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Ventilation for AcceptableIndoor Air Quality

62.1-2010

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

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What Is ASHRAE Standard

62.1?

The Industries Ventilation StandardConsensus StandardStandard of Care

Used in NFPA 5000 BuildingConstruction and Safety Code

LEED Requirement

2009 IMC Ventilation systemefficiency may be calculated byAppendix A (62.1-2004)

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History of the Standard

1905 Flugge 30 cfm

1936 Yaglou 10 cfm 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 office 20 cfm/p

2004 Key Changes

office 17 cfm/p

2007 Appendix H office 17 cfm/p 2010 Dropped Smoking office17 cfm/p

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Acceptable Indoor Air Quality

What Is It? Standard 62: Air in whichthere is no known

contaminants at harmful

concentrations as determinedby cognizant authorities and

with which a substantial

majority (80% or more) of thepeople exposed do not

express dissatisfaction.

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How Much Ventilation?

Unknown Chamber studies

Limited to body odor (olf)

Medical evidence

No evidence based

studies

Rule of thumb evidence

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Chamber Body Odor StudiesImpact of ventilation rate on visitors

From ASHRAEpresentation by

Steve Taylor

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Body Oder StudiesCain & Leaderer

From ASHRAEpresentation by

Steve Taylor

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Cain & Leaderer

1983 For nonsmoking occupancy, 47 combinationsof temperature, humidity, ventilation rate and

occupancy density were examined. Odor

level depended entirely on ventilation rate perperson irrespective of the number of personsin the chamber.

For both smoking and nonsmokingconditions, a combination of hightemperature (78F) and humidity (r.h. > 70

%) exacerbated the odor problem

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Recent Studies

Hillsborogh County Schools March 2011 Engineered Systems

9th

largest district in US

7.5 cfm/student 2 California Studies ongoing Anticipate ventilation rate changes

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62.1 New in 2010

PM2.5 non-attainment areas require air cleaning Smoking spaces no longer covered by thestandard Air intake separation distances revised Deletes requirements for health care spaces Revises IAQ procedure to make it more robust Most natural ventilation systems now requiremechanical systems for when natural vent cannot

be used (thermal comfort, noise, security)

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Fun Facts

Means to balance the system to achieve minimum

airflow. 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 other

devices with wetted surfaces.

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Two paths to compliance

Ventilation Rate Procedure

Most commonly used method

Lookup table (simple) or Appendix A (complex)

Need zone air distribution effectiveness

LEED requires this method

Indoor Air Quality Procedure

Design to maintain specific contaminant levels

Mass Balance Analysis

Methods used in similar buildings

Validation by contaminant monitoring

Single duct

systems such

as VAV

reheat

Multiple paths: Fan

powered VAV and

Dual duct

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Ventilation Rate Procedure

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Ventilation Rate Procedure

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Ventilation Rate Procedure

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Classroom ExampleSingle zone 2010

High School classroom 35x35 30 people Vbz = Rp

Pz

+ Ra

Az Vbz

= Breathing Zone OA

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 or14.9 cfm/person

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Short-Term Conditions

Peak occupancy of short duration Ventilation interrupted for a short period oftime T = 3V/ Vbz V = Volume of ventilation zone

+ Zone outdoor air flow

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Example Private Office

230 Sq Ft, 9 ft ceiling Work station and 2guest chairs

T= 3V/ Vbz = 9*230*9/(3*5 +230 *0.06) = 3.6hrs

Assume guests present 1/3 of time

Design occupancy = 1 + (2 * 1/3) = 1.7

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Multiple-Zone Recirculating

Systems

For each zone: Vbz = Rp

Pz

+ Ra

Az Just like previous example

Voz =Vbz /Ez Just like previous example

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Multiple-Zone Recirculating

Systems

Primary outdoor air fraction Zp Zpz = Voz

/Vpz (For each zone)

Voz -

zone outdoor airflow

Vpz - minimum zone primary airflow(supply air)

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Uncorrected Outdoor

Air Intake

Vou

= Dall zones

Rp

Pz

+ all zones

Ra

Az Vou

-

uncorrected outdoor air intake

D - occupant diversity = Ps / all zones Pz

Ps

-total population of area served

by the system

Pz

- largest number of peoplein the zone

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System Ventilation Efficiency

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Outdoor Air Intake

Vot = Vou /Ev Vot - design outdoor air intake flow

Vou

-

uncorrected outdoor air intake

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

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62MZCalc

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62MZCALC

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62MZCALC

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DYNAMIC RESET

VRP procedure gives the peak rate based on

worst case assumptions (design)

Reset based on Occupancy: time of day Occupancy sensors

Carbon dioxide

Air distribution efficiency

Multiple space equation solved

dynamically Economizer reset of VAV minimums

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Dynamic Reset

Air Distribution Efficiency If min OA determined in heating mode, OA can bereduced during cooling due to a higher Ez

Solve equations in appendix A dynamically based onzone and system flows to reset zone minimums andoutdoor airflow.

OA economizer reset of VAV Box minimum

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

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Demand Controlled Ventilation

CO2 .Time averaging to reduce zone population is notallowed

Constant Volume with no air flow measurementAt CO2

max, damper positioned to admit Vot design

occupancy

At ambient CO2

levels set minimum to admit required

air quantity with no occupants Vat

Linear reset between CO2

max and CO2

ambient

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Demand Controlled Ventilation

CO2 sensor location: In the breathing zone

Typically adjacent to the temp sensor

44 AFF

Return air sensing doesnt work

Sensor type Infrared Accuracy +- 75 PPM

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Constant Volume W/O air flow

measurement

Calculate Vot at design occupancy rate Calculate Vot with no occupants call it Vat

Reset min OA damper position from Vat to

Vot as CO2 varies from 400 (ambient) to 800(calculated or arbitrary setpoint)

Damper positions set in conjunction withbalancer

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Constant volume with air

flow measurement Solve equations A-H dynamically to reset therequired min OA qty

Cant reduce the number of occupants using

time averaging Can reset zone effectiveness based onsupply air temperature

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Multiple Zone Systems

ASHRAE Research 1547TRP is working on it

Old

method in 2004 handbook

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Learning More

Read the standard

2010 Handbook is available ASHRAE ALI courses

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Questions