Understanding Humidity in Ice Rinks June2014 - comfort level in the cool arena is easily lost, when…
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Understanding the Impact of Humidity in an Ice Rink
The Ontario Recreation Facilities Association Inc. (ORFA) regularly researches and writes about issues that could affect our clients. These documents provide an opinion on key risk management issues but are not meant to provide any form of legal opinion or
official interpretation. No one should act on such information without appropriate professional advice after a thorough examination of the particular situation. All rights reserved. 2014 Ontario Recreation Facilities Association Inc.
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IntroductionLike humans, a buildings health is directlyrelatedtoairquality.Failingtocontrolmoisturetrapped in the airwill dramatically reduce thelifecycle of the materials used duringconstruction. Further,moisture will impact icequalityandpatronsatisfaction.Anicetechnicianmust understand how the air and moisturefound in an ice rink can influence the sportplayed and the amount of maintenance andupkeep that will be required to maintain ahealthyfacility.Understanding Ice Rink Comfort Level vs.ProperOperationalConditionsWhen a patron arrives at their local rink on awarmspringday,theirfirstimpressionistherinkiscool(1014Cdb/5055F).Ifthaticerinkhasa wellcontrolled humidity level that samepatron will be comfortable. The cooltemperatureistheresultofthelargeicesurfacethatdominatesthesquarefootageofthearenaspace. While the iceplant constantly removesheat from the ice floor, the cold ice surfaceaboveitcoolsotherssurfacesaroundandaboveit (called radiant heat transfer). All the coolsurfacesbringdown the arena air temperaturethroughconvectiveheattransfer.Thecomfortlevelinthecoolarenaiseasilylost,whenthemoisture/humidity level (wecallthelatent heat) in the arenas air is not properlycontrolled.Patronswillnowperceivetheindoorenvironment tobedamp. Radiantheaterscancompensate for some of the discomfort fromthisdampair,butthishighhumiditystillcausesconcernswithpotentialbuildingdamageaswellasareductioninoperationalefficiency.One of the more accurate and reliablemethodsformeasuringhumidityistoreadthe
dewpointlevelintheair.Theeasiestchecktosee if moisture is going to condense on asurface is tomeasure the temperatureof thecoldsurfaceandcompareittothearenasdewpointlevel.Ifthedewpointhasclimbedabovethecoldsurfacestemperaturemoisturewillcondense on the surface causing problemssuch as drips and moisture damage. Thiscondensationthatformsfromahighdewpointisverymuch likethedripsthatformonacoldglassonahotsummerday.Itsnotuncommontomeasuretemperaturesof42 F (5 C) on the steel beams directly abovethe icesurface. Ifthedewpointhasreachedalevel above that surface temperature,condensation will occur. When enoughcondensationoccursonthebeams,dripsstarttoformontheice.Iceplantoperationandefficiencyisimpactedbydewpointaswell. Whenthedewpointclimbstoo high above the freezing point, unwantedfrostwillformontheicesurface.Thismoisturethat condenses on the ice from the highhumidity in the air creates an additionalrefrigerationloadontheiceplant(calledalatentheat load). Adewpointashighas45 F, cancausetheequivalentofanadditional32tonloadontheiceplant(ref.2006ASHRAERefrigerationCh35airat55Fdb,iceatsurface22F).Sowhatcausesthesehighhumiditylevelsortooa high dew point level in an ice arena. Thelargest contributor is the movement ormigration of outdoor humidity into the rink.Moisturecomesthroughanyopeningintherinkand of course the fans that ventilate fresh airthat are full ofhighhumidity. Warm air canholdhighlevelsofmoistureandwarmhumidairalsohasahighvaporpressure. Forexamplea
Ontario Recreation Facilities Association Inc. T. 416.426.7062 F.416.426.7385 2
springday that is20 C (68 F)and60%RHhasdewpointof10C(50F). The indoorarena istrying tohold the conditionsata60%RH levelbutata50Fdblevel,whichhasalowdewpointof 2.6 C (37 F). The high outdoor vaporpressure (or dew high dew point) will pushthroughanyopeningorcrackintotherinkthatisatthe lowervaporpressure(ordewpoint). Soinotherwords,wehave thiswarmoutdoorairat60%RHthatisaddingmoisturetothecooldryair inside the rinkandwhen leftunchecked (ornot dehumidified), themoisturemigrating intothe rink will eventually raise the dew pointinside. It is this large difference between thehigh outdoor and low indoor dew point thatalerts the building operator to potentialmoisture concerns. In periods of low or nooccupancy thehigh indoorhumidity in thecoolairwillformfogovertheicesurface.Sohowcanwecontrol thedewpoint inan icearena?Weknowthathighoutdoorhumidityaswellastheinternalsourcesofhumidity(skaters,spectators, iceresurfaces)areconstantlyaddinghumidity that will raise the humidity level ordewpoint,weneedtocounteractthesesourcesofhumiditywith thecorrectcapacityofdryair.Thedryordehumidifiedairmustbe introducedtothearenawithadewpointthatislowerthanthe design humidity level of the arena space(referencetheNHLforadesignlevel=35to40Fdewpoint) Inotherwords ifadewpointof3C(38F) is to be maintained, the dehumidifiermust introduceairatadewpointof1C (33F)orlower.Dehumidificationsystemsthatincludedesiccantscaneasilyconditionairdowntoalowdew point. If the facility requires largecontinuous levels of ventilation air, theventilation systems should include desiccanttechnologyaswell.HistoryofDehumidificationinIceRinksThe first generation of arenas were built toprovide a comfortable indoor environmentfrom the harsh cold outdoor conditions forskatersandspectatorsalike.Icewasputinforamuchshorterseason.Mostoftheoperatinghours were the cold winter months where
humiditywas not a concern. In fact in thecoldest days, a buildup of indoor humidityinside the building would find its way outthroughmanyof themanyof theopenings inthe building (remembering the indoor vaporpressure would now be higher than theoutdoorvaporpressureinwinter).SomeoftheoldestarenasinOntariohaveonlyrecently been modernized with the properdehumidification capacity to handle a longerseason of ice operation (e.g. Maple LeafGardens and Varsity Arena). Up until 1963,theStanleyCupfinalswerefinishedupbythethirdweekofApril. With theNHLexpansionof teams after 1967, the Cup finished up inmidMay.AstheendoftheNHLseasonmovedlaterintothespring,humiditybecameabiggerfactor. The thirdgameof the1975cup finalsheld inBuffaloonMay20th,madehistory fortheuncontrolledheavyfogintherink.ThenewBuffalo rink has retrofitted leading edgedehumidification equipment tomaintain idealconditions and shouldneverencounter fog inhighhumidityconditions.As demand for ice time increased at therecreational level as well as the demand foroffseason practice camps, tournaments andsummerleagues,humidityissuesbecamemoreapparent. Anearlyattemptatremovingtheformation of fogwasmoving air over the icewith fans. Unfortunately this caused moreproblemswith the icequality. Exhaustingaircontinuously was tried but unfortunately theairthatreplacedtheexhaustedair(orwhatwemight call make up air), was not treated ordehumidified properly and just made a badsituationworse.Tooffsettheformationofcondensationontheglass, refrigeration based dehumidifiers weredeveloped to push high volumes of slightlydrier over the glass to allow skaters andspectatorsaliketheopportunitytoseethroughtheglass.
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As the impact of high a humidity coming incontactwithcoldsurfaceswasstudiedfurther,theconcernsmovedbeyondtheproblemswithbeamsandboardsandtheunwanteddripsontheice.Whenleftunchecked,thebuildupofheavy condensation on the walls and floorscould allow the formation of unwantedbiologicalgrowthonthosesamesurfaces.Ice technicians are challenged to keep a safeand good sheet of ice when the indoorhumidity level or dew point increases to apoint that iswellabove freezing,because therate atwhich frost builds up on the ice alsoincreases.Tokeeptheicefrombeingtoosoft,operators are forced to run the ice plant atvery low temperatures, resulting in the easybuild up ruts and heavy snow accumulationfrom skaters. Typically these periods thatrequire colder iceare the sameperiodswhentheoutdoortemperaturesareelevated;whichnegatively impacts the ice plants efficiencyandthetotalhoursofoperation.Someofthebesticeconditionsandtheeasiesttomaintain sheets of ice are achievedwhenthe dew points are just above the freezinglevel. This allows the operator to run awarmer surface temperature on the sheet ofice. Beyond ice quality, a warmer surfacetemperaturereducesthe loadonthe iceplantaswell.ModernDehumidificationSystemsToday arenas should be designed with adehumidification system that will provide areliablesourceofverydryair.Inrecreationalfacilities,desiccantbasedsystemshaveproventobethemostcosteffectivesourceofverydryair.Inlargerfacilities,largeairhandlersusinglowtemperaturechilledwaterhavebeenusedwith mixed results but more recently thedesiccant based ventilation systems haveshown they can produce the preferred lowdewpointlevels.Thegoal for anyarena is tohavea sourceofventilation thatprovidesdrier than the arena
design level of humidity. In otherwords thenet dew point from all the air handlerssupplying thearenamustbebelow thearenadew point design level. This will make forsuccessfulconditions.HintstoHelpTechniciansControlHumidity1/ Get Comfortable knowing the DewPointLevelsinsideyourrink.There are number of low cost devices on themarket today thatprovideoperatorsan instantreading of the dew point inside their rink.Whenever thedewpoint remainsataconstantlevelclose to the freezingpoint, the icecanbesetuptoachieveahighqualitycondition.2/ Study the impact of high outdoorhumidityontheoperationofyourrink.With the same dew point sensing device,measureandrecordthedewpointlevelsoftheair outside. Any time the outdoor humidityclimbs above the ideal indoor humidity,monitor the ability of the dehumidificationscapacity tohold theproper indoorconditions.Adjustyouriceconditionsappropriately.3/ When the outdoor dew point levelmoves above the ideal indoor dew point,minimize the time intervals that doors areopen.Any door or opening into the arena spaceallowsthehigheroutdoorhumiditytomigrateinto the rink area. Remember that highhumidityhasahighvaporpressure(alsoahighdew point). Your indoor preferred level ordesigned level of humidity has a lower vaporpressure. All that high vapor pressuresurroundingtheoutsideofyourbuildingwantsto move to the low vapor pressure indoors.The greater the difference between the twovapor pressures (or dew points), the quickerthe humidity will move through an openinginto the rink. Even the newestdehumidification technology installed in a
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recreational arena cannot keep up with theloadproducedbyanopen resurfacingdoor inthesummer.4/ Avoid the trap of just watching (RH)Levels.Warmaircanholdmoremoisture. Operatorshave fallen in the trap of thinking if the aircoming intomybuildinghas a lowerRH levelthan the RH level in the building, the indoorhumiditywilldrop.Introducingoutdoorairat18C (65F) and 50% RH would elevate theindoor dew point above NHL conditions.Operators of even larger venue rinks havethought by heating the space up theycontrolled humidity. At a great energy costtheymayhaveheatedalargeindoorarenatoawarmer temperature and observed theRelativehumiditydropping,butunfortunatelynot removed any moisture from the arena.Forexamplearenaairat15.5C (60F)dband60% RH that is heated to a level of 23.9C(75F)dbwilldroptheRHlevelto36%,buttheabsolute humidity or dew point remains at aconstant7.8C(46F).Iftheairiscooledbackdown to 15.5C (60F) db, the RH willmovebackto60%.The only sureway to removemoisture fromthe air is to provide a drier source of air (orlowerdewpoint)totheindoorarenaspaceUsefulTermsWhenDiscussingHumidityDry Bulb Temperature most commontemperature discussed. It ismeasuredwith astandard thermometer thatmeasures dry bulblevels.RelativeHumidityReferstothepercentageofsaturation intheair. Itexpressesthemoisturecontentof air as apercentofwhat it canholdwhen it saturated (orat100%RH). It isnotameasureoftheabsolutehumidityintheair,butitmeasuresmoisturecontent in theair relativetotheassociateddrybulbtemperatureat100%RH(orsaturation).Ifweraisethetemperature
of air and without changing the absolutehumiditylevel,theRHleveldrops.Inthesameway, if we cool the temperature of the airwithout changing the absolute humidity level,the RH level goes up. Rememberwarmer aircanholdmoremoisture.SpecificHumidityisanabsolutemeasurementofhumidityorwatervapor intheair. Theunitsused tomeasurespecifichumidityaregrainsofwatervaporperpoundofair. It isactuallytheweight ofwatermoleculesmeasured in grainsagainsttheweightofair.Thereare7000grainsinapound.Vapour Pressure another measurement ofhumidity in the air Measurement is inchesofmercury. Desiccantsystems removemoisturein the vapor phase by attracting the vaporpressurefoundinthearenaairtothelowvaporpressure on the surface of their desiccantmaterial.Dew Point It is the temperature point atwhichthemoistureintheairwillcondenseoutof theairontoanysurface that iscooler thanthedewpointlevel.Itismostcommonwayofdetermining absolute humidity levels. Thedew point can be readily obtained fromsourceslikeweatherdatawebsites.SensibleHeat is themeasurementofdrybulbenergy in theair. The flowof sensibleheat isalways from awarm source to a cooler space,surfaceorobject.Latent Heat is the measurement of themoistureenergy intheair. Inreducing latentheatintheairweintroduceasourceofairwithalowerspecifichumidityorlowerdewpoint.Conductive Heat is the heat that istransferred through the direct contactbetween two surfaces. An ice surfacetouching a colder pipe is transferringconductiveheat.
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ConvectiveHeat isthetransferofheatfroma warmer source or surface through themovement of air. A unit heater introduceswarmer air into a space to bring thetemperatureup.RadiantHeatisthetransferofheatfromhotor warm surface radiating heat unto coldersurfaces.Radiantheatersarenotdesignedtoheattheairinthespacebuttoheatthepeoplestandingbelowthem.ConclusionTheissuesofairquality,humidityandbuildinghealthcanbeacomplextopicthatattimesrequiresexpertevaluationtodeterminehowbesttheycanbecontrolled.Notoneplanwillworkforeveryicerink.Thereareavarietyofcompaniesthatprovideevaluation,assessmentandequipmentoptions.Thefirststepisunderstandingtheissuessothatdiscussionswiththeseprofessionalscanoccurinamannerthatbothpartiesunderstandeachother.Wehopethispaperlendstothisobjective.Source:ThisdocumentwascreatedincooperationwithORFACorporatememberJohnGowingofEnergyInhybridSolutionsInc.www.eisolutions.ca DisclaimerOntarioRecreationFacilitiesAssociationInc.,2014Theinformationcontainedinthisreferencematerialisdistributedasaguideonly;itisgenerallycurrenttothebestofourknowledgeastotherevisiondate,havingbeencompiledfromsourcesbelievedtobereliableandtorepresentthebestcurrentopiniononthesubject.Nowarranty,guaranteeorrepresentation...