Ashrae 621 2008 High Performance Bldgr Presentation

8/6/2019 Ashrae 621 2008 High Performance Bldgr Presentation

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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

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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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Documents

Ashrae 621 2008 High Performance Bldgr Presentation