemperature.Otherthingsbeingequal,in-houseairtemperatureandhumiditybothtendtoriseasthegrowoutprogresses.
Figure 3: Large numbers of birds contribute large amounts of heat andmoisture to a poultry house. In-house airtemperatureandhumiditybothriseasagrowoutprogresses.
Duringthebroodingphase,youngchickswillneedsupplementalheat.However,asagrowoutprogresses,especiallyincoolerweather,thebirdsincreasinglyhelpkeepthemselvesandthehousewarmwiththeheattheygenerate.Asbirdsgrowlarger,ventilationisessentialforheatremoval,especiallyinwarmweather,tokeepthein-housetemperaturefromrisingtoapointwherebirdscannotcontinuegettingridoftheirexcessheatandtheirinternaltemperaturegoestoohigh.
Key Points
•20,0001.8kgbirdswilladdaround417,600kilojoulesperhourofheattothehouse.
•20,0001.8kgbirdswilladdaround3,785litresofwatertothehouseperday.
2-3 Heaters (379.8-506.4 MJ per hour)
3,785 litres of water per day
20,000 1.8 kg birds
How Birds Work and What They Need
Indian River Environmental Management in the Broiler House8
Indian River Environmental Management in the Broiler House9
Effects of Temperature and Relative Humidity on Birds
Temperatureandhumidityworktogethertodeterminebirdcomfort,butforsimplicityinthefollowingparagraphswe’lllookattemperaturefirst,thenhumidityandthenexplainhowtheirinteractionaffectsbirds.
Birds are basically air-cooled. That is, air moving over the birds picks up their body heat and transfers it to theenvironment.Birdsdonotsweat,andsodonotenjoythiskindofbuilt-inevaporativecoolingsystem.Theydogetsomeevaporativecoolingeffectthroughbreathingandpanting(Figure 4).However,theyrelymainlyondirectbody-to-airheattransferforcooling.Ifyouseebirdsliftingtheirwings,they’refeelinghotandexposingmoreoftheirbodiestotheairtogetridoftheexcessheat.
Figure 4: Birdsdonotsweatandsocannotcoolthemselvesinthisway.Theyshedalmostallexcessbodyheatbydirectbody-to-airheattransfer.Intimesofheatstress,theybeginpantinginordertoridtheirbodiesofmoreheat.
Forfullyfeatheredbirdstostaycomfortable,therehastobeasubstantialdifferencebetweenhouseairtemperatureandtheirowninternaltemperature,whichnormallyisabove37.8°C.Asthein-houseairtemperatureriseshigherandhigher,thebirds’heatsheddingmechanismsbecomelessandlesseffective.Thebirds’internaltemperaturesthenbegintorise,andtheyslowdownorstopeatingandgrowing.Ifthesituationisn’tcontrolled,theyeventuallywilldie.
Figure 5:Forfullyfeatheredbirds,astheairtemperaturerisesabovearound27°C,birds’heatsheddingabilitybecomeslesseffective.Astheybegintoexperienceheatstresstheyslowdownorstopeating.Ifheataccumulationintheirbodiesisn’tstopped,theyeventuallywilldie.
Under most conditions as birds give off heat, the house temperature can be kept from rising too high byexhausting warm air and replacing it with cooler outside air. Since birds get rid of excess heat mainly bywarming the air around them, the more rapidly that air is replaced the more excess heat they can lose.In most poultry houses, for outside air temperatures up to approximately 27°C, the ventilation system canbe operated so that the warmed-up in-house air is removed at the proper rate to maintain overall housetemperaturewithinthebirds’comfortrange.
Starting Heat Stress
38°C
27°C
How Birds Work and What They Need How Birds Work and What They Need
Indian River Environmental Management in the Broiler House10
Indian River Environmental Management in the Broiler House11
Inadditiontosimplychanginghouseair,gettingwindonthebirdscanhelpthemcopewithhightemperatures.Thewind-chilleffectofmovingaircreatesalowereffectivetemperatureforthem.Forexample,ifyouhaveairinthehouseat32°C(andaveragehumidity)movingat2.54m/s,itwillfeeltofully-featheredbirdslikeabout27°Cair.Theeffectisevengreaterforyoungerbirds,whichmaybechill-stressed.Tunnelventilationcreatesthemosteffectivewind-chillcooling.Innon-tunnelhouses,stirringorcirculationfanscanhelp.
Inveryhotweather,evaporatingwaterintotheaircanprovideadditionalcooling.Veryfinedropletsaresprayedintotheair,orwaterisevaporatedbyairflowthroughawettedpad.Asthewaterevaporates,theairtemperatureisreduced.Evaporativecoolingdependsonfansprovidingproperairflowinthehouse,andworksbestwhenrelativehumidityisnottoohigh.
Figure 6: Fastmovingairoverbirdscreatesawind-chilleffectthatcanbeverybeneficial,especiallyforlargerbirds.However,youngerbirdsaremoresensitivetowind-chilleffectsandmaybechillstressed.
Birdscantoleratehighertemperaturesduringthedayifnighttimetemperaturesdrop14°Cormorebelowdaytimehighs.Duringthecoolnighttimebirdscangetridofexcessbodyheatbuiltupduringtheday.Runningfanstogetairmovingoverthebirdsduringthenightcanhelpbyreducingthe“effective”nighttimetemperature.Thebirdsthencanstartthenextdayfresh,whichhelpskeepperformanceupandlessenstheriskofpossiblemortalitiesifdaytimetemperaturesareveryhigh.
Birdsalsolosesomebodyheatthroughbreathing.Thisiswhyyou’llseebirdsbegintopantwhentheyfeelover-heated.It’slikeaback-upcoolingsystem,thatusuallystartsworkingwhentemperaturesrisearound4-6°Cabovetheircurrent“comfortzone”temperature.What’shappeningisthebirdsaretryingtomaximizetheevaporativecoolingeffecttheygetfromtheairpassingoverthemoistliningsoftheirair-waysandlungs.Thiscoolingmethodworksbestwhentheairisrelativelydry.Iftheairisalreadyholdingagreatdealofmoisture,itcan’treadilyevaporatethebirds’moistureandtheevaporativecoolingeffectdoesn’tworkaswell.
Figure 7: Birdscantoleratehigherdaytimetemperaturesiftheyareabletocooloffduringthenight.Theeffectismostpronouncedwhennighttimetemperaturesdrop14°Cbelowdaytimehighs.Runningfansatnighttomoveairoverthebirdscanhelpbyreducingthenighttime“effective”temperature.
32ºC air at2.54 m/s
feels like 27ºC to the birds
How Birds Work and What They Need
Indian River Environmental Management in the Broiler House10
Indian River Environmental Management in the Broiler House11
The following section on heat stress is taken directly from Dr Jim Donald’s original imperial document and therefore the heat stress index calculation cannot be converted into metric values, i.e. degree Centigrade.
An old rule of thumb used by many poultry producers and managers in the US says that in non-tunnel conventional houses if the in-house air temperature is in the 80’s (°F) or above and the temperature and relative humidity numbers add up to 160 or more, birds begin to have trouble shedding their excess body heat. That is, temperature plus humidity gives you a heat stress index. For example, if air temperature is 85°F at 70% humidity (85 + 70 = 155) the birds will be reasonably comfortable. But if the relative humidity goes to 80% (85 + 80 = 165), you’re likely to be losing feed efficiency because of overheating. Note that this rule works only in conventional open-sidewall ventilation or in cold weather power ventilation when air is not moving over the birds. It does not apply to tunnel ventilation because of the wind-chill effect.
In cold weather when direct combustion heaters are being used, not only the birds but the house heaters add moisture to house air, since water vapour is one of the combustion products from burning most fuels. This is a small amount compared with the moisture coming from the birds, but the combination can produce high house humidity if the ventilation rate is too low. This means you can have a heat stress problem with the birds when you would least expect it, if the temperature (°F)/humidity index goes above 160. Too much moisture contributes to litter caking and ammonia problems. (If a heat exchange system is used so that combustion products are not released into the house, heating will not add moisture to house air.)
Figure 8:Aroughguidetowhetherthecombinationoftemperatureandrelativehumiditywillstressbirdsistoaddthenumbers.Ifthetemperatureisabove80°Fandthetemperatureandrelativehumidityaddupto160ormore,birdsarelikelytobestressed.
In warm weather, humidity is not often a problem, except in connection with rainstorms on hot days. For example, after an afternoon thunderstorm on a hot summer day the air temperature may reach 90°F, with relative humidity above 90%. You must have maximum air exchange and air movement under these conditions.
100ºF
80ºF
Temperature + Humidity = 160 or more = Heat Stress
100%70%
How Birds Work and What They Need How Birds Work and What They Need
Key Points
•Birdsdonotsweat;theyshedexcessbodyheatprimarilytoaircirculatingaroundtheirbodies.
•Ifyouseebirdsliftingtheirwings,they’retryingtoexposemoreoftheirbodiestotheairtogetridofexcessheat.
•Forairtemperaturesuptothelow27°Crange,ventilationusuallycanremovewarmedupin-houseairattheproperratetokeepbirdswithintheircomfortrange.
•Thewind-chilleffectofmovingaircankeepbirdscomfortableinhotconditions;evaporatingwaterintotheairprovidesadditionalcooling.
•Keepingbirdscoolatnighthelpsthemstandhighdaytimeheat.
•Pantingindicatesbirdsareover-heatedandaretryingtoshedadditionalbodyheat.
•Temperatureandrelativehumidityworktogether;highrelativehumiditycancauseproblemsevenatrelativelylowairtemperatures.
•Toomuchmoistureinahousecontributestolittercakingandammoniaproblems.
Indian River Environmental Management in the Broiler House12
Indian River Environmental Management in the Broiler House13
How Relative Humidity Works
Whenwaterevaporates,itpassesintotheairaswatervapour.Youcan’tseeit,butlitresandlitresofwaterarefloatingaroundintheairallthetime.Inthepoultryhouse,whatmattersmostisn’tsimplyhowmanylitresofwaterareintheair,buthowclosetheairistoholdingallitpossiblycan–thatis,tobeingsaturatedwithwatervapour.Theideaof“howclosetosaturation,”statedasapercentage,iswhatwemeanbythetermrelativehumidity.
Iftheair isholdinghalf itsmaximumwatervapourcapacity,that’s50%relativehumidity.Iftheair isholdingthree-fourthsofitscapacity,that’s75%relativehumidity.Whentheairissaturatedwithwatervapour,holdingallitcan,that’s100%relativehumidity.
Thekeythingtorealiseisthesaturationamount(inlitrespersomanycubicmetresofair)changesdependingontheairtemperature.Thisiswhyweusethetermrelativehumidity.Warmaircanholdalotmoremoisturethancoldair.Thismeansthatwarmeraircanabsorbalotmoremoisturefromthebirdsandthelitterwithoutapproachingsaturationthanwouldbepossiblewithcolderair.Also, ifyouhavecoldairathighrelativehumidity,warmingthatairautomaticallylowersitsrelativehumidity.Thisiswhatmakeswinterventilationpossible.Whenyourventilationsystembringscoldwinterairintothehouse,thisairgetswarmeduponceit’sinthehouse.Thatmeansitsrelativehumiditydrops,whichinturnmeansitswater-holdingcapacitygoesup,soitisabletopickupmoisturefromthelitterandcarryitonoutofthehouse.
Figure 9:Asairtemperaturerises,theamountofwateragivenamountofaircanholdincreases.Anapproximateruleofthumbisthatan11°Criseinairtemperaturecutsrelativehumidityinhalf.Thatis,raisingtheairtemperatureincreasestheabsorbencyoftheair.At27°Ctheairismoreabsorbentandcanholdalmosttwiceasmuchwatervapourasthesameairat16°C.
Key Points
•Relativehumidityindicateshowclosetheairistoholdingallthemoistureitcanbeforecondensationoccurs.
•Warmerairholdsmuchmoremoisture.An11°Cchangeintemperaturecandouble(orcutinhalf)therelativehumidityofair.
Air at 16C and 100% relative humidity
Holds 61 litres water - Maximum capacity
Holds 114 litres water - Maximum capacity
Holds 61 litres water - 50% of maximum capacity
Air at 27C and 100% relative humidity
Air at 27C and 50% relative humidity
How Birds Work and What They Need
Indian River Environmental Management in the Broiler House12
Indian River Environmental Management in the Broiler House13
Ventilation Basics
Becauseventilationissoimportantinprovidinganoptimumin-houseenvironmentforbroilerrearing,understandingbasicventilationprinciplesisessentialforproperhousedesignandmanagement.Therearetwobasicventilationtypes:naturalventilationandfan-poweredventilation.
Natural Ventilation
Naturalventilationreliesonopeningupthehousetotherightextenttoallowoutsidebreezesandinsideconvectioncurrentstoflowairintoandthroughthehouse.Thisisoftendonebylowering(orraising)sidewallcurtains,flapsordoors.Sidewallcurtainsaremostcommon,andnaturalventilationisoftenreferredtoas“curtainventilation”.
Incurtainventilation,thecurtainsareopenedtoletinoutsideairwhenitgetswarm;whenitgetscold,theyareclosedtorestrict theflowofair.Openinghousecurtainsallowsa largevolumeofoutsideair throughthehouse,equalisinginsideandoutsideconditions.Curtainventilation is idealonlywhenoutside temperature isclose to the targethousetemperature.Theairexchangeratedependsonoutsidewinds.Onwarmtohotdayswithlittlewind,circulationfansmaybeusedtoprovidesomewind-chillcoolingeffect.Foggersormisterscanbeusedwithcirculationfanstoaddasecondlevelofcooling.
Ifcurtainventilationisusedincoolerweather,itisessentialtohavecurtainmachinesoperatedonfrequenton-offtimersandwithbird-levelsafetythermostatsandcurtaindrops(orfail-safes)incaseofhightemperaturesorpoweroutages.Circulationfanscanhelpmixincomingcoldandin-housewarmair.Intheabsenceofstirringorcirculationfans,smallcurtainopeningscauseheavyoutsideairtoenteratlowspeedanddropimmediatelytothefloor,whichchillsthebirdsandcreateswetlitter.Atthesametime,warmerairescapesfromthehouse,resultinginlargetemperatureswings.Eveninmoderateweatherhowever,normalfluctuationsinairtemperatureandwindsduringtheday(ornight)cancallforfrequentadjustmentsincurtainsettings.Natural(curtain)ventilationrequiresconstant,24-hourmanagement.
Naturalventilationasasystemdoesnotallowagreatdealofcontroloverin-houseconditions.Intheearlydaysoftheindustry itwascommonlyused,especially inmildclimates,andhouseswerespecificallydesignedtofacilitatenaturalairconvectioncurrentsforventilationpurposes.Inmorerecenttimes,managersofmoremoderncurtainsidedhousesequippedwithfan-poweredventilationsystemshaveusednaturalventilationasan“inbetween”option,whenoutsideairtemperatureisclosetodesiredin-housetemperatureandneitherheating(andminimumventilation)norcoolingisneeded.
Figure 10: Natural (curtain)ventilationworkswellonlywhenoutsideconditionsarenearwhat isneeded inside thepoultryhouse.Inhotweather,strongwindsareneededtoachieveanacceptableairexchangerate;incoolweather,coldoutsideairislikelytodropdirectlyontothebirds.
How Birds Work and What They Need Ventilation Basics
WarmWeather
ColdWeather
WarmAir
ColdAir
Indian River Environmental Management in the Broiler House14
Indian River Environmental Management in the Broiler House15
However,full-timefan-poweredventilationhasprovenworldwidetoprovidebetterflockperformanceandreturnsinmostcases,eveninhousesstillequippedwithcurtainsidewalls.Naturalventilationthereforewillnotbefurtherdiscussedinthispublication.
Insidecirculationorstirringfansareoftenusedincurtainventilationsetupsandcanhelpwithmixingofoutsideandinsideair,preventingtemperaturestratificationincoolweather,andtosomeextentcoolingbirdswithdirectbreezes.Thistypeoffansetuphowever,doesnotmoveoutsideairintothehouse,soacurtain-ventilatedhousewithstirringfansisnotconsideredapower-ventilatedhouse.
Key Points
•Natural(curtain)ventilationworkswellonlywhenoutsideconditionsareneardesiredin-houseconditions.
•Curtainventilationrequiresconstant,24-hourmanagement.
•Thecurtainventilationhouseairexchangeratedependsonoutsidewinds;incoldweather,coldoutsideairislikelytodropdirectlyontothebirds.
•Stirringfanscanhelpimproveconditionsinacurtain-ventilatedhouse.
Fan-Powered Ventilation
Fan-poweredventilationusesfanstobringairintoandthroughthehouse.Poweredventilationgenerallyallowsmuchmorecontroloverboththeairexchangerateandtheairflow-throughpattern,dependingontheconfigurationoffansandairinletsandthetypeofcontrolused.
Fan-poweredventilationsystemscanuseeitherpositiveornegativepressure.Positive-pressurewall-mountedfansystems,whichpushoutsideairintothehouse,aremostoftenseeninsetupsusedforcoolerweather.However,mostpoultryhousefan-poweredsystemsnowusenegative-pressureventilation.Thismeansthatthefansareexhaustfans,pullingairoutofthehouse.Thiscreatesapartialvacuum(negativepressure)insidethehouse,sothatoutsideairisdrawnintothehousethroughinletsinthehousewallsorundertheeaves.
Achievingapartialvacuuminsidethehouseduringventilationallowsformuchbettercontroloftheair-flowthroughpatterninthehouseandformoreuniformconditionsthroughoutthehouse.Thatis,bothdeadairareasandhotorcoldspotsareminimised.
Figure 11: Negative-pressureventilationcreatesapartialvacuumthatpullsairintothehouseevenlythroughallinlets,creatingmoreuniformconditionsinthehouse.
Key Point
•Negative-pressurefan-poweredventilationcreatesapartialvacuuminthehouse,allowingcontroloftheventilationairflowpattern.
Ventilation Basics
Indian River Environmental Management in the Broiler House14
Indian River Environmental Management in the Broiler House15
Need for Tightly Sealed House
Modernnegative-pressureventilatedhousesmustbetightlysealed.Innaturallyventilatedhouses,tightnessisnotatallcritical.Butinusingnegative-pressureventilation,thekeyistotaketotalcontrolofhowandwhereairentersthehouse,sohousetightnesshasparamountimportance.Duringcoolweatheroperation,aircomingunderfoundations,arounddoorsorthroughcracksonlyservestochillordiscomfortbirds,createmoistureproblemsanddetractfromoptimumrearingtemperatureenvironments.Airleaksduringtunnelventilationdestroytheneededsingle-airpathfromoneendofthehousetotheother,causingreducedwindvelocityandwind-chillcooling.
Ahousetightnesstestusedinthepoultryindustryformanyyearsfor12mx122mor12mx152mhousesistoturnontwohigh-quality91cmfansoronehigh-quality122cmfanwithallinletsanddoorscompletelysealed.Thedifferentialstaticpressurereadingfromthehouse interior totheoutsidewillgivean indicationofthe levelofnegativepressureachievedbythefans.Thehigherthenegativepressureachieved,thetighterthehouse.Thegoalforahouseshouldbeaminimumof37.5Panegativepressure;fornewerhouses,staticpressureshouldfarexceed50Pa.
Key Point
•Havingatightlysealedhouseiscriticalforsuccessfulcontrolofin-houseconditionsinnegative-pressureventilation.
Types of Negative-Pressure Ventilation Operations
Fan-powered,negative-pressurepoultryhouseventilationcanbeoperatedwithdifferentfanandairinletsetupsinthreedifferentmodes,accordingtotheventilationneedstobeaddressed:
•Minimumventilation(alsocalledjust“powerventilation”oreven“powervent”)-operatedonatimerandusedforcoolerweatherand/orsmallerbirds.
•Transitionalventilation–operatedonthermostatortemperaturesensorandusedforheatremovalwhenwind-chill(tunnel)coolingisnotneededordesirable.
•Tunnelventilation–usedforwarmerweatherand/orlargerbirds;operatedonthermostatortemperaturesensor.
All three of these ventilation modes of operation use the negative pressure principle, but operateat different static pressures. Static pressure, in areas using metric units measured in Pascals, indicates thedifference between in-house and outside air pressure, or the degree of partial vacuum achieved in the house.Minimum-ventilation setups operate at higher static pressure (greater vacuum), usually between 17.5 Pa and 30 Pa.Tunnelventilationmayproducestaticpressuresrangingfrom10Pato25Pa,dependingonwhetherpad-typeevaporativecoolingisinstalled,andthetypeofevaporativecoolingsystemused.
Importantdistinctionssometimesgetoverlookedinthewaywetalkabouthouses.We’lltalkabouta“tunnelhouse”,forexample,asthoughtherewasonlyonekindormodeofventilationused.Thetunnelsetupisusedonlyinwarmtohotweather,andthe“tunnelhouse”forcoolweatherorsmallbirds isprobablyequippedforandswitchedeithertominimumortransitionalventilationasweatherandthesizeofthebirdsdictate.Thechangingneedsofbirdsastheygrowandthevariabilityofweather,especiallyinautumnandspring,requiresmanagerstobereadytoswitchtheirventilationsystemfromonemodeorsetuptoanotherwhenneeded.
Ventilation Basics Ventilation Basics
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Indian River Environmental Management in the Broiler House17
Thefollowingarebriefdescriptionsofhowthesebasicfan-poweredventilationsetupswork.Formoredetailedinformationonsystemsandmanagementconsiderations,seeKeys to Managing a Modern Tunnel House(Page 32).
Key Points
•Differentfanandairinletsetupsareusedinnegative-pressureventilationtoachievedifferentpurposes,accordingtoprevailingconditions.
•Thedifferentnegative-pressureventilationmodesworkincertainstaticpressureranges.
•Thechangingneedsofbirdsandchangingweatherrequiresmanagerstobereadytoswitchventilationmodesasneeded.
How Minimum Ventilation Works
The purpose of theminimum ventilation setup is to bring in just enough fresh air to exhaust excessmoisture andammoniafumesduringcoldweatherconditionsand/orwhenbirdsareverysmall,withoutchillingthebirds.Typically,fromtwotosix91cmexhaustfansareused,withthelocationoffansandairinletsvaryingasdescribedbelow.
Thekey tosuccessfulminimumventilation iscreating theproperpartialvacuumsothataircomes inwithsufficientspeedandatthesamespeedthroughallinlets.Withairinletsdistributedevenlyalongthewholelengthofthehouse,airflowisthenuniformthroughoutthehouse.Justasimportant,cooloutsideaircomesintothehouseatahighenoughvelocitytomixwithwarmin-houseairabovetheflock,ratherthandroppingdirectlyontoandchillingthebirds.
Severalvariationsofnegativepressureventilationsetupsareusedforminimumventilation indifferentregions (andfornon-tunnelheatremovalintransitionalventilation,asdescribedlater).ThemostcommonlyseenareillustratedinFigure 12.
Figure 12:FourCommonVariationsonFan/InletSetupsforMinimumVentilation
Forconvenienceinpresentationandbecauseitiscommonlyusedworldwide, setup A(fansonsidewallsandperimeterairinlets)isusedinthispublication.Readersshouldunderstandthatwhilenegative-pressureconfigurationsaroundtheworldvarywidelyintheirdetails,thesamebasicprinciplesapplytoalloftheabovefan/inletsetups,andallcanandmustbecapableofrunningproperlyintheminimumventilationmode.
A. Exhaust fans on sidewalls and air inlets around the perimeter (high on sidewalls or in ceiling). This setup works well in cool weather and for use in tunnel ventilated housesoperatingintransitionalmode.
B. Exhaust fans on one side of building and air inlets on the other. Commonly called “cross ventilation”, this setup is most popular in areas where tunnel ventilation is notneeded.
C. Exhaust fans in the roof and air inlets in the sidewalls. Often called “ridge extraction”, this type of setup is also most usedincoolerclimates.
D. Exhaust fans in sidewalls and air inlets in the apex of the roof. Often called “reverse flow” ventilation, this setup is similar to setup A above except for the location of the airinlets.
Ventilation Basics Ventilation Basics
Indian River Environmental Management in the Broiler House16
Indian River Environmental Management in the Broiler House17
TheairflowpatterncreatedinaminimumventilationsetupisillustratedinFigure 13. Togetthisneededairflowpattern,theairinletareamustbematchedtothefancapacitybeingused.Iftheairinletareaistoosmall(forthenumberoffansrunning),fanswillhavetoworkagainsttoo-highstaticpressureandwillnotdelivertheairexchangerateneeded.Ifairinletsareopenedtoowide,staticpressuredropstoolow,andairwillcomeinmostlyoronlythroughinletsclosesttothefans,creatingnon-uniformairflowandpoorconditionsforbirds.Usingcool-weatheradjustableperimeterinletsactuatedbyastaticpressurecontrollermakestheinletareaadjustmentautomatic.Curtaincracksandfixedboardinletsaremorelikelytoallowtoo-wideopeningsanddumpcoolincomingairontothebirds.Minimumventilationalsorequiresatighthouse:airleakswilltendtospoilthedesiredairflow-through.
Figure 13:Thegoalofminimumventilationistobringairinevenlyandathighvelocitythroughinletsspacedaroundthehouseabovebirdlevel,sothatcoldoutsideairmixeswithin-houseair,asshowninthisplanviewdiagram.Thisairflowpatternpreventscoldoutsideairfromdroppingontothebirds.
Minimumventilationistimer-driven,andmaybesettooperateaslittleasone-halfminuteinfiveearlyinagrowoutorinverycoldweather.Asbirdsgrowlargerand/orweatherwarms,thermostatsoverridethetimertoprovideanadequateventilationrate.
Notethatincoldweathertheneedtoremovemoisturefromthehousemeansthatsomeminimumventilationratemustbemaintainedevenwhenthethermostatdoesn’tcallforventilationandevenifasmallamountofhouseheatmustberemovedintheprocess.
Key Points
•Thepurposeofminimumventilationistobringinjustenoughfreshairtoexhaustexcessmoistureandammoniaincoldweatherorduringbrooding.
•Negative-pressurefanandairinletconfigurationsaroundtheworldvarywidely,butthesamebasicprinciplesapplytoall.
•Allminimumventilationsetupsbringoutsideairinhighinthehousetoavoidputtingcoldairdirectlyontotheflock.
•Togettheairflowpatternneededinminimumventilation,theairinletareamustbematchedtothefancapacitybeingused.
•Usingcool-weatheradjustableperimeterairinletsactuatedbyastaticpressurecontrollergivesbestminimumventilationairflow.
•Minimumventilationistimer-controlled,nottemperature-controlled.
Ventilation Basics Ventilation Basics
Indian River Environmental Management in the Broiler House18
Indian River Environmental Management in the Broiler House19
How Transitional Ventilation Works
The change fromminimum to transitional ventilation is basically a switch from timer-driven to temperature-drivenventilation. This is true nomatter what the particular fan/inlet setup is. That is, whenever temperature sensors orthermostatsoverridetheminimumventilationtimertokeepfansrunning,theminimumventilationsetupwillberunninginthetransitionalventilationmode.Additionalsidewallorotherfans(andairinlets)maybeaddedasoutsidetemperatureincreases.
Anadditionalstageintransitionalventilationisa“hybrid”setup,illustratedinFigure 14,usingsomeofthelargetunnelfanstobringairintothehousethroughperimeterairinletsinsteadofthroughthetunnelinlets,whicharekeptclosed.Outsideairentersandmixeswith in-houseair inmuchthesamewayas inaminimum-ventilationnegativepressuresystemusing sidewall fans.Thebigdifferenceover theminimumventilation setup is that the increased fancapacitygivesalargervolumeofairexchange.Runningfourtunnelfansinthetransitionalsetup,forexample,givesthesameventilation rate as running four fan tunnel ventilation, butwithout putting anywind directly on the birds. In somelocations,tunnelfansarenotusedfortransitionalventilationbecauseofconcernforuniformity.Useoftunnelfansfortransitionalventilationisbasedonclimateandtheabilitytomixandstirtheincomingair.
Figure 14: The transitionalventilationmodebeginswhenever temperature sensorsoverride theminimumventilationtimer.Whentheneedforheatremovalrequiresahigherairexchangeratethantheminimumventilationfans/inletssetupcanhandle,someofthetunnelfanscanbeusedtobringlargeamountsofairinthroughperimeterinlets,asshowninthisdiagramofthe“hybrid”transitionalmode,withoutputtingairdirectlyonthebirds.
Aswithminimumventilation,theairinletareaduringtransitionalventilationmustbematchedtothefancapacityused.Enoughsidewallinletareashouldbeprovidedtooperateatleasthalfoftheinstalledtunnelfansinthehybridtransitionalmodewithoutcreatingexcessivestaticpressure.Formostefficientoperation,airinletsarecontrolledbystaticpressure-operatedmachines,asinminimumventilation.
Key Points
•Transitionalventilationistemperaturedriven,whenheatremovalisneededbutwithoutputtingcoldairontobirds.
•Whentheneedforheatremovalrequiresahigherairexchangeratethantheminimumventilationsetupcanhandle,tunnelfanscanbeusedtobringlargeamountsofairinthroughperimeterinlets.
•Aswithminimumventilation,transitionalventilationinletareashouldbematchedtofancapacityandinletopeningadjustmentsmadebyanautomaticstaticpressure-operatedcontroller.
Tunnel Air Inlets(Normally closed) (Also may be used in Transitional Ventilation)
Sidewall Exhaust Fans
Brooding Area
Tunnel FansSidewall Air Inlets
Ventilation Basics
Indian River Environmental Management in the Broiler House18
Indian River Environmental Management in the Broiler House19
How Tunnel Ventilation Works
Thegoaloftunnelventilationistokeepbirdscomfortableinwarmtohotweatherbyusingthecoolingeffectofhigh-velocityairflow.Thetunnelsetupisespeciallysuitedtowarmerareasandwherelargerbirds(1.8-3.6kg)arebeinggrown.Tunnelsystemsaredesignedfirsttohandletheexpectedneedforheatremoval,providingtheairexchangerateneededtoexhaustexcesshouseheatinhotweather.Fulltunnelmodeoperation,withallfansrunning,mayproduceacompletehouseairexchangeinunderoneminute.
Thetunnelsetupalsoprovideswind-chillcooling,movingairasinawind-tunnelthroughthelengthofthehouse.Avelocityofatleast2.54m/sisneededformosteffectivewind-chillcooling.
Figure 15:Tunnelventilationisdesignedtomovelargeamountsofhigh-velocityairoverthebirds,achievingmaximumheatremovalplusawind-chillcoolingeffect.
Thewind-chilleffectcreatedbyhigh-velocityaircanreducetheeffectivetemperaturefeltbyfully-featheredbirdsbyasmuchas5.5-7°C.Figure 16showsestimatedeffectivetemperaturesthatresultwithdifferentairvelocities,forfourweekandsevenweekbirds.
AsFigure 16 shows, cautionmust be used in tunnel ventilating with younger birds, since they experience greaterwind-chilleffectforagivenairvelocity.Notethatthe“effective”temperaturecanonlybeestimated,notreadfromathermometerorcalculated.Birdbehaviourmustbetheguidetojudgingtherightnumberoffanstoturnontocreatetheairvelocityandairexchangeratethatisneededtokeepbirdscomfortable.
Figure 16:Thewind-chilleffectcreatedbyhigh-velocityairflowismuchgreaterforyoungerbirds.
Tem
per
atu
re (°
C)
Air Velocity (m/s)
32
30
28
26
24
22
20
18
0 0.5 1 1.5 2 2.5 3
34
Temperature felt by 7 week birds
Temperature felt by 4 week birds
NoteOutsidetemperate=32°C
Ventilation Basics Ventilation Basics
Indian River Environmental Management in the Broiler House20
Indian River Environmental Management in the Broiler House21
Thehigh-velocityairflowofthetunnelsetupmakesitwellsuitedtoaddingevaporativecooling.Thiscanbedoneeitherwithin-housefoggersorwithevaporativecoolingpadsplacedoutsidetheairinlets.Thisrealcoolingofincomingair,ontopofthe“effective”coolingproducedbywind-chill,cankeepbirdsperformingwelleveninveryhotweather.Usedalone,thewind-chilleffectoftunnelventilationbecomeslesspronouncedasairtemperaturesrisemuchabove32°C;above38°Ctheairbeginstowarminsteadofcoolthebirds.
Adequatetunnel inletarea isessential.Morearea isneededforpadcooling(asexplainedbelow).Tunnelhousesalsomustbetight,sinceanyairleakswillspoilthedesiredairflowpattern.
Key Points
•Thepurposeoftunnelventilationistoachievemaximumcoolingbythewind-chilleffectof
high-velocityairflow.
•The“effective”temperaturecreatedbythewind-chilleffectmustbeestimatedandvariesaccordingtobirdage/sizeandactualairtemperature.
•Thewind-chilleffectbecomeslesspronouncedasairtemperaturesriseabove32°C;above38°Ctheairbeginstowarminsteadofcool.
How Evaporative Cooling Works
Whenwaterevaporates,whateveritisincontactwithgetscooled.Evaporatingjust3.8litresofwaterintotheairtakes9,179kJofheatoutofthatair.Evaporativecooling(ECforshort)isthereforeaneffectivetoolforpoultryproductioninhotweather.
ThesimplestapplicationofECforbroilersistheuseoffoggingnozzlesmountedoverheadincurtain-ventilatedhouses.Themostefficientandeffectivemodernsystemshowever,aredesignedtocomplementandworkinconjunctionwithtunnel ventilation. By adding some actual temperature reduction on top of the wind-chill cooling effect of tunnel,properlydesignedandoperatedtunnel-houseECsystemscankeepbirdsperformingwellinveryhotweather.
The twomajor setupchoices for tunnel-houseECare in-house foggersandwettedpads (spray-onor re-circulating)mounted over the tunnel air inlets. Either setup can do a good job, but recirculating pad systems are becomingpredominant.Thesehigh-efficiencysystemsdemandlessmanagementattentionanddonotriskwettingbirdsorlitter.
HowwellECworks-thatis,howmuchcoolingitproduces-dependsonthreefactors:
•Thestartingoutsideairtemperature-thehigherthisis,themoredegreesofcoolingarepossible,otherthingsbeingequal.
•Therelativehumidity(RH)oftheoutsideair-thelowerthebetter.
•Howefficientthesystemisinevaporatingwater-typicalsystemsrangefrom50%-75%efficient.
Table 1showsthein-houseairtemperaturesthatresultgivenhigherorlowerstartingairtemperature,systemefficienciesandrelativehumidity.Forexample,ifitis35°Coutsideat50%relativehumidity,a75%efficientECsystemwillgive7°Cofcooling,to28°C.Ifthetunnelwind-chillgivesanother5.5-7°Cofeffectivecooling,fully-featheredbirdswillfeelliketheyarein21-22.5°Cair.
Ventilation Basics
Indian River Environmental Management in the Broiler House20
Indian River Environmental Management in the Broiler House21
Hot Outside Air - 35ºC
Evaporative Cooling Pads Tunnel Fans
7ºC Cooling + 6ºC Wind-Chill = 22ºC Effective Temperature
ResultingAirTemperature(°C)forGivenRelativeHumidity
50%
75%
50%
75%
75%
SystemEfficiency
32.2%
28.9%
26.7%
27.2%
24.4%
33.3%
30.6%
28.3%
28.3%
26.1%
34.4%
32.2%
31.7%
29.4%
28.9%
27.2%
40%RH 50%RH 60%RH
StartingAir Temperature (°C)
38.7
35
32.2
50% 29.4% 30.6%
Table 1:Evaporative Cooling Possible Under Different Conditions
Evaporativecoolingcanprovideusefulcoolingeveninareasusuallyconsideredquitehumid.Inmanyareasoftheworld,forexample,RHmayreach90%duringasummernight,buttypicallydropsto50%orevenlowerbymidday.Thereasonisthatnighttimeairtemperatureisusuallyinthelow20°Crange,sothatan11°Crisetothelow32°CrangecutstheRHinhalf.AruleofthumbisthatECisverypracticalifthereisatleastanaverage11°Cdifferencebetweennighttimelowtemperaturesanddaytimehighs.
Figure 17 illustratesthebasicprinciplesoftunnel-housecoolingthroughloweredeffectivetemperaturebyhighwindspeedplusloweredactualtemperaturebyevaporativecooling.
Figure 17:Basicprinciplesoftunnelplusevaporativecoolingareshownhere,representingtypicalresultspossiblewithawell-designedhigh-efficiencyevaporativecoolingandtunnelventilationsystemwithwindspeedat2.54metrespersecondormore.
Key Points
•Evaporatingjust3.8litresofwaterintotheairtakes9,179kilojoulesofheatoutofthatair.
•Howwellevaporativecoolingworksdependsonairtemperature,relativehumidityandefficiencyofthecoolingsystem.
•Evaporativecoolingisverypracticalifthereisatleastanaverage11°Cdifferencebetweennighttimelowtemperaturesanddaytimehighs.
Ventilation Basics Ventilation Basics
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Indian River Environmental Management in the Broiler House23
Making Good Ventilation Decisions
Inmakingdecisionsonhowtodesignandequipabroilerproductionhouse,itisimportanttounderstandthecapabilitiesof,andthekindofbenefitsthatcanbeexpectedfrom,modernenvironmentalcontroltechnology.
Figure 18 showsactuallymonitoredtemperaturevariationsrecordedbydata-loggingmonitorsincurtain-ventilatedvs.environmentally-controlledbroilerhouses in theU.S.Southeast inautumn.While theconventionalcurtain-ventilatedhouseallowsverylittle,ifany,temperaturecontrol,theenvironmentally-controlledhousetracksthetargettemperaturelinefairlyclosely.Thattheseresultswererecordedforthefirst28daysofagrowoutisparticularlysignificant.
Forlaterstagesofagrowoutandforwarmerweather,especiallywhenbirdsaregrowntolargersizes(1.8-3.6kg),tunnelventilationwithevaporativecoolinghasbeenshowntogiveadefiniteperformanceadvantage.
Table 2showsactualinfielddatarecordedbyacommercialbroileroperationduringsummergrowoutsintheSoutheastU.S.,comparingconventionalcurtainandtunnelventilatedhouseswithevaporativecooling.
AnotherstudyshowingthepotentialofthemoderntunnelhousetodeliverbetterbirdperformancewasdonebyU.S.Dept.ofAgricultureresearchers,comparingtheeffectsonbirdweightandfeedconversionefficiencyofdifferenttunnelwindspeedsinhotconditions(Table 3).
Figure 18:Temperaturemonitoringshowstheenvironmentally-controlledhousemaintainsclose-to-targettemperature;curtain-ventilatedhouseallowswidetemperatureswings.Shadedlinesshowtargettemperature.
Age (Days)
Tem
pera
ture
(°C
)
35.0
32.2
29.4
26.7
23.9
21.1
15.3
Fan-Assisted Curtain Sidewall Ventilation
Tem
per
atu
re (°
C)
35.0
32.2
29.4
26.7
23.9
21.1
15.3
Age (Days)
Negative Pressure, Minimum and Transitional Fan Ventilation
Target Temperature
Target Temperature
Making Good Ventilation Decisions
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Indian River Environmental Management in the Broiler House23
58DayBroilers
Table 2:PerformancefactorsrecordedfortunnelandECvs.conventionalcurtainventilationHousesinU.S.Southeastinsummer
Table 3: U.S. Department of Agriculture research study effects of different wind speeds on bird weight and feedconversioninhotconditions
Itmustbestressedthatthepotentialpayofffrominvestmentinventilationtechnologyisonlyrealisedwheresystemsareproperlydesignedforthepurposeandsetting,withcarefulattentiongiventochoosingcomponentparts,andequallyimportantaremanagedproperly.
StillAir 2.54 0.33 3.026
AirVelocity
LiveCost($cents/kg)
BirdWeight(kg)
BroilerWeight(kg)
TunnelandEC
Conventional
3.27
3.11
FeedConversion
2.18
2.24
%Liveability
92.4
88.1
%Condemnations
1.71
1.90
48.4
50.0
GaininPreceedingWeek(kg)
After4thWeek
3.05m/s 1.28 0.58 1.495
2.03m/s 1.27 0.57 1.482
StillAir 1.23 0.53 1.521
After5thWeek
3.05m/s 1.94 0.66 1.712
2.03m/s 1.92 0.65 1.698
StillAir 1.79 0.55 1.804
After6thWeek
3.05m/s 2.60 0.66 1.966
2.03m/s 2.52 0.60 2.080
StillAir 2.20 0.41 2.469
After7thWeek
3.05m/s 3.21 0.60 2.277
2.03ms 3.02 0.50 2.610
FeedConversionforthatWeek
Making Good Ventilation Decisions Making Good Ventilation Decisions
Indian River Environmental Management in the Broiler House24
Indian River Environmental Management in the Broiler House25
Key Points
•Researchstudiesandindustryexperienceshowmodernenvironmentalcontroltechnologiescanprovideasignificantperformanceadvantage.
•Data-loggingmonitorsincommercialpoultryhousesdocumenttheabilityofenvironmentalcontrolequipmenttomaintainclosetotargettemperature.
•IntheU.S.Southeastinsummer,tunnelventilationwithevaporativecoolingimprovedperformance.
•Researchundercontrolledconditionshasshownthathighwindspeedisespeciallybeneficialforperformanceoflargerbirds.
Thefollowingsectionsoutlinekeydecisionfactorsforthemostimportantventilationsystemcomponents.
Choosing Fans
Havinggoodfansisessentialforasuccessfulventilationprogramme.Thekeyconsiderationisairflowcapacity–thatis,them3/hr(cubicmetresperhour)afandelivers.Fansaretheair-movingmuscleofaventilationsystemandyouwanttobesurethefansyouinstalldeliverthem3/hrthatisneeded.
Fan Performance Factors
Fancapacity(m3/hr)variesaccordingtothestaticpressurethefanisworkingagainst.Infreeair(aswithastirringfan),withzerostaticpressure,afanwillmovethegreatestamountofair.Innegative-pressureventilationfanshavetopullairfromtheinletsthroughthehouseandexhaust it totheoutside,andsohavetoworkagainstacertainamountofresistance,whichwecallstaticpressure.Asstaticpressuregoesup,fanairflowcapacitygoesdown.Afan’sairflowratio(m3/hrat50Pa÷m3/hrat12.5Pa)indicateshowwellitmaintainsairflowcapacityathigherstaticpressure.Airflowratiosrangefromaround0.65-0.90.Higherisbetter.
Fanefficiency(m3/hrperwatt),matchedwiththeutilitycostperkilowatt-hour,tellsushowmuchitcoststorunafantogetagivenairflowinm3/hr.Fanefficiencyalsousuallygoesdownasstaticpressuregoesup.
Fanperformancecurvesareveryusefulincomparingfansandjudgingwhichfanwouldbebestforagivensituation.Fancurvesshoweitherfancapacityorfanefficiency.Thatis,theyplotorgraphhowafan’sm3/hrcapacitychangesasstaticpressureincreases,ortelluswhatafan’sm3/hr/wattefficiencywillbeatdifferentstaticpressures.TheexamplefancurvesshowninFigures 19 and 20showtheperformancedifferencesbetweentypicaldirectdrivelow-efficiencyandhigh-efficiencybelt-drive122cmfans.
Fansareusuallyadvertisedorratedform3/hroutputatastaticpressureof10or20Pa.Thisisthestandardcustomarilyusedforventilationdesignpurposesandisatypicaloperatingstaticpressure.Ifstaticpressureinahouserisestoofarbeyondthedesignoperatingrange–whichislikelytohappenifshuttersorcoolingpadsareallowedtogetdirtyorthereisinsufficienttunnelinletarea–fanswillnotdeliverthedesiredairflow.Thehigh-efficiencyfanshowninFigure19forexample,delivers39,105m3/hrat12.5Pastaticpressure.Butifthroughimproperdesign,managementormaintenanceofthepoultryhouseweallowstaticpressuretoriseto37.5Pa,theairflowdropstoonly32,984m3/hr,a16%decrease.
Making Good Ventilation Decisions
Indian River Environmental Management in the Broiler House24
Indian River Environmental Management in the Broiler House25
Figure 19:Fanairflowcapacitym3/hrcomparison
Figure 20: FanEfficiencym3/hr/wattComparison
Key Points
•Thekeyfanperformancefactorisairflowcapacityunderstaticpressureload.
•“Airflowratio”indicateshowwellafanmaintainsairflowcapacityathigherstaticpressure-higherisbetter.
•Fanefficiencyismeasuredinm3/hrperwatt.Amoreefficientfanwithahighairflowratiocostsmorebutperformsbetterandsavesonlong-termelectricitycosts.
•Fanairflowcapacityandefficiencycurvesshouldbeconsultedtojudgeperformanceovertherangeofstaticpressureitwillbeusedinandtoestimateoperatingcosts.
Airf
low
Cap
acity
(m3/h
r x
1,0
00
) 42.5
34.0
25.5
17.0
Static Pressure (Pa)
0.00 12.5 25.0 37.5 50.0
m3 /
hr
per
Wat
t Eff
icie
ncy
51
41
31
20
Static Pressure (Pa)
0.00 12.5 25.0 37.5 50.0
High-efficiency 122 cm belt-drive slant wall fan w/cone, fibreglass housing aluminium shutter, airflow ratio 0.74
Direct-drive 122 cm fan with aluminium shutter and guard airflow, ratio 0.71
High-efficiency 122 cm belt-drive slant wall fan w/cone, fibreglass housing aluminium shutter, airflow ratio 0.74
Direct-drive 122 cm fan with aluminium shutter and guard, airflow ratio 0.71
Airf
low
Cap
acity
(m3/h
r x
1,0
00
) 42.5
34.0
25.5
17.0
Static Pressure (Pa)
0.00 12.5 25.0 37.5 50.0
m3 /
hr
per
Wat
t Eff
icie
ncy
51
41
31
20
Static Pressure (Pa)
0.00 12.5 25.0 37.5 50.0
High-efficiency 122 cm belt-drive slant wall fan w/cone, fibreglass housing aluminium shutter, airflow ratio 0.74
Direct-drive 122 cm fan with aluminium shutter and guard airflow, ratio 0.71
High-efficiency 122 cm belt-drive slant wall fan w/cone, fibreglass housing aluminium shutter, airflow ratio 0.74
Direct-drive 122 cm fan with aluminium shutter and guard, airflow ratio 0.71
Making Good Ventilation Decisions Making Good Ventilation Decisions
Indian River Environmental Management in the Broiler House26
Indian River Environmental Management in the Broiler House27
Fan Shutter Factors
Shuttersshouldgivelittleornoairflowresistancewhenopen,butshouldcompletelyblockairflowwhenclosed.Recenttesting has shown even high-quality, new and clean louver-type shutters on 122 cm tunnel fans not to be closingtightly.Thesupposedlyclosedshuttersallowedenoughairleakagetocauseseveralhundreddollarsinheatlossesperhouseduringcool-weatherminimumventilation.Evenmoreimportant,theairleakagealsodisruptstheneededairflowpattern,whichcanhurtbirdperformance.
Iflouvre-typeshuttersareused,acommitmentmustbemadetokeepthemclean.Enoughdirtcanaccumulateontheseshutters inaweektoreduceairflowby25%.Onereasonforconsideringconeorslantwallfans is thatshuttersaremountedinsidethehousewheretheyaremucheasiertoclean.
Key Point
•Fanshuttersmustclosetightlytoavoidairleakageandmustbekeptcleantomaintainratedfancapacity.
Integrated Control System Decision Factors
Anintegratedelectroniccontrolsystemprovidesconsistentcontrolofthein-houseenvironment24hoursaday,sevendaysaweek.Suchsystemsaddsignificantcost,butcanpayoffinimprovedbirdperformancebylimitingtemperatureswingsaboveandbelowthetargetoptimumtoamuchnarrowerrange.AsshowninFigure 21,anelectroniccontrolleriscapableofplusorminus1.1°Ccontrol,wheretypicalmechanicalthermostatsallowswingsofplusorminus3-4°C.Anintegratedcontrolleralsoeliminatesthelabourofchangingindividualsettingsonseparatecontrolssuchasthermostats.However,agoodhumanmanagerisstillneededtooverseeandoperatetheintegratedcontrolsystem.
Agoodsystemwillbeeasytolearn,whichusuallymeanshavingagooddisplayscreenandbeingmenu-driven.Itshouldbecapableofkeepingheatingandventilationsystemsfromfightingeachotherandmovingthehouseautomaticallyfromheatingtominimumventilationtotransitionaltotunnelandevaporativecooling(andback).Italsoshouldhaveenoughdatachannelssoyoudon’thavetoaddextracontactors.Animportantpartofagoodintegratedcontrollerisadequatebuilt-inprotectionagainstpowerlinevoltagespikesandsurges.
Agoodcontrolsystemalsowillincludezoningcapability,allowingthemanagertoplacetemperaturesensorsinvariouspartsofthehouseandsetupthecontrollertousedifferentsetsofsensorsfordifferentconditions.Forexample, ifhalf-housebroodingisused,thecontrollerwouldworkonlyoffsensorsinthebroodareaforearlygrowoutminimumventilation,butworkonlyoffsensorsatthefanendofthehouseforhotweathertunnelventilation.
Figure 21:Asthegraphicofrecordedtemperaturesshows,integratedelectroniccontrollersachievefarbetterin-housetemperaturecontrolthanthermostat-operatedsystems.Controllercostsareusuallyfullyjustifiedbytheimprovementinflockperformance.
Tem
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(°C
)
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27
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Timea.m. p.m.
10.00 11.00 12.00 1.00 2.00
24ºC target temperature
Integrated electronic controller +/-1.1ºC
Manual mechanical thermostats+/-3-4ºC
Making Good Ventilation Decisions
Indian River Environmental Management in the Broiler House26
Indian River Environmental Management in the Broiler House27
The better controllers incorporate data collection and display, so that a manager can, for example, look at housetemperaturesatdifferentintervalsforthepast24hours,orfortheentiregrowout.Thiscapabilityisextremelyusefulfor troubleshooting.Remotemonitoring and control, usually throughnetworking through apersonal computer, is adesirableoptionincontrollers,allowingamanagerorownertocheckonhouseconditionsfromhisseparateofficeorresidenceandtakecareoftroublesastheyarise.
Key Points
•Modernelectroniccontrollerscansaveagreatdealofmanagementtime,suchasinresettingthermostats.
•Agoodcontrollerwillhavearangeofcapabilities–beingoperator-friendlyisamust.
•Agoodcontrollerwillbeabletokeepin-housetemperatureontargetplusorminus1.1°C.
•Acontrollerwithdatacollectionanddisplaycanbeveryhelpful in troubleshootingand improvingmanagementpractices.
Air Inlet Design Considerations
Designofair inletsusedduringminimumandtransitionalventilationisveryimportantforachievinggoodmixingofcoolincomingandwarmin-houseair,withoutallowingcoldoutsideairtoflowdirectlyontobirds.Asmentionedearlier,thereareseveralvariationsinplacementoffansandinletsthatcanaccomplishthesegoals;thefundamentalprincipleistobringairinhighandathighvelocity.Adjustablehinged-doorinletsmountedhigharoundtheperimeterofthehouse(onsidewallsorinceilingopenings)havebeenfoundsuperiorinproducingtheairflowpatternneeded.Figure 22showsthedesiredairflowpatternachievedbyadjustableperimeterinlets,ascontrastedwithcurtainventilationinletarrangements.
Figure 22:Duringminimumortransitionalventilation,itisimportanttoavoidputtingcoldoutsideairdirectlyontheflock.Adjustableinletslocatedhigharoundtheperimeterofthehouseaccomplishthisgoal,directingairintothehouseabovebirdlevelsoitmixeswithwarmin-houseairbeforecontactingbirds.
The size of the opening is critical, and this varieswith the number of fans running and changes in static pressure.Manuallyadjusting these inlets toconsistentlymaintainproperairflow,however, isnext to impossible.Cool-weatherinletsactuatedbystaticpressuresensorsaccomplishproperadjustmentsautomatically,providingmuchbetterconditionsforbirdsthanwouldotherwisebepossible.Formoreinformationoninletmanagement,seepage 36.
Key Point
•Adjustablehinged-doorperimeterairinletshavebeenfoundsuperiorinproducingtheairflowpatternneededforminimumandtransitionalventilation.
Curtain Crack Fixed Board Crack Adjustable Perimeter Inlets
Making Good Ventilation Decisions Making Good Ventilation Decisions
Indian River Environmental Management in the Broiler House28
Indian River Environmental Management in the Broiler House29
Benefits of Using Stir Fans
Evenwiththebestmanagementofadjustableairinletstoprovidegoodairmixingduringminimumventilation,minimumventilationfansrunonlyafractionofthetime.Whenthefansareturnedoff,mixingofwarmerairintheupperpartofthehousewithcoolerairtowardsthefloorstops.Stirring(or,circulating)fansmountedinsidethehousecanhelppreventthistemperaturestratification,keepingyoungchickswarmerandhelpingremovemoremoisturefromthelitter.
Anotherincreasinglyimportanteffectofusingstirringfansistoreduceheatingfuelcosts.Wellinsulated,wellmanagedhouseswithadjustableairinletshavebeenfoundtoexperiencesomewherebetween15%and20%fuelsavings.Olderhousesoftenachievehigherfuelsavings,althoughthetotalfuelcostwillprobablystayhigherthanforawell-managedandinsulatedmodernhouse.Ahousewithconvectiveheatingand/orahigh-ceilinghousewouldexperiencethegreatestfuelsavings,sometimesashighas40%.
Bothpaddle(Casablanca-type)andaxialvanefanshavebeenfounduseful.Paddlefansusuallyworkbestintheup-draftmode.Axialfansaremountedalongthecentre-lineofthehouseandblowairhorizontally.Theaircirculationpatternsachievedandinstallationdetails(typicalforSoutheastU.S.)areshowninFigures 23 and 24.
Figure 23: Typicalinstallationdetailsandaircirculationpatternachievedbyaxialvanestirringfansina12mx152mpoultryhouse
Figure 24: Typicalinstallationdetailsandaircirculationpatternachievedbypaddlestirringfansina12mx152mpoultryhouse
24m 24m 24m 24m3m 3m
15m 15m 7.5m 7.5m15m 15m 15m23m 23m 15m
5 paddle fans in brood chamber
8m 8m15m15m15m 23m23m 15m 15m 15m
Making Good Ventilation Decisions
Indian River Environmental Management in the Broiler House28
Indian River Environmental Management in the Broiler House29
Key Points
• In-housecirculationorstirringfanscanhelpreducetemperaturestratificationandsaveonheatingfuelbillsduringminimumventilation.
• Bothaxialvaneandpaddle(Casablanca)typestirringfanshaveprovenusefulformixingin-houseairlayers.Paddlefansworkbestintheup-draftmode.
Evaporative Cooling: Foggers or Pads?
Pad cooling has becomemuchmore common than in-house fogging, primarily because pad systems are easier tomanage and do not risk wetting the house down. Evaporative pad systems also provide more cooling capability.However,aproperlydesigned in-house foggingsystemwithorwithout tunnelventilationcanbeveryefficientandeffectiveinsuitableclimatesifoperatedproperly.
Thedifficultywith in-house fogging is that ifmorewater isput into the air than it can absorb,waterdropson thebirdsandlitter.Afoggingsystemmustbemanagedsothatjusttherightamountofwaterisfoggedintotheairtogetmaximumcooling,butstayingjustthissideofwettingthehouse.Thiscanbeverydifficultandrequiresavigilantandactivemanager.Cloggingofnozzlesisalsocommon,requiringfrequentchecking.Waterqualitycanbeanissueandthesupplyforthesystemmustbefiltered.
Key Point
•Recirculatingpadevaporativecoolingsystemsprovidemorecoolingthanfoggingsystems,areeasierto manageanddonotriskwettingthehousedown.
Evaporative Pad Cooling: How much pad is needed?
Areasonablegoalistoachievethedesiredcoolingefficiencywiththeleastpadarearequired,andatthesametimekeephousestaticpressurefromrisingabove25Pa.ThemostcommonmistakemadeinpadECsystemsisnothavingenoughtotalinstalledpadarea.Thisforcesstaticpressuretoohigh,whichreducestheoutputofthefansbelowtheratedm3/hrwearecountingon.Nothavingenoughpadareaalsomeanslowercoolingefficiencybecauseairvelocitythroughthepadwillbetoohigh.Thelowertheairvelocitythroughawettedpad,thehigherthecoolingefficiency.
Notethattheairvelocitythroughcoolingpadsisnotthesameasthevelocitythroughahouse,orthevelocitythroughthetunnelinlets.Itisthecross-sectionalareaofthehousethatdeterminestheairvelocityaftertheairmovesintothehouse.Thepadareaalmostalwaysmustbelargerthanthehousecross-section,becausealowerairvelocityisneededthroughthepadsinordertoachieveadequatecoolingefficiency.Theformulafordeterminingthepadarea,assumingweknowtheinstalledfancapacityandthedesignairvelocityneededthroughthepadsis:
Manufacturersrecommendthatoptimumairvelocitythroughthepadsbeobtainedfromtestdata.
Key Point
• Acriticalfactorinachievingeffectiveevaporativepadcoolingwithoutexcessiveloadingoffansisto
haveanadequateinstalledpadarea.
Padarearequired(m2)
Installedtunnelfancapacity(m3/hr)
Recommendedairvelocitythroughpads(m/s)
= ÷
Making Good Ventilation Decisions Making Good Ventilation Decisions
Indian River Environmental Management in the Broiler House30
Indian River Environmental Management in the Broiler House31
Need for Backup and Fail-Safe Systems
Themoreenvironmentalcontrolahousehasthemoreneedithasforbackupsorfail-safestopreventcatastrophiclossesfromfailureofthecontrols.Inacurtain-ventilatedhouse,thereshouldbeathermostatwiredtoacurtaindropdevicewhichwilldropthecurtainiftemperaturegoestoohigh.Inafan-ventilatedhouse,curtaindropsalsomustoperateincaseofpowerfailure.Abackupgeneratorisessentialinmodernpoultryhouses.Itcannotonlypreventcatastrophebutkeepthesystemgoingandthebirdsperformingduringanoutage.Integratedcontrolsystemsalsomustbebackedupwithanindependentcontrollerthatallowsthemainsystemtooperateonlywithina“window”ofacceptableconditions,usuallyplusorminus5.5°C.Thecontrolsbackupmusthaveitsownindependentsensor,usuallyplacedmid-house.
Alarmsareneededtosignalproblemswithvariousfunctions,suchastemperature,power,waterpumpactivation,etc.Inadditiontoa localalarm,remotesignallingcapability isvaluable, includingconnectionthroughphonediallersandbeepers.One very useful alarm is built into static pressure actuated air inlet controllers. It senses and signals staticpressurevariations,andsinceitisindependentofthemaincontrolleritcanactasasentryontheprimarysystem.Allbackuporfail-safesystemsshouldbeasindependentaspossible;thatis,notsubjecttofailurebecauseanothersystemfailed.
Key Points
•Themoreenvironmentalcontrolahousehas,themoreitneedsbackupsandfail-safestoprevent catastrophiclossesfromfailureofthecontrols.
•Allbackuporfail-safesystemsshouldbeasindependentaspossible;thatis,notsubjecttofailurebecauseanothersystemfailed.
House Orientation
How a poultry house is placed on the land in respect to sun angle is important. The best house orientation foroptimum in-house conditions is with the roof ridge (long axis of the house) running at least approximately east-west. Inwinter thisallows the lowwinter sun tohit thesun-facingsidewall in themiddleof thedayandcontributeto house heating. In summer, when you want to minimise heat build-up, the mid-day sun is much higher in thesky, so the eave overhang keeps the sun from hitting the sun-facing side-wall for most of the day. The middaysun hits only the roof, which is typically the best insulated part of the house. Houses lined up more than 10-15degrees off east-west are likely to use more fuel in winter and need a higher summer ventilation rate and closerventilationmanagement.
Key Point
•Thebesthouseorientationforoptimumin-houseconditionsiswiththeroofridgerunningatleastapproximatelyeast-west.
Making Good Ventilation Decisions
Indian River Environmental Management in the Broiler House30
Indian River Environmental Management in the Broiler House31
Insulation Requirements
Thevalueofinsulationinsavingheatingfuelcostsiswidelyrecognisedinmoderateandcoldclimates.HouseswithatticspaceaboveaceilingshouldhaveatleastU=0.053W/(m2K)(R-19)insulationabovetheceiling.Open-trusshouseswithoutanatticshouldhaveatleastU=0.125W/(m2K)(R-8)insulationundertheroof,whichcanbeaccomplishedwith 38mmpolyurethane foamboard or 50mmpolystyrenebead-board.Neither foil-type reflective insulationnorreflective roof coatings have proven adequate when used alone in poultry houses, without batt, board or loose-fillinsulation. Any exposed insulationmaterialmust be robust enough towithstand regular cleaning and bird damage.Specialattentionmustbepaidtopreventingabsorptionofwaterintoinsulatingmaterials.
Inwarmerareas,managers sometimes feel insulation tobeunnecessaryanduneconomical.Whatmustbe realised isthatregardlessofthelocation,birdsmustbeprotectedduringthewarmseasonfromsolarheatradiatingdownfromanuninsulatedroof.ThisisconfirmedbystudiesintheU.S.Southeastinfan-ventilatedopen-trussbroilerhouses,identicalexceptforhavingornothavingunder-roofinsulation.Withoutsidetemperatureat33°C,temperatureintheinsulatedhouseranaround33.3°C,withnegligiblemortalities.Intheuninsulatedhouse,insidetemperatureranto37°Cwith14%mortality.
Heatradiatedfromanuninsulatedrooforceilingcanaddmoreheatthanisproducedbyanentireflockofsix-weekoldbirds.Ventilationsystems,evenwithevaporativecooling,cannotbeexpectedtohandlesuchanadditionalheat load.Radiantheat isespeciallydangerousbecause itgoesdirectly tothebirdswithoutdirectlywarmingthe insideair.It isonlyafterthebirdshavealreadyabsorbedthisextraheatloadthathouseairtemperaturestartstoriseandtheproblembecomesevident.Ifnootherinsulationalternativeispossible,foil-typereflectiveinsulationorreflectiveroofcoatingsmayprovidesomerelieffromradiantheat.
Key Points
•Insulationtosaveheatingfuelisessential;batt,board,andloose-fillinsulationaresuperior.
•Insulationundertherooforabovetheceilingisessentialinwarmweathertokeepsolarheatfromradiatingdownontotheflock.
Making Good Ventilation Decisions Making Good Ventilation Decisions
Indian River Environmental Management in the Broiler House32
Indian River Environmental Management in the Broiler House33
Keys to Managing a Modern Tunnel House
Tunnel ventilation was invented to provide growers with a tool to keep birds eating and gaining weight in warmto hot weather. The method has become so popular and the setup is so distinctive that houses with this setupare usually called “tunnel ventilated houses”, although they are operated in the tunnel mode for only part ofthe year. Tunnel ventilation is not needed in all climates, but is widely used in many poultry-producing regions.Forbasicsonhowventilationmodeswork,refertopages 16-21.
There are actually three basic ventilationmodes used inmost “tunnel” houses.Terminology used to describe theseventilationmodesvaries;forconvenienceinthispublicationwedescribethemas:minimummodeforcoldweatherandsmallbirds(brooding),transitionalmodeformoderateweatherandmedium-sizebirdswhenheatremovalisneeded,andtunnelmodeforadditionalcoolinginhotweather.
Managingamoderntunnelhouseyear-roundfortopbirdperformance(andagoodreturnontheinvestment)firstofallrequiresbeingabletojudgewhichventilationmodeisbestforthebirdsatanygivenmoment;andthenmakingthefine-tuningadjustmentstokeeptemperatureandotherairqualityfactorsasclosetooptimumaspossible.Integratedelectroniccontrolsystemsnowmakethemanagementjobeasier,sincetheycanautomaticallyswitchmodesandadjustventilationratesasconditionschange.However,eventhesmartestcontrollerisnotinfallibleandmustbemonitored.Evenmoreimportant,thecontrollersettingsthemselvesmustbedeterminedbyaknowledgeablehuman.Thereisjustnosubstituteforagoodpoultrystockmanwhoisinthehousefrequently,watchingthebirdsandmakingthecontroladjustmentstheyneedforbestperformanceandwelfare.
Key Point •Moderncontrolsreducemanagementlabourtimebutdonoteliminatetheneedforagoodmanager.
Which Ventilation Mode Is Needed?
Thekeytomakingtherightventilationmodedecisionisknowinghowmuch,ifany,heatneedstoberemovedfromthehouse,andwhetheroutsideairshouldbeallowedtoflowdirectlyoverthebirds.Thebasics:
Minimum Ventilation:
•Wedonotneedtoremoveheatfromthehouseanddonotwantoutsideairtocontactthebirdsdirectly. Eitherthebirdsaretoosmalland/oroutsideairistoocold.
•Fansareonatimer,notathermostat,andtheventilationgoalistopreventmoisturebuild-upandprovide freshair.
•Wewanttostayinminimumventilationaslongasitispossibletokeepbirdscomfortablethisway.
Key Point
•Maintainminimumventilationuntilthereisaneedtoexhaustheatfromthehouse.
Transitional Ventilation:
Startswhenbirdsgrowlargerand/oroutsideairgetswarmersothatin-houseairtemperaturerisesandwebegintoneedtoexhaustexcessheatfromthehouse.Weneedahigherairexchangerate.Butwestilldonotwantoutsideairtocontactthebirdsdirectly.
•The first stage of transitional ventilation is often simply by a temperature sensor overriding the timer to run theminimumventilationfans,andinsomesystemsbybringingadditional(non-tunnel)fansandairinletson.
Keys to Managing a Modern Tunnel House
Indian River Environmental Management in the Broiler House32
Indian River Environmental Management in the Broiler House33
•Evenmoreheatremovalcanbeaccomplishedbyusingtunnelfanstobringairinthroughsidewallairinlets(hybridtransitionalmode).
•Transitionalmodeshouldbemaintainedaslongaswecanadequatelyremovetheexcessheatfromthehouseinthisway.
Key Point
•Transitionalmoderemovesexcessheatbutkeepscoldairoffbirds.
Note:One common alternative description lumps minimum ventilation and transitional ventilation under the term “power ventilation.” The distinctions between timer-driven and temperature-driven ventilation on the one hand, and between non-wind-chill heat removal and wind-chill cooling on the other, are very important and are maintained by the terminology used here.
Tunnel Ventilation:
•Starttunnelventilationwhenbirdsneedcooling;airexchangewillnolongerkeepin-housetemperature fromrisingabovebirds’comfortzone.
•Weswitchtotunnelmodeonlywhenitisnolongerpossibletokeepbirdscomfortableusingthetransitionalsetup.Thatis,weneedtobecoolingthebirdsbythewind-chilleffectoftunnelventilation.
•Wehavetobeverycarefulinswitchingfromtransitionaltotunnelmodewhenbirdsareunderfourweeksold,becausetheyexperienceagreaterwind-chillandmaybestressedbythesuddendropintheeffectivetemperature.
•Wewanttobein(andstayin)tunnelonlywhenbirdsneedwind-chilltostayintheircomfortrange.
Importance of Staying on Target Temperature
Eachgivendayduringagrowout,theoperatorneedstoknowwhatthetargettemperatureshouldbeforthatday,andmanagetheventilationsystemtomaintainthattemperature.Maintainingoptimumtemperatureismostcriticalearlyinagrowout.Performancelossesinyoungbirdscannotbemadeuplater.It’sagoodideatopostthetargettemperatureonthewallbythecontrollereveryday.Forbroilers, theoptimumtemperaturetypicallystartsnear32°Condayoneanddropsgradually to around21°Cby the6thweek (Figure 25). Someone shouldbe comparing actual and targettemperaturesatregularintervalsthroughouteachdayofthegrowoutandmakingadjustmentsasneeded.
Figure 25:Thetemperatureatwhichbirdsmakebestuseoffeedtogainweightbeginsatnear32°Condayoneanddeclinestoaround21°Ctowardtheendofasevenweekgrowout,butforbestflockperformancemanagersshouldstrivetokeepactualin-housetemperatureswithin0.5-1.0°Cofthetargetuntiltunnelventilationisstarted,whentheeffectivewind-chilltemperatureiswhatmatters.
35
ºC
30
25
20
15
Days
0 7 14 21 28 35 42 49
Target Temperature
Example only: Exact optimum temp curve varies depending on feed, breed and sex.
Keys to Managing a Modern Tunnel House
Indian River Environmental Management in the Broiler House34
Indian River Environmental Management in the Broiler House35
Whatmattersiswhatisbeingexperiencedbythebirds,notbythemanagerorevenbyathermometer,especiallyonemountedonemetreabovebird level.All thermometers, thermalsensorsorthermostatsneedtotracktemperatureatbirdlevel.Further,whenahouseisswitchedintothetunnelventilationmode,thetemperaturethebirdswillexperienceisNOT the same as the thermometer reading. In the tunnelmode, themanagement goal is to keep the equivalenttemperatureontarget.Wedonotneedtoanddonotwanttolowerthethermometertemperaturetotargetifthebirdsareexperiencingwind-chill.Thisisespeciallyimportanttorememberearlyinagrowout.Itcanbedisastroustowind-chillstressyoungbirdsthatneedtofeelhighertemperaturesthanfully-featheredbirds.
Key Points
•Duringtunnelventilationthegoalistokeeptheeffectivetemperatureontarget–whatthebirdsfeel, notwhatthethermometersays.
•Wedonotwanttolowerthethermometertemperaturetotargetifthebirdsareexperiencingwind-chill.
Keys to Managing Minimum Ventilation
Thegoalofminimumventilationistomaintainairqualityduringanytimewhenitisnotnecessarytoexhaustheatfromthehouse.Thismeansbringinginjustenoughfreshairtoprovideadequateoxygenandtopreventmoisturebuild-upandammoniaproblems.
1 - It is imperative as long as birds are present to ventilate at least some minimum amount of time, no matter what the outside weather is, and even when there is no need to remove heat from the house.
Theamountofhouseheatlostduringproperminimumventilationisinsignificantcomparedwiththebenefitsgainedinbirdperformance.Evenwhenammoniaisnotanissue(aswithnewlitter),failuretoprovideadequatefreshairandtobreakupin-houseairstratificationcanbeverycostlyintermsofbirdhealthandperformance.OneresearchstudyintheU.S.,forexample,foundthatjusttwelvehoursofmildtomoderateoxygendeficiencyondayonecausedasignificantincreaseinascites(“waterbellies”)andreducedweightgainattheendofthegrowout.
It’s also important to realise there is no need to worry about moisture coming into the house during minimumventilation. Cold air can’t hold that much moisture to start with and as it is warmed by mixing with house airits relative humidity drops drastically. This enables the ventilation airflow through the house to absorb andexhaust excess moisture. We can and must operate minimum ventilation even when an all-day cold rain isfallingoutside.
Key Points
•Evenwhenheatremovalisnotneeded,ventilationisessentialtomaintainairquality.
•Househeatlostduringminimumventilationisinsignificantcomparedtothebenefitsgained.
2 - While air quality must not be sacrificed to save heating fuel, it is extremely important to keep young birds from being chilled.
Evenmild chilling during brooding results in decreasedweights and increased feed conversion, vaccine reactions andmortalities.Monitoringthermometersandthermostatsmustbesetatbirdlevelandoutsidecoldairmustnotbeallowedtoflowdirectlyontobirds.
Key Point
•Youngbirdsespeciallymustbekeptwarm;pre-heathouseandlitterbeforechickplacementandmonitortemperatureatbirdlevel.
Keys to Managing a Modern Tunnel House
Indian River Environmental Management in the Broiler House34
Indian River Environmental Management in the Broiler House35
3 - It is critical to pre-heat the house and litter before chick placement.
Placingchicksoncoldlitterwillhurtperformance.Agoodruleofthumbisthatlittershouldideallybeatleast30°Catthetimeofplacement.Thiscanonlybeachievedifbroodersarelit24hoursaheadofplacement.Ifconvectiveheatersarethesolesourceofbroodingheat,theyshouldbeturnedon48hoursbeforeplacement.Thecostsofnotpre-heatingareillustratedbyonepoultrycompanystudywhichfoundthatthebesttenflocksforlowestearly(sevenday)mortality,at0.7%,placedchicksonlitteratrecommendedtemperatures.Theworstten,whichplacedchicksonlitteraveraging22.5°C,experienced4.0%sevendaymortalities.
4 - Minimum ventilation should be operated on a five-minute timer. As birds grow larger and put out more moisture and heat, system on-time and/or number of fans on needs to be increased.
Usingafive-minutetimerprovidesshort(frequent)on-offcycles,whichresultinmuchbetteruniformityandconsistencyofhouseconditions.Usinga10minuteorlongertimingcycleallowshousetemperatureandairqualityconditionstoswingwidelybetweenextremes.Althoughaverageconditionsmaybethesameasforthefive-minutecycle,thebirdswillnotbeexperiencingconsistentlyoptimumconditions.Aruleof thumbfordeterminingtimersettings is that theminimumventilationrateneededforstartingchicksisabout0.047-0.094m3/sper1,000chicks,dependingonoutsideairtemperature.In-houserelativehumidityandlittermoisture,alongwithbirdbehaviour,serveasguidesinsettingtheminimumventilationrate.
Key Point
•Operatingminimumventilationonafive-minutetimerminimisestemperatureandRHextremesand
providesabetterrearingenvironment.
5 - A critical factor for successful minimum ventilation is making sure that incoming cold air mixes uniformly with, and is warmed by, in-house air before coming in contact with the birds.
Adjustableperimeterairinletsoperatedbystaticpressure-sensingcontrollersarebyfarthebestwaytoaccomplishthisonaconsistentandcontinuingbasis.Iftheinletareaisnotadjustedproperlyaccordingtothefanm3/hrbeingused,eithertheventilationratewillbechokeddownbelowwhatisneeded,orincomingcoolairislikelytofalldirectlytoandchill-stressthebirds(Figure 26).
6 - The switch to transitional ventilation mode comes when birds are producing too much heat for the minimum ventilation fans to cope with.
Thecoolertheoutsideairandtheyoungerthebirds,thelongerittakestogettothepointwhereventilationmustbeswitchedfromminimumtotransitionalmode.Thewarmertheoutsideairandthelargerthebirds,thesoonerwewillneedtoswitch.
Key Point
•Switchtotransitionalmodeonlywhenheatremovalisneededandminimumventilationcannotkeepbirdscomfortable.
Keys to Managing a Modern Tunnel House Keys to Managing a Modern Tunnel House
Indian River Environmental Management in the Broiler House36
Indian River Environmental Management in the Broiler House37
Keys to Managing Transitional Ventilation
Thegoaloftransitionalventilationistoexhaustenoughheattokeepthehousetemperaturewithinthebirds’comfortrange,whileatthesametimenotallowingoutsideairtoflowdirectlyontothebirds.
1 - To be successful with transitional ventilation, it is essential to have the sidewall inlets on a static pressure controller.
Itisverydifficultorimpossibletomanuallyadjustthesizeoftheinletopeningstokeeptheproperstaticpressureasthenumberoffansrunningchanges.
2 - We never want to switch to tunnel ventilation while it is still possible to maintain bird comfort in transitional ventilation mode.
Asbirdsgetolderandgiveoffmoreheatperkilogrammeofbodyweight,orasoutsideweathergetshotter,wemustgetridofmoreandmoreheatfromthehouse.Forlargebirdsinawell-designedhouse,iftheoutsidetemperatureismorethan5.5°Ccoolerthantheinsidetarget,thenweshouldbeabletomaintaintargettemperaturewithtransitionalventilation. We should not be using tunnel ventilation. If birds are smaller, we should be able to maintain targettemperature with transitional when there is even less than 5.5°C spread between inside and outside temperature.Switchingintotunnelmodetoosoonisalsolikelytoproducealargetemperaturedifferencefromoneendofthehousetotheother,whichwillhurtflockperformance.
Key Point
• Switchingfromtransitionaltotunnelventilationtoosooncanhurtbirdperformanceseverely.
3 - There is no problem with switching from one ventilation mode to another, minimum, transitional or tunnel, as conditions change.
Aflockmayneedtransitionalventilationduringthenightandintheearlymorning,butsomeformoftunnelduringtheheatoftheday.Thequestionis,whatwillkeepthebirdsperformingbest?
4 - In judging the time and need to switch to tunnel, we must keep the wind-chill effect in mind.
Ifweareusingmaximumtransitionalventilationcapacity–running,say,fourtunnelfansandswitchintotunnelmode,thebirdswillexperienceadropinthe“equivalent”or“effective”temperature,whichmaybequiteabitlowerthanthethermometerreading.Whenbirdsareyoungerandmoresensitivetowind-chill,theeffectivetemperaturedropmaybedifficultforthemtocopewith.
Keys to Perimeter Inlet Management
In bothminimum and transitional ventilation, achieving proper airflow through the perimeter air inlets is essential.Inlets control direction of air movement and affect the velocity of air entering the house, and thus air mixing. Incoldweather, inletsarethetooltohelpblendcoldoutsideairwithwarminsideairtosavefuelandmaintainprecisetemperatures.Goodinletmanagementpreventsallthehotairfrombeinginthetopofthehouse.Inhouseswithpoorinletmanagement,asmuchas8-11°Cdifferenceinfloorandceilingtemperatureareobserved.Goodinletmanagementcankeepthistemperaturedifferenceto3°C.
Key Point•Incoldweather,perimeterairinletsarethetooltohelpblendcoldoutsideairwithwarminsideair.
Good inletmanagement also saves fuel costs.Houseswithpoor airmixingwill use20-25%more fuel. In addition,the combination of temperature and air quality from day one is probably the most significant factor in broilerflock performance. Extreme temperatures can be devastating during the brooding period especially. Too cold
Keys to Managing a Modern Tunnel House
Indian River Environmental Management in the Broiler House36
Indian River Environmental Management in the Broiler House37
conditionsdramaticallyimpacttheabilityofyoungbirdstogetadequatefeedandwater,andifearlygrowthisslowedtheperformancelossescannotbemadeupduringthelifeoftheflock.Propermanagementofairinletstoprovidebirdsthetemperatureandairqualitytheyneedisabsolutelyessential.
Key Point
•Properperimeterinletmanagementcancutheatingfuelbillsbyasmuchas20%.
1 - Inlet management starts with making sure the house is tight, with no air leaks around doors, curtains, torn insulation, etc. to rob from the inlet air stream.
2 - The next step is to make sure inlets are opening properly. The size of the inlet openings must be set so as to achieve both the static pressure desired and the airflow “throw” needed (Figure 26).
Forperimeterinletstoflowairproperlytheymustopenaminimumof5-7.5cmforasidewallinletor2.5-4cmforaceilinginlet.Inletsopenedbeyondthe“fullyopen”position(openingattipofboardequaltoinletthroatopening)don’tincreaseairflow.Toowideboardopeningstendtodirectairdownwardtowardsthebirds.Therightairflowhappensonlywiththerightamountofinletopening.
Key Point
•Sidewallairinletsshouldopenatleast5-7.5cmandceilinginlets2.5-4cmtoprovidegoodairflow.
3 - Use a static pressure-operated controller to operate air inlets.
Managinginletsmanuallyisawell-nighimpossiblejob.Eachtimeafancameonandwentoffaninletopeningadjustmentwouldneedtobemade.Thestaticpressurecontrolsensesthestaticpressureinthehouseandthenopensorclosestheinletstoachievetheproperopeningthatwillproducethestaticpressuredesired-andthusproducetheairflowpatterndesired.Thesemachinesworkverywellandhavegreatlybenefitedourindustry.
4 - The number of air inlets allowed to operate must be matched to the total fan capacity being used.
Decidinghowmanyoftheinstalledinletswillactuallybeusedisoneaspectofinletmanagementthatdoesneedtobetakencareofmanually.A typicalbroilerhousewillhaveenough inlets installed tohandlehalf the total installed fancapacity,butwhenonlyoneortwofansarebeingused,asinbrooding,wealsoneedtocutbackonthenumberofinletsthatwillopen.Thereasonforthis is that if toomany inletsareoperatingfor thenumberoffansrunning, thestaticpressuremachinewillhavetochoketheinletopeningsdowntoofarinordertomaintainstaticpressureandtheairflow“throw”neededwillnotbeachieved.
Withallinletsinuse,runningonlyone122cmfanresultsinthestaticpressuremachineopeningtheinletsonlyabout0.5-1.5cm,andtheairbarelyleaksintothehouseattheinletsandthenfallstothefloor.Inthissituation,properairmixingcannothappenbecausethereisnorealairstreamwithanyairvelocity.Thisleadstowetlitter,highhumidity,ammonia,highfuelusageandpoorairquality.Thekeyistomatchthenumberofinletsinusetothefancapacitythatwillbeusedduringagivendayorperiodofthegrowout.
Togetgoodairflowduringtheearlydaysofagrowoutwhenusingonlyone122cmfan(ortwo91cmfans)inhalf-housebrooding,weusuallyneedtolatchclosedeveryotherinletinthebroodchambers(andalltheinletsinthegrowoutend).Thisallows15evenlydistributedinletsinthebroodchambertorespondtotheinletmachine.Wewouldunlatchmoreinletsinthebroodchamberonlyiftherewasneedtorunadditionalfans.Afterturnout,moreinletsinthegrowoutendareunlatchedasmorefansareused.
Agoodruleofthumbinatunnelhouseistohaveabout15operatinginletsforeach122cmfanthatwillbebroughtonduringthatphaseofthegrowoutorthatprevailingweather.
Key Points
•Thenumberofairinletsallowedtooperatemustmatchthetotalfancapacitybeingused.
•Aruleofthumbistohaveabout15operatingperimeterairinletsforeach122cmfanbeingused.
Keys to Managing a Modern Tunnel House
Indian River Environmental Management in the Broiler House38
Indian River Environmental Management in the Broiler House39
5 - Avoid having any obstructions to airflow being placed directly in the air stream from the inlet.
Waterlinesandelectricalconduitareoftenstrappedtotheceilingrightinthepathofairflowfromtheinlets.Whentheairflowstreamhitssuchanobstructionitbreaksupanddriftsdownward.Thisdefeatsthegoalofhavingahigh-velocityairstreamflowingsmoothlyalongtheceilingtothecentreofthehouse.
Figure 26:Correctandincorrectairinletopenings
Keys to Managing Tunnel Ventilation
The goal of tunnel ventilation is cooling. We are in the tunnel mode only when it is no longer possible to keepbirdscomfortablebyremovingheat fromthehouse.Theyneedthewind-chilleffect;and inhotterweather, therealtemperaturereductionofevaporativecooling.
1 - Success in managing tunnel ventilation depends on understanding effective or equivalent temperature produced by the wind-chill effect.
Todetermineeffectivebirdtemperature,youmusttakethein-housethermometerreadingandsubtractthenumberofdegreesofwind-chillcoolingyouestimatethebirdsareexperiencing.Determiningequivalenttemperatureisnotanexactscience.Thefelttemperatureisverymuchaffectedbybirdage(thatis,featheringandbodysize)andthespeedoftheair.Otherthingsbeingequal,theeffectivetemperaturedropwillbe:
•Greaterforyoungerbirds,lessforolderbirds.
•Greaterforlowertemperatures,lessforhighertemperatures.
Thewind-chilleffectdecreasesasweapproach35°Candcompletelygoesawayasweapproach38°C.
Key Point
•Wind-chilleffectdependsmostofallonbirdageandairvelocity.
2 - Extreme caution should be exercised when tunnel ventilating young birds.
Theeffectofwind-chillonfourweekbirdsmaybedoublethatforsevenweekbirds.Growersoftengetintotroublewhentryingtotunnelventilateyoungbirdswhentheweatheristoocold.Butunderextremelyhotconditionsitmaybenecessarytoventilatedayoldbirdsusingtwoorthreetunnelfans.
3 - To determine the wind-chill effect in a given situation, you must observe the birds’ behaviour to pick up any signs of their being too warm or too cool.
Thereisnowaytopredictorcalculateexactlywhatthewind-chilleffectwillbe.Thekeysignsofbirddiscomforttolookforare:
Forbestairflowandmixing,sidewallinletsshouldopen5-7.5cm
Ceilinginletsshouldopenatleast2.5cmintheclearforproperairflowpatternandmixing
Toosmallopeningsdonotallowadequateairflowor“throw”
Fullyopenairinletallowsmaximumairflowbutreducesairvelocityand“throw”
Toowideopeningdirectsairdownward,givesnoaddedairflow
Pipes,wiresorductsonceilingbreakupairflowanddirectairdownward
20 cm board opening
20 cm throatopening
Keys to Managing a Modern Tunnel House
Indian River Environmental Management in the Broiler House38
Indian River Environmental Management in the Broiler House39
• Whenbirdsaretoowarmtheymigratetocoolerorhigherairflowareas,holdfeathersclosertothebody,drooporlifttheirwingstogetmoreaircooling,drinkmoreandeatless.Iftheystopeatingandbeginpanting,andespeciallyifnormallypinkskinareasturndarkred,theyaredefinitelygettingover-heated.
•Whenbirdsaretoocold,theytendtogotothefloortotrytoavoidthecoolairstream,moveawayfromthedirectionofairmovementandhuddletogether,and“fluff”featherstoincreasetheirinsulatingvalue.
4 - It can be very helpful to develop guidelines for using tunnel ventilation based on your situation and experience.
Thefollowingaresomeexampleguidelinesforjudgingwhetheryoushouldbeintunnelortransitionalmode.Thesearegeneralguidelinesonly,andmustbecheckedagainstbirdbehaviour.
•Iftheoutsidetemperatureislessthan21°Candbirdsarefourweeksold,stayintransitionalmode.
•Iftheoutsidetemperatureis18°Candthebirdsarebetweenfiveandeightweeksold,stayintransitionalmode.
•Iftheoutsidetemperatureis15.5°Corlowerandthebirdsareeightweeksold,stayintransitionalmodeventilation.Thefactis,ifit’stoocoldoutside,tunnelventilationhurtsratherthanhelps.
•Undernormalconditionswithfully-featheredbirds,don’tconsiderrunning intunnelmodewithfewerthanhalfofyourtunnelfans.Thishasmoredrawbacksthanbenefits,especiallyregardingtemperatureuniformity.Ifyoucandothejobwithfewerthanhalfofthefans,stayintransitionalventilationmode.
Key Point
• Ifitiscooloutside,tunnelcanhurtmorethanithelps;birdageisthecriticalfactor.
5 - Monitor the temperature difference in the house from inlet end to fan end. This can indicate two different things, depending on the situation:
•Duringtunnelinhotweather,atemperaturedifferencemuchgreaterthan3°C(normal)canindicateinsufficientairfloworairleakslettinghotairintothehouse.Inthissituation,checkairvelocityandlookfordirtyfans,huttersand/orpads,andforopendoorsorotherleaks.
•Incoolerweatherwithsmallerbirds,amorethan3°Crise in temperaturefromoneendof thehousetotheotherduringtunnelventilationmay indicateyoushouldbe intransitionalventilation,nottunnel.Undertheseconditions,thetemperaturerisefromoneendofthehousetotheothermaybetellingyouthattheincomingairistoocoldandasitpassesthroughthehouseispickingupmoreheatthanisdesirable.Youdon’texperiencethiswithtransitionalventilationbecausetheairiscominginuniformlythroughtheperimeterventsallaroundthehouse.
Key Point
•Endtoendtemperaturedifferencecanindicatepoorairflow,ortheneedtobeintransitional,nottunnel ventilation.
6 - Migration fences should be installed as soon as we move from the brooding phase to full house ventilation.
Whenusingtunnelventilationforcooling,birdswilltendtomovetowardandcrowdintothecooler,inletendofthehouse.Migrationfenceswillkeepthemspreadout.Keepingbirdsuniformlyspreadoutensuresconditionsforgrowtharethesamethroughoutthehouse.Properlyinstalledfencesarevitalfortheproperoperationoftunnelhouses.Fencesmustbeconstructed45-60cmhighandallowairtopassthroughthefencetoallowgoodaircirculationaroundbirds.
Keys to Managing a Modern Tunnel House Keys to Managing a Modern Tunnel House
Indian River Environmental Management in the Broiler House40
Indian River Environmental Management in the Broiler House41
Key Point
•Usingmigrationfenceskeepsbirdsspreadoutandensuresconditionsforgrowthareuniformthroughoutthehouse.
7 - If you see any sign of birds being too warm during full tunnel ventilation (and the system is operating properly), it’s time to turn on evaporative cooling. However, on any day when the temperature is expected to go at least into the 32°C range, it may be best to turn on evaporative cooling before getting to the point where all tunnel fans are running.
Seemoreexplanationofthisissueinthenextsection.
Key Point
• Turnonevaporativecoolingbeforebirdsbegintofeelheatstress,andbeforereachingfulltunnel(allfans).
Keys to Managing Tunnel and Evaporative Cooling
Thegoalofevaporativecoolinginamoderntunnelbroilerhouseistoworkincombinationwithwind-chillcoolingtokeepbirdsinorneartheircomforttemperaturezone.Evaporativecoolingextendstherangeofconditionsunderwhichwecangettopperformancefrombirds.Anevaporativecoolingsystemdoesnothavetolowertheairtemperaturetotheactualtargetthermometerreading–itonlyhastogetitintotherangewheretheaddedeffectivetemperaturedropproducedbythetunnelairflowwilldothejob.
Forexample,ifitis35°Coutsideandwecanget7°Cofevaporativecoolingfromoursystem,therealairtemperaturecoming into the house is 28°C. If thewind-chill effect from the 2.54m/s air velocity is another 6°C, the effectivetemperaturefeltbythebirdswillbe22°C–veryclosetooptimumforfully-featheredbirds.
Key Point
• Evaporativecoolingonlyneedstolowerthermometerreadingtorangewherewind-chillcankeepbirdscomfortable.
1 - Evaporative cooling should be turned on or programmed to come on before birds begin to feel heat discomfort.
Forfully-featheredbirds,thismaybeinthe27-29°Cairtemperaturerange.Itiseasierandbettertokeepheatbuild-upfromhappeninginahousethanitistoreducetheheatloadafterithasprogressedtoofar.
2 - Evaporative cooling does not have to be delayed until we are in full tunnel and running all fans.
Running,saysixofeightfanswithevaporativecoolingoncanbeespeciallybeneficialtoyoungerbirds,whicharemoresensitivetowind-chill.Usingfewerfansreducesthewindspeed,andevaporativecoolingismoreefficientwhenrunwithslowerairspeed,sothatyoucangetthesameeffectivecoolingatlowercost.
Key Point
• Turningonevaporativecoolingwithlessthanallfansrunningiseconomicalandcanhelpyoungerbirds.
3 - A good rule of thumb is that evaporative cooling systems should not be used when the relative humidity is above 80%, which in many locations includes after dark or before 9 a.m.
Keys to Managing a Modern Tunnel House
Indian River Environmental Management in the Broiler House40
Indian River Environmental Management in the Broiler House41
Nighttimetemperaturesusuallydropsignificantly,andinmanyareashumidityduringnighttimehoursmaybesohighinsummerthatalmostnocoolingwillbeexperienced.Ontheotherhand,thereisrarelyhighenoughrelativehumidityduringahotsummerdayinmostregionstonecessitateturningoffproperlystagedfoggersorpads.Evaporativecoolingdoes littlegood if therelativehumidity ismuchover80%.However,asawarmdayprogressesandair temperaturesincrease,thecoolingwecangetfromevaporativecoolingalsoincreases.
Key Point
•Ruleofthumb:Donotrunevaporativecoolingafterdarkorbefore9a.m.
4 - Pad cooling systems work well only when all incoming air goes through a completely wetted (and clean) pad – which means it is especially important to properly maintain and monitor the system and the house. No doors can be open or any air leaks permitted. Side curtains must fit tight against the house. Water pumping rates must be right and pads must not be allowed to clog. Reducing the number of on-off cycles helps, as does allowing pads to dry out completely during the night, turning the water off but keeping fans on.
Key Point
•Goodmaintenanceisespeciallyimportantforsuccessfulevaporativecooling.
Management Includes Monitoring
Probablythehardestpartofdoingventilationrightisthatyoucan’tusuallyseeairmovement.Birdbehaviouristhefirstandmost important itemtomonitor. Ifbirdsareeatinganddrinkingnormallyanddistributedevenly throughthehouse,they’reokay.Iftheyaren’t,youhaveaproblemtoinvestigate.It’salsoimportanttokeepwatchonotherkeyindicators.Monitoringtemperature,airmovement,relativehumidityandstaticpressurecanshowyouexpensiveproblemsyouweren’tawareofandhelpyouheadoffproblemsbeforetheyoccur.Herearesomewaystokeepwatch:
Key Point•Monitoringjob1:watchbirdbehaviour.
Temperature
•The large dial thermometers seen inmost houses are convenient but inaccurate. High/low recordingmercurythermometersaremoreaccurateandallowyoutoseeandkeepa logoftemperatureupsanddowns.Recording(“datalogging”)thermometersandhumidistatsprintoutarecordoftemperatureorhumidityswingsinthehouse,whichcanbeextremelyvaluable.
•Mountthermometershighandlowinthehousetoseehowmuchair/temperaturestratificationyouhave.Thecriticalreadingisthetemperaturewherethebirdsare.Youneedatleastthreethermometersatbirdlevel:atthefront,atthemiddleandattherearofthehouse.
•Handhelddigitalthermometer/humidistatcombinationsarenottooexpensive,arefastreactingandcanbeusedtocalibratemercuries.
•Aninfraredthermometershowsyouthetemperatureofanysurfaceyoupointitat,nottheairtemperature.Thesearemoreexpensivebutcanshowupexpensiveproblemsyoumightotherwisemiss,suchasceilinginsulationbreaks,coldfloors,overheatingmotorsorcircuitbreakers,etc.
Key Points
•Temperatureisextremelyimportant:investingoodthermometersandputthemintherightplaces.
•Aninfraredthermometerhelpsspotanumberofdifferentkindsofproblems.
Keys to Managing a Modern Tunnel House Keys to Managing a Modern Tunnel House
Indian River Environmental Management in the Broiler House42
Indian River Environmental Management in the Broiler House43
Air Movement
• Simple to use, accurate and affordable airspeed meters are now available. These electronic gadgets are not tooexpensiveandareaccurateenoughtobeuseful.Ahandheldmodelthatincludesathermometerisespeciallyusefulandconvenientforsurveyinghouseconditions.
•Strategicallyplacedlengthsoflightribbon,likesurveyor’sflags,areusefulairflowindicators.Generallyyouwantthemalongtheceilingandatbirdlevel.Aflutteringstreamerdoesnottellyouthatairmovementatthatplaceisperfectlyok,justthatthereissomeairmoving.Astreamerhangingstillwhenitshouldbeflutteringdefinitelysignalsaproblem.
Key Point •Airspeedmetersandstreamerstakealotoftheguess-workoutofventilationmanagement.
Relative Humidity
• Monitoring relativehumidity also requires some instrumentation.There isnowayyoucan“feel” relativehumiditydifferences thatcanspell lossofbirdperformance if theycontinue.Toeasilycheck relativehumidity trendsupordown,useaninexpensivedigitalrelativehumiditymeter(humidistat),accuratetoabout+/-5%.Ahigh-accuracydigitalcostsmorebutisaccuratetoabout+/-2%.Again,youwanttoknowwhat’sgoingonatbirdlevel,sogetdownwiththebirdstomakeyourchecks.
Static Pressure
• Monitoringstaticpressureovertimeandingivenconditions isespeciallyusefultospotproblemssuchasair leaks,shuttersnotopening fully,declining fanperformanceetc.Easy touseand inexpensivehand-heldorwall-mountedmanometersareavailable.Magnehelictypemetersareslightlymoreexpensivebutalsomoreaccurate.
Key Point• Astaticpressuremeterhelpsspotairleaks,shutterproblems,poorfanperformanceandmore.
Note: Get expert help wherever you can. Company service personnel, consultants, and university specialiits (where available) will have, or have access to, good monitoring equipment. They can give advice, help you check your house periodically and show you how to do it all yourself.
Keys to Managing a Modern Tunnel House
Indian River Environmental Management in the Broiler House42
Indian River Environmental Management in the Broiler House43
AirVelocity
Helpful Conversion Factors
Following are approximate Imperial (English) to metric and metric to Imperial (English) conversion factors formeasurementsandunitscommonlyencounteredindiscussionsofcommercialpoultryhouseenvironmentalmanagement.
Area Insquarefeet÷10.76=squaremetresInsquaremetresx10.76=squarefeet
Airflow Incubicfeetperminute÷2119=cubicmetrespersecondIncubicmetrespersecondx2119=cubicfeetperminute
StaticPressure Ininchesof waterx249=PascalsInPascals÷249=inchesof water
Volume Ingallonsx3.785=litres Inlitres÷3.785=gallons
Heat InBTU’sx1.055=kilojoulesInkilojoules÷1.055=BTU’s
HeatLoss
InBTU’sperhourperpoundx2.323=kilojoulesperhourperkilogramme
Inkilojoulesperhourperkilogramme÷2.323=BTU’sperhourperpound
Length
Ininchesx2.54=centimetresIncentimetres÷2.54=inchesInfeetx0.305=metresInmetres÷0.305=feet
Weight Inpounds÷2.2=kilogrammesInkilogrammesx2.2=pounds
LightIntensity Inlux÷0.093=foot-candlesInfoot-candlesx10.764=lux
Infeetperminute÷197=metrespersecondInmetrespersecondx197=feetperminute
Keys to Managing a Modern Tunnel House Helpful Conversion Factors
Indian River Environmental Management in the Broiler House44
Indian River Environmental Management in the Broiler House45
Measurement Units Conversion Table
NOTEIn converting temperature differences or intervals, the +/-32° constant is not used. For example, a 15°F interval equals an 8.3°C interval: 15 (F) ÷ 1.8 = 8.333 (C)
CelsiustoFahrenheit1.8°C+32
°F
105
100
95
90
85
80
75
70
65
60
55
50
45
40
35
30
25
20
°C
40.56 40
37.78 35
35.00 30
32.22 25
29.44 20
26.67 15
23.89 10
21.11 5
18.33 0
15.56 -5
12.78 -10
10.00
7.22
4.44
1.67
1.12
3.90
6.68
°C
104
86
°F
95
77
68
59
50
41
32
23
14
FahrenheittoCelsius(°F-32)÷1.8
Measurement Units Conversion Tables
Indian River Environmental Management in the Broiler House44
Indian River Environmental Management in the Broiler House45
NotesMeasurement Units Conversion Tables
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Indian River Environmental Management in the Broiler House46
Indian River Environmental Management in the Broiler House47
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Notes
Indian River Environmental Management in the Broiler House46
Indian River Environmental Management in the Broiler House47
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Notes Notes
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