ASHRAE62.1-2007ChapterPresentation

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Ventilation for Acceptable

Indoor Air Quality62.1-2004

Dave Kahn, P.E.Dave Kahn, P.E.



The Industries Ventilation Standard

Consensus Standard

Standard of CareUsed in NFPA 5000 BuildingConstruction and Safety Code

LEED Requirement

Adopted by the 97 UniformBuilding Code

Not adopted by 03 or 06 IMC



1973 First Issued office 15 cfm/p

1981 Lower Rates office 5 cfm/p

1989 Higher Rates office 20 cfm/p

1999 Little Change office 20 cfm/p

2001 More Mandatory Language

2004 Key Changes



Area-related and occupancy-related ventilationcomponents (62N 2001)

Minimum Ventilation Rate Table revised to applyonly to nonsmoking spaces

Appendix G Existing buildings

Indoor air humidity (65% max) and pressure

requirements (positive when dehumidifying)Requirement to deliver outdoor air to occupiedspaces



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.



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









Single zone 2004

High School classroom 35 x35 30 people

Vbz

= Rp

Pz

+ Ra

Az

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 / Ez

447 /1 = 447 cfm or 14.9 cfm/person



Single zone 2001

High school classroom 35 x 35 30 people

15 cfm /person 15 * 30 = 450 cfm cfm



Single zone IMC

High school classroom 35 x 3530 people

15 cfm/person

50 people/1000 ft2

50/1000 * 35 * 35 = 61.25 people

62 * 15 = 930 cfm

403.3 Ventilation rate. The occupant load utilized

for design of the ventilation system shall not be less

than the number determined from the estimated

maximum occupant load rate indicated in

Table 403.3.Exception: The occupant load is not required to be

determined, based on the estimated maximum occupant

load rate indicated in Table 403.3 where approved

statistical data document the accuracy of an alternate

anticipated occupant density.



Single zone 2004

Hotel auditorium 40 x30 , 170 people

Vbz = RpPz + RaAz

5 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 / Ez

922 /1 = 922 cfm or 5.4 cfm/person



Single zone 2001


15 cfm/person

15 * 170 = 2,550 cfm



Single zone 2003 IMC


15 cfm/person

15 * 170 = 2,550 cfm

Estimated maximum occupancy:120 people/1000 ft2 or 144 people



Smoking areas shall have more ventilationand/or air cleaning than comparable

non-smoking areas.

Specific ventilation rate requirements cannotbe determined until cognizant authorities

determine the concentration of smoke thatachieves an acceptable level of risk



Primary outdoor air fraction Zp

Zp = Voz /Vpz

Voz - zone outdoor airflow

Vpz - minimum zone primary airflow(supply air)





Vou = D all zonesRpPz + all zones RaAz

Vou - uncorrected outdoor air intakeD - occupant diversity = Ps / all zones Pz

Ps -total population of area servedby the system

Pz - largest number of peoplein the zone



Vot = Vou /Ev

Vot - design outdoor air intake flow

Vou - uncorrected outdoor air intake

Ev - ventilation efficiency from Table 6-3or Appendix A



0.070.300.070.15Primary outdoor air fraction, Voz/VpzmZp

1200120012001200The minimum value of the primary airflow tozone from air handler. In CAV systems, Vpzm= Vpz. cfm

Vpzm

1200120012001200Primary airflow to zone from air handler. InVAV systems, use the design value. cfm

Vpz

#DIV/0!8935689178Outdoor airflow to the zone corrected for zone

air distribution effectiveness, (Pz*Rp +Az*Ra)/Ez, cfm

Voz

0.90.90.90.9Zone air distribution effectiveness, Table 6.2Ez

0301206060Az*Ra

05020020100Pz*

Rp

0.060.060.120.060.06People outdoor air rate from Table 6.1,cfm/person

Ra

551055Area outdoor air rate from Table 6.1, cfm/ft2Rp

1020420Zone population, largest # of people expectedto occupy zone

Pz

500100010001000Floor area of zone, ft2Az

Office

space

Conference /

meeting

Classrooms (age 9

plus)

Reception

areas

Office

space

Space type (select from pull-down list)

Zone 4Zone 3Zone 2Zone 1Zones served by system



= Vot/Sum of Vpz11%552Minimum outdoor air intake, Vou/Ev, cfmVot

Percent outdoor air intake

0.80System ventilation efficiency, Table 6.3 based on maxZpEv

0.30Max ZpMax Zp

SYSTEM EFFICIENCY

Not used in calculation0.09Mixing ratio at primary air handler of uncorrected outdoor air intaketo system primary flow, = Vou/Vps

Xs

441Uncorrected outdoor air intake, = D* Rp*Pz + Ra*Az, cfmVou

0.46Occupant diversity, ratio of system peak occupancy to sum of spacepeak occupancies, = Ps/ Pz

D

25System population, maximum simultaneious # of occupants of

space served by system

Ps

SYSTEM LEVEL



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 andsystem flows to reset zone minimums and outdoor airflow.

Don t drop below the area outdoor air rate Ra.Economically limited to high-density occupancies.



CO2.

Time averaging to reduce zone population is not

allowedConstant Volume with no air flow measurement

At CO2 max, damper positioned to admit Vot designoccupancy

At ambient CO2 levels set minimum to admit requiredair quantity with no occupants Vat

Linear reset between CO2max and CO2 ambient



CO2 with VAV Systems%CO2 = (CR -400)/(CR-max 400) 400 ppm ambient assumed

VAV Box Primary Air

ResetSystem OA Setpoint Reset

CR zone concentration

Cooling Max



Read the standard

Handbook is available

ASHRAE courses



Documents

ASHRAE62.1-2007ChapterPresentation