Indian River Environmental Management in the Broiler House

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Environmental Management in the Broiler House

Indian River Environmental Management in the Broiler House2


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



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



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

l Met

abol

isabl

e E

nerg

y

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



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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-1 1 2 3 4 5 60

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Cen

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Deviation from Ideal Temperature ºC

Target Temperature

Target

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Introduction Introduction



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



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



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




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



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




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.



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






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



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



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



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.




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.




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



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




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



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.




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




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



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.




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


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


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

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m3 /

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per

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t Eff

icie

ncy

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0.00 12.5 25.0 37.5 50.0


Direct-drive 122 cm fan with aluminium shutter and guard airflow, ratio 0.71


Direct-drive 122 cm fan with aluminium shutter and guard, airflow ratio 0.71




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

pera

ture

(°C

)

29

28

27

26

25

24

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Timea.m. p.m.

10.00 11.00 12.00 1.00 2.00

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Integrated electronic controller +/-1.1ºC

Manual mechanical thermostats+/-3-4ºC




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




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




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)

= ÷




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.




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.




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.




•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.




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.




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



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




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.




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




• 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.




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.




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.




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.




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



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



NotesMeasurement Units Conversion Tables

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Notes Notes

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Everyattempthasbeenmadetoensuretheaccuracyandrelevanceoftheinformationpresented.However,Aviagenacceptsnoliabilityfortheconsequencesofusingtheinformationforthe

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Forfurtherinformation,pleasecontactyourlocalAviagenTechnicalServiceManagerortheTechnicalDepartment.

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