designing with natural forces

Architecture 418 Spring 2014 Designing with Natural Forces Peter Simmonds

Course Syllabus of 1

Course Title: Designing with Natural Forces 418 "Investigation of how natural forces affect Architecture and Natural Ventilation of spaces to provide ventilation and occupant comfort."

Course: ARCH 418 Instructor: Peter Simmonds Course Description: The phenomenon of natural ventilation is quite often misunderstood. It is not simply a way of orientating the building in the correct direction or having openings in the façade that will facilitate air movement through a space. This course will examine the physical factors in design through a series of lectures and design Charrettes. In this process the students will learn the various ecological factors that can impact the environment such as:

Topography and the site Sun exposure Wind dynamics Aero Physics Wind Driven Ventilation Buoyancy Driven Ventilation Stack Ventilation in High Rise Buildings Adaptive Comfort for Occupants

The course will be broken down into two sections, with the following subsections: Part One- Natural ventilation a. Introduction to terminologies and analytical tools through readings from reader b. Introduction to available computer tools c. Introduction to adaptive comfort for naturally ventilated spaces. d. Analysis of wind driven ventilation e. Analysis of buoyancy driven ventilation f. Stack ventilation in High Rise Buildings g. Discussions of practical applications

Part Two- Adaptive Comfort a. Introduction to Adaptive Comfort b. Analysis of comfort criteria c. Mean Monthly and Running Mean Temperatures d. Practical examples of adaptive comfort compliance e. Midterm Exams (2x) f. Homework g. Final Exam

Initssimplestform,naturalventilationisassimpleasopeningawindowordoor;itpermitssomeformofairexchangewiththeoutdoors.Attheotherendofthespectrum,naturalventilationimpliesanengineeredbalanceofdrivingforcesandpressurelossestomoveairthroughabuildingatpredictableminimumflowrates,toprovideadequateventilationforairquality,forthermalcomfortandtomanageheatloads.Humanshavealonghistorywithnaturalventilation.Ithasbeenusedtoventilateall‐typesofbuildingsfromhospitals,schoolsandhomes,toelectricalsub‐stationsandindustrialfacilities.Naturalventilationrequiresthemanagementofthetwoprincipaldrivingforces:thebuoyancyforceassociatedwithatemperaturedifferenceandthekineticforceassociatedwithwindmovement.Ineachcase,pressuredifferencesaresetupbetweentheindoorandoutdoorenvironment,whichdrivestheairflow.Therestraintonnaturalventilationisassociatedwithpressurelossesasairmovesthroughopenings(expansionandcontractionofflowarea),turnscornersandpassesthroughscreensorfilters.Somebuildingsaredifficulttoventilatenaturallyina“managed”way.Verytallbuildingscanbedifficulttoventilatenaturallybecausethecombinationofwindandstackeffectpressurescanleadtoadverseflowdirections—peopleinonelocationreceivingthestaleairfromthoseinanother.Wind



pressurescanalsoleadtouncomfortableconditions.Itispossibletonaturallyventilatesuper‐tallbuildingsbutthisfeaturemustbedesigned‐infromthebeginning.Somejurisdictions(e.g.Chicago)requirethatallresidenceshaveoperablewindows,eventhoughinsomecases,thesewindowsarenotusefultotheoccupant.Ingeneral,naturalventilationworksbestwhentheoutsideairtemperaturesarejustbelowwhatwouldgenerallybeconsideredcomfortableindoorconditions.However,theoutdoortemperaturethatwillleadtoacceptableindoortemperaturesdependsgreatlyontheinternalheatloads(fromhumanoccupants,equipment,lights,solargain,etc.)andtheflowratethatcanbeachieved.TheAmericanSocietyofHeating,VentilatingandAirConditioningEngineers(ASHRAE)Standard55(2010)hasadiscussiononthermalcomfortthatincludesacharthighlightingtheacceptableindoortemperaturesinnaturallyventilatedbuildings.Thekeyisthatoccupantsmustbegivensomemeasureofcontrolovertheirenvironment.Designofnaturalventilationinacomplexbuilding,orwherenaturalventilationistheonlyformofventilation,caninvolveintuitiveexperienceaswellashardscience.Ineachcase,theformofthebuildingwillbeimportantandvariousfeaturesofthebuilding’sarchitecturecanenhancenaturalventilationorworkagainstit.Designingnaturalventilationistheartofbalancingdrivingforcesandpressurelossestoachieveadesiredminimumairflowrate.Therequiredminimumflowrateneednotbeconstant.Ingeneraltherearethreedifferentcriteriaforidentifyingtheminimumflowrate:

a. Thehumanbiologicalrequirementestablishedincodesandbyorganizations(e.g.ASHRAE,NBCC,CIBSE)andsometimessimplyreferredtoas20cfm/person(10L/s/person);

b. Theflowrequiredtomaintainhumanorequipmenttemperaturelimits.ASHRAE55suggeststhatacceptabletemperaturesrangefrom17ºto31ºCdependingontheoutdoortemperature;

c. Theflowtomaintaincontaminants(e.g.carbondioxideconcentrations)atamaximumallowablelimit.

Varioustoolsareavailabletoassessnaturalventilationandtheuseofonetooloveranotherdependsonthedrivingforcesandcriticalnatureoftheflow.Stack effect Stackeffectisaphenomenonpresentinallverticalshaftsthatareatdifferenttemperaturesfromoutdoors.Thisincludeschimneysandbuildings.Abuilding’sshaftsincludetheverticalHVACrisers,elevatorandstairwellshafts.Thetemperaturedifferencesetsupascenariowherethereisadensitydifferenceindoorstoout.Thispressuredifferenceprovidesadrivingforceforairmovement.Ifthereareopeningsinthebuildingfaçade(eveniftheyareverysmallcracks)thentherewillbeairflowinatthebottomandoutatthetopforaheating‐climatescenario.Stackeffectflowsinshorterbuildingsandchimneys(e.g.5story’s)areafewPascal’s(PSI),comparedtowindpressureswhichcanbemeasuredin10sofPascal’s(PSI).Henceitispossibleforaslightwindtooverwhelmthenaturalstackeffect.Arobustdesignofnaturalventilationinabuildingthatusesstackeffectasadrivingforcewillbeconfiguredsothatatworstthewindeffectswillbebenignandifpossibletheywillassist.Itisimportantthatallwindconditionsanddirectionsbeconsideredbecausethe“prevailing”windisnotalwaysonethatexistsmorethan50%ofthetime.Thiscoursewillcoverbothresidentialandcommercialbuildingsandwillalsodiscusstheapplicationofnaturalventilationandoccupantcomfortfordifferentclimates,suchashotandhumidclimateforexample.Vasariwillalsobeusedtoevaluateambientconditionsonthebuildings. You will be graded on attendance and participation in the following three areas: Classroom Discussion /Team presentation 10% Assignments 20%



Midterm Papers (2x) 40% Final exam & Quizzes 30% Total 100% Assignments Therewillbetwoassignmentstoevaluatethepotentialofnaturalventilationandad.thesewillbereturnedanddiscussedinclasswithsolutions. Afinalgradeshallbeawardedusingthefollowingguidelines:1.Generalrule:A.Excellent~weightedaverage≥90%B.Superior~weightedaverage≥80%butlessthan90%C.Medium~weightedaverage≥70%butlessthan80%D.Inferior~weightedaverage≥60%butlessthan70%F.Failure~weightedaveragelessthan60%(Note:Thisisafirmcut‐offaverage,notsubjecttotheexceptionidentifiedhereafter!)2.Exception:Theinstructorreservestherighttoadjustthelowendweightedaveragecut‐offscorebaseduponthestatisticaldistributionofthesemesteraveragesforA,B,orCfinalgrades.Forinstance,ifthereisalargegapintheweightedaveragesat88%,thentheinstructormaydecidetoawardanAgradetoallstudentsabovethatvalue.Thisisdoneattheinstructor’sdiscretionandinnowayshouldbeconstructedtomeanthatitwillbedoneeachandeverysemester.Ifastudentwishestoearnaparticularfinalgradethenthestudentshouldonearningtheminimumweightedaveragesdescribedinthegeneralrule.EXTRA‐CREDITS:Therewillbeextracreditproblems,assignmentsorparticipations.Theseextraproblemsorassignmenttohelpthosestudentswhofeelthatthereisaneedtoimprovetheirgradebyperformingsomeextrawork.QUALITY:Alldeliverablesshallbegradedforqualityandcontent,60%and40%respectively.Seetheinstructor’smemorandum:QualityStandardsforDeliverables.Sloppy,illegible,disorganizeddeliverablesarenotacceptableforengineerworkandshallnegativelyimpactyourcoursegrade.STATEMENTFORSTUDENTSWITHDISABILITIESAnystudentrequestingacademicaccommodationsbasedonadisabilityisrequiredtoregisterwithDisabilityServicesandPrograms(DSP)eachsemester.AletterofverificationforapprovedaccommodationscanbeobtainedfromDSP.Pleasebesuretheletterisdeliveredtome(ortoTA)asearlyinthesemesteraspossible.DSPislocatedinSTU301andisopen8:30a.m.–5:00p.m.,Monday\throughFriday.ThephonenumberforDSPis(213)740‐0776.STATEMENTONACADEMICINTEGRITYUSCseekstomaintainanoptimallearningenvironment.Generalprinciplesofacademichonestyincludetheconceptofrespectfortheintellectualpropertyofothers,theexpectationthatindividualworkwillbesubmittedunlessotherwiseallowedbyaninstructor,andtheobligationsbothtoprotectone’sownacademicworkfrommisusebyothersaswellastoavoidusinganother’sworkasone’sown.Allstudentsareexpectedtounderstandandabidebytheseprinciples.Scampus,theStudentGuidebook,containstheStudentConductCodeinSection11.00,whiletherecommendedsanctionsarelocatedinAppendixA:http://www.usc.edu/dept/publications/SCAMPUS/gov/.StudentswillbereferredtotheOfficeofStudentJudicialAffairsandCommunityStandardsforfurtherreview,shouldtherebeanysuspicionofacademicdishonesty.TheReviewprocesscanbefoundat:http://www.usc.edu/student‐affairs/SJACS/. Required reading:



USC Natural Ventilation Guidelines (produced from 418 in 2012) Mechanical and Electrical Systems, by Grondzik, Kwok, Stein and Reynolds, CIBSE, Natural Ventilation Design Guide. AIVC Design Guide ASHRAE Standard 55, 2013



Proposed schedule of classes Week 1 Introduction Week 2 Discussion on AIVC and CIBSE Methods Week 3 Student Self-study- Comparison of different methods Week 4 Buoyancy Driven Ventilation Week 5 introduction to COMFEN Week 6 Analysis using COMFEN Week 7 Wind Driven Ventilation study with Vasari Week 8 Wind Driven Ventilation study using COMFEN Week 9 Neutral plane Week 10 spring Break Week 11 Introduction to Adaptive Comfort Week 12 Practical Examples 1 Week 13 Practical Examples 2 Week 14 Stack Ventilation in High Rise Buildings Week 15 design guide revue Week 16 final review of design guide References: [1]J.W.Axley,S.J.Emmerich,Amethodtoassessthesuitabilityofaclimatefornaturalventilationofcommercialbuildings,in:ProceedingsoftheIndoorAir,2002.[2]J.W.Axley,ApplicationofNaturalVentilationforU.S.CommercialBuildings–ClimateSuitability,DesignStrategies&Methods,andModelingStudies.GCR‐01‐820,NationalInstituteofStandardsandTechnology,2001.[3]S.J.Emmerich,W.S.Dols,J.W.Axley,NaturalVentilationReviewandPlanforDesignandAnalysisTools.NISTIR6781,NationalInstituteofStandardsandTechnology,2001.[4]ASHRAEStandard55‐2004,ThermalEnvironmentalConditionsforHumanOccupancy,Am.Soc.ofHeatingRefrigeratingandAir‐conditioningEngineers,2004.[5]ASHRAE,ASHRAEHandbook–Fundamentals,ASHRAE,2009.[6]R.J.deDear,G.S.Brager,Developinganadaptivemodelofthermalcomfortandpreference,ASHRAETransactions104(Part1A)(1998).[7]G.J.Levermore,A.M.Jones,A.J.Wright,Simulationofanaturallyventilatedbuildingatdifferentlocations,ASHRAETransactions106(Part2)(2000).[8]ASHRAE,Standard62.1‐2010,VentilationforAcceptableIndoorAirQuality,ASHRAE,2010.[9]ASHRAE,IndoorAirQualityGuide–BestPracticesforDesign,Construction,andCommissioning,ASHRAE,2009.[10]J.Axley,S.J.Emmerich,G.Walton,W.S.Dols,AnApproachtotheDesignofNaturalandHybridVentilationSystemsforCoolingBuildings(2002)IndoorAirProceedings,in:9thInternationalConferenceonIndoorAirQualityandClimate,2002.[11]G.S.Brager,R.J.deDear,Thermaladaptationinthebuiltenvironment:aliteraturereview,EnergyandBuildings27(1)(1998)83–96.[12]J.F.Nicol,M.A.Humphreys,Adaptivethermalcomfortandsustainablethermalstandardsforbuildings,EnergyandBuildings34(6)(2002)563–572.[13]J.F.Nicol,M.A.Humphreys,Derivationoftheadaptiveequationsforthermalcomfortinfree‐runningbuildingsinEuropeanStandardEN15251,EnergyandBuildings45(1)(2010)11–17.

designing with natural forces

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