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SmartVent®HazardEvaluatorBetav.1.3.2RedefiningtheproperevaluationofsafefloodventingNicholasAgnoli,P.E.|ManagingPartnerRevisedDecember20,2016

EXECUTIVESUMMARYAccording to statistics from the Federal EmergencyManagement Agency (FEMA) NationalFlood Insurance Program (NFIP), floods are the number one natural disaster in theUnitedStates1. Additionally, from2011to2015theaveragefloodclaimwasover$46,000andthetotal flood insurance claims annually exceeded $1.9 billion dollars (U.S.). Understandingproper methods of mitigating flood damage to the structural stability of an enclosure(basementand/or crawl space) that complieswithnational standardsandbestengineeringpracticehasneverbeenmoreimportanttothebuildingowner,contractorandregulator.Agnoli Engineering, LLC, in evaluating the Smart Vent® engineered,mechanically operatedfloodvents,reviewedavailableguidelinesandengineeringdatarelatedtotheirperformance.WhatwasnotavailablewasasimplemethodtoevaluatetheexpectedperformanceofSmartVents®foraspecificpropertywithastandardrateofriseandfalloffloodwaterof5.0feetperhour (1.52metersperhour)perASCE24-142. Thispaperpresentsa tooldevelopedbyAgnoliEngineeringwithMicrosoft®OfficeExcel®2007thatallowsanevaluatorwithminimalbackgroundinfloodcontrolandabasicunderstandingofapropertytodeterminethesizingand level of protection provided by the Smart Vent® flood vents. The tool includes aconservative discharge coefficient of 0.44 as required by Table 2-2 in ASCE 24-14 and theminimumofoneventforevery200squarefeetintheICCEvaluationService(ES)Report3.The tool also allows the evaluation of alternative openings, including non-engineeredopenings. In the attachedAppendixA, findings from the use of non-engineeredopenings,includingafailuretomeetASCE24-14guidelineswhensetattheallowable12inchesabovegrade,arediscussed indetail. Additionally,non-engineeredventsalso failed tomeetASCE24-14guidelinesifblockedbydebrisatnearlyanydegree(percentage).

1FederalEmergencyManagementAgency."FloodRisksNationwide."September2013.2AmericanSocietyofCivilEngineers."FloodResistantDesignandConstruction(ASCE24-14)"3ICCEvaluationService."ESR-2074SmartVentAutomaticFoundationFloodVents."February2015(exp.Feb.2017)

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Currently,theSmartVent®istheonlyengineeredventthathasasoftwarespreadsheetthatcanproduceastagehydrographforenclosureflooding,headdifferentialsalonganenclosurewall,and/orproduceanexternalhydrostaticpressurecurve.Thesetoolsarevaluabletothevarious interests related to real estate ownership, including insurance and mortgagecompaniesaswellasconstructioncodeofficials.

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1.0INTRODUCTIONThepurposeof thisWhitePaper is toprovide themethodologyand test case resultsof theSmartVent Hazard Evaluator Beta developed by Agnoli Engineering, LLC. The Hazard Evaluator wasdevelopedtoprovidedesigners,owners,contractors,regulatorsandinsurerswithatooltoevaluatetheperformanceofaproposedSmartVentconfigurationagainstnational standards. Theprincipaldesigncriteriaincluded:

ü Easeofuseandeaseofincorporatingfielddataü Transparency(equationsandmethodology)ü Flexibilityfordifferentanduniquesystemlayoutsandconfigurationsü Detailedoutputsforengineersandregulators

2.0LITERATUREREVIEWAgnoliEngineeringsoughttoreviewbothliteratureavailabledirectlyfromSmartVentProducts,Inc.specifictothedimensionsandintendedperformanceoftheSmartVent®devicesbutalsoavailableliteratureonfederalrequirementsandthird-partytesting:

ü AmericanSocietyofCivilEngineers."FloodResistantDesignandConstruction(ASCE24-14)."(2014). This document provides criteria for design as well as expected performance ofengineeredopeningsinSection2.7.2.2.

ü ICCEvaluationService. "ESR-2074SmartVentAutomaticFoundationFloodVents."February2015.ThisdocumentprovidesanevaluationofphysicaloperationandwaterflowthroughtheSmartVent® floodvents. It includestheminimumcoverage (square feet)providedbyeachmodelnumber.

ü FederalEmergencyManagementAgency."TechnicalBulletin1,OpeningsinFoundationWallsandWallsofEnclosures."August2008.ThisbulletinprovidesguidanceontheNationalFloodInsuranceProgram(NFIP)regulationsconcerningtherequirementforopeningsinbelowBaseFloodElevation(BFE)foundationwallsandwallsofenclosuresforbuildings located inFloodZonesA,AE,A1-A30,AR,AO,andAH.

3.0SOLUTIONTheSmartVentHazardEvaluatorBetatoolwasdevelopedusingMicrosoft®OfficeExcel®tosimplifythe experience for novice users. The tool consists of three worksheets: Smart Vent® Tool,ModelLookup,andCalculations.3.1SmartVent®ToolWorksheetTheSmartVent®Toolworksheetprovidestheuseraninputinterfaceandreturnstheresults.Therequiredinputsinclude:

ü SmartVent®ModelorNon-EngineeredOpeningType;

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ü NumberofVents;ü FloodWaterProperties(freshwaterorsaltwater);ü PercentObstruction;ü InstalledHeightAboveGrade;ü SmartVent®DischargeCoefficientü Non-EngineeredOpeningParameters(width,height,cover)ü EnclosureArea;ü EnclosureDepthBelowGrade;ü EnclosureHeightAboveGrade;ü GradeElevation;ü BaseFloodElevation;andü RateofFloodRise.

MostoftheinputscanbeobtainedfromastandardFEMAElevationCertificateandratemap. TherateofriseofsurroundfloodwaterisgivenasfivefeetperhourperASCEStandard24-14;however,it canalsobeobtained fromanavailablehydraulicanalysis. Theevaluation time incrementcanbeadjustedtoencompassthefullflooddurationasneeded.TheSmartVent®modelnameisapulldownmenuthatpopulatesthedimensionsprovidedontheModelLookupWorksheet.Thenumberofventsand installedheightabovegradearethetwoprimarydesignparameters.Theusercanadjusttheseparametersuntiltheminimumdesigncriteriaaremet:

ü Minimumnumberofvents(2)perTechnicalBulletin1:"eachenclosedareaisrequiredtohaveaminimumoftwoopeningsonexteriorwallstoallowfloodwaterstoenterdirectly."

ü MinimumnumberofventstomeettheareacoverageratingperventasprovidedinTable1ofICC-ESReportESR-2074.

ü MaximumheightofopeningabovegradeperTechnicalBulletin1:"thebottomofeachopeningistobelocatednohigherthan1footabovethegradethatisimmediatelyundereachopening."

ü Maximumhead differential requirements per ASCE 24-14: "the performance of engineeredopeningsshallensurethatthedifferencebetweentheexteriorandinteriorfloodwaterlevelsshallnotexceed1foot."Tocheckthisrequirement,thetoolverifiesthatthemaximumheadonthewallabovegradepriortoequalizationislessthan1foot.Whenfloodwatersrisetotheadjacentgradeelevationpriortothefloodventactivation,theenclosurewouldbeginasdry.Theadditionalloadingonthewallbeyondthetypicalfoundationdesignwouldbeexpectedtooccurwhenthefloodwatersareabovetheadjacentgrade.Therefore,thetoolchecksthattheSmartVent®configurationenteredbytheuserallowstheenclosuretofillupfastenoughfortheheaddifferentialbetweentheinteriorandexteriorfloodlevelstobelessthan1foot.

TheSmartVentToolworksheetprovidesthefollowingresults:

ü OrificeDischargeCoefficientusedinthecalculationsü Timeforenclosurefloodingtoequalizewithexternalfloodü Timetofilltheenclosureü Maximumenclosureflooddepthü Maximumheaddifferentialbetweenfloodlevelsinternalandexternaltowall

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ü Maximumheadonwallabovegradeü Maximumheadonwallabovegradepriortoequalizationü Maximumupliftpressureü Maximumlateralhydrostaticforceonenclosurewallü Lateralhydrostaticforceonenclosurewallduringmaximumheaddifferentialü Maximumuplift(buoyancy)forceduetohydrostaticpressureü Stagehydrographfigureü Headdifferentialbetweenfloodlevelsinternalandexternaltowallfigureü Externalhydrostaticpressureabovegradefigure

Ifadesigncriterionisnotmet,thetoolprovidessuggestionstotheusertomodifytheconfiguration(i.e.addventsoradjustinstalledheightabovegrade).3.2ModelLookupWorksheetTheModelLookupworksheetprovidesthelookuptableofdimensionsforeachSmartVent®model.Thedimensionsincludethewidth,ventopeningheightsaboveandbelowthedoor,ventdoordepth,andheightaboveventinvertforactivation.ThedimensionsassociatedwiththeSmartVent®modelchosenbytheuserarepopulatedontheSmartVent®ToolworksheetandCalculationsworksheet.3.3CalculationsWorksheetTheCalculationsWorksheetcontainsthecalculationsperformedbythetool.ThetoolevaluatestheperformanceoftheSmartVent®configurationenteredbytheuserwithaquasi-unsteadyapproach.Thetoolcalculatestherisingfloodelevation,inflowthroughthevents,andresultantflooddepthintheenclosureforeachtimestepduringthefloodriseuntilthefloodlevelintheenclosureequalstheexternal floodelevation.Once the internal andexternal floodelevationsequalize, the internal andexternal floodelevation riseat the same rate for the remainderof the simulation.Basedon theseresults,thetoolcalculatestheresultsprovidedontheSmartVent®Toolworksheet.The tool calculates the flowthrougheachSmartVent®ateach timestep.The flow foreachSmartVent® is thenmultiplied by the number of vents to calculate the total inflow into the enclosure.When the Smart Vent® is activated, the door swings open to provide a lower and an upper slotopening. Figure 1 below provides typical dimensions of the openings through Smart Vent® whenactivated.

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Figure1–SmartVentDimensions

ThetoolwasdevelopedtoconsiderthechangingflowconditionsthatwouldbeexpectedthroughtheSmartVentasthefloodlevelrises,theventactivates,floodwatersflowthroughfirstthelowerslotthenupperslot,and theenclosure fills.TheSmartVentactivateswhen the flood level reaches1.5inchesabovetheinvertofthevent.Whenthefloodlevelislessthan1.5inchesabovetheinvertofthevent,theventisassumedtobeclosedandthetoolassumesnoinflowforthetimestep.For time steps when the Smart Vent® is activated and the flood level is below the top of a slotopening(eitherlowerorupper),thetoolassumesweirflowthroughtheappropriateopeningusingthebroad-crestedweirequation4:

Q=2.64b*h3/2 Equation1Where: Q=discharge(cfs) b=widthofslottedopening h=head(feet)Thedischargecoefficient(2.64)acrosstheweirwasselectedasthemostconservativefora"broad-crested"weirfromthereferencebelow(4).However,theweirdischargecoefficientisadjustedwhenascreenisinstalledontheopening.Whentheuserselects"Yes"regardingascreeninplace,thetooladjuststheweirdischargecoefficient(CW)withthefollowingequation:

CW=COSx2.64 CORWhere: CW=Weirdischargecoefficient COS=Orificedischargecoefficientofanopeningwithascreen(0.2) COR=Orificedischargecoeff.ofarectangularopeningwithalonghorizontalaxis(0.4)The tool thereforeusesaweirdischargecoefficientof2.64whennoscreen is inplace,andaweirdischargecoefficientof1.32whenascreenis inplace.TheweirdischargecoefficientadjustmentisprovidedincellH23onthecalculationssheet. 4KingandBrater."HandbookofHydraulics."1977(5thEdition).

Reference:SmartVent,Inc.:CertificationofEngineeringOpening(July,2007)

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When the flood level is above topof a slot (eitherupperor lower) the tool treats each slot as anorificeusingtheequation5:

Q=Co*A(2gH)1/2 Equation2Where: Q=discharge(cfs) Co=dischargecoefficient(0.6)perTable2-2,ASCE24-14 A=OpeningArea(squarefeet) g=accelerationduetogravity(32.2.feet/second2) H=head(feet)ThecoefficientofdischargefromTable2-2inASCE24-14normallyusedfora“Rectangular,longaxishorizontal, shortaxisvertical,unobstructedduringdesign flood,” isdesignatedas0.4. However,afootnote allows for “different coefficients of discharge … (1) where a designer has performeddetailed, opening-specific calculations, a coefficientof dischargeup to10%different thangiven inTable2-2shallbepermitted;or(2)wherelaboratorytestingornumericalmodelingofflowthroughtheopeninghasbeenconducted,theresultingcoefficientofdischargeshallbepermitted.Innocaseshallacoefficientofdischarge>0.60bepermitted.”Unsubmergedorifice coefficients are typically 0.60 to0.61 for fully contractedorificeopenings forcircular, squareor rectangular shape4The toolallows theuser to selecta coefficientof0.44,0.60,and0.20toevaluatethesensitivityof thedischargecoefficientontheirselectedconfiguration. Ifanon-engineered opening is selected, the model will not use the Smart Vent discharge coefficientparameter.The user can also select non-engineered rectangular, square, circular, and other shaped floodopenings from the pull-down list in addition to Smart Vent products. When a non-engineeredopeningisselected,theusermustenterthenon-engineeredopeningparametersincludingthewidth,height, net opening area, andwhether the opening has a cover. The toolwill then use the non-engineeredopeninginputparameterstoselecttheappropriatedischargecoefficientperASCE24-14as shown in Table 1 below. Per ASCE 24-14, an opening shall be classified as partially obstructed(dischargecoefficientof0.20)iflouvers,blades,screens,grilles,faceplates,orothercoversordevicesarepresentduringthedesignflood.Therefore,ifthereisacoverontheopening,thetoolwillselectadischargecoefficientof0.20regardlessoftheopeningshape.Otherwise,ifthereisnocoverontheopening, the tool will select the appropriate unobstructed discharge coefficient based on theopening’sshapefromTable1. Themodelwillnotusethenon-engineeredopeningparametersifaSmartVentproductisselected.

5Asabove(Ref.4)

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Table1–FloodOpeningCoefficientofDischargea(ASCE24-12Table2-2)OpeningShapeandCondition C

Circular,unobstructedduringdesignfloodb 0.6

Rectangular,longaxishorizontal,shortaxisvertical,unobstructedduringdesignflood 0.4c

Square,unobstructedduringdesignflood 0.35

Rectangular,shortaxishorizontal,longaxisvertical,unobstructedduringdesignflood 0.25d

Othershapes,unobstructedduringdesignflood 0.3

Allshapes,partiallyobstructedduringdesignflood 0.2a Different coefficients of discharge shall be permitted: (1)where a designer has performed detailed, opening-specificcalculations, a coefficient of discharge up to 10% different than given in Table 2-2 shall be permitted; or (2) wherelaboratorytestingornumericalmodelingofflowthroughtheopeninghasbeenconducted,theresultingcoefficientofdischargeshallbepermitted.Innocaseshallacoefficientofdischarge>0.60bepermitted.

b Openings shall be classified as partially obstructed if louvers, blades, screens, grilles, faceplates, or other covers ordevicesarepresentduringthedesignflood.

cWhenthehorizontaldimensionistwiceormoretheverticaldimension,use0.4;asthedimensionsapproachasquare,interpolatefrom0.4to0.35.

d When thehorizontaldimension ishalfor less theverticaldimension,use0.25;as thedimensionsapproachasquare,interpolatefrom0.25to0.35.

Reference:ASCE24-12Table2-2Theusercanevaluateiftheopeningweretobeobstructedbyenteringthepercentobstruction(typeindecimalformat)intothetool.PerASCE24-14andasshowninTable1,adischargecoefficientof0.20 should be used for all shapes when partially obstructed. When the user enters a percentobstruction greater than zero, the tool assigns a discharge coefficient of 0.20. The percentobstructionenteredbytheuseristhenusedtoreducetheopeningareausedintheorificeequationandopeningwidthusedintheweirequation.Fornon-engineeredopenings,thepercentobstructionwillreducethetotalopeningareabytheuserinputvalue.ForSmartVentopenings,lowerandupperopeningsareeachreducedbyhalfof the totalpercentobstructionby theuser inputvalue.Duringweir flow, thepercentobstructionreduces theopeningwidthby theuser inputvalue to representthereducedconveyancethroughthevent.ThetoolprovidesnumericalmodelingofflowthroughtheopeningandchecksthatthemodeledflowcalculatedusingEquation2, is lessthantheidealflow.Ifthemodelflowislessthantheidealflow,then the discharge coefficient used in themodel flow calculation (Equation 2) is appropriate. TheidealflowequationforarectangularorificepertheHandbookofHydraulics(BraterandKing)isgivenas:

Qt=2/3*L*(2g)0.5*(h23/2–h13/2) Equation3Where: Qt=discharge(cfs) L=WidthofOrifice(feet) g=accelerationduetogravity(32.2.feet/second2) h1=headabovetopoforifice(feet)

h2=headaboveinvertoforifice(feet)

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The tool calculates the ideal flow for the lower slot opening and upper slot opening for eachtimestep.Theseflowsarethencombinedtoprovidethetotal ideal flowthroughasinglevent.Thetoolthenchecksiftheidealflowisgreaterthanthemodelflow.Thisanalysisshowsthatthemodelflow is less than the ideal flow. Therefore, Agnoli Engineering, LLC recommends that dischargecoefficientof0.6isappropriateforSmartVentProducts,Inc.Themaximumhydrostatic/uplift pressure andmaximum lateral hydrostatic force on the enclosurewallarecalculatedusingtheequations inFigure2below.Themaximumlateralhydrostaticforce istheresultant lateralforceduetohydrostaticpressureforthefullheadfromtheBFEtothebaseoftheenclosurewall. The toolalsouses theequation inFigure2 to calculate the lateralhydrostaticforceontheenclosurewallduringthemaximumheaddifferential.Thisvaluesprovidestheuserwiththemaximumlateralforceactingexternallyonthewallduringthefloodeventpriortoequalizationoftheinteriorandexteriorfloodlevels.Thetoolalsocalculatestheresultantvertical(buoyant,oruplift)forceduetohydrostaticpressureontheenclosureusingtheequationsinFigure3below.Theuserhastheoptiontoselectfreshwaterorsaltwaterforthehydrostaticpressureandloadingcalculations.Thetoolwillusetheappropriatespecificweightofwaterbasedontheuser’sselection(62.4lb/ft3forfreshwaterand64lb/ft3forsaltwater).Figure2–LateralHydrostaticPressureandForce

Reference:FEMANFIPTechnicalBulletin1-93(1993)

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Figure3–Uplift/BuoyancyForce

Reference:FEMANFIPTechnicalBulletin1-93(1993)

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4.0TESTINGANDVALIDATIONTheSmartVent®HazardEvaluatorBetawasrunwitheighttestcasestoevaluatevariousenclosureconfigurations.Table1summarizestheenclosureconfigurationsassumedineachtestcase.

Table2–TestCases

TestCase Diagram*Heightof

Enclosure(feet)Subgrade(feet)

1 2 8 0.42 2 8 3.33 9 3 0.84 9 3 1.65 9 3 0.56 7 6 07 7 8 08 8 3 0

*FEMAElevationCertificateBuildingDiagramNumber

Thefollowingparameterswereassumedforallofthetestcases(Table3):

Table3–InputParametersEnclosureArea: 1,000 squarefeetGradeElevation: 100 feetBaseFloodElevation: 105 feetRateofFloodRise: 5 feet/hourFloodWaterType: FreshWater

Thenumberofventsand installedheightabovegrade inputswereadjustedtomeet theminimumdesigncriteriaforeachtestcase.The results of the test case runs are provided in Table 4. For each run, various combinations ofnumberofventsand installedheightabovegradewereevaluatedto find theminimumnumberofventsrequiredtomeetthedesigncriteria.PerESR-2074,theenclosedareacoverageperventis200squarefeet.Thetestcasesassumeda1,000squarefeetenclosedareaandgiventherecommendedcoverageinESR-2074,aminimumof5vents.TheresultssupportthecoverageprovidedinESR-2074foreachtestcasewiththeappropriateinstalledheightabovegradechosenbythedesigner.

Table4–Results

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TestCase

HeightofEnclosure(feet)

Subgrade(feet)

NumberofVents

InstalledHeightAbove

Grade(inches)

MaxHeadonWallAboveGradePriortoEqualization

(feet)

TimeforEnclosuretoEqualizewithExternalFlood(minutes)

1 8 0.4 5 8 0.9 122 8 3.3 5 7 1.0 133 3 0.8 5 8 1.0 114 3 1.6 5 8 1.0 125 3 0.5 5 8 1.0 126 6 0 5 8 1.0 07 8 0 5 8 1.0 08 3 0 5 8 1.0 0

Figure2–TestCase1ScreenImageoftheSmartVentHazardEvaluatorBeta

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5.0CONCLUSIONSTheSmartVent®HazardEvaluatorBetaisabletoverifythatthecurrentsizingpracticefortheSmartVent®product is adequate. Duringa rateof floodwater riseof5 feetperhour recommendedbyASCE 24-14, the tool shows that with the appropriate configuration, the Smart Vents® allow theenclosuretofillupfastenoughfortheheaddifferentialbetweentheinteriorandexteriorfloodlevelsto be less than 1 foot. This small differential will significantly reduce the potential for structuraldamage as a result of hydrostatic pressureon an enclosurewall. Theuser can further refine theiranalysiswiththistoolbyusingarateofrisebasedonahydraulicmodel.ThistoolshouldbeusedtoevaluatesitespecificdeploymentofeachSmartVent®productandcanbeusedtoquantifythelikelyreductioninstructuraldamagetoanenclosureandreductioninfinancialloss.Additionally, the tool can be used to evaluate existing installations that include non-engineeringopeningsandtheneedforadditionalventingtomeettheaboverequirements.