EPA Program Impacts Office Zoning

A S H RA E J O U R N A L

J a n u a r y , 1 9 9 7 A S H R A E J o u r n a l 37

The following article was published in ASHRAE Journal, January 1997. © Copyright 1997 American Society of Heating, Refrigerating and Air-Conditioning Engineers,Inc. It is presented for educational purposes only. This article may not be copied and/or distributed electronically or in paper form without permission of ASHRAE.

EPA Program Impacts Office Zoning

y the 1950s individual room tem-perature control was favored by

many engineers in the exterior spaces ofoffice buildings. Of major concern was aproblem that some called “travelingshadows,” meaning that some buildingsshaded other buildings at times. Thiscould result in wide variation in loads onthe same exposure. In some cases therecould be a heating load in one module ofspace adjacent to a significant coolingload in another. The air-water inductionsystem was one that addressed this prob-lem, offering individual temperatureselection and control on a modular basis,typically with 4- to 6-foot- (1.22 to 1.82m) wide modules. Lighting dominatedthe interior load, and the building thathad many zones on the exterior of a floormight have but one or very few zones inthe interior.

In the 1960s, temperature selectionand control were provided for interiormodules of space by design that includedvariable air volume terminals that couldbe individually controlled by system-powered or pneumatic equipment.

Energy conservation became a muchhigher priority in the early 1970s, whichcontributed to building designs andmaterials that reduced solar loading,also reducing the impact of travelingshadows. Individual temperature selec-tion became regarded as energy-waste-ful and helped lead to regulations thatlimited allowable room temperatures.Later these regulations were relaxed inmost buildings. Less costly multi-roomzoning increased in design practice and

for several years has been regarded asadequate by many engineers.

Now the need for modular control hasagain appeared, but this time the need isdue to the distribution of internal heatgains in both interior and exterior spacesof both new and existing buildings. Asharp acceleration of this trend is occur-ring today due to the Energy Star OfficeEquipment Program of the United StatesEnvironmental Protection Agency (EPA)and Department of Energy (DOE).

This article will address:1. A choice for HVAC system design-

ers.2. The nature of the changes.3. The Energy Star Office Equipment

Program sponsored by the EPA and bythe DOE.

4. Impact on meeting ASHRAE Stan-dard 62-1989.

5. How energy cost savings alone willpay for meeting these changes while dra-matically improving comfort andworker productivity.

A Choice for System DesignersAs a designing engineer, imagine you

have two sets of plans on your desk. Oneplan provides traditional thermal zoning.The other plan provides individual roomcontrol (IRC) in which the individualcan control the temperature of their ownspace. Also, assume you know that therelative first costs, energy costs andmaintenance costs result in an owningcost that favors IRC.

So you have the choice of providing asingle uniform temperature or individual

room control. Which plan do youchoose? All other things being equal,you choose the IRC based on the notionthat the occupants will be happier. Youknow that people prefer different spacetemperatures. In fact even the same per-son prefers different space temperaturesdepending on their own level of activity,health, etc.

The above example serves as evi-dence, and we can all agree IRC is adesirable HVAC feature. With this inmind, this paper will discuss how thechanging office environment will all butrequire IRC. Traditional thermal zoningcan no longer be depended upon to pro-vide a single uniform temperature con-

About the Authors

Robert J. Rose is a mechanical engi-neer for the U.S. Environmental Pro-tection Agency in Washington, D.C.His work with the Atmospheric Pollu-tion Prevention Division focuses onprofitable pollution prevention. Hiswork involves HVAC systems as wellas lighting and office equipment. Hereceived his bachelor’s degree in 1990and master’s degree in 1992, both inmechanical engineering, from theUniversity of Maryland.

Jack Dozier, Life Member ASHRAE,resides in Shreveport, La. and hasbeen involved in the design and salesof HVAC products since 1948. He hasa strong interest in system conceptsand has been heavily involved in ma-jor equipment, controls, and computerroom environmental systems.

B

By Robert J. Rose and Jack DozierLife Member ASHRAE

3 8 A S H R A E J o u r n a l J a n u a r y , 1 9 9 7

sistently. Lastly, this paper will concludethat the time spent to further analyzeIRC and its effects would be better spentdesigning and implementing IRC.

The Nature of the ChangesHistorically HVAC designers have

considered internal heat gains as beingevenly distributed in office space. Loadcalculation has typically input heat gainsfrom lighting and office equipment as asingle watts-per-square-foot value. Nochange in that practice is likely unlesscloser detail is known at the time ofdesign, and expected to be permanent.Also, such an approach is generally ade-quate for the sizing of major equipment.Until recent years the expectation of an

evenly distributedinternal heat gainwas reasonable forzoning too, as thelighting load wasdominant. With theenergy awareness ofrecent years, lightingloads have beenreduced while theuse of heat generat-ing office equip-ment has increased.It is important to

recognize that each piece of officeequipment represents a spot load, ascontrasted to the even load distributionfrom a symmetrical pattern of light fix-tures.

The ASHRAE Fundamentals Hand-book of 1993, Table 9, Chapter 26 (Table1) lists the recommended rate of heat gainfor selected office equipment, for the pur-poses of load calculation. Scanning theright hand column of the table, onebecomes aware of the variety of loads thatmay appear almost anywhere in the mod-ern office. One microcomputer may con-tribute 300 BTU/h (88 W) to the load of itsmodule of space, while the microcomputerin another module of space contributes sixtimes that amount. Still another module of

space may have a minicomputer thatreleases 15,000 BTU/h (4397 W). We Sim-ply do not know what load to expect in alocation, and when (not if) this mobile loadwill change. As a frame of reference to thesignificance of the office equipment inroom sensible load, the same chapter of thehandbook lists the sensible heat gain froman occupant as 250 BTU/h (73 W).

For the student who may not havelooked beyond the sizing of the systemto meet maximum load, the basic func-tion of room temperature control is tomatch the capacity being delivered to theactual load that exists. When capacityand load are not equal, temperaturechange occurs. Considering (for sim-plicity) interior zones, the multi-roomzone of control and the large multi-outletzone are usually designed, built and bal-anced for uniform air delivery through-out. When temperature excursionsignals a different load in some location,the system operators may attempt man-ual adjustment of air flow (“re-balanc-ing”) to restore a uniform and stabletemperature. This is and must be a “cutand try” operation, and several attemptsmay be required. Zone temperature setpoint may be adjusted to satisfy the mostpersuasive current complaint, but thatchange will probably trigger the nextcomplaint(s).

Table 1: Table from Fundamentals Handbook of 1993 shows the variety of loads that may appear almost any-where in the modern office.

Figure 1: Diagram at top shows a “common system” thatblends outdoor air and return air and serves roomsthrough a single duct. Diagram at bottom shows a “ded-icated system” that serves room through two separateduct systems.


Contributing heavily to the change isthe migration of the loads of electronicdata processing. Take for example a highrise in 1985 that had an entire floor ded-icated to data processing. Large main-frames and peripherals were served bycomputer room air-conditioning equip-ment, not a part of the loads or zoning ofoffice space.

Today the mainframes and computerroom a/c units are gone. As much (prob-ably more) data is processed in thatbuilding now by smaller computers,printers and the like scattered through-out the office space. Now the loads ofdata processing clearly influence zoningneeds of office space.

The rate of change in office equip-ment can be seen by comparing informa-tion on that subject in the three mostrecent ASHRAE Handbooks of Funda-mentals. Attention is called to Page26.22 in 1985, Page 26.11 in 1989 andPage 26.14 in 1993. There is officeequipment out there today that simplydid not exist a short while ago.

Where each office load change hasbeen recognized and promptly met withcareful air-flow adjustment, room tem-perature has been more stable. Fortu-nately (for room temperature stability),many computers have been left on.Announced in late 1993 for FederalAgencies, office equipment with theEnergy Star logo is now advancing intothe private sector.

Energy Star Program

According to the findings of U.S.EPA Energy Star Office Equipment Pro-gram personal computers account for5% of commercial energy use and coulddouble by Year 2000. In fact, energyconsumption by office equipment repre-sents the fastest growing use of electric-ity in the country. Worse yet, officeequipment is often in use only half of thetime and 30% to 40% are left on over-night and on weekends.

In response, the EPA and DOE haveimplemented the Energy Star OfficeEquipment Program. Under this pro-gram manufacturers of computers, mon-itors, printers, copiers and faxesvolunteer to produce equipment whichpower down to a nominal power levelwhen not in use. This powered-downstate is referred to as the “sleep mode.”In return, manufacturers use an Energy

Star logo identifying the equipment asenergy saving.

As a result, currently 80% of new com-puters, 95% of new monitors and 95% ofnew printers made today have thesepower-down features. Historically, the

technology to power down equipmenthad been used in laptop computers to con-serve battery power. Due to the ever-changing and adaptive nature of the com-puter industry, the technology was easilyincorporated into other equipment. Notsurprisingly, the technology is becomingstandardized and is spreading even fur-ther. In all cases, this technology poses noincrease in cost for the consumer.

Table 2 outlines the performancespecifications for Energy Star OfficeEquipment. Equipment meeting orexceeding the power levels during“sleep mode” can label the equipment asEnergy Star. As stated earlier, 80% to95% of office equipment made todaymeets Energy Star criteria.

Currently, the power draw for officeequipment when not in “sleep mode” canvary greatly from one machine to another.Following the 1993 ASHRAE Funda-mentals Handbook, Table 9, Chapter 26,microcomputers can consume 90 to 530watts. Printers can consume roughly 300

watts and small copiers 1,700 watts to6,600 watts. Typical office monitorstoday can consume 90 to 200 watts.

Depending on the equipment, EnergyStar Office Equipment can power downanywhere from 66% to 94%, presenting asignificant task load change in the work-station, occupied or unoccupied. “Sleepmode” is entered minutes after the lastprint request, keystroke, mouse move-ment, fax, etc. Because these electricloads are largely convective, the resultingreduction in cooling load is nearly instan-taneous.

The Impact of Standards“Attorneys to Engineers: Protect

Self,” ASHRAE Journal, December1995 addresses the legal exposure ofengineers with regard to ASHRAE Stan-dard 62-1989. It is the position of thisarticle that whether or not a designshould meet the Standard is no longerjust a matter for engineering evaluation.Rather, this has become a matter for con-sideration by legal and insurance advi-sors of the owner and all involved indesign and construction of the project.This article addresses meeting the Venti-lation Rate Procedure of the Standard ina manner that can be demonstrated in thefield beyond reasonable doubt. This arti-cle will not address the quality of indoorair, nor is the Indoor Air Quality Proce-dure of the Standard discussed.

6.1.3, Ventilation Requirements ofthe Standard states “Indoor air qualityshall be considered acceptable if therequired rates of acceptable outdoor airare provided for the occupied space.”The standard calls for 20 CFM (9.4 L/s)per person in office application. 5.2 callsfor ventilation air to be delivered“throughout the occupied zone.”

An ASHRAE spokesman in the Tech-nical Services Department verified thatthis means each occupied zone. InHVAC we have occasion to introduceOA to serve system needs, such as toreplace air that is being exhausted. TheStandard is intended to address thehealth and safety needs of people. Sim-ply introducing OA into the system doesnot assure adequate OA delivery to eachoccupied zone.

One magazine article (1) addressestwo basic methods of delivering OA toan example of five identical single occu-pant interior rooms.

E N E R G Y C O N S E R V A T I O N

epending on the

equipment, Energy Star

Office Equipment can power

down anywhere from 66% to

94%, presenting a significant

task load change in the

workstation, occupied or

unoccupied. “Sleep mode”

is entered minutes after the

last print request, keystroke,

mouse movement, fax, etc.

Because these electric loads

are largely convective, the

resulting reduction in cooling

load is nearly instantaneous.

D


Figure 1 shows a “common system”that blends OA and RA, delivering themixture in a common duct system. Fig-ure 1 also shows the “dedicated system”which has two separate duct systemssupplying each room. One system dealswith thermal conditioning, while thesecond is a “dedicated” supply of 100%OA. The OA is constant volume condi-tioned to about room temperature andhumidity by a “ventilation air treatmentunit.” This article will not deal with sys-tem ramifications such as the need ofpreheat, or the application of the econo-mizer cycle, either of which may be con-sidered with the common or thededicated system of ventilation.

A basic problem of the commonapproach as cited in (1) is that total airflow is a function of room sensible load,while the ventilation need is a functionof occupancy. Each room needs 20 CFM(9.4 L/s) per person of OA in this exam-ple, but room loads may differ widely.For a common mixture to provideenough OA to all rooms the percentageof OA must be high enough to meet theneeds of the room with the lowest load.This is true of constant volume systemsas well as VAV. In article (1) the systemwould have to condition almost threetimes 20 CFM per person to provide theamount needed in each room. ApplyingASHRAE Standard 62-1989 Equation6-1 to this example resulted in 60% ofthe rooms getting less than 20 CFM ofOA, and still exceeded OA need of thededicated system by over 40%.

The dedicated system delivers onlythe OA to each space that is required byASHRAE Standard 62-1989. A case iscited in (1) where an 1100 ton (3 869kW) chilled water plant was used toserve all loads of a building using thededicated system.

The added OA to meet ASHRAEStandard 62-1989 Equation 6-1 wouldhave caused the common system toincrease that plant to 1474 tons (5 184kW). The cost of the added capacityexceeded the dedicated system’s addi-tional air handling system cost. In firstcost and in energy cost, the dedicatedsystem was the best choice, in the cir-cumstances of that system.

The dedicated system decouples thethermal and ventilation needs, allowingeach system to perform without interfer-ing with or depending upon the other.Hopefully software will soon be avail-able to assist evaluation.

Reheat is sometimes mentioned inconnection with meeting ASHRAEStandard 62-1989. In the dedicated sys-tem of ventilation the “ventilation airtreatment unit” may require reheat attimes when dehumidification alsoinvolves sensible cooling. Several man-ufacturers offer equipment that reheatswith energy that has been extracted fromincoming outdoor air and/or recoveredfrom energy rejected from the building.Such equipment may reheat ventilationair with little or no “new energy” tobecome reheat.

Reheat to support local ventilation isan entirely different matter. Article (1)

addresses the “Reheat Option.” The con-clusions of that article state “In the future,there just has to be a better way than toreturn to reheat in office buildings.”

Energy Cost Savings Pay forSystem Concept

Over-cooling is common in spaces thatare unoccupied, unlighted and with officeequipment off, when these spaces are partof a multi-room zone. A study was con-ducted by an independent consultingengineer to determine how much energyis wasted in conditioning and deliveringair to spaces in excess of the actual need.Figure 2 shows six single-occupant inte-rior rooms. For the purpose of this study,heat transfer between conditioned spacesis ignored. Each occupied room is consid-ered to be fully loaded while unoccupiedrooms (cross-hatched) have zero load.

In Figure 2, the thermostat is in anoccupied room. To maintain the desiredroom temperature (yellow) at full loadthat space must receive 100% capacity,or full air-flow in this VAV example. Todeliver full flow to any space the VAVbox must deliver full flow to all spaces,as the box cannot discriminate betweenthe rooms of a multi-room zone. Unoccu-pied rooms over-cool (blue). Eventhough half of the rooms are unloaded,the multi-room zone VAV (MRZVAV)takes 100% air-flow from the system.Under the same conditions IndividualRoom Control VAV (IRCVAV) adjustsair flow to the needs of each room taking50% air-flow from the system.

1cpm - copies per minute. Energy Star performance specifications for copiers are a function of cpm2ppm - pagers per minute. Energy Star performance specifications for printers are a function of ppm

Table 2: Performance specifications for Energy Star Program are outlined. Eighty to 90% of office equipment being man-ufactured today now meets specifications.

Copiers Effective Date “Sleep Mode”(0 ‹ cpm1 ‹ 20)

“Sleep Mode”(20 ‹ cpm1 ‹ 44)

“Sleep Mode”(44 ‹ cpm)

Tier 1 July 95 ‹5W ‹40W ‹40W

Tier 2 July 97 ‹5W ‹10W ‹15W

Printers Effective Date "Sleep Mode"(0 ‹ ppm2 ‹ 7)

"Sleep Mode"(7 ‹ ppm ‹ 14)

"Sleep Mode"(14 ‹ ppm)

Oct. 1995 15W 30W 45W

Personal Computers/Monitors Effective Date "Sleep Mode"

Oct. 1995 30W


To quantify energy usage of the twoconcepts (IRCVAV and MRZVAV),detailed energy analyses were conductedby computer. Hourly loads were calcu-lated, partial load performance of actualequipment selections were considered,and an effort was made to fairly evaluateboth zoning concepts.

A bulletin (2) outlines the study insome detail. A significant difference wasexpected because the operating schedulerevealed that each office is unoccupiedmuch of the time that the HVAC system isin operation. The first computer run didnot show a predicted contrast. It was thenlearned that the program had considered“averaging” control for the MRZ system,as shown in Figure 3.

With averaging control, the tempera-ture of each (or selected) space(s) is mea-sured and the zone responds to theaverage of those temperatures.

The three unoccupied rooms wouldover-cool, lowering the average, andcausing the box to reduce airflow to allrooms of MRZVAV. Being fully loadedthe occupied rooms over-heat (red).Allowing this to continue could produceextremes like 85°F (29°C) in three roomsand 65°F (18°C) in the remaining threerooms. The computer “sees” the 75°F(24°C) average and calculates energyusage at 50% capacity for the MRZ.While this is possible, it is very unrealis-tic to assume that humans will toleratebeing over-heated just because somerooms are unoccupied. In some mannerreal-world occupants will cause anadjustment so spaces are comfortable(yellow). With full load that means fullairflow to the occupied and 100% airdelivery by the system to the box. That

the unoccupiedrooms over-cool isthe lesser of the evilspresented by MRZ-VAV. To achieve“reality-in” for“reality-out,” thestudy was adjustedto simulate “dis-criminator” control of the MRZVAV. Inthis case that means that no room isallowed to over-heat due to reduction ofairflow.

The study was input in an effort torepresent the operating schedule andprocedures of a “typical” building man-aged by the General Services Adminis-tration. IRCVAV used 29% to 57% lessenergy than MRZVAV in this example,depending on the location in the buildingof the spaces considered.

This was only one example of onebuilding, but the example was by nomeans a worst-case scenario. The sav-ings were due to the ability of IRCVAVto take advantage of the load change inindividual rooms. In the study the loadchange was due to rooms being unoccu-pied. Now, with the Energy Star pro-gram, occupied rooms will experienceload change too, and IRCVAV will enjoya greater advantage over MRZVAV thanthe study revealed.

This energy contrast was presented tomany groups in 1995 including engi-neers, architects, utilities and end users.The comment of one consulting engi-neer was “this is obvious when you lookat it, but few of us have looked.” How-ever, some who are not that close toHVAC design simply assume thatgreater comfort means energy waste.

One architect said “give them individualcontrol and they will use more energythan they need.”

A first cost addition for IRCVAV(over MRZVAV) will be repaid fromenergy savings, whether very quickly orless quickly. This is not a situation thatcalls for an analysis of the paybackperiod, as is appropriate for machinesthat have different costs and efficiencies,but that do the same job. The really fastpayback is in occupant comfort, and inthe productivity increase that resultsfrom individual temperature selectionand control.

Productivity and ComfortRecent scientific studies have

addressed the influence of individualcontrol as a means to minimize workerdistraction by thermal conditions.

Providing personal control on a one-to-one basis (one person per diffuser andcontroller) yielded a measured produc-tivity increase of 2-3% in an actualproject, as cited by Prof. Volker Hart-kopf at Carnegie Mellon University. Ascontrasted to the conditions experiencedin the typical multi-room zone, or thelarge multi-diffuser zone. This evalua-tion was made when most computerswere left on during occupency. Withsuch equipment going in and out of a

Figure 2: Diagram shows six single-occupant interiorrooms. Occupied rooms are considered to be fully loaded,and unoccupied rooms (cross-hatched) have zero load.

E N E R G Y C O N S E R V A T I O N

Figure 3: With a multi-room zone, the temperature ofeach space is measured and the zone responds to the av-erage of those temperatures.


“sleep mode” worker distraction due totemperature change is observed to begreater.

An ASHRAE Journal article (3) usesan occupancy density level of 7 personsper 1000 ft2 (93 m2) in connection withoffice ventilation. In the writer’s experi-ence modular zoning that involves onediffuser and one controller for a singleoccupant office costs about $1.50 persquare foot more than the typical multi-room zone. Combining these factorswith the lower percentage of productiv-ity increase from the CMU research(2%), and assuming the total cost of anemployee to be $30,000 per year yields asimple payback on the investment in 4.3months.

If the these figures are applied to anowner-occupied office building of100,000 ft2 (9 290 m2), the productivityincrease would reward the owner-employer on the order of $420,000 peryear after the first cost of $150,000 hasbeen repaid.

This article will not attempt to refinethese rough figures to the net gain ofindividual control to a building owner,or to a tenant. It is obvious withoutcostly research that there is great valuein individual control that minimizesworker distraction due to thermal dis-comfort.

Payback prediction (based on workerproductivity) really may not be withinthe engineer’s scope of responsibility orexpertise. The client may have othermeans to evaluate the cost of employeedistraction.

Where the engineer can help his client(architect and/or end user) is to clearlyexplain the limitations of the traditionalmulti-room zone when faced with thewidely varying internal loads that havedeveloped in the modern office. The clientexpects the system to provide a consistentroom temperature, and the MRZ may nolonger provide that with load changes thatare taking place. The client will recognizethat office equipment has changed dra-matically, he may have heard of theEnergy Star Program, but he may not haverelated these changes to an increase inworker distraction due to discomfort.

How can the engineer prepare his cli-ent to invest more than he might pay forthe obsolete multi-room zone? A start isto explain why the design of the past isnot adequate for the needs of today. Fur-ther, the client may believe thatimproved comfort means energy cost

increase, when the opposite is true withindividual room control by VAV.

On energy cost alone a payback willresult. If the client will not invest in adesign that assures comfort, the resultsbecome his or her responsibility. If the

engineer does not alert the client to thesechanges, it is the engineer who will beresponsible for the client’s disappoint-ment.

This is no hard choice that the engi-neer offers. This is more like offering aluxury vehicle that will pay for itself atthe gas pump when compared to basictransportation that has become inade-quate.

ConclusionThere is clearly a determined and

effective effort on the part of the EPA tominimize energy use. In this effort, ade-quate indoor air quality will be provided,but over-ventilation is recognized aswasteful. By decoupling the ventilationsystem from the system that conditionsthermally we are free to consider optionsthat ventilate to actual rather than topotential needs.

An excellent article in ASHRAE Jour-nal (4) has addressed the fact that thepower consumption data of office equip-ment manufacturers “is not accurate andsignificantly overstates the heat genera-tion” of automatic data processing

(ADP) equipment. This does not con-tradict the fact that ADP and other officeequipment have impacted the zoningneeds of the modern office.

That equipment loads do differwidely is seen by the example in Figure1 of that article (4), where actual “mea-sured maximum” power ranged from 55watts in some locations to 660 watts inothers. “Nameplate power” ratings at thesame location are shown as 180 and 875respectively. Further in Tables 3a, b, c,and d actual maximum watts of ADPitems ranged from 26 to 840. Where willthese spot loads be located, and whenwill they be moved? As to change, this(1994) article was apparently writtenbefore the EPA Energy Star Programcould be considered, as maximum wattsand idle watts are shown as the same forcomputers and monitors.

Obviously the office load today ismodular and ever-changing. The onlyway to consistently control temperaturein each module of space is to meet mod-ular load change with individual controlof each module of space. To do this withenergy efficiency and maximum diversityof capacity calls for control by variableair volume. A system that meets theseneeds is called “modular vav.” For thepurposes of this article a “module ofspace” could be a small office or an indi-vidual workstation within a larger office.

References

1. “Meeting ASHRAE 62-89 at LowestCost” Heating/Piping/Air Conditioning Jan-uary, 1995, Dozier

2. Acutherm Form 2.3G494. For a copy,call (800) 544-1840

3. “Determining Ventilation Rates: Revi-sions to Standard 62-1989,” ASHRAE Jour-nal, February 1996, Taylor

4. “Measuring Computer Equipment LoadsIn Office Buildings” Wilkens and McGaffin,ASHRAE Journal, August 1994

Please circle the appropriate numberon the Reader Service Card at the backof the publication.Extremely Helpful ........................708Helpful .......................................709Somewhat Helpful .......................710Not Helpful.................................711

ow can the engineer

prepare his client to invest

more than he might pay for

the obsolete multi-room

zone? A start is to explain

why the design of the past is

not adequate for the needs

of today. Further, the client

may believe that improved

comfort means energy cost

increase, when the opposite

is true with individual room

control by VAV.

H

Documents

EPA Program Impacts Office Zoning