Leading by example,

saving energy and

taxpayer dollars

in federal facilities

DOE/EE-0295

Internet: www.eere.energy.gov/femp/

No portion of this publication may be altered in any form without

prior written consent from the U.S. Department of Energy, Energy

Efficiency and Renewable Energy, and the authoring national laboratory.

Alternative Air Conditioning Technologies:

Underfloor Air Distribution (UFAD)

An overview of UFAD technology and its potential in federal facilities

Introduction and Background

Recent trends in today’s office environment make it increasingly more difficult for conventional centralized HVAC systems to satisfy the environmental preferences of individual office workers using the

standardized approach of providing a single uniform thermal and ventilation environment. Since its

original introduction in West Germany during the 1950s, the open plan office containing modular

workstation furniture and partitions is now the norm. Thermostatically controlled zones in open

plan offices typically encompass relatively large numbers of workstations in which a diverse work

population having a wide range of preferred temperatures must be accommodated. Modern office

buildings are also being impacted by a large influx of heatgenerating equipment (computers, printers, etc.) whose

loads may vary considerably from workstation to workstation. Offices are often reconfigured during the building’s

lifetime to respond to changing tenant needs, affecting

the distribution of within-space loads and the ventilation

pathways among and over office partitions. Compounding this problem, there has been a growing awareness of

the importance of the comfort, health, and productivity

of individual office workers, giving rise to an increased

demand among employers and employees for a high-quality

work environment.

Task Ambient Conditioning

During recent years an increasing amount of attention has been paid to air distribution systems that

individually condition the immediate environments of office workers within their workstations to

address the issues outlined above. As with task/ambient lighting systems, the controls for the “task”

components of these systems are partially or entirely decentralized and under the control of the occupants. Typically, the occupant has control over the speed and direction, and in some cases the temperature, of the incoming air supply. Variously called “task/ambient conditioning,” “localized thermal

distribution,” and “personalized air conditioning” systems, these systems have been most commonly

installed in open-plan office buildings in which they provide supply air and (in some cases) radiant

heating directly into workstations. TAC systems can be classified into the following two major categories:

1) furniture-based, and 2) floor-based, underfloor air distribution (UFAD). A majority of these systems include a raised floor system with which underfloor plenums are used to deliver conditioned air

to the space through floor grills, or in conjunction with the workstation furniture and partitions.

Illustration of typical

swirl diffuser used in

UFAD systems.
Underfloor Air Distribution

In the 1970s, underfloor air distribution

was introduced into office buildings in

West Germany as a solution to cable

management and heat load removal

issues caused by the proliferation of

electronic equipment throughout the

office [1]. In these buildings, the comfort of the office workers had to be considered, giving rise to the development

of occupant-controlled localized supply

diffusers to provide task conditioning. Some of the first UFAD systems

in Europe used a combination of desktop outlets for personal comfort control and floor diffusers for ambient

space control [2].

Prior to the 1990s, office installations

using underfloor systems had been

found primarily in South Africa,

Germany, and other parts of Europe.

The technology was not commonly

used in North America prior to about

1995, in part due to the downturn in

office building construction beginning

in the mid-1980s. Japan did not experience this same downturn, and as a result,

significant growth in UFAD technology

was observed during this period. Between

1987 and 1995, more than 250,000 m2

(2.7 million ft2) of office space in more

than 90 buildings were installed with

UFAD systems in Japan [3].

However, in the late 1990s growth

for raised floor installations in the

US was dramatic and designers and

manufacturers predicted that 35%

of new offices would use raised floors

by 2004. Half of these installations

were expected to incorporate UFAD

technology. This rate of increase has

slowed now (2003) due to the economic downturn and much reduced

office construction.

The purpose of this technology review

is to provide federal facilities managers

an overview of the principles, features,

benefits, and limitations of this important innovation in building conditioning technology.

 Technology Description

A task/ambient conditioning system is

defined as any space conditioning system that allows thermal conditions in

small, localized zones (e.g., regularly

occupied work locations) to be individually controlled by building occupants,

while still automatically maintaining

acceptable environmental conditions

in the ambient space of the building

(e.g., corridors, open-use space, and

other areas outside of regularly occupied work space).

UFAD systems are uniquely characterized by their ability to allow individuals

to have some degree of control over their

local environment, without adversely

affecting that of other nearby occupants.1

Depending on the UFAD system design,

ambient environmental control in

non-work areas may be provided by

additional local supply outlets, or by a

separate space conditioning system, but

in either case under automatic control.

The types of diffusers supported,

active or passive, further distinguish

UFAD systems from furniture-based

TAC systems. Active diffusers (for

purposes of this report) are defined

as those with local means of volume

adjustment (such as an integral variable

speed fan or damper) that is amenable

to automatic zone control (in addition

to means for occupant control). Passive

diffusers, although they may have means

for occupant adjustment, are combined

with terminal or system elements to

achieve zone control. Systems designed

with all fan-assisted active diffusers

typically utilize zero-pressure plenums.

Passive diffusers require pressurized

plenums. The majority of UFAD

systems currently being deployed

have pressurized plenums with either

active or passive diffusers.

Principles of Operation

Figures 1 and 2 illustrate the fundamental differences between traditional

overhead and furniture-based TAC and

UFAD systems, respectively. As shown

in Figure 1, overhead systems (in office

buildings, these are predominately variable air volume [VAV] all-air distribution systems) employ an extensive array

of ductwork and terminal devices to

provide supply air through the ceilingmounted diffusers. Often referred to as

mixing ventilation systems, these systems are designed to promote complete

mixing of supply air with room air,

thereby maintaining the entire volume

of air in the space at the desired temperature setpoint. Space air is typically

returned to the AHU via an open ceiling plenum that also contains various

other systems for lighting, electrical,

communications, and fire protection.

UFAD systems turn this concept

upside down and have in common

the following characteristics:

• Supply air, including at least the

minimum required volume of outside air, is filtered and conditioned

to the required temperature and

humidity by a conventional AHU

and passed through a minimum

amount of ductwork to an underfloor plenum. The underfloor plenum is formed by installation of a

raised floor system, typically consisting of 0.6 m x 0.6 m (2 ft x 2 ft)

concrete-filled steel floor panels

positioned 0.3–0.46 m (12–18 in.)

above the concrete structural slab

of the building. The raised floor

system also allows all cable services,

such as power and communication,

to be located in the plenum and

provides easy access for modifications and maintenance.

1

 In open plan settings there is less control due to airflow rate change associated with opening and closing floor diffusers than in private offices. Better

occupant control is achieved by designs that allow the airflow to be directed toward the occupant.

2 — FEDERAL ENERGY MANAGEMENT PROGRAM
personal comfort preferences. Different supply outlet configurations

may be used depending on the

conditioning requirements for a

particular zone of the building, as

discussed below.

• UFAD systems benefit from a floorto-ceiling airflow pattern that takes

advantage of the natural buoyancy

produced by heat sources in the

office to efficiently remove heat

loads and contaminants from the

space. Air is returned from the room

at ceiling level through recessed

lighting fixtures and return grilles

via a conventional ceiling return

plenum or return grilles located

high in the space when a return

plenum is not used.

• Because the air is supplied directly

into the occupied zone (up to 6 ft

(1.8 m) height), supply outlet temperatures are generally maintained

above 17 to 18°C (63 to 64°F) to

avoid uncomfortably cool conditions for the nearby occupants and

to minimize cool temperatures near

the floor.

There are a wide variety of approaches

being used to provide a combination of

individual and automatic zone control

for UFAD systems.2 (See reference [4]).

Typically, these systems use variable-airvolume (VAV) or constant-air-volume

(CAV) methods for general zone control (i.e., overall zone control other

than local occupant control).

• Six types of diffusers are currently

being offered;

1. Fan-assisted, active

2. Variable area, active

3. Swirl, passive

4. Swirl, active

5. Linear bar grille, passive

6. Linear bar grille, active

Figure 1. Overhead system.

Figure 2. TAC system.

2 The author has identified over a dozen variations of these systems.

• Individual office workers can control

their local thermal environment over

a relatively wide range (typically

by adjusting the volume and/or

trajectory of the supply air entering

the space), giving them the opportunity to fine-tune the thermal conditions in their workstation to their

FEDERAL ENERGY MANAGEMENT PROGRAM — 3
• The heating and cooling loads of

perimeter zones are handled by fanpowered constant volume or variable

volume terminal reheat units located

in the underfloor plenum (similar

to those shown in Figure 3). Passive

or active diffusers are located in

occupied areas of the zone normally

within about 4.5 m (15 ft) from the

exterior walls. Passive diffusers are

generally supplied by a (series) fan

can accommodate individual differences.

In today’s work environment, there can

be significant variations in individual

comfort preferences due to differences

in clothing and activity level (metabolic rate) as well as differences in the

local heat gains and losses. By allowing

personal control of the local thermal

environment, UFAD systems could

satisfy virtually all occupants, including those out of thermal equilibrium

with their surrounding ambient environment, as compared to the 80% satisfaction quota targeted in practice by

existing thermal comfort standards [5].

Improved air movement and ventilation

effectiveness; cleaner environment – Some

amount of improvement over conventional uniformly-mixed systems is

expected by delivering the fresh supply

air near the occupant and at the floor.

Improved occupant satisfaction and

increased worker productivity – UFAD

systems have the potential to increase

the satisfaction and productivity of

occupants as a result of their having

the ability to individually control their

workspace environments. The financial

implications of such improvements can

be extremely large as salary costs typically make up at least 90% of all costs

(including construction, operation,

and maintenance) over the lifetime

of a building.

Energy Savings – Energy savings over

conventional overhead systems are

predominately associated with two

factors: cooling energy savings from

economizer operation and increased

chiller COP, and fan energy savings.

Details of how these savings are

achieved can be found in [6].

Limitations

Among the items that limit the widespread acceptance and application of

UFAD technology are the following:

New and unfamiliar technology – For

the majority of U.S. building owners,

Figure 3. Pressurized plenum UFAD system.

Figure 4. Typical interior swirl diffuser layout.

powered mixing box or fan coil unit,

or a VAV box either connected to the

diffuser by ducting or by supplying

air to a partitioned area of the plenum where the diffusers are located.

• Interior zones are generally large

zones each controlled by one thermostat, but with diffusers located

near the occupants within or close

to their workstations.

Figure 3 shows a schematic diagram and

Figure 4 a typical diffuser layout for a

pressurized plenum UFAD system. This

system is being commonly applied to

office buildings due to its simplicity and

cost savings. Although this floor-based

air distribution system provides somewhat limited individual comfort control

for occupants, it still affords many of

the same flexibility and energy-saving

benefits associated with the others.

Potential of UFAD

Applications

Benefits

Improved thermal comfort for individual

occupants – Occupant thermal comfort

is perhaps the area of greatest potential

improvement in that UFAD systems

4 — FEDERAL ENERGY MANAGEMENT PROGRAM
developers, architects, engineers, and

equipment manufacturers, UFAD systems still represent a relatively new and

unfamiliar technology. The decision

to select a UFAD system will initially

require changes in common practice,

including new procedures and skills in

the design, construction, and operation

of such systems as well as changes in

responsibilities of the various installation trades. This situation creates some

amount of perceived risk to designers

and building owners.

Perceived higher costs – An industry survey found the perceived higher cost of

UFAD systems to be one of the two top

reasons that UFAD technology is not

used more widely by the industry today.

Many designers immediately eliminate

underfloor UFAD systems from consideration out of concern for higher first

costs of the raised flooring. However, as

described above, there are many factors

associated with raised floor systems that

contribute to reduced life-cycle costs in

comparison to traditional air distribution systems. In UFAD systems using

fan-powered supply diffusers, the additional cost of installing and maintaining many small units must be balanced

against the benefits of providing personal environmental control (reduced

occupant complaints) and reducing

the size of other system components

(e.g., central fan).

Limited applicability to retrofits and

certain building types/areas – The installation of UFAD systems and the advantages that they offer are most easily

achieved in new construction. Some

of the key system features are not always

suitable for retrofit applications (e.g.,

access floors cannot be installed in existing buildings with limited floor-to-floor

heights). Although widely applicable,

there are building types and areas

within buildings where access floors

and underfloor air distribution are not

appropriate. These areas are generally

those in which spillage has the potential to occur, including bathrooms,

laboratories, cafeterias, and shop areas.

Lack of information, design guidelines,

and evaluation methods – Although

in recent years there have been an

increased number of publications on

UFAD technology (see References),

there is still not a complete understanding of some fundamental fluid

mechanics and thermal issues and no

standardized design methods exist

yet. System operating sequences and

control techniques are likewise are

under development.

Earlier versions of ASHRAE Standard

55 [7] were based on the assumption

of a well-mixed and uniformly conditioned environment. UFAD systems,

however, usually involve greater variability of thermal conditions over both

space and time. The effect of providing

occupant-control has not been fully

taken into account, although it is well

established that occupants will tolerate

greater fluctuations in environmental

conditions if they have control over

them. The current version of the standard (55-92) was revised (see Figure 3

of the standard) to allow higher air

velocities than the previous version, if

the occupant has control over the local

air speed.

ASHRAE Standard 113-90 [8] is the

only currently available building standard for evaluating the air diffusion performance of an air distribution system.

The current version of Standard 113,

however, is based on the assumption of

a single uniformly mixed indoor environment, as provided by a conventional

overhead air distribution system. This

assumption is not necessarily appropriate for evaluating the performance of

UFAD systems that deliver conditioned

air directly into the occupied zone of the

building through supply outlets that are

in close proximity to and under the

control of the building occupants.

Potential for higher building energy use –

As with any space conditioning system,

a poorly designed and operated UFAD

system has the potential to use more

energy than that used by a well-designed

conventional system. For example, the

energy use of UFAD systems using

large numbers of small local fans3

 may

increase due to the relatively poor fan

and motor efficiencies in these units.

Thermal discomfort – UFAD systems

are perceived by some to produce a

cold floor, and because of the close

proximity of supply outlets to the occupants, the increased possibility of excessive draft exists. Some systems appear

to be designed and operated in such a

manner that they produce hot and cold

complaints similar to existing conventional systems despite the potential to

achieve better comfort performance.

Problems unique to underfloor plenums –

In UFAD systems, concern is sometimes expressed about the increased

probability of spillage and dirt entering directly into the underfloor supply

air stream, and therefore being more

widely distributed throughout the

occupied space. There is also some

concern about improperly dehumidified air being delivered to the plenum

where condensation could occur on

cool structural slab surfaces.

Virtually all of the issues listed above

are actively being researched [9] or

addressed by design and construction

professionals and equipment vendors

in response to market demand. Some

of these issues (e.g., plenum dirt and

moisture) have not been shown to be

problems in projects installed to date.

Many of the problems that do occur

can be traced to inadequate design and

operating strategies that have resulted

from lack of knowledge and experience

3

 Either integral to the floor diffuser or in terminal units.

FEDERAL ENERGY MANAGEMENT PROGRAM — 5
typically associated with early installations of any nascent technology.

Cost-Effectiveness

Cost considerations will be different

depending on whether the installation

represents new or retrofit construction.

Total first costs (shell and core plus tenant improvement) for UFAD systems

utilizing raised flooring will likely be

somewhat higher than those for a conventional system. Preliminary results

from research studies [9] have shown

total building first costs of pressurized

UFAD systems in new construction

(including raised floor and structural

differences) to be about 4-6% greater

than conventional. However, if a raised

floor system has already been justified

for other reasons, such as improved cable

management, the cost differential is

often eliminated altogether. In new construction, UFAD can lead to reduced

floor-to-floor heights thus reducing

structural costs. Furniture-based and

active diffuser based systems will generally cost more than other solutions.

Operating costs can be reduced in accordance with the energy-saving strategies

discussed above. With the improved

thermal comfort and individual control

provided by UFAD systems, occupant

complaints requiring response by facility

staff can be minimized. UFAD systems

using raised flooring provide maximum

flexibility and significantly lower costs

associated with reconfiguring building

services (when changes are being made

in the office layout) due to churn—and

thus reduce life-cycle costs substantially.

First cost for retrofits, generally the bulk

of construction activity is most likely

greater than those for new construction. And as indicated previously, some

facilities are not amenable to retrofit

by UFAD systems.

To determine total life cycle cost differences between UFAD systems and

conventional designs the following

factors must be considered in addition

to first cost:

Churn – This is the cost associated with

relocating personnel and is defined as

the ratio of total workplace moves in

a year to the total number of building

occupants. These figures vary widely

by industry type and building activities. Results of a study by IFMA [10]

are shown in Table 1.

As shown government facilities have

significantly lower churn than other

industries, which is also reflected in the

much lower percentage of open plan

space. This indicates that the benefits

of reduced churn costs in federal facilities may be limited. It should be noted

that the cost of churn can vary considerably depending on the extent of the

reconfiguration; i.e., simply moving

to a new cubicle is much different that

reconfiguring the layout of cubicles and/

or offices. The high proportion of offices

in government facilities could drive these

costs significantly if the reconfiguration

involves more than office to office moves.

O&M – This item includes the costs of

facility management and energy. While

energy savings estimates are limited due

to the lack of appropriate capabilities in

energy simulation programs and data

from monitored projects, indications

are that savings in annual HVAC system energy can be in the range of 10-

20% depending on system design and

weather conditions. Maintenance costs

are expected to be less than conventional systems due to the ease of access

to the distribution system. However,

commissioning/startup costs may be

greater since the location and operation of the diffusers may require

fine-tuning to optimize the occupant

interaction benefits.

Productivity and health – The savings

associated with productivity and health

benefits are difficult to measure and

require considerably more research. However, recent studies [11] indicate that

work performance improvements of 0.5

to 5% may be possible when the indoor

environmental quality is improved.

Federal-Sector Potential

The potential for deployment of UFAD

technology in the federal sector will

depend on cost-effectiveness and

availability of suitable buildings. Each

project must be considered on its own

merits. Overall the federal government

owns and operates over 500,0005

 residential and non-residential buildings

totaling about 3 billion ft2

 [12]. The

floor space is broken down between

agencies as shown in Table 2.

4 This study did not distinguish between various types of government facilities (i.e., state, local, federal) so it is unclear as to how representative these figures are for federal facilities.

5

 About 85% of these buildings are military housing.

Table 1. Churn rates.

Office plan

Churn (% office/

Group % open/bullpen)

Services 37 35/55/10

Manufacturing 40 34/58/8

Institutional/

Government4 23 67/20/13

Table 2. Federal building floorspace.

Agency % of Floor space

Defense 65.4

Postal 10.7

GSA 6.1

VA 5.0

DOE 2.6

Other 10.2

6 — FEDERAL ENERGY MANAGEMENT PROGRAM
There are roughly 76,000 existing nonresidential federal buildings [13] comprising 1.7 billion ft2

 of floor space. Of

this floor space, 51% (7% health care,

23% mercantile services, and 21%

offices) is suitable for the application

of UFAD. Assuming a rate of growth

in federal floor space roughly equivalent to the private sector at 2%6

 per

year, and assuming that the ultimate

penetration of UFAD technology

could reach that of VAV systems in

new construction (i.e., 75%) then

about 13 million ft2

 per year of new

construction could be considered for

a UFAD solution. Likewise, using the

same criteria, about 650 million ft2

 of

existing facilities could be considered

for UFAD retrofits.

Summary and Conclusions

UFAD systems have significant potential advantages compared with traditional VAV systems. Rarely has there

been a space conditioning technology

that promises the combined benefits

of improved thermal comfort, energy

efficiency, and productivity and health

improvement. While this technology

has seen significant adoption in other

countries, its use in the United States

has only been notable since 1995.

UFAD technology, like all nascent

technologies, is being advanced both

in theory and practice by researchers,

designers, manufacturers, and “early

adopter” owners who are working to

bring the design, operation, and costs

to the point where it can be more easily

and reliably applied. UFAD technology may someday displace overhead

VAV as the “system of choice” for

space conditioning.

While the use of UFAD systems in particular is becoming more common in

the private commercial sector, the overall potential for UFAD in federal facilities may be limited by low churn that

reduces life-cycle cost benefits. In addition, the overall federal building stock

is not as amenable to UFAD installations as the private sector due to the

higher cost of retrofits (i.e., a greater

ratio of fixed private offices) and less

overall applicable building types (51%

of the federal building floor space

versus 62% for private commercial).

However, in those situations where it

is appropriate there are many compelling reasons to consider UFAD for the

space conditioning solution.

Acknowledgment

Much of the material for this report has

been derived from the work of Fred

Bauman at the Center for the Built

Environment (CBE) at the University

of California, Berkeley. The author

would like to gratefully acknowledge

the support of Mr. Bauman, CBE

and its industry partners, CBE sponsor the National Science Foundation

(NSF), and the Regents of the University of California.

Manufacturers

Greenheck

(Fan-powered terminals)

P.O. Box 410,

Schofield, WI 54476-0410

(715) 359-6171

www.greenheck.com

Krantz

(Swirl diffusers)

Eurotech Products Inc.

3835 Deer Run

Denver, NC 28037

(704) 483-2050

Titus

(Swirl diffusers and

fan-powered terminals)

990 Security row

Richardson, TX 75801

(972) 699-1030

www.titus-hvac.com

Trox USA

(Swirl diffusers and

fan-powered terminals)

1005 Alderman Drive, Suite 103

Alpharetta, GA 30202

www.troxusa.com

Nailor Industries

(Swirl diffusers and

fan-powered terminals)

4714 Winfield Rd.

Houston, Texas 77039

(281) 590-1172

www.nailor.com

York International Corp.

(Complete product line for

pressurized plenum systems)

P.O. Box 1592

York, PA 17405

(717) 771-6878

www.york.com

6 This also assumes that the rate of growth in the three most applicable building types is equal to the nominal rate.

FEDERAL ENERGY MANAGEMENT PROGRAM — 7
Produced for the U.S. Department

of Energy, Energy Efficiency and

Renewable Energy, by the Lawrence

Berkeley National Laboratory

DOE/EE-0295

March 2004

For More Information

EERE Information Center

1-877-EERE-INF or

1-877-337-3463

www.eere.energy.gov/femp

General Program Contacts

Ted Collins

New Technology Demonstration

Program Manager

Federal Energy Management

 Program

U.S. Department of Energy

1000 Independence Ave., SW, EE-92

Washington, D.C. 20585

Phone: (202) 586-8017

Fax: (202) 586-3000

theodore.collins@ee.doe.gov

Steven A. Parker

Pacific Northwest National

Laboratory

P.O. Box 999, MSIN: K5-08

Richland, WA 99352

Phone: (509) 375-6366

Fax: (509) 375-3614

steven.parker@pnl.gov

Bill Carroll

Lawrence Berkeley National

Laboratory

One Cyclotron Road

Berkeley, CA 94720

Phone: (510) 486-4890

Fax: (510) 486-5454

wlcarroll@lbl.gov

Technical Contact and Author

Tom Webster, P.E.

Center for the Built Environment

University of California

Lawrence Berkeley National

Laboratory

Berkeley, CA 94720

Phone: (510) 643-6915

Fax: (510) 643-5571

twebster@uclink4.berkeley.edu

Disclaimer

This report was sponsored by the United States Department of Energy, Energy Efficiency and

Renewable Energy, Federal Energy Management Program. Neither the United States Government nor any agency or contractor thereof, nor any of their employees, makes any warranty,

express or implied, or assumes any legal liability or responsibility for the accuracy, completeness, or usefulness of any information, apparatus, product, or process disclosed, or represents

that its use would not infringe privately owned rights. Reference herein to any specific commercial product, process, or service by trade name, trademark, manufacturer, or otherwise does not

necessarily constitute or imply its endorsement, recommendation, or favoring by the United

States Government or any agency or contractor thereof. The views and opinions of authors

expressed herein do not necessarily state or reflect those of the United States Government or

any agency or contractor thereof.

References

[1] Sodec, F., and R. Craig., “The underfloor air supply system—the European experience,”

ASHRAE Transactions, vol. 96, No. Part 2. 1990.

[2] Sodec, F., “Air distribution systems report no. 3554A,” Krantz GmbH & Co, September 19,

1984.

[3] Tanabe, S., “Task/ambient conditioning systems in Japan,” presented at Workshop on task/

ambient conditioning systems in commercial buildings, San Francisco, May 4–5 1995.

[4] Bauman, F. Underfloor Technology [Website]. Center for the Built Enviornment. Available from:

www.cbe.berkeley.edu/underfloorair.

[5] ASHRAE, “Thermal environmental conditions for human occupancy,” ANSI/ASHRAE Standard 55-1992, American Society of Heating, Refrigerating, and Air-Conditioning Engineers,

Inc., 1992.

[6] Bauman, F., “Outlook for Underfloor Air Distribution,” ASHRAE Journal, June 2001, p. 18.

[7] ASHRAE, “ANSI/ASHRAE Standard 55-1992: Thermal Environmental Conditions for Human

Occupancy,” American Society of Heating, Refrigerating, and Air-Conditioning Engineers,

Inc., 1992.

[8] ASHRAE, “ANSI/ASHRAE Standard 113-1990: Method of testing for room air diffusion,”

American Society of Heating, Refrigerating, and Air-Conditioning Engineers, Inc., 1990.

[9] CBE. [Website]. Center for the Built Enviornment (CBE), 2001. Available from:

www.cbe.berkeley.edu.

[10] IFMA, “Benchmarking,” International Facilities Management Association, 1997.

[11] Fisk, W. J., “Health and Productivity Gains from Better Indoor Environments and Their

Relationship with Building Energy Efficiency,” LBNL-45484, Lawrence Berkeley National

Laboratory, July 31, 2000.

[12] DOE/BTS. 2001 BTS Core Databook: Table 2.3, Federal Buildings and Facilities Characteristics

[Website]. DOE/Office of Building Technology, State and Community Programs (BTS),

July 31, 2001. Available from: http://btscoredatabook.eren.doe.gov/frame.asp?p=

chapterdisplaymain.asp?ChapterID=2.

[13] EIA, “CBECS: Commercial Buildings Characteristics 1995,” DOE/EIA-E-0109, Energy Information Administration (EIA), U.S. Department of Energy, August 1997.