engineeringedition no. 29 january 2008 the international mechanical code and ansi/ashrae standard...

Edition No. 29 January 2008

The International Mechanical CodeAnd ANSI/ASHRAE Standard62.1-2004For nearly 20 years, the InternationalMechanical Code (IMC), publishedby the International Code Council(ICC), has used ANSI/ASHRAEStandard 62.1-1989 (Standard 62.1-1989), Ventilation for AcceptableIndoor Air Quality, to define theminimum outdoor air ventilationrates required for commercial,institutional and high-rise residentialbuildings. Using advancements inindoor air quality (IAQ) research,and the experience gained indesigning ventilation systems, theASHRAE Standing Standard ProjectCommittee 62.1 (SSPC 62.1)introduced new minimumventilation rates in breathing zonesand calculation procedures in 2004.Most notable about the new

minimum ventilation rates in therevised ANSI/ASHRAE Standard62.1-2004 (Standard 62.1-2004) isthat the rates are lower than thoselisted in Standard 62.1-1989 formost applications. This changeprovides opportunities for energysavings in treating outside air,improved indoor air quality andequipment cost reductions.

In May 2007, the ICC adopted theventilation rate procedure (VRP)from ANSI/ASHRAE Standard 62.1-2004 into the IMC. The newrequirements will be included in the2007 IMC Supplement. The IMC isused as the mechanical code at thestate or local level in 47 states andWashington D.C. (Figure 1).

Edition 29 of EngineeringSystem Solutions provides abrief tutorial on the

ventilation rate procedure (VRP)from ANSI/ASHRAE Standard62.1-2004 and examines its impacton energy savings and indoor airquality.

In May 2007, the VRP wasadopted into the InternationalMechanical Code, replacingANSI/ASHRAE Standard 62.1-1989 to define minimumoutdoor air ventilation rates. Thischange reduces the ventilationrequirements for many applications,providing an opportunity for energysavings. At the same time, the VRPprovides for improved indoor airquality by better defining outdoorair required to dilute contaminantsoriginating from occupants(cfm/person) and the buildingenvironment (cfm/ft2).

This article was prepared by DuaneRothstein, Applications Engineer forMcQuay and a Member of SSPC62.1. For more information on theequations presented in thisnewsletter, we encourage you torefer to ANSI/ASHRAE Standard 62.1-2004. For help in designingyour next ventilation system,contact your local McQuayrepresentative or visitwww.mcquay.com.

Jay EldridgeApplications ManagerMcQuay International

ENGINEERINGS Y S T E M S O L U T I O N S

Figure 1 – State-by-state adoption of the IMC1

1Map courtesy of the International Code Council. For updates, visithttp://www.iccsafe.org/government/adoption.html.

What does this mean?Designing with the VRP can provideimproved ventilation and indoor airquality in buildings. How can abuilding have improved ventilationand indoor air quality with lowerventilation rates? The simple answer isthat Standard 62.1-1989 definedventilation rates only as cfm perperson based on an estimatedmaximum occupancy and theapplication. These rates could beexcessive, causing many buildings tobe over-ventilated. The VRP inStandard 62.1-2004 fixed two factorsin determining minimum ventilationrates – people and area – whichaccount for contaminants originatingfrom occupants (cfm/person) and thebuilding environment (cfm/ft2). Thus,the new procedure does a better job of defining where buildings needventilation.

Comparing Ventilation RatesTable 1 lists commonly referencedoccupancy categories with theircorresponding outdoor air ventilationrates (additional occupancy categoriesare listed in Table 6-1 of theStandard). In most cases, the outdoor

air ventilation rates in Standard 62.1-2004 have been loweredcompared to Standard 62-1-1989. Anexception is the retail category, whichwas increased by adding a cfm/personrate. In all other categories, the dropin the cfm per person rate is modifiedby adding a cfm per area rate, knownas the Area Outdoor Air Rate (Ra).

Ventilation Rate ProcedureStandard 62.1-2004 defines the VRPas a prescriptive procedure todetermine minimum outdoor airflowrates based on the application,occupancy and floor area. Theminimum ventilation rates prescribedby the VRP are based on contaminantsources and strengths that are typicalfor the occupancy categories listed inTable 6-1 in Standard 62.1-2004.

The VRP can be found in Section 6.2(Ventilation Rate Procedure) ofStandard 62.1-2004. The following isa brief tutorial of the VRPcalculations. It is important to notethat there are a number of items toaddress when determining minimumventilation requirements, includingoutdoor air treatment, particulatematter and contaminants. Obtain a

copy of Standard 62.1-2004 to findout more about each of these items.

Breathing Zone Outdoor Airflow,VbzThe heart of the ventilation rateprocedure is the equation used tocalculate the breathing zone outdoorairflow. It calculates the designoutdoor airflow required in thebreathing zone for the occupiablespace or in a zone. The equation is asfollows:

Vbz = Rp Pz + Ra Az (6-1)

where:

Az = zone floor area: the net occupiablefloor area of the zone ft2 (m2)

Pz = zone population: the largestnumber of people expected tooccupy the zone during typicalusage. If the number of peopleexpected to occupy the zonefluctuates, Pz may be estimatedbased on averaging approachesdescribed in Section 6.2.6.2.

Rp = outdoor airflow rate required perperson as determined from Table6-1.

Ra = outdoor airflow rate required perunit area as determined fromTable 6-1.

The first part of the equation (RpPz) isthe per-person ventilation rate. Itcoincides with the ventilation ratesused in the IMC before Standard62.1-2004 was adopted, although therates in Standard 62.1-2004 aregenerally lower. The second part of theequation (Ra Az) is new and representsthe per-area ventilation rate. Referringto Table 1, the per-area ventilation rateis relatively small compared to the per-person rate. It is intended to moreaccurately address the amount ofoutdoor ventilation air required todilute building contaminants from theoccupied space.

Table 1: Comparison of Standard 62.1-1989 and -2004 ventilation rates2

Occupancy Category

62.1-1989 62.1-2004

Outdoor AirRequirements

EstimatedMaximumOccupancy

PeopleOutdoor Air

Rate

AreaOutdoor Air

Rate

OccupantDensity

Rp Ra

cfm/person cfm/ft2 #/1000ft2 cfm/person cfm/ft2 #/1000ft2

Classrooms (ages 5-8) 15 - 50 10 0.12 25

Classrooms (age 9+) 15 - 50 10 0.12 35

Laboratories 20 - 30 10 0.18 25

Office Space 20 - 7 5 0.06 5

Reception Areas 15 - 60 5 0.06 30

Conference Rooms 20 - 50 5 0.06 50

Restaurant Dining Rooms 20 - 70 7.5 0.18 70

Hotel Multipurpose Assembly 15 - 120 5 0.06 120

Retail Mall - 0.2 20 7.5 0.06 40

Auditorium 15 - 150 5 0.06 150

22004 ASHRAE Standard—62.1. © American Society of Heating, Refrigerating and Air-Conditioning Engineers, Inc., www.ashrae.org.

Zone Air DistributionEffectiveness, EzThe zone air distribution effectivenessis determined using Table 2 (Table 6-2in Standard 62.1-2004). Dependingon the zone air distributionconfiguration (diffuser and return grilllocation and supply air temperature),not all supply air will be distributedevenly throughout the breathing zonein a given space. For example, if boththe supply diffusers and return grillsare located in the ceiling, the supplyair will be colder and denser in thecooling mode than the air in theoccupied space, causing it to fall intothe breathing zone. Once in thebreathing zone, its temperature willincrease, causing it to rise to theceiling and exit the space via thereturn grill. This is an example ofgood zone air distribution with aneffectiveness value of 1.0. However,during the heating mode, the supplyair is usually less dense than the air inthe space. As the warm air enters the

space at ceiling level, some of it willexit through the return grill and notreach the breathing zone. This short-cycled or bypassed warm supply airresults in an effectiveness value of 0.8.As a result, it is important toremember that the zone airdistribution effectiveness value needsto be determined for both the coolingand heating modes. Note that thevalues for Ez in Table 2 are defaultvalues and can be adjusted by thedesign engineer.

Zone Outdoor Airflow, VozOnce the zone air distributioneffectiveness has been determined, thezone outdoor airflow, Voz, can becalculated for each ventilation zoneusing the following equation:

Voz = Vbz / Ez (6-2)

Voz represents the outdoor airflow thatmust be supplied to the zone by thesupply air distribution system,regardless of whether the system is inheating or cooling mode.

Outdoor Air Intake Flow, VotOnce the zone outdoor airflow hasbeen calculated for each zone, theoutdoor air intake flow (Vot) can becalculated for the entire system. Theventilation rate procedure accounts forthree types of systems – single-zone,100% outdoor air and multiple-zonerecirculating systems. The processvaries for calculating the outdoor airintake flow for each of these systems.

Single-zone systems supply a mixtureof outdoor air and recirculated air toonly one ventilation zone. Theoutdoor air intake flow for single-zonesystems is calculated using thefollowing equation:

Vot = Voz (6-3)

Simply put, the outdoor air intakeflow for single zone systems it equal tothe zone outdoor airflow.

100% outdoor air systems contain anair handler supplying only outdoor air(no recirculated air) to one or morezones. These systems are also known asdedicated outdoor air systems(DOAS). The outdoor air intake flowfor this system is calculated by addingall zone outdoor airflow requirementstogether.

Vot = Σall zones Voz (6-4)

Multiple-zone recirculating systemscontain an air handler supplyingoutdoor air and recirculated return airto more than one zone. Thecalculation for outdoor air intake flowis a bit more complex due to systemventilation efficiency. For multi-zonesystems, there will always be a criticalzone, which requires the highestamount of outdoor air in its supply airstream. Since multi-zone systemsprovide the same mixture of outdoorair and return air to each zone, therequired ventilation in the critical zonecan result in other zones being over-ventilated.

1. "Cool air" is air cooler than space temperature.2. "Warm air" is air warmer that space temperature.3. "Ceiling" includes any point above the breathing zone.4. "Floor" includes any point below the breathing zone.5. As an alternative to using the above values, Ez may be regarded as equal to air change effectiveness

determined in accordance with ASHRAE Standard 129 for all air distribution configurations exceptunidirectional flow.


Table 2: Zone Air Distribution Effectiveness3

Air Distribution Configuration Ez

Ceiling Supply of Cool Air 1

Ceiling Supply of Warm Air & Floor Return 1

Ceiling Supply of Warm Air 15°F (8°C) or More Above Space Temperatures & Ceiling Return. 0.8

Ceiling Supply of Warm Less Than 15oF (8°C) Above Space Temperature & Ceiling Return ProvidedThat The 150 fpm (0.8 m/s) Supply Jet Reaches To Within 4.5 ft (1.4 m) of Floor Level. Note: ForLower Velocity Supply Air, Ez = 0.8.

1

Floor Supply of Cool Air & Ceiling Return Provided That The 150 fpm (0.8 m/s) Supply Jet Reaches4.5 ft (1.4 m) or More Above The Floor. Note: Most Underfloor Air Distribution Systems ComplyWith This Provisio.

1

Floor Supply of Cool Air & Ceiling Return, Provided Low-Velocity Displacement Ventilation AchievesUnidirectional Flow & Thermal Stratification.

1.2

Floor Supply of Warm Air & Floor Return 1

Floor Supply of Warm Air & Ceiling Return 0.7

Makeup Supply Drawn In On The Opposite Side of The Room From The Exhaust &/or Return. 0.8

Makeup Supply Drawn In Near To The Exhaust &/or Return Location. 0.5

Two things can happen to the extraoutdoor air in over-ventilated zones. Itcan exit the zone via the return airstream, mix with the incomingoutdoor air and re-enter the supply airstream, causing the outdoor airdemand to decrease, or it could exitthe zone via the exhaust andexfiltration air streams, causing theoutdoor air demand to increase.

There are multiple steps required tocalculate the outdoor air intake flowfor multiple-zone recirculatingsystems. First, the primary outdoor airfraction, Zp, needs to be determinedusing the following equation:

Zp = Voz / Vpz (6-5)

The zone primary outdoor air fractionis the ratio of zone outdoor air to zoneprimary air for each zone served bythe system. Zp must be calculated foreach zone and the highest value mustbe chosen among all zones; this will bethe value of Zp that represents theprimary outdoor air fraction for thesystem. Within the equation, thevariable Vpz represents the zoneprimary airflow or the total amount ofsupply air (both outdoor and returnair) from the air handler.

Once the zone primary air fraction hasbeen determined for the system, thesystem ventilation efficiency, Ev, canalso be determined in one of twoways. The first is to use the defaultmaximum value in Table 3 below andthe second is to calculate the valueusing Appendix A located in the backof the Standard. Note: if Zp is greaterthan 0.55, Table 3 cannot be used and

the approach in Appendix A of theStandard must be used to determinethe value. Interpolation is allowedwithin the table.

For multiple-zone systems, it is usuallysafe to assume that people are not atpeak occupancy in every space at thesame time. For example, in an officebuilding, if all the occupants were intheir offices, the conference roomswould be below design occupancy.The same can be said for schools; if allof the students are in the classrooms,the multipurpose assembly room orauditorium are more than likelyunoccupied. Diversity is more likely tohappen in larger systems. To accountfor occupant diversity, D, thefollowing equation is used:

D = Ps / Σall zones Pz (6-7)

Ps is the system population andrepresents the total population in thearea served by the system. Pz is the zonepopulation which is defined as thelargest number of people expected tooccupy the zone during typical use.Alternative methods can be used to

calculate population diversity, providedthe alternative method does not producea value for the uncorrected outdoor airintake less than equation 6-6.

Now that diversity has been factoredin, the uncorrected outdoor air intakerate can be determined using equation6-6. The uncorrected outdoor airintake is the minimum outdoor airrequired by all zones before adjustingfor system ventilation efficiency.

Vou = D Σall zones Rp Pz + Σall zones Ra Az

(6-6)

Finally, the designer can determine theoutdoor air intake, Vot, for themultiple-zone recirculated systemusing the following equation:

Vot = Vou / Ev (6-8)

VRP SummaryTable 4 summarizes the steps fordetermining the required minimumoutdoor air intake using the VRP forsingle-zone, 100% outdoor air(DOAS) and multiple-zonerecirculating systems.

Table 3: System Ventilation Efficiency4

(Table 6-3 Standard 62.1-2004)

Table 4: Steps to determine outdoor air intake using the VRP

Max (Zp) Ev

≤ 0.15 1

≤ 0.25 0.9

≤ 0.35 0.8

≤ 0.45 0.7

≤ 0.55 0.6

≤ 0.55 Use Appendix A


Single-Zone Systems 100% Outdoor Air Systems Multiple-Zone Systems1 Determine Zone Population, Pz Determine Zone Population, Pz Determine Zone Population, Pz

2 Determine Zone Floor Area, Az Determine Zone Floor Area, Az Determine Zone Floor Area, Az

3Calculate Breathing Zone OutdoorAirflow,Vbz = Rp Pz + Ra Az (Use Table 6-1)

Calculate Breathing Zone OutdoorAirflow,Vbz = Rp Pz + Ra A (Use Table 6-1)

Calculate Breathing Zone OutdoorAirflow,Vbz = Rp Pz + Ra Az (Use Table 6-1)

4Determine Zone Air DistributionEffectiveness, Ez (Use Table 6-2)

Determine Zone Air DistributionEffectiveness, Ez (use Table 6-2)

Determine Zone Air DistributionEffectiveness, Ez (use Table 6-2)

5Calculate Zone Outdoor Airflow, Voz = Vbz / Ez

Calculate Zone Outdoor Airflow, Voz = Vbz / Ez

Calculate Zone Outdoor Airflow, Voz = Vbz / Ez

6Calculate Outdoor Air Intake Flow, Vot = Voz

Calculate Outdoor Air Intake Flow, Vot = Σall zones Voz

Calculate Primary Outdoor AirFraction, Zp = Voz / Vpz

7 N/A N/ADetermine System VentilationEfficiency, Ev (Use Table 6-3 orAppendix A)

8 N/A N/ACalculate Occupant Diversity, D = Ps / Σall zones Pz

9 N/A N/ACalculate Uncorrected Outdoor AirIntake; Vou = D Σall zones Rp Pz + Σall

zones Ra Az

10 N/A N/ACalculate Outdoor Air Intake Flow, Vot = Vou / Ev

Calculating Energy SavingsThe reduction in outdoor airflow thatcan result from using Standard 62.1-2004 to design a ventilationsystem (versus the 2006 IMC orStandard 62.1-1989) can have asignificant impact on the energy use ofan HVAC system. To illustrate thepotential energy savings, we willexamine an office building and aschool, each in two different climatezones (Minneapolis, MN andHouston, TX).

Office BuildingThe first example is a 39,000 squarefoot office building with seven zones.The building uses seven single zonerooftop systems, with each zonecontaining a constant volume rooftopunit with gas heat. Table 5 shows theoffice zone details, population densityand zone outdoor air comparisonusing Standard 62.1-2004 and the

2006 IMC. The zone outdoor airflowfor the Standard 62.1-2004 examplewas derived using the steps outlined inTable 4. The zone outdoor airflow forthe IMC example was derived usingthe ventilation rates in Chapter 4 ofthe 2006 IMC.

As Table 5 demonstrates, there is a37% reduction in the total amount ofoutdoor airflow required for the officebuilding when it is designed using theVRP in Standard 62.1-2004. The totalzone outdoor airflow of this system is4,660 cfm for the cooling mode and5,825 cfm for the heating mode. Inorder to avoid underventilating, thehigher value (5825 cfm in the heatingmode) should be used to size thesystem. The same system designedusing the 2006 IMC will require a totalzone outdoor airflow of 9280 cfm.

Table 6 compares the electric and gasconsumption of each system using

eQuest for this same office buildinglocated in Minneapolis, MN, andHouston, TX.

What is surprising from Table 6 is thatthe bulk of the energy savings resultfrom reduced energy consumed in theheating mode. In fact, in theMinneapolis example, the electric costfor cooling was actually higher for theStandard 62.1-2004 example. This ismost likely due to the free coolingeffect of the outside air. The gassavings in Houston were significantlyless due to its warmer climate zone.

In both locations, there are energysavings resulting from bringing in lessoutdoor air during the heating andcooling seasons. While it is notaddressed in this newsletter, furthercost savings may be available in theform of reduced installed costs (i.e.smaller equipment, smaller ducts).

Table 5: Office building ventilation design

Table 6: Office building energy use comparison in Minneapolis, MN and Houston, TX.

Standard 62.1-2004 2006 IMC(Standard 62.1-1989)Cooling Heating

Ventilation ZonePeople

Outdoor AirRate

AreaOutdoor Air

Rate

ZonePopulation

Zone FloorArea

BreathingZone

OutdoorAirflow

ZoneVentilationEfficiency

ZoneOutdoorAirflow


ZoneOutdoorAirflow

OutdoorAir

ZoneOutdoorAirflow

Rp Ra Pz Az Vbz Ez Voz Ez Voz

cfm/per cfm/ft2 people ft2 cfm cfm cfm cfm/per cfm

West Offices 5 0.06 30 5000 450 1 450 0.8 563 20 600

North Offices 5 0.06 27 4000 375 1 375 0.8 469 20 540

North Conference Room 5 0.06 75 1500 465 1 465 0.8 581 20 1500

East Offices 5 0.06 30 5000 450 1 450 0.8 563 20 600

South Offices 5 0.06 27 4000 375 1 375 0.8 469 20 540

South Conference Room 5 0.06 75 1500 465 1 465 0.8 581 20 1500

Interior Offices 5 0.06 200 18000 2080 1 2080 0.8 2600 20 4000

Total Zone-Level Outdoor Airflow 4660 5825 Total 9280

Single-Zone Systems Total Intake Air 5825*

Minneapolis, MN Houston, TX

Electric ($) Gas ($) Total ($) % Savings Electric ($) Gas ($) Total ($) % Savings

IMC $ 40,161.00 $ 10,564.73 $ 50,726.00 –– $ 51,394.00 $ 1,179.97 $ 52,574.00 —

Std 62.1-2004 $ 40,218.00 $ 7,560.63 $ 47,779.00 5.81% $ 50,336.00 $ 997.15 $ 51,333.00 2.36%

* 37% reduction

School BuildingThe second example is a 24,000square foot elementary school buildingusing a constant volume single zonesystem. The classrooms each have afloor-mounted unit ventilator. Theoffices, multi-use assembly room andother zones each have a dedicatedrooftop unit. Table 7 shows the schoolzone details, population density andzone outdoor air comparison usingStandard 62.1-2004 and the 2006IMC.

As in the office building example, theventilation system was designed usingthe rates found in the 2006 IMC foreach ventilation zone of the school.Depending on the zone type, theventilation requirement is 15cfm/person or 20 cfm/person,

resulting in a total system volume of17,225 cfm.

Designing the school using the VRPin Standard 62.1-2004 involves severalvariables depending upon the zone.For example, the zones containingrooftop units will use ceiling supplydiffusers and return grills in the samemanner as the office example.Therefore, during the cooling seasonEz will have a value of 1.0. In theheating mode Ez will have a value of0.8. For the classrooms using floormodel unit ventilators, Ez will have avalue of 0.8 in the cooling mode dueto the short cycling of cool dense air.In the heating mode, the classroomswill have an Ez of 1.0 due to the warmair rising in the space and the coolerreturn air entering at the base of the

unit. To avoid under-ventilating anyparticular zone, the larger value for thezone outdoor airflow between theheating and cooling mode should beused to size the ventilation system forthat particular zone. These values areshown in bold italic font in Table 7.Added together they total 14,521 cfmof outdoor air for the school. This is a16% reduction in total outdoor air forthe school compared to the 2006 IMCrates.

Table 8 compares the electric and gasconsumption of each system usingeQuest for this same school located inMinneapolis, MN, and Houston, TX.

As the table indicates there areminimal energy savings (~1%) usingStandard 62.1-2004 ventilation rates.

Table 7: School building ventilation design

Standard 62.1-2004 2006 IMC(Standard 62.1-1989)Cooling Heating

Ventilation ZonePeople

Outdoor AirRate

AreaOutdoor Air

Rate

ZonePopulation

Zone FloorArea

Breathing ZoneOutdoor Airflow


ZoneOutdoorAirflow


ZoneOutdoorAirflow

Outdoor AirZone

OutdoorAirflow

Rp Ra Pz Az Vbz Ez Voz Ez Voz

cfm/per cfm/ft2 people ft2 cfm cfm cfm cfm/per cfm

Wood/Metal Shop 10 0.18 30 1575 58445 1.0 584 0.8 729 20 600

Library 5 0.12 35 2500 475 1.0 475 0.8 594 15 525

Laboratory 10 0.18 35 2100 728 1.0 728 0.8 910 20 700

Music Room 10 0.06 100 1575 109545 1.0 1095 0.8 1368 15 1500

East Classroom #3 10 0.12 40 1500 580 0.8 725 1.0 580 15 600

East Classroom #2 10 0.12 30 900 408 0.8 510 1.0 408 15 450

East Classroom #1 10 0.12 30 900 408 0.8 510 1.0 408 15 450

South Offices 5 0.06 20 2700 262 1.0 262 0.8 328 20 400

West Classroom #1 10 0.12 30 900 408 0.8 510 1.0 408 15 450

West Classroom #2 10 0.12 30 900 408 0.8 510 1.0 408 15 450

West Classroom #3 10 0.12 40 1500 580 0.8 725 1.0 580 15 600

Multi-Use Asssembly 7.5 0.06 700 7200 5682 1.0 5682 0.8 7103 15 10500

Total Intake Air Total 14521* 17225

Table 8 - Energy usage: school single zone rooftops and unit ventilatorsMinneapolis, MN Houston, TX

Electric ($) Gas ($) Total ($) % Savings Electric ($) Gas ($) Total ($) % Savings

IMC $ 23,741.00 $ 14,537.60 $ 3,8279.00 – $ 26,868.00 $ 3,978.92 $ 30,847 –

Std 62.1-2004 $ 24,791.00 $ 13,134.00 $ 37,925.00 0.92% $ 26,743.00 $ 3,781.58 $ 30,525 1.04%

* 16% reduction

However, there is an important benefitto using Standard 62.1-2004ventilation rates. Table 9 shows thecfm per person using Standard 62.1-2004 ventilation rates versus the cfm/person rate used in the 2006IMC.

The amount of fresh outdoor air beingbrought into the classroom has clearlybeen increased over the 2006 IMCrates. This increased ventilation willimprove the classroom indoor airquality and the learning environmentfor the students. The reduction in the

total building cfm results from thelower cfm/person in the offices andmulti-use assembly room/auditorium.For these zones, the designer caninvestigate using smaller equipmentsizes to reduce installed costs. The netresult of designing a school ventilationsystem using 62.1-2004 is thatclassrooms will receive moreventilation to provide a better learningenvironment without raising theoperating or installed cost expenses forthe school building.

Installed Cost SavingsThe analysis performed in this articleis solely focused on energy savings andimproved indoor air quality. Thedecrease in minimum ventilation ratesmay result in first cost and installedcost savings due to smaller equipmentsizes, smaller duct sizes, etc. Furtheranalysis would need to be performedin order to validate these potentialsavings. It appears that the largestsavings will result from systems thatare built-to-order and systems that can save material costs with smallerduct sizes.

ANSI/ASHRAE 62.1-2007Since the ICC has adopted theminimum ventilation rates and the

ventilation rate procedure found inANSI/ASHRAE Standard 62.1-2004into the IMC, ASHRAE haspublished the ANSI/ASHRAEStandard 62.1-2007. Standard 62.1-2007 incorporates 62.1-2004and Addenda a, b, c, d, e, f, g, and hto 62.1-2004. To purchase a copy ofANSI/ASHRAE Standard 62.1-2007go to www.ashrae.org.

ConclusionThe minimum ventilation rates in thebreathing zone and the ventilation rateprocedure from ANSI/ASHRAE 62.1-2004 can have a positive impacton energy savings, indoor air qualityand first/installed costs. Theventilation rate procedure also allowsdesigners to properly ventilate forpollutant sources from the buildingand the building’s occupants whiletaking into account system efficienciesfor different ventilation systems suchas single-zone, 100% outdoor air andmultiple-zone systems.

This article only analyzed the effect ofStandard 62.1-2004 rates for single-zone systems. Further analysis wouldneed to be performed to demonstratethe impact on 100% outdoor airsystems and multiple-zone systems.

Table 9: Ventilation air for school zonescompared VRP versus IMC incfm/person.

Ventilation Zone62.1-2004 IMC

cfm/person cfm/person

Wood/Metal Shop 24 20

Library 16 15

Laboratory 26 20

Music Room 13 15

East Classroom #3 18 15



South Offices 16 20

West Classroom #1 17 15



Multi-Use Asssembly 10 15

For comments or suggestions, please call or write:Engineering Newsletter EditorMcQuay International13600 Industrial Park BoulevardMinneapolis, MN 55441Phone: (800) 432-1432E-mail: [email protected] more information on McQuay products and services, or to speak with your local representative, call (800) 432-1342, or visit our web page at www.mcquay.com.©2008 McQuay International

The data and suggestions in this document are believed current and accurate at the time of publication, but they are not a subs titute for trained, experiencedprofessional service. Individual applications and site variations can significantly affect the results and effectiveness of any information. The reader must satisfyhim/herself regarding the applicability of any article and seek professional evaluation of all materials. McQuay disclaims any responsibility for actions basedon this document.

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