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Ventilation for Acceptable
Indoor Air Quality62.1-2007
Dave Kahn, P.E.Dave Kahn, P.E.
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The Industries Ventilation Standard
Consensus Standard
Standard of CareUsed in NFPA 5000 BuildingConstruction and Safety Code
LEED Requirement
Not adopted by 06 IMC Somesimilarities
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1973 First Issued office 15 cfm/p
1981 Lower Rates office 5 cfm/p
1989 Higher Rates office 20 cfm/p1999 Little Change office 20 cfm/p
2001 More Mandatory Language
2004 occupancy component +
area component
2007 Incorporate Addendums
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Exceptions to 65% RH requirements fordehumidification systems
Appendix B references expanded & updated
Added Appendix H documentation requirements
Separation of ETS areas
Requirement for residential spaces in buildingsover 3 stories
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Means to balance the system to achieve minimumairflow.
Design documentation to state ventilation rate andair distribution assumptions.
Controls to enable the fan to operate wheneverthe spaces served are occupied.
VAV systems with fixed OA dampers must complyat minimum supply airflow.
MERV 6 filters upstream of all coils or otherdevices with wetted surfaces.
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Treatment of Outdoor air is required if in anonattainment area.
National Ambient Air Quality StandardsNAAQS
1. Ozone
2. Particulate Matter
3. Carbon Monoxide
4. Sulfur Oxides
5. Nitrogen Dioxide
6. Lead
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Prescriptive
Space must be within 25 of permanent wall or
roof openingOpenable area 4%of net occupiable floor area
Free area of opening must be used
Ventilation through adjoining rooms can be used
EngineeredMust be approved by the Authority HavingJursdiction
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Ventilation Rate ProcedureMost commonly used method
Lookup table
Need zone air distribution effectiveness
LEED requires this method
Indoor Air Quality ProcedureDesign to maintain specific contaminant levels
Mass Balance Analysis
Methods used in similar buildings
Validation by contaminant monitoring
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Ventilation
Rate
Procedure
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Use of building code occupantdensities is not required by the
standardUse actual number ofoccupants (maximum)
Use ASHRAE default valves
form Table 6-1
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Single zone 2007
High School classroom 35x35 30 people
Vbz = RpPz + RaAz (Breathing Zone air flow rate)10 cfm /person 10 * 30 = 300 cfm
0.12 cfm/ft2 0.12 * 35 * 35 = 147 cfm
300 + 147 = 447 cfm
Zone outdoor airflow Voz =Vbz/Ez447 /1 = 447 cfm or 14.9 cfm/person
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Single zone 2001
High school classroom 35 x 35 30 people
15 cfm /person 15 * 30 = 450 cfm cfm
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Single zone 2007
Hotel auditorium 40x30, 170 people
Vbz = RpPz + RaAz5 cfm /person 5 * 170 = 850 cfm
0.06 cfm/ft2 0.06 * 40 * 30 = 72 cfm
850 + 72 = 922 cfm
Zone outdoor airflow Voz =Vbz/Ez922 /1 = 922 cfm or 5.4 cfm/person
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Standard does not prescribespecific ventilation rate
requirements for spaces thatcontain smoking or that do notmeet the requirements in thestandard for separation fromspaces that contain smokingETS free areas shall be at a
positive pressure with respect toany adjacent or connected ETSareas
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Vou = DSall zonesRpPz + Sall zones RaAz
Vou - uncorrected outdoor air intakeD - occupant diversity = Ps/ Sall zones PzPs -total population of area servedby the system
Pz - largest number of peoplein the zone
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Vot = Vou/EvVot - design outdoor air intake flow
Vou - uncorrected outdoor air intake
Ev - ventilation efficiency from Table 6-3or Appendix A
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Table 6-3 approach
Manual calculation may result in more OA
Appendix A approach
Spreadsheet
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Zones served by system Zone 1 Zone 2 Zone 3 Zone 4
Space type (select from pull-down list) Officespace
Receptionareas
Classrooms (age 9plus)
Conference /meeting
Officespace
Az Floor area of zone, ft2 1000 1000 1000 500
Pz Zone population, largest # of people expectedto occupy zone
20 4 20 10
Rp Area outdoor air rate from Table 6.1, cfm/ft2 5 5 10 5 5
Ra People outdoor air rate from Table 6.1,cfm/person 0.06 0.06 0.12 0.06 0.06
Pz*Rp
100 20 200 50 0
Az*Ra
60 60 120 30 0
Ez Zone air distribution effectiveness, Table 6.2 0.9 0.9 0.9 0.9
Voz Outdoor airflow to the zone corrected for zoneair distribution effectiveness, (Pz*Rp +Az*Ra)/Ez, cfm
178 89 356 89 #DIV/0!
Vpz Primary airflow to zone from air handler. InVAV systems, use the design value. cfm
1200 1200 1200 1200
Vpzm
The minimum value of the primary airflow tozone from air handler. In CAV systems, Vpzm= Vpz. cfm
1200 1200 1200 1200
Zp Primary outdoor air fraction, Voz/Vpzm 0.15 0.07 0.30 0.07
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SYSTEM LEVEL
Ps System population, maximum simultaneious # of occupants ofspace served by system
25
D Occupant diversity, ratio of system peak occupancy to sum of spacepeak occupancies, = Ps/ Pz
0.46
Vou Uncorrected outdoor air intake, = D* Rp*Pz + Ra*Az, cfm 441
Xs Mixing ratio at primary air handler of uncorrected outdoor air intaketo system primary flow, = Vou/Vps
0.09 Not used in calculation
SYSTEM EFFICIENCY
Max Zp Max Zp 0.30
Ev System venti lation efficiency, Table 6.3 based on maxZp 0.80
Percent outdoor air intake
Vot Minimum outdoor air intake, Vou/Ev, cfm 552 11% = Vot/Sum of Vpz
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Time Averaging
Fluctuating occupancy
Intermittent interruption of the supply airflow
Intermittent closure of the OA damper
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Reset outdoor air intake flow.Occupancy
Expected occupancy scheduled by time of day.
Occupancy sensors.Estimate occupancy based on CO2.
Air Distribution EfficiencyIf min OA determined in heating mode, OA can be reduced duringcooling due to a higher EzSolve equations in appendix A dynamically based on zone and
system flows to reset zone minimums and outdoor airflow.Dont drop below the area outdoor air rate Ra.Economically limited to high-density occupancies.
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CO2 with VAV Systems%CO2 = (CR -400)/(CR-max 400) 400 ppm ambient assumed
Zone Minimum Primary
Airflow Setpoint ResetSystem OA Setpoint Reset
CR zone concentration
Cooling Max
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DCV for multiple zone recirculating systemshas not been adequately developed at this
time.
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Read the standard
Handbook is available
ASHRAE courses
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