NBS BUILDING SCIENCE SERIES 133

Performance of the Norris Cotton

Federal Office Building for the

First 3 Years of Operation

U.S. DEPARTMENT OF COMMERCE • NATIONAL BUREAU OF STANDARDS
NATIONAL BUREAU OF STANDARDS

The National Bureau of Standards' was established by an act ot Congress on March 3, 1901. The Bureau's overall goal is to strengthen and advance the Nation's science and technology

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the Institute for Computer Sciences and Technology.

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or STANDaRDH

LTBRAnr NBS BUILDING SCIENCE SERIES 133 sep 1 6 mi

Performance of the Norris Cotton '^m^^

Federal Office Building for the ^^'^^ First 3 Years of Operation z^?/

James E. Hill

William B. May, Jr. Thomas E. Richtmyer

Jacqueline Elder

Robert L. Tibbott

Gary T. Yonemura

Charles M. Hunt

Phillip T. Chen

Center for Building Technology

National Engineering Laboratory

National Bureau of Standards

Washington, DC 20234

Prepared for the Architecture and Engineering Systems Branch Buildings Division Office of Buildings and Community Systems

Department of Energy

Washington, DC 20545

U.S. DEPARTMENT OF COMMERCE, Malcolm Baldrige, Secretary

NATIONAL BUREAU OF STANDARDS, Ernest Ambler, Director

Issued August 1981
Library of Congress Catalog Card Number: 81-600082

National Bureau of Standards Building Science Series 133

Nat. Bur. Stand. (U.S.), BIdg. Sci. Ser. 133, 140 pages (Aug. 1981)

CODEN: BSSNBV

U.S. GOVERNMENT PRINTING OFFICE

WASHINGTON: 1981

For sale by the Superintendent of Documents, U.S. Government Prmting Office, Washington, DC 20402

Price $5.50

(Add 25 percent for other than U.S. mailing)
Performance of the Norris Cotton Federal Office Building

for the First Three Years of Operation

by

James E. Hill, William B. May, Jr., Thomas E. Richtmyer,

Jacqueline Elder, Robert L. Tibbott, Gary T. Yonemura,

Charles M. Hunt, and Phillip T. Chen

Abstract

The Norris Cotton Federal Office Building is a medium-size seven-story

Government office building of approximately 11,000 m^ (117,000 ft^) total

floor area. It Is located in Manchester, New Hampshire, and was designed to

demonstrate a number of energy saving concepts.

Some of the major energy conserving features of the building are the use of

solar collectors; heavy masonry construction with exterior insulation; small

overall window area; heat recovery from heat pumps, chillers, a natural gaspowered engine/generator, and the ventilation system; modular boilers; thermal

storage tanks; and a variety of energy conserving lighting systems.

A team from the Center for Building Technology, National Bureau of Standards

(NBS), has been monitoring the performance of the building since it was occu- pied in September 1976. The project has involved not only an analysis of

building energy consumption, but also a study of the effectiveness of the various lighting systems, a determination of the response of the occupants to

the building, and a cost analysis of the construction and operation of an energy conserving building. This report will describe the building's

performance for the first 3 years of operation.

Key Words: Building models, computer; energy conservation, user acceptance;

energy conservation in commercial buildings; lighting measurements; performance data for commercial office buildings in New

England; solar energy in commercial buildings.

iii
PREFACE

This report is one of a series of reports documenting National Bureau of

Standards (NBS) research and analysis efforts in developing energy and cost

data in support of the Department of Energy (DoE)/NBS Building Energy Conservation Criteria Program. The work described in this report was supported by

DoE/NBS Task Order No. A008-BCS under Interagency Agreement No. EA 77A 01 6010.

Cover photo:

The Norris Cotton Federal

Office Building

iv
TABLE OF CONTENTS

Page

1. INTRODUCTION 1

2. BUILDING DESCRIPTION 3

2.1 Climatic and Geographical Data 3

2.2 Building Facade 6

2.3 Mechanical Systems ' 6

2.4 Lighting Systems 9

2.5 Mini-computer Data Acquisition System 9

3. BUILDING THERMAL PERFORMANCE 15

3.1 Energy Consumption 15

3.2 Thermographic Analysis 22

3.3 Air Exchange Analysis 26

3.4 Performance of the Solar Sub-system 37

3.5 Comparison of Energy Use With Computer Predictions 51

4. PERFORMANCE OF THE LIGHTING SYSTEMS 81

4.1 Lighting Systems 81

4.2 Evaluation Procedure 82

4.3 Reference Lighting System 84

4.4 Reference Task 86

4.5 Measurement Locations 86

4.6 Results 89

5. OCCUPANT RESPONSE 99

5.1 Interior Space Occupancy and Design 100

V
TABLE OF CONTENTS (Continued)

Page

5.2 Research Approach - Interviews and Questionnaires 100

5.3 Questionnaire Results 101

6. COST ANALYSIS 107

6.1 Building Construction Costs 108

6.2 Annual Energy Consumption 109

6.3 Life-cycle Cost Model 109

7. CONCLUSIONS 117

8. REFERENCES 123

9. BIBLIOGRAPHY „ 125

vi
FIGURES

No. Page

1 Average monthly outside air temperatures in Concord, New Hampshire .. 5

2 Actual monthly average outside air temperatures versus 1962 monthly

average values in Concord, New Hampshire 5

3 Norris Cotton Federal Office Building in Manchester, New Hampshire .. 7

4 Schematic diagram of Norris Cotton Federal Office Buillding

mechanical system 7

5 Diagram of Johnson Controls JC-80-55 minicomputer system

configuration at Norris Cotton Federal Office Building 10

6 Total energy consumption at the Norris Cotton Federal Office

Building 16

7 Natural gas consumption at the Norris Cotton Federal Office

Building 16

8 Fuel oil consumption at the Norris Cotton Federal Office Building ... 19

9 Electric energy consumption at the Norris Cotton Federal Office

Building 19

10 Breakdown of monthly electric energy consumption by load for the

Norris Cotton Federal Office Building 21

11 Measured total energy consumption versus average monthly ambient

temperature for the Norris Cotton Federal Office Building 21

12 First floor east, interior wall of the Norris Cotton Federal

Office Building 24

13 Results of the thermogram on the first floor, east, interior

wall of the Norris Cotton Federal Office Buiding 24

14 First floor east, exterior wall of the Norris Cotton Federal Office

Building 24

15 Results from the thermogram on the first floor east, exterior wall

of the Norris Cotton Federal Office Building 24

16 Ceiling with one tile removed on the second floor, west interior

wall of the Norris Cotton Federal Office Building 25

vii
FIGURES (Continued)

No. Page

17 Results of the thermogram on the second floor, west interior wall

of the Norris Cotton Federal Office Building 25

18 Properly insulated wall, sixth floor, east interior wall of the

Norris Cotton Federal Office Building 25

19 Results of the thermogram on the sixth floor, east interior wall

of the Norris Cotton Federal Office Building 25

20 Simplified schematic of the main ventilation system of floors

1-3 in the Norris Cotton Federal Office Building 27

21 Simplified schematic of the main ventilation system of floors

4-7 in the Norris Cotton Federal Office Building 28

22 Diagram of the ventilation systems in the Norris Cotton Federal

Office Building 29

23 Collector performance for the modules^ in row 1 at Norris Cotton

Federal Office Building as determined by a test of one module in

a commercial testing laboratory 38

24 Collector performance for the modules in row 2 at the Norris Cotton

Federal Office Building as determined by a test of one module in

a commercial testing laboratory 38

25 Collector performance for the modules in row 3 at the Norris Cotton

Federal Office Building as determined by a test of one module in

a commercial testing laboratory 39

26 Collector performance for the modules in row 4 at the Norris Cotton

Federal Office Building as determined by a test of one module in

a commercial testing laboratory 39

27 Optimum solar collector tilt angle for the Norris Cotton Federal

Office Building as a function of time of year 41

28 Incident solar energy on the solar collector panels of the Norris

Cotton Federal Office Building under clear sky conditions 43

29 Hourly average solar collector array efficiency values and ASHRAE

Standard 93-77 test data for individual rows of the collector

array at the Norris Cotton Federal Office Building 44

viii
FIGURES (Continued)

No. Page

30 Total energy consumption at the Norris Cotton Federal Office

Building as predicted by simulation 57

31 Electric energy consumption at the Norris Cotton Federal Office

Building as predicted by simulation 57

32 Natural gas consumption at the Norris Cotton Federal Office

Building as predicted by simulation 59

33 Fuel oil consumption at the Norris Cotton Federal Office Building

as predicted by simulation 59

34 Total energy consumption at the Norris Cotton Federal Office

Building as predicted by the "as-operated" simulation compared

with actual consumption for three years 61

35 Monthly total heating requirements per unit area for the Norris

Cotton Federal Office Building as predicted by the "as-operated"

simulation 65

36 Monthly total cooling requirements per unit area for the Norris

Cotton Federal Office Building as predicted by the "as-operated"

simulation 65

37 Monthly total heating requirements per unit area for the Norris

Cotton Federal Office Building as predicted by the "design

alternative" simulation 66

38 Monthly total cooling requirements per unit area for the Norris

Cotton Federal Office Building as predicted by the "design

alternative" simulation 66

39 Monthly total heating and cooling requirements for the Norris

Cotton Federal Office Building as predicted by all simulations ..... 68

40 Comparison of heating and cooling requirement components for the

Norris Cotton Federal Office Building as predicted by simulation ... 68

41 Third order least squares fit of predicted and actual fuel use plus fan energy for the Norris Cotton Federal Office Building

versus monthly average ambient temperature 69

42 Fuel use efficiency for the Norris Cotton Federal Office Building

as predicted by simulations . . . ^ 69

ix
FIGURES (Continued)

No. Page

43 Cooling performance factor for the Norris Cotton Federal Office

Building as predicted by simulations 71

44 Third order least squares fit of predicted and actual total energy

used for HVAC at the Norris Cotton Federal Office Building 71

45 Total heating efficiency for the Norris Cotton Federal Office

Building as predicted by simulations 73

46 Total cooling factor for the Norris Cotton Federal Office

Building as predicted by simulations 73

47 Total energy for heating versus heating requirements for the

central and heat pump mechanical subsystems at the Norris Cotton

Federal Office Building as predicted by the "as-operated"

simulation 74

48 Total energy for cooling versus cooling requirements for the

central and heat pump mechanical subsystems at the Norris Cotton

Federal Office Building as predicted by the "as-operated"

simulation 74

49 Comparison of actual and predicted boiler fuel input at the Norris

Cotton Federal Office Building using "as-operated" simulation data . 76

50 Comparison of actual and predicted heat pump and service hot water

input at the Norris Cotton Federal Office Building using "asoperated" simulation data 76

51 Comparison of actual and predicted energy to central chillers at

the Norris Cotton Federal Office Building using "as-operated"

simulation data 77

52 Energy use components and total energy use per year at the Norris

Cotton Federal Office Building using simulation results and

measured data from September 1978 to August 1979 77

53 Comparison of actual and predicted lighting-miscellaneous and

operating energy at the Norris Cotton Federal Office Building

using "as-operated" simulation data 80

54 Reference hemispherical lighting system used in lighting

measurements for the Norris Cotton Federal Office Building 85

X
FIGURES (Continued)

No. Page

55 Lighting system test measurement locations shown relative to

luminaire orientation and location in the Norris Cotton Federal

Office Building 87

56 Viewing angle for contrast measurements at the Norris Cotton

Federal Office Building 88

57 Diagram showing the three measurement directions for the same observing spot when making contrast measurements in the Norris

Cotton Federal Office Building 88

58 Illuminance at the task surface with contrast rendering instrumentation in place at the Norris Cotton Federal Office Building 91

59 Contrast rendition factors obtained by a photometric technique

at the Norris Cotton Federal Office Building 93

60 Luminous efficacy values obtained by a photometric technique at

the Norris Cotton Federal Office Building 96

61 The effect of daylight on illuminance, contrast rendition factor,

and luminous efficacy in the Norris Cotton Federal Office Building 97

62 Present value cost vs. lifespan for NCFOB, ECB & DAB 115

xi
TABLES

No. Page

1 Analog sensor types installed in the Norris Cotton Federal

Office Building 13

2 Norris Cotton Federal Office Building annual energy consumption .... 17

3 Results of air exchange measurements in the Norris Cotton Federal

Office Building 31

4 Carbon dioxide in air samples taken from various floors in the

Norris Cotton Federal Office Building, February 15, 1977, 3:00

to 5:00 p.m 34

5 Carbon dioxide in air samples taken from various floors in the

Norris Cotton Federal Office Building, February 16, 1977, 10:30

to 12:00 a.m 35

6 Carbon dioxide in air samples taken from various floors in the

Norris Cotton Federal Office Building, February 17, 1977, 1:00

to 2:30 p.m. 36

7 Test data for the solar collectors on the Norris Cotton Federal

Office Building 40

8 Predicted collector output for the existing collectors on the

Norris Cotton Federal Office Building in GJ (10^ Btu)/month for

a tilt angle of 60° 46

9 Predicted thermal and total energy requirements for the Norris

Cotton Federal Office Building based on computer simulation 47

10 Predicted collector output for 557 m^ (6000 ft^) of evacuated

tubular collectors located on the Norris Cotton Federal Office

Building 47

11 Norris Cotton Federal Office Building annual energy consumption .... 61

12 Summary of effects of modifications made to the "as-operated"

simulation 64

13 Energy use components for the "as-operated" simulation 79

14 Energy use components from actual data 79

15 Lighting systems installed in the Norris Cotton Federal Office

Building 83

xii
TABLES (Continued)

No» Page

16 Luminance (cd/m^) of hemisphere wall with center of task area

as the viewing point 85

17 Illuminance (dekalux) at task surface with contrast measuring

instruments in place at the Norris Cotton Federal Office Building .. 90

18 Contrast rendition factors obtained with photometric techniques

at the Norris Cotton Federal Office Building 92

19 Effective lumens per watt obtained with photometric techniques at

the Norris Cotton Federal Office Building 95

20 Summary of occupant "likes" in the Norris Cotton Federal Office

Building 102

21 Summary of occupant "dislikes" in the Norris Cotton Federal Office

Building 102

22 Building construction costs in 1976 dollars 109

23 Annual energy consumption in 10^ Btu 110

24 Cost of annual energy consumption in 1979 dollars 110

25 Annual percentage change of energy escalating rate 112

26 Present value cost at year ending ($1000) for three buildings for

the period ending in a given year 113

27 Present value costs and calculation of present value savings 114

xiii
DISCLAIMER:

The mention of company names in this publication is done only to identify

firms awarded General Services Administration contracts for services ren- dered in the planning and construction of the Norris Cotton Federal Office

Building. In no case does such identification imply endorsement or recom- mendation by the National Bureau of Standards.

Facing page:

Aerial view of Manchester

,

New Hampshire, with Norris

Cotton Building in center of

photograph

xiv
1 . INTRODUCTION

In the fall of 1972, architects Nicholas Isaak and Andrew C. Isaak of

Manchester, New Hampshire, were awarded a contract by the General Services

Administration (GSA) to design a Federal office building to be constructed

in Manchester. At that time, the construction industry was becoming acutely

aware of the term "energy crisis." The "energy crisis" was not yet dominating the headlines, but its implication was clear: The age of cheap fossil

fuels was over. Energy consumption, which had been taken for granted in the

past, had become an important design parameter.

1
GSA's Administrator Arthur F. Sampson responded to the challenge posed by the

energy crisis by designating the Norris Cotton Federal Building an "energy

conservation demonstration project." The purpose of this project was to (a)

dramatize the firm commitment of the Federal Government to the conservation

of energy in the design, construction, and operation of Government buildings;

(b) provide a laboratory for the installation of both recognized and innovative energy conservation technologies (with a goal of obtaining at least 20

percent energy saving with reference to comparable buildings); and (c) inspire

others in the building industry to pursue energy conservation as a goal.

In January 1973, the consulting engineering firm of Dubin, Mindell, Bloome,

and Associates, of New York City, was awarded a contract to develop a set of

recommendations for the design and construction of the Norris Cotton Building.

Staff members of the National Bureau of Standards (NBS), at the request of

GSA, collaborated with Dubin, Mindell, Bloome, and Associates in evaluating

the effect of various building parameters on the building's annual energy

consumption. This was done by using the National Bureau of Standards heating

and cooling load calculation program, NBSLD [1,2]. Based upon the resulting

recommendations, the firm of Isaak and Isaak prepared working drawings and

specifications for the buildings. The mechanical/electrical design, which

included the design of the heating, ventilating, and air-conditioning systems, was in turn subcontracted to the R. D. Kimball Company of Cambridge,

Massachusetts. Staff members from NBS also assisted the R. D. Kimball Company

in sizing various components of the heating and cooling systems.

GSA designated NBS to be responsible for designing and operating the instrumentation system which would allow the determination of energy consumption

as well as other pertinent performance characteristics of the building and

its systems. In this connection, NBS drafted specifications to be used for

purchasing and installing a computerized data acquisition system [3], The

building was completed and occupied in September 1976 and designated as the

Norris Cotton Federal Office Building (NCFOB). Since that time, NBS staff

members have been monitoring the building's performance.

Facing page:

Southwest exterior of

the Norris Cotton Building

2
2. BUILDING DESCRIPTION

2.1 CLIMATIC AND GEOGRAPHICAL DATA

Manchester, New Hampshire, is located along the Merrimack River, 97 km (60 mi)

north of Boston, Massachusetts, at an altitude of 89 m (290 ft) above sea

level. It is situated approximately at the geographical center of New

England. At one time it was one of the largest mill and shoe manufacturing

towns in New England. Its population, although less now than in the heyday

of the textile mill activities, still exceeds half a million. The surrounding

3
countryside is hilly and dotted with many lakes and woods. Mount Washington

is approximately 140 km (90 mi) north of the town. The building site is in

the center of the downtown section and is surrounded by several buildings of

two to three stories, as well as an eight-story building directly to the south.

Historical hour-by-hour weather data are not generally available for Manchester

Consequently, climatic data from nearby Concord, New Hampshire, 24 km (15 mi)

north of Manchester, were used in the original design studies [1,2] and again

in the analysis of data described in this report. The exact location of

Concord is latitude 43* N, longitude 71°30' , at an elevation of 104 m (342 ft).

When conducting the original design studies, climatic data for Concord for

the year 1962 were used because the monthly average dry-bulb temperatures for

1962 were found to be very close to the 30 year norm values. The actual

weather since the building was occupied has generally been more severe than

in 1962, Figure 1 is a plot of outside air temperatures for each month of

the first three years of operation. It can be seen that the actual weather

(solid line) has been somewhat colder in winter yet slightly warmer in summer than it was in 1962 (dotted line). This is also apparent in figure 2 where

the actual monthly average air temperatures have been plotted against 1962

monthly average air temperatures. A second order curve has been fitted for

each year of operation. All years fall below the design year (solid line)

in winter and, on the average, above it in summer.

Other annual norm values of climatic data of interest as reported for Concord

are:

Average rainfall 0.986 m (38.3 in.)

Average snowfall 1,63 m (64.1 in.)

Average wind speed, yearly 3,4 m/s (7.6 mi/h)

Average wind speed, summer 2.9 m/s (6.5 mi/h)

Average wind speed, winter 3.7 m/s (8.3 mi/h)

Prevailing wind direction, summer NW

Prevailing wind direction, winter NW

Average percent of possible sunshine 54%

Average sky cover 6.1*

The ASHRAE Handbook of Fundamentals [4] lists the following percentile values

used for mechanical equipment design for both Manchester and Concord, New

Hamp shire:

* Zero is a completely clear sky and 10 is completely cloudy.

4
1.0 4.0 7.0 10.0 13.0 16.0 19.0 22.0 25.0 28.0 31.0 34.0 MONTHS AFTER OCCUPATION OF BUILDING

Figure 1. Average monthly outside air temperatures In Concord, New Hampshire

"F

-20.0-16.0 -12.0 -8.0 -4.0 0.0 4.0 8.0 12.0 16.0 20.0 24.0 28.0 1962 TEMPERATURE C

Figure 2. Actual monthly average outside air temperatures versus 1962

monthly average values in Concord, New Hampshire

5
Winter percentile values

99% 97 1/2%

Concord

Manchester

-25 °C (-13 °F)

-21 °C (-5 "F)

-22 °C (-7 °F)

-17 °C (1 °F)

Summer percentile values

1% 2 1/2% 5%

Concord

Manchester

33 °C (91 °F)

33 °C (92 °F)

31 °C (88 °F)

32 °C (89 °F)

29 °C (85 °F)

30 °C (86 °F)

2.2 BUILDING FACADE

The Norris Cotton building is shown in figure 3. The shell is nearly cubical

in shape and thus has a low surface to volume ratio. Its exterior walls are constructed with relatively heavy, 30 cm (12 in) thick masonry blocks and are insulated on the outside rather than inside. The wall has an overall heat

transfer coefficient (U value) of 0.34 W/m^x^C (.06 Btu/ (hxf t^x^F ) . This

"inside-outside" construction creates a thermal flywheel effect which reduces

peak heating and cooling loads. Overall window area makes up only about 6

percent of the total exterior wall with the north wall being completely

windowless. Each window is double-glazed and surrounded on the outside by

granite fins that provide shading in summer and reduce convection heat losses

due to wind. The air gap between glazings is 2-3 cm (approximately 1 in) and

contains a set of adjustable louvers that control solar gain and reduce con- vection. The windows have a U value of 3.3 W/m^x^C (0.58 Btu/(hxf t^x^F) ).

2.3 MECHANICAL SYSTEMS

The mechanical systems at the building can be divided into two major parts

which supply different areas of the building. The first three floors are served by a unitary water loop heat pump system consisting of 57 water-to-air

heat pumps in various ceiling and floor mounted configurations and having a combined capacity of 350 kW (1200 x 10^ Btu/h) for heating and 280 kW (79

tons) for cooling. A closed water loop supplies all of the heat pumps with

thermal energy for heating and acts as a heat sink for cooling. The upper

four floors are served by several types of central systems. These upper

floors are heated by a hot water heating system which uses fin tube perimeter

radiation on the fourth floor and various types of ceiling or floor mounted

fan coil units on floors 5, 6, and 7. Cooling is provided on the upper

four floors by central chillers used to produce chilled water which is pumped

to the fan coil units or to a cooling coil in the variable air volume (VAV)

air handling unit for the core area. Untreated ventilation air is provided

for two below-grade parking levels and a mechanical equipment penthouse is

heated and ventilated.

6

1
Figure 4. Schematic diagram of Norris Cotton Federal Office Building

mechanical system

I
The building has two separate systems for handling outside air. One system,

the heat pump air system, supplies ventilation air to the lower three floors

by bringing outside air down from the penthouse mechanical room where the

supply fan, return fan, and outside air and return dampers are located.

Cooling and heating of the air is acomplished by having the air pass in parallel through six floor-mounted heat pumps before reaching interior areas of

the lower three floors. This air system is a variable air volume type.

The upper four floors are supplied with ventilation air through a second air

handling system also located in the penthouse. This system, which is also a variable air volume system, is configured much like the heat pump air system

except that the only heating and cooling equipment in the air stream is a chilled water coil in the air handling unit. A heat pipe heat recovery

system is used to preheat the outside air using energy recaptured from the

exhaust air.

The building has a number of energy conversion devices utilizing natural gas,

fuel oil, and electricity to provide heated and chilled water for the building water loops. Figure 4 is a schematic of the energy conversion and supply

equipment. Four 55 kW (187 x 10^ Btu/h) natural gas modular boilers and two

108 kW (370 X 10-^ Btu/h) number 2 fuel oil modular boilers can supply heating

energy to the heat pump and hot water loops. A 211 kW (60 ton) electric

reciprocating chiller and an 88 kW (25 ton) hot- water- driven absorption

chiller provide chilled water. Electric power for the reciprocating chiller

can be purchased or supplied by a 150 kVA natural-gas-fueled engine-generator

set in the penthouse. Thermal energy for the absorption chiller is supplied

by recovery of waste heat from the engine generator or by the oil boilers.

A solar energy system is installed on the building and includes 353 m^ (3800

ft^) of liquid-type flat-plate collectors mounted on the roof of the building

and able to be tilted at angles from 20 to 60 degrees. In the winter, the

system is operated with an ethelyene-glycol/water solution as the collector

fluid and a heat exchanger is used between the collector loop and the building

solar storage loop. For summer operation, water is used as the collector

fluid and the heat exchanger is bypassed. Energy collected in the solar array

can be stored in one of three 37.850 k= (10,000 gallon) storage tanks located

in the basement. The design calls for solar heated water to be used to fire

the absorption chiller, to be used in the hot water heating system, and solar

heated water could potentially be used in the heat pump system (the control

system which existed during the first 3 years of operation prevented this

from happening). The solar system can also supply energy to the domestic hot

water system. If no solar energy is available, the domestic hot water is

heated by a natural-gas-fired storage water heater. In the summer, one tank

is available as a chilled water storage tank.

In addition to engine-generator heat recovery, two other energy recovery

options were designed into the mechanical systems. One was to utilize

condenser water from the chillers in the hot water heating system by means

of a double-bundle condenser. The other scheme was to operate the electric

8
chiller as a heat pump to produce hot water for the hot water heating system

from low temperature water stored in the tanks (false loading). These

options have not proven to be feasible in the operation of the building

because hot water heating system temperatures have been elevated above max- imum condenser operating temperatures (41 °C (105°F)) during mid-winter to

insure occupant comfort. During mild weather, when the hot water heating

system temperature is lowered, the solar system can supply energy to meet

the heating requirements.

The building has two distinct control systems for the mechanical equipment.

A pneumatic system provides basic control functions and device actuation.

Linked to the pneumatic system is a minicomputer which was installed primarily for data collection. However, the computer was also designed to provide

some overall control functions such as solar system mode selection, nighttime

thermostat setback, and maintenance management. In addition, the computer

monitors over 900 binary and analog sensors, allowing the building operators

to watch critical equipment and set up alarm signals for changes of state.

The computer will be described in more detail in section 2.5.

2.4 LIGHTING SYSTEMS

Various types of lighting systems are used throughout the building. The

fourth floor uses high pressure sodium lamps. The fifth uses floor lighting

that is built into furniture and illuminates only the task areas. The

remaining floors use fluorescent lighting systems with various lamp spacings

and lens arrangements. All systems will be described more fully in chapter 4.

2.5 MINI-COMPUTER DATA ACQUISITION SYSTEM

The installed minicomputer is a Johnson Controls JC-80/55 system.* It was designed to perform a number of monitoring and control functions as well as

to serve as a data acquisition system (DAS). Use of the JC-80 as a DAS is

accomplished by using software packages and hardware supplied with the system.

Loop Remotes : Figure 5 illustrates the system configuration for the JC-80.

Each of the sensors for the instrumentation system interfaces to the computer

through a cabinet called a loop remote. There are 19 loop remotes in the

building. A loop remote contains up to 50 point module cards, each of which

may be connected to from four to eight sensors depending on the sensor type.

The loop remotes contain the circuitry to convert the sensor analog signal

(electrical current) to a digital value. The loop remotes are interrogated

* Commercial equipment is identified in this publication in order to

adequately describe the data acquisition system used. Such identification

does not imply recommendation or endorsement by the National Bureau of

Standards, nor does it imply that the materials or equipment identified

are necessarily the best available for this purpose.

9
Central System

LINE \

V PRINTER J

COMMUNICATIONS

GEAR

Hi CRT )

TTY 3

LOOP J 1 CONTROLLER COMPUTER

Figure 5. Diagram of Johnson Controls JC-80-55 minicomputer system

configuration at Norris Cotton Federal Office Building

10
sequentially by the loop controller, which is actually a separate 16K (16 bit

words) processor, and updated sensor values are transmitted to the central

system.

JC-80 Central System; The JC-80 central system makes a scan of the system

points approximately every 20 seconds. Sensor point values which have

changed by an amount called the filter increment are updated and stored

in the central system 1/2-megaword magnetic disc storage. The central system executes the software to convert the digital value coming from the loop

controller to a digital number in engineering units by using equations

appropriate to the sensor type.

A number of software programs allowed the JC-80 to function as a DAS. One of

these is the calculated point software which is used to calculate a quantity

using the sensor point values as input to a specified equation. The most

important equation used is one which calculates an average value from instantaneous values for a particular sensor over an hours' time. The averaging

equation is executed a number of times during an hour and is set up so that

the average stored in the JC-80 is the average up to that point in time. The

average is reset to zero at the start of each hour. The number of times the

equation is applied to each point in an hour is determined by a quantity which

may be called the calculated point interval (CPI). For each analog data point,

there is a CPI in minutes representing the time period between applications

of the averaging equation. As the specified value of calculated point interval

is decreased, the value of the calculated average approaches the true average

value.

A second calculated point equation is used to totalize values from pulse

counters over an hours' time. Pulses are generated by contacts mechanically

connected to electric watt-hour meters with the number of pulses per hour

being proportional to the number of kilowatthours passing through the meter.

One other calculated point equation converts air flow differential pressure

values to units of ft-'/min.

In order to store hourly averaged values of the system points on magnetic

tape, data logger software takes the averaged values for each hour and places

them in storage locations on the system disc. Each night at midnight, the data

logger routines write 24 hours of data on magnetic tape.

A cathode ray tube terminal (CRT), lineprinter, and teletypewriter (TTY) are available as peripherical devices for operator interface to the JC-80. It is

possible to display or log current values of system data points on the CRT,

TTY, or lineprinter. A trend log can be programmed to produce lists of system

point values as a function of time.

DAS functions of the JC-80 can be influenced through the operator interfaces.

Points which are written to magnetic tape by the data logger can be selected

and changed and the filter increments associated with the points can be varied.

11
One other valuable peripherial is a modem-telephone coupler which allowed NBS

to access the JC-80 from Washington, D.C. via telephone lines using an NBS

terminal. This feature allowed studies to be made of the adequacy of the

hourly averaging process and enabled NBS to study equipment performance on a minute-by-minute basis.

Instrumentation Sensors : The JC-80 data logger software writes hourly averaged values to magnetic tape for 720 instrumentation sensors. Of these 720

points, 107 are from binary sensors indicating on-off or mode status for vari' ous pieces of equipment in the building. Of the remainder, 98 points are kilowatt-hour points and 515 are analog points. The analog point values are derived from nine types of analog sensors, listed in table 1.

A detailed description of all the software and procedures used at NBS to

reduce and analyze the data from the JC-80 system and analysis of one year of

data are in reference [5].

12
! Table 1. Analog sensor types Installed in the Norrls

Cotton Federal Office Building

Sensor type

Liquid flow meters

Air flowmeters

Liquid temperature

Air temperature

Air dew point temperature

Air humidity

Flue gas temperature

Natural gas flow

Illumination

Solar radiation

Quantity

79

55

286

49

6

7

7

15

5

Description

Impact tubes combined with

reversed static tube; pressure

differential fed into transducer

Array of pitot tubes to determine average air velocity in

ducts.

Nichrome wire-wound resistance

temperature elements.

Nichrome wire-wound resistance

temperature elements combined

with dew-cells.

Humidity elements

Thermocouples

Positive displacement meters

Photo-electric cells

Pyranometers
Facing Page:

Solar system piping located

the Norris Cotton Building

mechanical penthouse
3. BUILDING THERMAL PERFORMANCE

3.1 ENERGY CONSUMPTION

Overall building energy consumption for the first 3 years of operation was compiled on a month-by-month basis and is shown in figure 6. The three lines

represent usage during the three separate years. A decline in energy consump

tion is obvious. Values of total annual energy consumption per unit of floor

area are given in table 2 for various 12 month periods. Again the decline

in consumption is apparent. The total consumption for the third operating

15
1400.0

1200.0 -

400.0

200.0 -

0.0 4

76-77.

o 78-79

p- - -

1400.0

1200.0

- 1000.0

800.0 g

600.0

400.0

- 200.0

f- 0.0 SEP OCT NOV DEC JAN FEB MAR APR MAY JUN JUL AUG

MONTH OF OPERATING YEAR

Figure 6. Total energy consumption of the Norris Cotton

Federal Office Building

500.0

if) <

<

3

O

3

CD

77-78

\78-79

0.0

Figure

0.0 -f 1 1 1 1 1

I I y y f SEP OCT NOV DEC JAN FEB MAR APR MAY JUN JUL AUG

MONTH OF OPERATING YEAR

7. Natural gas consumption at the Norris Cotton Federal

Office Building

16
year, 641 MJ/m^ (56.2 x 10^ bTU/ (ft^xyr)). is within 5 percent of the

original design goal of 625 MJ/m^ (55 x 10^ BTU/(f t^xyr ) ) . However, even though the actual energy consumption was close to the design value during the

third year, it must be emphasized that the building was still not operating

entirely as designed. The operation of some mechanical equipment and the performance of the building envelope have not met design expectations. On the

other hand, operating strategies not in the design have been used and have

resulted in a savings in energy.

Effect of Building Operation; During the first year of operation, several

minor problems occurred such as simultaneous heating and cooling of a space

by adjacent heat pumps on the second floor, and improper set points and

adjustments in the controls. Such problems are typical of any new building;

but in this particular case, the extra complexity of this experimental building created proportionately more problems. Other events which have impacted

energy consumption over the 3-year period are the operation of the solar

collectors, which began in the spring of 1978, the way in which the building

has been cooled during the summers, and reduction in air infiltration through

caulking of the building facade (December 1978) and modification of the outside air dampers (October 1977).

The building was designed to be cooled with two chillers, as explained previously. During periods of strong sunshine, the absorption chiller was to

be run on solar-heated water and the electric chiller (if needed) to be run

on purchased electricity. Excess solar energy would be placed in storage for

later use. With no solar energy available and stored energy depleted, the

electric chiller was designed to operate from electric power produced by the

natural-gas-fired engine-generator. A waste heat recovery system on the

engine would produce the hot water required to drive the absorption unit.

Excess cooling would be stored in the form of chilled water for use at a later time.

Table 2. Norris Cotton Federal Office Building

annual energy consumption

Year Total energy used. MJ/m^* (Btu/ft^ )*

September 76 - August 77

January 77 - December 77

September 77 - August 78

January 78 - December 78

April 78 - March 79

September 78 - August 79

919 (80.6 X 103)

813 (71.3 X 103)

758 (66.5 X 103)

730 (64.0 X 103)

693 (60.8 X 103)

641 (56.2 X 103)

* equivalent gross floor area = 10,900 m^ (117,334 ft^)

17
During the first summer, attempts were made to use the solar collectors but

they were not able to heat any of the 37,85 kL (10,000 gallon) storage tanks

in the basement of the building to the required minimum of 88 °C (190°F) for

driving the absorption chiller. As a result, the engine-generator was put

into operation manually. However, the engine-generator could not produce

the required waste heat to drive the absorption chiller and the electric

chiller alone was not able to maintain design conditions in the building.

GSA contractors spent time throughout the first summer attempting to operate

the engine-generator as designed. In late July, GSA had the plumbing in the

penthouse modified so that the fuel oil boilers, originally included as backup equipment, could be used to directly fire the absorption chiller. During

the second year, the oil boilers were used as before, but the engine-generator

was only used for a short period at the beginning of the summer. Thus, while

summer oil consumption remained about the same, the second year natural gas use was greatly decreased. This trend can be seen in figures 7 and 8 where

the energy use for natural gas and fuel oil, respectively, are plotted on a month-by-month basis.

With regards to the engine-generator, a modification was made prior to the

start of the 1978 cooling season. Additional electrical loads were placed

on the generator in order to boost the engine's heat output. However, automatic controls that were designed to protect the engine from overheating

still prevented the production of usable waste heat. Before the exiting

water from the engine reached a high enough temperature for full operation

of the absorption chiller, the controller diverted the engine cooling loop

through an evaporative cooling tower, "dumping" the waste heat without using

it.

During both of the first two summers, an attempt was made to meet peak daytime cooling loads by making use of stored chilled water that had been cooled

by the electric chiller during the previous evening. In concept, such a control scheme should have enhanced chiller efficiency because it allowed the

chiller to operate at night when the outside air was normally cooler compared

to the daytime temperatures. Another advantage of using thermal storage in

this way is that high daytime demand peaks, which are usually subject to

additional charges by the utility company, should have been reduced. However,

this mode of operation proved to be ineffective. Safety interlocks within

the chiller that protect it from freezing prevented the water in the storage

tank from reaching a suitably low temperature. As a result, the storage tank was normally depleted of its cooling capacity well in advance of the peak

daytime cooling period. In addition, since the tank could not be dropped

from the circuit, jacket and piping heat gains tended to decrease the chiller's

ability to meet the loads. During the third summer, the storage tank was not

being used for chilled water. Instead, the building engineers made maximum

use of cool outside air at night and the thermal capacity of the masonry

walls. By starting the day with the building pulled down to a reasonably

low temperature, the chiller was generally able to maintain comfortable

temperatures without the need for stored chilled water.

18
275.0 -I

SEP OCT NOV DEC JAN FEB MAR APR MAY JUN JUL AUG

MONTH OF OPERATING YEAR

Figure 8. Fuel oil consumption at the Norris Cotton Federal Office Building

o

180.0

170.0 -

160.0

150.0 UO.O

130.0

120.0

110.0 -T 100.0 90.0 -

80.0 -

70.0

60.0 H

50.0 40.0

30.0 20.0

10.0 0.0

Figure 9.

SEP OCT NOV DEC JAN FEB MAR APR MAY JUN JUL AUG

MONTH OF OPERATING YEAR

Electric energy consumption at the Norris Cotton Federal

Office Building

19
Figure 9 shows the electrical energy consumption for the building on a month-by-month basis. As with the other two energy sources, the electrical

consumption declined and the month-to-month variation smoothed out over the

three year period.

In October 1978, a majority of the 98 kilowatt-hour meters installed throughout the building were proven to be incorrectly wired and were rewired. During November 1979, the kWh meter data were used to produce an energy balance

for the electrical energy consumed at the building on a monthly basis. Even

though the data include two months from the fourth year of operation, they

provide a breakdown of electric energy consumption into a number of categories

such as floor-by-floor lighting energy consumption, energy consumed by elevators, and electrical consumption by HVAC equipment such as pumps, fans, and

chillers. Figure 10 shows the monthly consumption of electrical energy by

major categories of load. The data show that the lighting load is relatively

constant, as expected. Miscellaneous electrical load, which includes

receptacles, elevators, and other-HVAC loads, varies through the year with a maximum in midwinter. This miscellaneous electrical energy peak is due to

the use of driveway snow-melting equipment (resistance heaters). The HVAC

load exhibits expected seasonal variation with its maximum in the summer.

For the third year of operation, the electrical energy consumption accounted

for 73 percent of the total, natural gas, 24 percent, and fuel oil, 3

percent. Use of fuel oil to fire the absorption chiller accounted for less

than 1 percent of the total.

Effect of Weather on Energy Consumption : The weather conditions in Manchester

have not been the same from year to year. Thus, it is useful to normalize the

data in figure 6 to the ambient temperature. By plotting energy consumption

for each month versus the average monthly ambient temperature and fitting

lines through the points for each year, a set of curves such as those shown in

figure 11 result. The data for each year can be fit by two straight lines, one representing summer operation and one representing winter operation, with

residual* standard deviations less than 150 GJ (10^ Btu)/month. The curves

for each succeeding year of operation are lower, indicating lower energy

consumption. The winter curve for 1977-78 is skewed with respect to the 1976-

77 and 1978-79 curves. The apparent cause of this is the way in which the

building was operated during part of the 1977-78 winter. In order to achieve

acceptable comfort levels in the building, the system operators kept the

building in the occupied mode 24 hours per day only during the coldest months

of that winter, eliminating the night set-back. This produced higher energy

consumption at lower outside temperature levels. The most noticeable improvement which may be observed in this figure is for summer operation. The low

1979 curve reflects the use of early morning flushing of the upper four floors

with outside air and the abandoning of chilled water storage.

* A residual is the difference between the value of an actual data point and

the value predicted by a least squares fitted curve.

20
130.0 -

120.0 -

110.0

100.0

90.0

80.0

70.0

60.0

50.0

40.0

30.0

20.0

10.0

o o o Total a Lighting

A- -A- -A HVAC

Heat pumps

Miscellaneous

A.

NOV DEC JAN FEB MAR APR MAY

1978-79

JUN JUL AUG SEP OCT

Figure 10. Breakdown of monthly electric energy consumption by load for the

Norris Cotton Federal Office Building

o

X

I—z

o

o

5.0 9.0 13.0 17.0 21.0 25.0 29.0 33.0 37.0 41.0 45.0 49.0 53.0 57.0 61.0 65.0 69.0 73.0 77.0 —I I I I I I \ L—J L--_J I I'll!

1400.0

>-O 1200.0

trz

UJ

1000.0

800.0

600.0 -

400.0

200.0 -

0.0

-15.0 -10.0

First year: 1976-77

Second year: 1977-78

Third year: 1978-79

-5.0 0.0 5.0 10.0 15.0 20.0

1400.0

1200.0

1000.0

400.0

- 200.0

0.0 25.0 MONTHLY AVERAGE AMBIENT TEMPERATURE C

Figure 11. Measured total energy consumption versus average monthly ambient

temperature for the Norris Cotton Federal Office Building

21
3.2 THERMOGRAPHIC ANALYSIS

During the first winter of operation (1976-77), energy consumption was higher

than expected and many of the occupants seated near exterior walls complained

of feeling cold. This prompted NBS staff members to conduct special studies

of heat and air leakage through the building's exterior walls. During the

week of February 14-18, 1977, thermographic equipment was used at the building in an attempt to determine the location, if any, of serious heat leaks

in the building.

Thermography is a technique for "viewing" surface temperatures through infrared (IR) radiation. IR radiation is emitted by virtually all objects. The

intensity and spectrum of the radiated IR is a complex function of surface

temperature and surface optical properties. However, for most building materials, there is a reasonably direct correlation between surface temperature

and total radiated energy.

The IR scanner used for thermographic tests looks and acts much like a closed

circuit TV system. A camera picks up an image which is then converted to an electrical signal. The camera, however, is sensitive not to visible light

but to IR. Electric circuitry conditions the camera's output signal to produce a visible image on a cathode ray tube (CRT). For black and white CRT

monitors, the IR intensities are translated to varying shades of grey. For

color units, the intensities are broken down into 10 levels which are each

arbitrarily assigned a color. The color assignments are chosen with colors

ranging from dark blue for cooler objects to bright yellow for warmer ones. For the tests conducted at the building, color images were used because

they offered a higher degree of resolution. In this report, the actual

images have been replaced by line drawings which are intended to portray

the same results.

Measurements were made during the evening and generally on the inside of the

building. The outdoor temperature was near -7° C (20° F) during the test

periods which imposed a sufficient temperature difference across the building

walls and windows so that variation in the surface temperature due to differences in insulation effectiveness in the building structure could be detected.

Although some measurements were made on the outside of the building, in

general they were of little value in doing the qualitative analysis. The

primary reason is that the surface temperature across the outside of the

building varied due to other factors besides insulation effectiveness, such

as retention of absorbed solar radiation by the more massive parts of the

facade, variation of air flow and wind velocity around the building, and

differences in angle factors between the various surfaces on the facade and

the IR camera. As a result, measurements of a more exact nature could only

be made on interior wall surfaces.

One of the areas analyzed was the east wall on the first floor. Figures

12 and 13 show both an actual photograph and the results of a thermogram of

the same area. Based on the difference between inside and outside dry-bulb

22

Z.
temperature and the design Insulation values of the insulated concrete wall

and double-glazed window, it was calculated that the wall should have been

several degrees warmer than the window. However, it was observed that portions of the wall near the floor were at temperatures equal to the surface

of the window (this phenomenon was found to exist at several locations

throughout the building, often to a greater extent than is shown in figure

13). In order to obtain additional insight into this phenomenon, the

thermographic equipment was moved outside the building and a thermogram

was taken from the outside of the same section of the wall as shown in

figures 12 and 13. It was felt that if the insulation in this space had

been omitted or damaged so that heat loss here were purely a result of

increased conduction and convection, the area under the window would have

indicated a temperature as warm as the glass. However, the thermogram

(figure 15) revealed this to be one of the coldest areas in the scan, much

colder than the adjacent glass. Thus it appeared that thermal conduction

through the insulation was not the cause of the cold inner surface since

the outer surface would have been much warmer than it actually was.

A probable cause that explains why both the inner and outer wall surfaces were cold is the leakage of air into the building. Negative pressure within

the building, created in part by a natural stack effect, causes cold air to

be drawn in through window frames, cracks in the mortar and walls, breathing

holes, and openings that may have inadvertantly been left open during construction. As this cold air seeps into the building, it comes into direct

contact with the inner masonry blocks and causes cooling. To test this

theory, the suspended ceiling was removed near the wall on the second floor

as shown in figure 16. Cold air was found to be leaking into the ceiling

space at a location where a steel supporting structure extended through

the insulation (circled area in figure 16). The corresponding thermogram,

figure 17, shows the location as being quite cold. Subsequent examination

of visual photographs taken during the building's construction showed that

(1) steel struts extending through the insulation are used to support the

granite facade overhangs on this floor and the glass fiber insulation was pieced together around the struts with no special precaution taken to seal

against air leakage, and (2) several cracks existed in the exterior of the

masonry wall before application of the insulation. These cracks appear to

have resulted from either pipes built into the wall or defective mortar

joints.

Based on these findings, a general survey was made of the entire building.

This consisted of spot temperature measurements of wall sections, additional

thermograms, and qualitative examination by simply feeling walls and ceiling

plenums for cold temperatures and leaking air. More complete details on this

survey are given in reference [6]. It was found that cold surfaces were more

numerous on the first three floors and that they generally occurred on the

east and west walls. However, all exterior walls had sections that exhibited.

23
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25
to some extent, the same problems found on the second floor. Even the north

wall on the third floor was found to be substantially cool. This was surprising since there are no windows on the north wall and the construction is

different than on the other three. Air must have been infiltrating the cavity

space here along some path different than that on the other three walls.

There were some areas that were free of this air leakage problem. Figures 18

and 19 for example, were taken along the east wall of the sixth floor and the

results were indicative of what should have existed throughout the building;

a much warmer wall and floor surface than window surface.

Independent of the thermographic study, measurements of air change rates in

the building were made using a tracer gas technique and are discussed in

section 3.3. The results indicated higher air change rates on the first three

floors than on the upper four floors. This was consistent with the thermographic analysis that indicated more cold air in the cavities on the lower

three floors.

3.3 AIR EXCHANGE ANALYSIS

Along with the thermographic measurements made in February 1977, tests were

conducted to determine the rate at which outside air was entering the building

[7,8]. Subsequently, the outside air dampers were modified to reduce excessive leakage and the building facade received extensive caulking. Two years

later, in February 1979, the air exchange rates were re-determined [9].

A tracer gas techique was used to measure air exchange rates [10,11]. Sulfur

hexaflouride (SF5) was injected into the building and its concentration levels

were monitored closely. By determining the rate at which the gas dissipated,

it was possible to calculate the rate at which outside air was replacing air

in the building. SF5 was used because it can be detected at extremely low

concentrations. Thus, only a minute quantity of gas was needed. The result

was an odorless, non-toxic mixture which could be safely used in an occupied

building.

Floors one through three and four through seven of the building are served

by separate ventilating systems. The main features of these systems are represented schematically in figures 20 and 21. These diagrams include only

elements which control the main air flows to and from the building. Figure

22 is a more detailed diagram showing toilet exhausts and components of the

HVAC system.

Tests before Caulking of Building and Damper Modification : The results of

the tests conducted in 1977 will be described first. Measurements were made

not only of the overall building air exchange rates but also of the air

exchange rates between the floors. These will then be compared with the

results of the measurements made in 1979.

26
^6

BASEMENT

SUB-BASEMENT

Figure 20. Simplified schematic of the main ventilation system of floors

1-3 in the Norris Cotton Federal Office Building

27
3

2

I

BASEMENT

SUB-BASEMENT

Figure 21. Simplified schematic of the main ventilation system of floors

4-7 in the Norris Cotton Federal Office Building

28

In conducting the measurements, SF5 was Injected into the ventilating system

immediately upstream from the return fans, F2 and F4, in figures 20 and 21

respectively, and its concentration was monitored in the output of these fans.

Injections of approximately 100-120 ml SF5 for each air-handling system were

required to establish initial concentrations slightly less than 10 parts per

billion in the ventilated space. In repeat runs, smaller amounts were injected

to bring the concentration back to the initial starting level. Initially

about an hour was allowed for the tracer to distribute and for the concentration decay to stabilize, followed by an hour of concentration measurements.

Thereafter, about 10 minutes were allowed for stabilization before each run.

The ventilating systems were operated with the outside air dampers, Dl and D4

in figures 20 and 21, closed to obtain nominal 100 percent recirculation while

dampers D3 and D6 were open. In the first measurements, SF5 was introduced

only to the main ventilation systems of floors 4 through 7. In this way, any

air rising from the lower floors due to thermal convection or any other mechanism should have been essentially free of tracer. It was felt that comparison of measurements obtained using tracer on the upper floors only with

measurements obtained with tracer distributed throughout the entire building

would provide an approximate estimate of the relative amount of air leakage

to floors 4 through 7 from the outside and from the lower floors. The result

after adding SF5 to floors 4 through 7 is shown on line one of table 3.

Tracer was then added to the entire building, and the result is shown on line

two of the table. An apparent exchange rate of 0.7 air change per hour was obtained for floors 4 through 7 when air from the lower floors contained no tracer, and 0.54 air change per hour when tracer was introduced into the

entire building. This suggests that approximately 0.1 to 0.2 air change per

hour were due to air rising from the lower floors. The air exchange rates

for floors 1 through 3 were higher than those of the upper floors when operating in the nominal 100 percent recirculation mode. This is consistent with

the findings of the thermographic analysis where the lower three floors had

a greater problem with cold walls.

In the final tracer measurements during February 1977, the outside air dampers

to floors 4 through 7 were opened and operated in the variable volume mode.

The dampers for floors 1 through 3 were not opened because of problems in

supplying sufficient heat to these floors at that time. Under these conditions, air exchange rates for the upper floors were higher than for the lower

floors, as might be expected. The results are shown on line three of table 3,

The air leakage rates for floors 1 through 3 were lower when the outside air

dampers to the upper floors were opened than when the whole building was operated nominally with 100 percent recirculated air. The reason for this

apparent decrease is not known. It suggests that (1) possibly there was some unidentified leakage path from the upper to lower floors, or (2) the

building was operating under slight negative pressure when all the outside

air dampers were closed, and opening dampers raised this pressure to where

it was more nearly equal to the outside pressure.

30

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Weighted average exchange rates for the entire building were calculated

assuming that floors 1 through 3 represented three sevenths (3/7) of the

building volume and floors 4 through 7 represented four sevenths (4/7).*

The results are shown in the right-hand column of table 3. Air exchange

rates on the order of 0.7 to 0.8 air change per hour were obtained with

complete recirculation, and 0.9 to 1 air change per hour with the upper

floors operating in the variable volume mode. These estimates include air

exchange rates due to toilet exhausts which are designed for 1.873 m^/s

(3968 cfm). This corresponds to 0.22 air change per hour in a 31^150 m^

(1,100,000 ft^) building. There is also a special exhaust to a medical

examination room on the fourth floor which can be turned on. This has

a rated capacity of 0.7513 m^/s (1592 cfm) or about 0.09 air change per

hour averaged over the entire building when operating.

To determine how much air leaked into the building from the basement, 200-220

ml of SF5 were released in the basement and concentrations were monitored on the upper floors. Small increases in tracer concentration were observed on floors 1 through 3 and 4 through 7, but they were too small to measure quantitatively under the conditions of the experiment. A slightly greater

increase in concentration was found in the penthouse near the elevator.

This suggests that the elevator shaft is one of the leakage paths. However,

the results also suggest that air exchange with the basement is not a major

pathway of air leakage in the building.

Tests After Caulking of Building and Damper Modification ; During February

1979, measurements were taken over a two-day period. On the first day, the

building was operated with the outside air dampers closed, much like the

first phase of the 1977 test. Minor changes occured throughout the day

in the operation of certain exhaust fans and dampers but these were judged

to have minimal effects. The following day, the outside air dampers to both

systems were opened and the ones to floors 4-7 were operated in the variable

air volume (VAV) mode. In 1977, this configuration was not used, as mentioned

previously, because heating problems prevented opening the dampers to floors

1-3. Therefore, when making comparisons between the 1977 and 1979 results,

the first case (dampers closed) is of greater importance since this configuration was the same for both tests. The second case is important for

estimating energy use, however, since it is more representative of the way

in which the building is actually operated.

* The volume of the ventilated space was estimated from floor areas and

ceiling heights. The floor area of floors 1 through 7 is approximately

1330 m2 (14,300 ft2). The floor-to-floor heights are 4.0 m (13 ft),

except for the first floor where it is 5.2 m (17 ft). These dimensions

correspond to a gross volume of approximately 36,800 m^ (1,300,000 ft^).

Allowing 15 percent for inside partitions and furnishings results in a rounded estimate of 31,150 m^ (1,100,000 ft^).

32
The results of the 1979 test are shown on lines 4 and 5 of table 3. With

the outside air dampers closed, the air exchange rate was 0.75 air change

per hour for floors 1-3 and 0.39 for floors 4-7. The weighted average for

the building was 0.54 air change per hour which was a decrease of approximately 28 percent from the 1977 value of 0.75. This improvement is considered

to be due to the caulking and modifications to the air dampers. However, it was approximately 7°C (13''F) colder at the time of the 1977 measurements

compared to 1979,

The average inside volume of the Building has been estimated to be about

31,150 m^ (1,100,000 ft^) as explained previously. The average air exchange

rate of 0.54 air change per hour (outside air dampers closed) corresponds to

about 4,7 m-^/s (9900 cfm). If the number of occupants is assumed to be 280

people (an estimate based on counts made in 1977), the amount of outside air

corresponds to 0,017 m-^/s (35 cfm) per person. This can be further broken

down for the lower three and the upper four floors where the air exchange

rates were different. On floors 1-3, with an average air exchange rate of

0.75 per hour, and an average occupancy of 135, the average ventilation rate

per person is about 0.021 m^/s (45 cfm), while for floors 4-7, with an air

exchange rate of 0.39 per hour and an average occupancy of 168, it is about

0.012 m3/s (25 cfm) per person. The recommended level for office space is

0.007-0.012 m3/s (15-25 cfm) per person in ASHRAE Standard 62-73 [12], and

may be reduced in a subsequent revision. Thus, after retrofit to reduce

leaks, the average ventilation rate of the building still meets or exceeds

the requirements of the present ASHRAE Standard with outside air dampers

closed.

At the time of the 1977 measurements of air exchange rates, measurements were made of the CO2 concentration within the building. On the two days prior to

making the air exchange measurements, February 15 and 16, the main ventilating

system to floors 4-7 was shut down while adjustments were being made to the

heating system. The system to floors 1 through 3 was operated with outside

air dampers closed. This afforded an opportunity to measure carbon dioxide

levels in the building under conditions of restricted ventilation. An air

sample was collected from each floor and analyzed for CO2. Sampling points were not selected to be representative of the entire floor but were located

in the rooms containing the most people. This was done to obtain approximate

maximum levels of CO2. The results are shown in tables 4 and 5. About 65

percent of the values ranged from 700 to 1200 ppm or roughly two to three

times normal ambient levels (400 ppm). The highest concentration of CO2

observed was 2440 ppm or 5-1/2 times the outdoor level. This concentration

was obtained in a room on the fourth floor, where 11 people were taking an examination.

CO2 measurements were also made on February 17 with the main ventilating fans

to floors 4-7 operating. The results are shown in table 6. The change in

average CO2 concentration was small, but there was slightly greater uniformity

from floor to floor, also, with 16 people in the fourth floor room, the CO2

level was less than for the preceding day with 11 people.

33
Table 4. Carbon dioxide in air samples taken from various floors in the

Norris Cotton Federal Office Building, February 15, 1977, 3:00

to 5:00 p.m.

Ratio of indoor

No. of people No. of people CO2 to outdoor CO2

Floor on floor in room sampled ppm concentration

1

2 48 30 700 1.6

3 32 9 675 1.5

4 17 4 1500 3.4

5 55 15 1250 2.8

6 60 17 1175 2.7

7 26 12 1225 2.8

Main supply and return fans to floors 4-7 shut off. Main supply and

return fans to floors 1-3 on with outside air dampers closed.

34
Table 5. Carbon dioxide In air samples taken from various floors In the

Norrls Cotton Federal Office Building, February 16, 1977, 10:30

to 12:00 a.m.l

No. of people

on ^ 1 AftT* No. of people CO 2

Rfl LVCl t"U X1 nU ofJ. XIItiHoot I.U \J\J L. to outdoor CO2

1X 39 7 SO 1 7

2 52 26 700 1.6

3 52 12 700 1.6

4 56 11 22402 5.52

5 48 23 990 2.3

6 58 19 1075 2.4

7 34 17 875 2.0

1 Main supply and return fans to floors 4-7 shut off. Main supply and

return fans to floors 1-3 running with outside air dampers closed.

2 Sample taken In 40 m^ (430 ft^) room while people were taking an examination.

Comfort conditions were rather poor due to high temperature and relative

humidity.

35
Table 6, Carbon dioxide In air samples taken from various floors In the

Norrls Cotton Federal Office Building, February 17, 1977, 1:00

to 2:30 p.m.l»2

Floor

No. of people

on floor

No. of people

in room sampled

\j\JO

ppm

Ratio of indoor

to outdoor CO2

concentration

1 36 21 875 2.0

2 55 32 800 1.8

3 36 12 650 1.5

4 51 16 1350 3.1

5 31 22 850 1.9

6 47 16 865 2.0

7 21 12 775 1.8

Main supply and return fans to floors 4-7 turned on with outside air

dampers cloased.

Outside air concentration of CO2 440 ppm at 5:50 p.m.

36
Reference [8] includes an analysis showing the relationship between CO2

concentrations and ventilation rates. The results of the analysis show the

levels of CO2 implicitly tolerated by ASHRAE Standard 62-73 [12]. The minimum outside air of 0.0024 m^/s (5 cfm) per person which is specified in the

standard implicitly allows 2900 ppm CO2 at an assumed generation rate of 5.9

X 106 m3/s (0.75 ft^/h) per person [13], while the recommended levels for

office space of 0.007 to 0.012 m^/s (15 to 25 cfm) per person correspond to

900 to 1200 ppm CO2. Inspection of tables 4 and 5 indicates that most of the

measured concentrations fell within the recommended limits even with the main

ventilating fans to floors 4-7 off and that all levels were below the maximum

allowable value. This analysis based on the CO2 measurements leads one to

conclude that the ventilation rates were not as large as indicated by the

air exchange measurements described above. However, this is because the CO2

samples were taken from rooms of highest occupancy in order to look for areas

of inadequate ventilation.

3.4 PERFORMANCE OF THE SOLAR SUB-SYSTEM

Performance of Individual Solar Collector Panels : Solar energy is collected

by four rows of roof-mounted flat-plate solar collector panels. Each row has panels of a slightly different design. In order to determine potential

collector array performance, NBS had one of each type of collector tested in

accordance with ASHRAE Standard 93-77 [14] by a commercial testing laboratory

[15,16]. Figures 23 through 26 show a comparison between the collector

module performance and the performance as specified in the original request

for proposals sent out by GSA. When based on aperture area (as required by

the original specifications), the performance of all four collector modules

is reasonably close to the requirements for operation at normal incidence.

Table 7 includes a list of performance parameters determined from the tests,

the area for each row of the array on the building, and the flow rate for

the row if the panels in the row were operating at the test flow rate.

Tilt Angle of Collector Array ; One unique feature of the collector array

designed for this building is that even though fixed in the south-facing

orientation, the modules were installed on racks which could be tilted at

different angles from the horizontal to better utilize the sun's energy

throughout the year. Shortly after the building was put into operation,

analyses were conducted to determine optimum tilt angle. Figure 27 shows

the results as a function of the time of year. Two different calculation

techniques were used. A calculation was first made based solely on being

able to obtain an incident angle of 0" at solar noon throughout the year.

Secondly, a more refined calculation was done using the recommended computer

routines in the 1977 ASHRAE Handbook of Fundamentals [4] to compute the

hourly, daily, and monthly incident solar radiation on a south-facing tilted

surface. This latter technique accounts for direct, diffuse, and ground

reflected solar radiation including the fact that the diffuse radiation from

the sky tends to be greater in the summer than the winter. Both techniques

produced comparable results and enabled GSA to determine the eight times

during the year when the collector tilt should be changed to follow the

37
>-' o

Figure 23.

0,0

100.0

90,0

80,0 -

70.0 -

60,0 -

50.0

40.0 H

30.0

20.0 -

10.0 -

0.0

0.1

0.00 0.01

(r-h-ft')/Btu

0.2 0.3 0.4 0.5

Specified performance based on aperture area Actual performance based on gross area(ROW 1) Actual performance based on aperture area(ROW l)

0.02 0.03 (Tovg0.04 0.05 -Tamb)/I0.06 0.07 (°C-m')/W0.08 0,09 0.10

Collector performance for the modules in row 1 at Norris Cotton

Federal Office Building as determined by a test of one module in

a commercial testing laboratory

UJ

0.0

100.0

90,0 -

80,0

70,0

60.0

50.0

40.0 -

30,0 -

20,0

10,0

0,0

0.1 _l

(T-h-ft^)/Btu

0,2 0.3 —I I 0.4 -J

0.5

Specified performance based on aperture area Actual performance based on gross area(ROW 2) Actual performance based on aperture area(ROW 2) |

I I I I I I I 0.00 0.01 0.02 0.03 0.04 0.05 0.06 007

(T -T J/I (°C-m')/W

T

0.08 0.09 0.10

Figure 24. Collector performance for the modules in row 2 at the Norris

Cotton Federal Office Building as determined by a test of one module in a commercial testing laboratory

38
0.0

o

LjJ o

iZ

(jj

100,0

90.0

80.0

70.0

60.0

50.0

40.0

30.0

20.0

10.0

0.0

0.1 (°F-h-ft')/Btu0.2 0.3 0.4 0.5

Specified performance based on aperture area Actual performance based on gross area(ROW 3) Actual performance based on aperture area(ROW 3)

0.00 0.01 0.02 0.03 0.04 0.05 0.06 0.07 0.08 0.C9 0.10

Figure 25. Collector performance for the modules In row 3 at the Norris

Cotton Federal Office Building as determined by a test of one module in a commercial testing laboratory

>-"

UJ

0.0 100.0 -

90.0

80.0

20.0 -

10.0 -

0.0

0.1 (T-h-ft')/Btu

0.2 0.3 0.4 _l \ ^ 1

0.5

Specified performance based on aperture area

Actual performance based on gross area(ROW 4)

Actual performance based on aperture area(ROW 4)

1

0.00 0.01 0.02 0.03 0.04 0.05 0.06 0.07 0.08 0.09 0.10 -T_J/I (°C-m^)/W

Dvg amb'

Figure 26. Collector performance for the modules in row 4 at the Norris

Cotton Federal Office Building as determined by a test of one module in a commercial testing laboratory

39
Table 7. Test data for the solar collectors on the Norrls Cotton Federal Office Building

Fr (t«)e,n

W/(m2.

bo Gross

panel

area,

(ft2)

Panel

test

flow, kg/s*m2)

(lb/(h.ft2))

Gross

row

2 area,

(ft2)

Flow

for

array, i/s

(gpm)

Row*

1 0.A87 3.77 0.195 2.61(28.1) 0.407(300) 65.3(703) 0.953(15.1)

2 0.579 4.41 0.160 1.96(21.1) 0.366(270) 117(1260) 2.06(32.6)

3 0.650 4.27 0.122 1.64(17.7) 0.312(230) 73.8(794) 1.31(20.8)

4 0.627 2.90 0.200 3.34(36.0) 0.614(453) 100(1080) 1.72(27.3)

Total 356.1(3837) 6.04(95.8)

* Row 1: single-glazed, flat -black absorber, plastic convection suppressor

Row 2 Row 3 Row 4single-glazed, flat-black absorber

double-glazed, selective surface absorber

double-glazed, flat-black absorber

40
90.0

(/)

Ld

UJ

o

UJ

_J

o

<

80.0 -

70.0 -

60.0

50.0 -

40.0 -

30.0 -

20.0 -

10.0 -

0.0 ^ r

43° N LATITUDE

BASED ON INCIDENT ANGLE OF 0" AT SOUVR NOON

BASED ON MAXIMUM MONTHLY ENERGY INCIDENT. ASHRAE

ALGORITHMS. 02

o

0Ln

Oin

oID

LD

CO CM

CM

—1

FEB.

>-

MA API MA

O oin o m 0 in

CO m CM

in in CO

in

CO id ^o o

<

I I I I I I I I I T JAN FEB MAR APR MAY JUN JUL AUG SEP OCT NOV DEC

MONTH

Figure 27. Optimum solar collector tilt angle for the Norris Cotton

Federal Office Building as a function of time of year

41
sun's declination (specified along the bottom of the curve). However, by

examining the computer results closely, it was found that simply setting

the collector tilt at 60° from October to March and at 20° from April to

September resulted in the incident radiation being almost identical to that

achieved by the eight changes. This is shown in figure 28 and as a result,

NBS staff recommended only two changes in collector tilt per year.

Analysis of Solar Sub-system Operation ; The collector array itself has

performed adequately when operated. However, major problems have occurred

in solar system control and interface of the array with the mechanical

systems in the building so that the contribution of solar energy to the

building energy use over the first three years of operation has been minimal.

This will be explained further below. Figure 29 shows hourly average total

collector array efficiency taken from the JC-80 data tapes from October 1979

through January 1980 after the end of the third year of operation. The data

were filtered to remove all data points where the solar irradiation was less

than 600 W/m2(190 Btu/(h« f t^)). During the period of data collection shown,

the collectors were operated with an ethylene-glycol/water solution moving

through the collectors at a total array flow rate of approximately 6.3 i/s

(100 gallons/min) . Superimposed on the hourly average data points are the

efficiency curves for the four solar collectors in the array which were

tested in accordance with ASHRAE standard 93-77. The laboratory tests were

performed with water at the manufacturer's recommended flow rate and the

legend of figure 29 lists the flow rates that the rows in the array would

have to be operating at to have the same module flow rate occur. The sum

of the laboratory test flow rates is similar to the actual flow rate; however, the existing instrumentation does not allow a determination of whether

the rows in the solar array are properly balanced.

The solar energy sub-system was not included in the original design of the

HVAC system. This fact is perhaps an underlying cause of many of the control

and interface problems experienced at the building during the first three

years. At the time the solar sub-system was added, much of the architectural

and HVAC design was firmly set. Consequently, integration of the collector

array with the rest of the system was subject to a number of constraints.

For example, collector piping was tied into the main system in such a way

that the collector's output can only go to the basement storage tanks. If

the temperature of water in the storage tanks is too low, the entire volume

of water must be increased in temperature before any useful heat can be

extracted. The piping design should have been modified so that the collector

array energy could be used directly for meeting building loads.

As already described when discussing the building overall energy consumption,

during the first three years the collector array was never able to increase

the temperature of any of the storage tanks sufficiently to drive the absorption chiller during summer days. In addition, for space heating the solar

collectors were only of use during off-season periods when outdoor air temperatures were relatively mild. This was because during severe weather, it

was generally necessary to raise the space heating water loop temperature

42
1100.0 -

1000.0 -

900.0

800.0

700.0

600.0

500.0 -

400.0 -

300.0

± 200.0 -

100.0 -

0.0

43° N LATITUDE

V

v\

COLLECTOR TILT CHANGED 8 TIMES PER YEAR

COLLECTOR TILT = 20'*

COLLECTOR TILT = 60^

DEC JAN FEB MAR APR MAY JUN JUL AUG SEP OCT NOV DEC JAN

MONTH

Figure 28. Incident solar energy on the solar collector panels of the

Norris Cotton Federal Office Building under clear sky conditions

43
o

00

05

o

SftMQ«3 D< ft ft

s

o

o

CO

^ V

CD C

OS a

< xn o

_^

ID

OS

Jh r

^ ^ ^ ^ ^^^^

T3 t: ,^

-fJ ^ ^

C\2 CO ^

^ ^ ^ ^

o o o o ^

o

d

o

1^ o

d

o

d

00

rH r-«. O

3 1 4J o fn o

DC <Ti o

(V3dV SSOdO) % 'A0N3I0IJJ3

44
to a level above the normal operating range of the collector array.

Consequently, the solar collectors were used mainly during spring and fall

for space heating and domestic hot water and during summer for domestic hot

water only, over the Ih years of the first 3 years of operation.

Following the end of the third year of building operation when it was fully

apparent that the solar collector array was not contributing significantly

to the building's energy needs, GSA considered making several modifications

to the system. In support of their study, the analysis described below was completed [17], As of the publication of this report, no final decision has

been made on the extent of any changes to be made.

In order to estimate what the total annual output from the existing collector

array might be under ideal conditions, calculations were made using the

"phibar" method of calculating collector output [18], Calculations were made

under the following assumptions:

1, The collector fluid was assumed to be water,

2, The collector array was balanced so that each row performed

as specified by the collector parameters in table 7.

3, The inlet temperature was assumed to be held constant at 21 °C

(70°F) for supplementing heat pump operation, at GO'C (140°F)

(and 43 °C (110°F)) for use in the hot water heating system

or at 104 °C (220°F) for use by the absorption chiller.

4, Weather data used were for Concord, New Hampshire and represented average weather conditions over a long time period.

The effects of cloudy days are accounted for in the method,

5, Collectors were tilted at 60 degrees from the horizontal

all year and gross collector area was fixed at its present

value of 353 m2 (3800 ft^).

Table 8 gives the results of the calculations for each row and inlet temperature in GJ (10^ Btu) per month.

Detailed computer modeling of the building and its systems as operated was

also performed and will be discussed in section 3,5, For comparison of

collector array output with building requirements, results of the modeling

will be cited here. Table 9 lists total energy and thermal energy requirements for the building based on the computer simulation. The building has

two major mechanical sub-systems in which solar energy could be used. One,

the heat pump system on the first three floors, requires water at 27 °C

(80°F) or less. The hot water heating system, serving the upper four floors,

requires water from 43*'C (110°F) to 60°C (140*F), depending on the outside

air temperature. If the collector output values in table 8 are compared to

the building requirements and the assumption is made that the collectors

45
Table 8. Predicted collector output for the existing collectors on the Norris Cotton

Federal Office Building in GJ (10^ Btu)/month for a tilt angle of 60°

Tin.'C

Row ("F) Jan Feb Mar Apr May

1 21(70 3.2(3.0) 3.8(3.6) 5.5(5.2) 7.1(6.7) 8.8(8.3)

1 43(110) 1.9(1.8) 2.2(2.1) 3.3(3.1) 4.2(A.O) 5.1(4.8)

1 54(130) 1.3(1.2) 1.6(1.5) 2.3(2.2) 3.0(2.8) 3.6(3.4)

1 104(220) - - - - 0.5(0.5)

2 21(70) 7.2(6.8) 8.4(8.0) 12.2(11.6) 15.5(14.7) 19.3(18.3)

2 43(110) 4.2(4.0) 5.1(4.8) 7.4(7.0) 9.3(8.8) 11.3(10.7)

2 54(130) 3.0(2.8) 8.6(3.4) 5.3(5.0) 6.6(6.3) 7.9(7.5)

2 104(220) - _ _ _ 1.3(1.2)

3 21(70) 6.1(5.8) 7.1(6.7) 9.9(9.4) 12.1(11.5) 14.7(13.9)

3 43(110) 3.8(3.6) 4.5(4.3) 6.4(6.1) 7.8(7.4) 9.2(8.7)

3 54(130) 2.8(2.7) 8.5(3.3) 5.0(4.7) 6.0(5.7) 7.0(6.6)

3 104(220) _ _ - _ 1.6(1.5)

4 21(70) 9.4(8.9) 10.7(10.1) 14.5(13.7) 16.9(16.0) 19.5(18.5)

4 43(110) 7.0(6.6) 8.0(7.6) 10.9(10.3) 12.6(11.9) 14.2(13.5)

4 54(130) 5.8(5.5) 6.6(6.3) 9.1(8.6) 10.6(10.0) 11.9(11.3)

4 104(220) _ _ _ _ _

Tin/C

Row CF) Jun Jul Aug Sep Oct Nov Dec

1 21(70 - _ _ 9.4(8.9) 7.9(7.5) 3.8(3.6) 2.6(2.5)

1 43(110) - - - 5.8(5.5) 5.0(4.7) 2.2(2.1) 1.5(1.4)

1 54(130) - - - 4.3(4.1) 3.7(3.5) 1.6(1.5) 1.1(1.0)

1 104(220) 0.6(0.6) 0.7(0.7) 0.9(0.9) _ _ _ _

2 21(70) _ _ _ 20.4(19.3) 17.4(16.5) 8.4(8.0) 5.9(5.6)

2 43(110) - - - 12.8(12.1) 11.0(10.4) 5.0(4.7) 3.4(3.2)

2 54(130) - _ - 9.4(8.9) 8.0(7.6) 3.5(3.3) 2.3(2.2)

2 104(220) 1.4(1.3) 1.8(1.7) 2.0(1.9) _ - _ _

3 21(70) - - _ 15.3(14.5) 13.4(12.7) 6.9(6.5) 5.0(4.7)

3 43(110) - - - 10.2(9.7) 9.0(8.5) 4.2(4.0) 3.1(2.9)

3 54(130) - - - 8.0(7.6) 7.0(6.6) 3.2(3.0) 2.3(2.2)

3 104(220) 1.6(1.5) 2.0(1.9) 2.3(2.2) _ - - -

4 21(70) - _ _ 19.9(18.9) 18.0(17.1) 9.9(9.4) 7.6(7.2)

4 43(110) - -. - 15.3(14.5) 13.8(13.1) 7.2(6.8) 5.5(5.2)

4 54(130) - - . 13.0(12.3) 11.8(11.2) 5.9(5.6) 4.5(4.3)

4 104(220) 4.6(4.4) 5.6(5.3) 6.0(5.7) - - - -

46
Table 9. Predicted thermal and total energy requirements for the

Norris Cotton Federal Office Building based on computer

simulation

Heat pump system Hot water system Total energy

Month thermal requirements, GJ thermal requirements, GJ requirements

CIO" Btu; (10" Btu) (10" Btu)

Jan 236(224) 127(120) 1001(949)

Feb 224(212) 129(122) 938(889)

Mar 137(130) 76(72) 742(703)

Apr 56(53) 35(33) 497(471)

May 20(19) 15(14) 444(421)

Jun 0(0) 0(0) 476(451)

Jul 0(0) 0(0) 488(463)

Aug 0(0) 0(0) 540(512)

Sep 8(8) 5(5) 388(368)

Oct 44(42) 27(26) 490(464)

Nov 121(115) 68(64) 695(659)

Dec 222(210) 119(113) 954(904)

Table 10. Predicted collector output for 557 m'' (6000 ft'') of

evacuated tubular collectors located on the Norris

Cotton Federal Office Building (Fr (Ta)jj = ,546,FrUl

= 2.12 W/m2«°C, tilt = 60°

Collector output in GJ (10^ Btu) for

inlet temperatures

2rc 60°C 104°C

Month (70''F) (140°F) (220°F)

Jan 49.5(46.9) 27.7(26.3)

Feb 55.5(52.6) 32.0(30.3)

Mar 73.9(70.0) 43.1(40.9)

Apr 84.5(80.1) 49.5(46.9)

May 96.1(91.1) 55.5(52.6) 19.9(18.9)

Jun 20.3(19.2)

Jul 24.1(22.8)

Aug 26.0(24.6)

Sep 97.8(92.7) 60.1(57.0)

Oct 89.5(84.8) 54.9(52.0)

Nov 50.3(47.7) 28.1(26.6)

Dec 40.0(37.9) 21.7(20.6)

47
operate with an inlet temperature of 21 °C (80°F) in the winter and SA^C

(130°?) in the spring and fall, it appears that under ideal conditions,

the solar collector array could supply, at most, 26 percent of the annual

heat pump system thermal energy requirements and 4 percent of the annual

hot water heating system thermal energy requirements with a total collector

output of 299 GJ (283 x 10^ Btu) per year. If boiler efficiency is assumed

to be 75 percent, then the total savings that the solar sub-system could

provide would be 398 GJ (377 x 10^ Btu) or 5 percent of the total annual

energy consumption. It is important to remember that this is a maximum

and that operational factors would tend to reduce the solar contribution.

Such operational factors include:

1. the use of the ethylene-glycol/water solution in the collectors

instead of only water (would reduce the output by approximately

10 percent),

2. control system inadequacies and piping and storage thermal

losses, and

3. the collector output and building load requirements are not in

phase 100 percent of the time.

Table 8 indicates that the solar collector array should have useful output

at an inlet temperature of 104 °C (220°F). Actual data from the building

during 1978-79 indicated that the absorption chiller energy consumption

was only 1 percent of the total energy consumption 63 GJ(60 x 10^ Btu) of

fuel oil). The output indicated in table 8 would provide 47 percent of the

absorption chiller thermal requirements or 0.39 percent of the total energy.

After taking into account tank and piping losses, load-supply phase problems

and an oversized storage which must be heated to the operating temperature

before any solar energy can be used, the benefit from solar assisted cooling

appears negligible.

It should be noted that table 8 gives collector output for the array tilted

at 60°. A similar prediction for the collectors tilted at 45° resulted in

the same percentage of building energy supplied by solar as for the array

tilted at 60°, The reason for this is that the 60° array would collect more

energy in mid-winter than the 45° array but less in the spring and fall.

Changing the collector tilt has proven to be a very difficult and costly

operation and this analysis has shown a change in tilt to have little effect

when solar energy is not used for cooling purposes.

The heat pump loop was originally designed to operate without any input from

the collector array. One of the three storage tanks was intended to serve

as a thermal capacitor for the system and a two-way valve was included to

route the heat pump loop either through the tank or through an evaporative

cooler, depending on the loop temperature. When a solar system was added to

the design, the system was modified slightly so that other tanks could be

selected for the loop to run into, depending on the temperatures in the tank

48
and the loop. A separate control tied to another sensor in the heat pump loop

brings in boiler-heated water through a modulating valve if the loop temperature falls below a setpoint. If solar-heated water exists in one of the

tanks, the two-way valve attempted to route the heat pump loop into one of

the tanks. Usually, however, the water in the tank was far above the heat

pump loop setpoint and the two-way valve diverted the water in the heat pump

loop into the evaporative cooler. In order for solar-heated water to be used

in the heat pump loop, a modulating valve would have to be installed to bleed

water into the loop from a tank in the same way that boiler-heated water is

added to the loop. The controls would have to be carefully studied and

modified to bleed solar-heated water into the heat pump loop before bleeding

boiler-heated water into the loop.

The control of the solar sub-system actually involves three control systems.

A pneumatic control system defines a set of basic operational modes for (1)

winter operation with solar, (2) winter operation without solar, (3) summer operation with solar, and (4) summer operation without solar. The mode

controls determine where the solar-heated water being collected by the solar

system will be sent. Based on the outlet temperature from the array, the

system was designed to send the water to one of three storage tanks or bypass

all tanks and loop back into the array. The modes, as designed, were beset

with problems throughout the 3 years because solar modes (2) and (4) activated the engine-generator set to drive the electric chiller. This enginechiller arrangement did not work sucessfully as indicated in section 3.1.

A second control system determines the solar system pump speed. This control system senses the temperature difference across the collector array and

changes the speed of the variable speed collector pumps to keep the temperature rise across the collectors at 6°C (10°F). On system startup, there is a delay which causes the pumps to run at maximum speed until the system

stabilizes. If not enough incident solar energy is available, the controller

will run the pumps at a minimum speed. This arrangement caused problems at

first but adjustment of the minimum speed allowed the speed control to operate

acceptably.

The third control system was intended to determine which of the pneumatic

system control modes to select based on the incident irradiation and other

factors. The JC-80 minicomputer was supposed to execute this control function

but software problems prevented the use of the computer for this function

throughout the 3-year period. Actually, the building operators by-passed

the JC-80 system and simply turned the collector pumps on and off manually

using the JC-80 console or manual controls at the interface panel between

the pneumatic system and the JC-80. Changes in the JC-80 software are

not easily accomplished and consequently no changes were made to the solar

mode selection software during the 3-year period.

Based on the analysis and discussion above, NBS recommended that GSA:

49
1. continue to use all existing collectors and carefully balance the system

so that each row of the collector array will operate at its optimum flow

rate,

2. fix the collector array tilt at 60 degrees from the horizontal,

3. add modulating valves and controls to the system so that the solar-heated

water can be successfully used in the heat pump system,

4. modify the controls for storage tank selection so that only one or two

tanks are used and the set-point temperature of the tanks can be adjusted,

and

5. introduce enough automatic control into the solar system so that manual

operation will no longer be necessary. This could be implemented by

installing a hardware controller at the pneumatic control interface with

the mini-computer. The controller would use storage and collector temperature sensors and would be designed specifically for solar system

control.

Analysis of Improvements to Solar Sub-system; One option that was considered

but not recommended was replacing one or more rows of collectors with new collectors having a higher performance. The information in table 8 was used

to predict what effect this might have on the percentage of the load that the

solar sub-system could supply. Row 4 collectors appear to have the best

performance of the collectors on the array and the entire array could be

outfitted with this type. The predicted output of such an array was obtained

by scaling the row 4 output in table 8 up to the area of the total array.

The result of such calculations was that the array would then be able to

provide 30 percent of the heat pump system thermal energy requirements, 7

percent of the hot water heating system thermal energy requirements, and

could reduce the total building energy consumption by 7 percent. The additional energy savings over continuing to use the existing collectors would

be about 1 percent. Again, actual system performance would be expected to

be lower than the calculations indicate.

Another option considered was to replace all of the solar collectors with a larger area of evacuated tubular collectors. This might allow solar cooling

to be a reality. The benefits from this were estimated by again using the

phibar method. Table 10 lists the predicted output for an array of 557m^

(6000 ft^) of evacuated tubular collectors. Using the same assumptions as before, the collector output was determined for inlet temperatures of 21, 60,

and 104''C (70, 140, and 220''F). As table 10 shows, the output of the array

would increase. However, the output of the collectors at 60**C (140**?) would

still not be very large compared to the building loads in table 9. If solarheated water were used in the heat pump loop as a first priority, as before,

the new array could provide 38 percent of the heat pump system requirements,

11 percent of the hot water heating system requirements and would reduce the

building energy consumption by a total of 8 percent as a maximum.

50
If the prediction of collector output at 104°C (220°F) is examined, the

output of the collector could supply 86 percent of the total absorption

chiller thermal energy requirements for the summer of 1979 under ideal

conditions. However, this would involve replacing the existing absorption

chiller with one that could accept lower temperature water. This would

undoubtedly improve the portion of absorption cooling that solar energy

could provide. Again the contribution to the overall building energy

needs would be less than 1 percent and therefore such a major modification was not felt to be warranted.

3.5 COMPARISON OF ENERGY USE WITH COMPUTER PREDICTIONS

Even though the building had been modeled during the design phase it was decided to predict the thermal performance of the building using a stateof-the-art hour-by-hour computer program for the following reasons:

1. The original modeling of the building with NBSLD [1,2] predicted

the thermal performance of the building based on heating and cooling loads but did not actually simulate the mechanical systems in

the building. A simulation of the building using a mechanical

system simulation program was felt desirable in order to verify

the original design predictions for the building (625 MJ/m^^year)

(55 X 103 Btu/(ft2. year)).

2. Actual building energy consumption data is available for the

building over three years of operation. By comparison of

actual data and predicted data from a simulation of the building

as it has operated, a contribution could be made to the validation of building simulation computer programs.

3. Assuming that the results of computer modeling could be validated

for the original design, a simulation could be used to predict how

this building might have performed had the design been different,

with less emphasis on energy conservation and as if the building

had been designed for commercial use.

4. The model could also be used to examine possible improvements to

present building operation and to predict their effect on building

energy consumption.

Description of Computer Simulations ; The Ross Meriwether Energy System

Analysis program* was used for the simulations and was felt to represent the

state-of-the-art in building load and mechanical systems modeling. The

* Identification of a proprietary computer program in no case implies a recommendation or endorsement by the National Bureau of Standards.

51
popular public-domain programs such as DOE-2 [19] and BLAST [20] were not

generally available at the time this analysis was begun.

Five different simulation runs were made. The characteristics of the building

simulated by each run will be described in the next several paragraphs, followed by a presentation of the simulation results. A complete description

of the analysis of the simulation results may be found in reference [21].

The first simulation, the "as-designed" case, was intended to represent the

building as it was originally designed. The design plans and specifications

for the building were used as input to the program. A solar energy sub-system

was not included in the original design and was therefore excluded from the

"as-designed" simulation.

The complete building was divided into two sub-buildings for this simulation

in order to represent the two main mechanical sub-systems, the heat pump

system and the combined central systems. Each of the two sub-buildings

was further sub-divided into major zones. The heat pump system sub-building

consisted of the first three floors of the building and was divided into a core zone and perimeter zone, each zone spanning three floors. The central

system sub-building was divided into four major zones; the fourth floor, the

fifth floor, the sixth and seventh floor core, and the six and seventh floor

perimeter. In the real building, each major zone utilizes a different type

of air-side HVAC and control system and thus each zone had to be simulated

differently. As mentioned previously, the fourth floor uses a standard

variable air volume system with finned tube radiation to offset transmission

losses. The fifth floor uses a variable air volume system with a separate

single-duct system to offset transmission losses. The sixth and seventh

floors both have variable air volume systems for the core and four-pipe fan

coil units for perimeter heating and cooling. Each of the zones was simulated

with a design thermostat setting of 20°C (68°F) for heating and 26°C (78°F)

for cooling with a winter setback to 16°C (60°F) from 6 pm to 5 am during

the week and all day on weekends and holidays. Mechanical equipment simulated

included four gas-fired modular boilers used to provide hot water to the heat

pump or central systems. Central chilled water was assumed supplied by the

electric chiller, always driven by the engine-generator, as called for in the

original design. Waste heat from the engine generator was assumed used to

drive the absorption chiller in parallel with the electric chiller. Energy

storage was available to store excess heat from the engine generator and this

storage could supply energy for heating or the absorption chiller if no other

sources were available.

The second simulation run used the final building design which included a solar energy sub-system added to the original design. This simulation was basically the same as the "as-designed" simulation with the exception that

the central electric chiller was assumed always to run on purchased power

rather than power produced by the engine-generator. The "with solar" design

called for the solar sub-system to provide thermal energy to run the absorption chiller. With the solar sub-system, the engine-generator was designed

52
to operate and the recovered heat used only if the solar sub-system did not

have sufficient output to operate the absorption chiller (on cloudy days,

for example). Simulation of this complex control scheme was not possible

with the program and therefore engine-generator use was not simulated for

this case.

At the time the simulations were run, the program had no provision for

direct solar system simulation. The operation of the solar sub-system

in the building was approximated by a room with south-facing windows.

This room had no space heating capabilities and cooling was provided by an "imaginary" chiller which acted as a "heat" pump to remove solar gain

from the room and pump it to storage. This chiller differed from a real

chiller in that it required no compressor power. The thermostat setting

in the room for cooling was set to 88 °C (190''f) during the summer and 37 °C

(99 °F) during the winter to simulate collector temperatures. These settings

insured that the simulated collector array would operate at a minimum output

temperature for the loads it was required to supply. The design of the

solar sub-system called for a storage tank to be heated with solar energy

to a specified temperature level before solar energy could be used. Due

to limitations in the simulation program it was assumed that energy from

the solar system could be used directly. The use of this assumption yielded

a slightly higher solar sub-system performance than might be expected from

the design.

Prediction of the amount of solar energy entering the room was accomplished

by having the program generate a table of solar heat gain values for each

hour of the day throughout the year. The regular function of this table is

to predict solar heat gain through windows using as input a series of absorptance and transmittance constants. For a solar system, these constants can

be given values so that the program simulates the energy arriving at the

absorber plate of solar collectors. This gives the same result as applying

a transmittance-absorptance product and an incident angle modifier to the

energy incident upon the solar panels. Energy loss from the solar collectors

by heat transfer to the environment was approximated by the transmission

loss through the walls of the solar room. Original design specifications

for collector performance were used for the collector simulation.

Following building start-up in September 1976, differences between the design

predictions for the building and the actual operational performance became

apparent. In many cases, problems with the controls forced building operators

to resort to manual operation of systems. Because of the differences between

the actual operation of the building and what was assumed during the design

phase a simulation was felt to be required that would predict the energy

consumption of the building "as-operated." Some of the most important

differences between the assumptions made at the time of design and what has

occurred with the actual building were incorporated in the "as-operated"

simulation and are as follows:

53
Different air infiltration rates. In the "as-designed" simulation,

0.5 air change per hour were used. As has already been described,

average rates of 0.75 air change per hour were measured initially

after occupancy of the building. After recaulking of the building

exterior, lower rates were measured (0.75 air change per hour on the

first three floors and 0.39 on the upper four floors or an average

of 0.54 air change per hour for the building). The lower rates

were used in the "as-operated" simulation. In the "as-designed"

case, infiltration was assumed to be constant on the first three

floors and exist only on the upper four floors when the fans were

off (a pressurized building). The air exchange measurements showed

that there is constant infiltration throughout the building even when fans are operating. Consequently the infiltration rate for

the "as-operated" case was input as constant.

Two manually controlled oil-fired boilers were added. Originally,

these boilers were only intended as back-up equipment in the event

of an interruption of natural gas but have been used routinely

during winter operation in sequence with the gas boilers to meet

higher than expected heating loads. The oil-fired boilers have

also been used in the summer as the source of hot water for the

absorption chiller as has been described. Gas is not used to heat

water for the chiller because retrofit piping was only added between

the chiller and the oil boilers to avoid modifications to gas boiler

controls.

For the "as-operated" simulation, the operation of the gas-fired

boilers was limited to the months of October through April for heating and the operation of the chillers was limited to the months of

May through September.

The building operators increased the hot water heating system temperature from the design value of 41°C (105°F) to 60°C (140°F) during

mid-winter to improve comfort conditions and meet peak heating loads

in the building.

Recovered heat from the engine generator has never successfully

driven the absorption chiller. The electric chiller is always

driven by purchased power since the waste heat produced by the

engine generator cannot be put to any use. The absorption chiller

is driven by water heated in the oil-fired boilers. Also, the

two other heat recovery options for the electric chiller (doublebundle condenser and false loading) have never been used successfully.

No heat recovery from the engine generator or electric chiller was simulated in the "as-operated" case.

In the actual building, the solar array output is used only during

the spring and fall to provide energy for the hot water heating

system. During mid-winter, the heating water system temperature

54
is raised to 60°C (140°F) and at this temperature the efficiency

of the existing solar array is too low for any usable energy to

be collected. In the summer, the solar array has been unable to

produce usable energy for the absorption chiller. To simulate

this situation, the "as-operated" simulation allowed the solar

array to provide energy for the hot water heating system only

during the months of April, May, September, and October (when

heating water temperatures are lowered). The only other system

in which solar energy was assumed used in the simulation was the

service hot water system (used all year),

7. Thermostat settings were changed to 18°C (65°F) for occupied

heating and to 13°C (55°F) for unoccupied setback.

8. In the "as-operated" simulation the lighting loads were raised

slightly and redistributed to more accurately reflect the

electrical energy requirements of the various agency tenants.

A fourth simulation of the building was made to predict what the effect

would be of several easily implemented changes to the current operation

of the building. The "as-operated" simulation was taken as a baseline

and several changes were made to the input data. The changes consisted

of the following:

1. The heat pump fans were cycled by room thermostats with the

heating or cooling load. As presently operated, the heat

pump fans operate continuously during occupied hours.

2. The variable air volume air handling unit cooling coil discharge temperature was raised from 13°C (55°F) to le'C (60°F).

3. The water loop temperature for the heat pump system was operated at the maximum temperature consistent with the

safety of the heat pump units.

4. The temperature of the central chiller condenser water was lowered to the minimum consistent with chiller safety and

cooling tower capability (The use of (40°C) 105°F condenser

water was required only to allow heat recovery and has reduced

chiller efficiency). Also in the simulation, the absorption

chiller was sequenced to run after the electric chiller was

at full load rather than in parallel.

The fifth and final simulation run was intended to be a prediction of

how a design alternative to the building might have performed, had it

been built instead of the existing building. The design of the alternative chosen did not stress energy conservation as much as the actual

building and represented what was felt to be typical design practice

for an ordinary commercial building during the early 1970 's. Basically,

55
the "design alternative" had the same configuration as the "as-designed"

building, with the same shape, occupancy, layout and floor area. The

differences were In the thermal quality of the building envelope and the

types of mechanical systems used. In addition, the alternative building

had none of the demonstration character of the existing building. The

major differences between the "as-designed" and the "design alternative"

building were as follows:

1. The alternative used approximately twice as much electricity for

lighting per unit of floor area and had higher total Internal

gains.

2. The alternative had no solar or heat recovery systems.

3. The overall wall U-value Including the effect of windows was

changed from 0.57 to 1.59 W/ (m2. °C) (0. 10 to 0.28 Btu/(h. f t^. °F)).

4. The window area was changed from 6 percent to 29 percent of the

total wall area and windows were used on the north wall. A shading

coefficient of 0.5 was used to calculate solar gain.

5. The wall and roof U-value was changed from 0.34 to 0.85 W/Cm^'^C)

(0.06 to 0.15 Btu/(h.ft2. °F)).

6. The design alternative used a hot water system for heating with

a central boiler and hot water coils on the perimeter.

7. The design alternative used through-the-wall air conditioning units

on the perimeter and packaged air conditioning units in the core for

cooling.

8. A pressurized building was assumed and infiltration rates were those

with fans off.

Predicted Overall Energy Consumption ; Each of the simulation runs resulted

in a prediction of the consumption of various fuels and the building overall

energy consumption, on a monthly and annual basis. The following paragraphs

will describe the simulation results.

Total energy consumption predicted in each of the five simulation runs is

shown in figure 30 for each month of the year. The total consumption is the sum of the maximum energy contents of electricity and all forms of fuel as they pass through the building boundary. It is Important to remember that

while different buildings may use the same amounts of energy at the boundary,

the cost of the energy will differ between buildings using different fuels

and having different demand characteristics. The basic shape of the energy

consumption curves is the same for all runs and shows that for an office

building in this climatic region, the predominant energy use is for heating

rather than for cooling. Differences between the individual curves are the

56
1000.0

900.0 -

800.0

700.0

600.0

500.0 H

400.0

300.0 -\ AS-DESIGNED

G O AS-DESIGNED WITH SOLAR

200.0 [— /^....^ AS-OPERATED

O O AS-OPERATED WITH MODIFICATIONS

-\ h DESIGN ALTERNATIVE 100.0 H

0.0 -1 ^

^

^

^ ^, 1

, JAN FEB MAR APR MAY JUN JUL AUG

^ ^

SEP OCT NOV DEC

CALENDAR YEAR 1962

Figure 30. Total energy consumption at the Norris Cotton Federal

Office Building as predicted by simulation

140.0 -

120.0 -

^ 100.0 z

o

80.0 H X

60.0 O

40.0

20.0 -

C3 AS-DESIGNED

G---0 AS-DESIGNED WITH SOLAR

^----A AS-OPERATED

O OAS-OPERATED WITH MODIFICATIONS

H h DESIGN ALTERNATIVE

0.0 I ' I ' I ' I ' 1 ' 1 JAN FEB MAR APR MAY JUN JUL AUG SEP OCT NOV DEC

CALENDAR YEAR 1962

Figure 31. Electric energy consumption at the Norris Cotton Federal

Office Building as predicted by simulation

57
result of a number of factors. The "as-designed with solar" consumption is

slightly lower than in the "as-designed" case since some of the solar energy

collected replaces purchased energy. The energy consumption for the "asoperated" case is higher in winter than for the "as-designed" case due to

factors such as higher heating loads. The effect of the modifications to

the building in the "as-operated with modifications" case is a slight overall

decrease in the energy consumption. A surprising result is that the "design

alternative" case, energy consumption levels are predicted to be similar to

those in the "as-operated" case. The reasons for this result will be

examined in later paragraphs.

The electric energy consumption per month predicted for the building is shown

in figure 31. For the "as-designed" case, electric energy is used for lights,

receptacles, the mini-computer, miscellaneous, pumps, fans, and for heat pumps

all year. The greater electrical use in winter can be attributed to the heat

pump system which must meet the heating load for the first three floors. The

addition of the solar sub-system has little effect on the electric energy con- sumption compared to the "as-designed" case except in the summer months. The

increase in the summer is the result of running the electric chiller on purchased power and never with the engine generator. The electric energy

consumption for the "as-operated" case is significantly higher than for the

"as-designed" case due to higher heating and cooling loads, greater energy use

by pumps, fans, controls, lighting, and the operation of the electric chiller

solely on purchased power. The slight reduction in electric consumption

for the "as-operated with modifications" case is due to savings in fan energy

and heat pump electric consumption, and more efficient electric chiller

operation. A noticeable difference exists between the electrical consumption

for the "design alternative" and the other cases. The "design alternative"

does not use heat pumps for heating, but does utilize electricity for cooling.

Therefore this results in a lower curve during the winter and a higher one in

the summer.

Predicted natural gas consumption is shown in figure 32. The "as-designed"

curve shows a large winter usage of gas (used in boilers for heating) and a smaller but significant use of gas in summer (to operate the engine-generator

to drive the electric chiller). The "as-designed with solar" gas consumption

is lower all year reflecting the replacement of boiler generated thermal

energy with solar thermal energy. Some gas consumption exists in the summer even though this simulation case did not allow use of the engine-generator.

Gas is used to heat water to fire the absorption chiller when the solar

sub-system can not supply all of the absorption chiller requirements. In

the original design with solar the engine-generator was supposed to be used

when solar energy was not available and therefore the gas boilers were not

permitted to fire the absorption chiller. Thus, the summer gas use in figure

32 only approximates gas use in the engine-generator as called for in the

original design with solar.

In the "as-operated" case, the engine-generator is never used and the electric

chiller operates on purchased power while the absorption chiller is fired by

58
800.0

JAN FEB MAR APR MAY JUN JUL AUG SEP OCT NOV DEC

CALENDAR YEAR 1962

Figure 32, Natural gas consumption at the Norris Cotton Federal

Office Building as predicted by simulation

80.0

70.0 -

60.0

50.0 -

40.0 —

30.0 -

20.0 —

10.0 -

A- ----A AS-OPERATED

O O AS-OPERATED

WITH MODIFICATIONS

A-

-e80.0

h 70.0

60.0

50.0 — 40.0

- 30.0

20.0

- 10.0

—

o

Figure 33.

JAN FEB MAR APR MAY JUN JUL AUG SEP OCT NOV DEC

CALENDAR YEAR 1962

Fuel oil consumption at the Norris Cotton Federal Office

Building as predicted by simulation

59
water heated in the oil boilers. Thus there is no natural gas use in the summer for this case. The winter natural gas consumption is higher than for

the "as-designed" case because of higher heating loads. The modifications

to the "as-operated" case are not of the type which would save boiler energy

and therefore there is no change in the gas consumption for the "with modifications" case. The gas consumption for the "design alternative" case is

significantly higher than for the other cases but it must be kept in mind

that the "design alternative" does not use heat pumps and all of the energy

for heating is supplied by natural gas boilers.

No fuel-oil-fired equipment was included in the original design and therefore

no consumption is predicted for the first two simulation cases. Fuel oil

boilers were added to the actual building as supplementary boilers and in the

"as-operated" case and the "as-operated with modifications" case oil boiler

capacity was included. In the winter, the oil boilers have been used when

the demand on the boiler system exceeded the gas boiler capacity. In simulating the complex control scheme of the building more gas boiler capacity had

to be included in the simulation than the building actually has. The "asoperated" simulations predicted that the extra gas boiler capacity was exceeded

and that fuel oil would have been used in the winter. This agrees with the

actual operation of the building where the fuel oil boilers were used during

the winter.

Figure 33 depicts use of fuel oil in the summer predicted by the simulation

cases. Piping was added to the building so that the oil boilers could be

used to heat water to fire the absorption chiller. Figure 33 shows a large use of oil for the absorption chiller and a reduced usage for the "as-operated

with modifications" case. The lower usage after the "modifications" results

from a reduction in absorption chiller operating hours due to use of the

absorption machine in sequence with the electric chiller rather than in

parallel with it.

Comparison of Actual and Predicted Overall Energy Consumption; The simulation

runs were all made using weather data for Concord, New Hampshire for the

calendar year 1962. In comparing actual energy consumption data with the

results of the simulations it is important to consider that the actual weather

has been different from the 1962 weather assumed in the simulations. Although

it would have been desirable to use input weather tapes from the period during

which the actual building has been operating, detailed hourly weather tapes were not obtainable. Figure 1 is a plot of the average monthly ambient drybulb temperature in Concord for 1962 and for the 3 years that the building

has been in operation.

A comparison of the building overall energy consumption for the "as-operated"

case and the actual consumption for the three years of building operation is

shown in figure 34. The energy consumption for the first 2 years of operation was quite variable and much higher than predicted by the simulation.

The first two years represent the long period required to "debug" the building

as operators attempted to make the mechanical systems perform as called for

60
1400.0 -

1200.0

ZL 1000.0 I—

I—z

o

2 800.0 H \ZD

I—CD 600.0 -

400.0 -

200.0

Figure 34.

0.0

X

-A 1962,simulation

Sep 1978 - Aug 1979 X Sep 1977 - Aug 1978 + Sep 1976 - Aug 1977

- 1400.0

- 200.0

JAN FEB MAR APR MAY JUN JUL AUG SEP OCT NOV DEC

Total energy consumption at the Norris Cotton Federal Office

Building as predicted by the "as-operated" simulation compared

with actual consumption for three years

Table 11. Norris Cotton Federal Office Building

annual energy consumption

SIMULATION CASES

(1962 weather data)

2* 2* Energy consumption In MJ/(m -yr) (kBtu/(ft 'yr)) Total Gas Electric Oil

Design Goal 625(55 0)

"As-designed" 686(60 2) 251(22 0) 436(38 2)

"As-designed with solar" 616(5A 0) 174(15 3) 441(38 7)

"As-operated" 705(61 8) 197(17 2) 442(38 8)

"As-operated with modifications" 662(58 1) 194(17 0) 468(41 0)

"Design alternative" 676(59 3) 303(26 5) 373(32 8)

ACTUAL DATA

September 1976-August 1977 919(80 6) 280(24 6) 563(49 4)

January 1977-December 1977 813(71 3) 237(20 9) 514(45 1)

September 1977-August 1978 758(66 5) 225(19 7) 498(43 7)

January 1978-December 1978 730(64 0) 208(18 3) 495(43 4)

September 1978-August 1979 641(56 2) 153(13 4) 459(40 3)

January 1979-December 1979 619(54 3) 141(12 3) 459(40 3)

24(2.1)

1(0.1)

76(6.6)

61(5.3)

35(3.1)

27(2. 3)

28(2.5)

19(1.7)

2 2 *equivalent gross floor area = 10,900 m (117334 ft )

61
in the original design. During the third year of operation, the building

was finally operated in the best way possible given the shortcomings of

the installed systems and equipment. The agreement between the actual

energy consumption and the "as-operated" simulation results is fairly

close for the third year.

The expression of overall building energy consumption on a per unit area

basis has been used to make comparisons between buildings and to establish

energy consumption design goals. In making such comparisons, it is important

that all buildings involved in the comparison have their areas calculated in

a consistent manner and that all references to a single building use the same

area. The GSA Public Buildings Service (PBS) uses two methods of computing

floor area. The "equivalent gross floor area" (EGFA) method of calculating

building area is used as a basis for energy consumption goals [22]. This

method identifies three types of building area: office space, mechanical

equipment space, and garage areas. Since garage and mechanical areas use

energy for lighting, elevator service, and ventilation, GSA/PBS felt that

it was important to include such areas in the total but not "weight" them

as fully as conditioned office areas. Equivalent gross floor area as defined by GSA/PBS is one quarter of the mechanical and garage areas plus

the total office area. A different area, the total gross floor area, is

used for reporting of building performance. This area includes all areas

of the building.

In order to be consistent with the GSA/PBS conventions, an EGFA of 10^900 m^

(117,334 ft2) is used here. This includes 9072 m^ (97,648 ft^) of office

space, 643 m^ (6,925 ft^) of mechanical space, and 6672 m^ (71,818 ft^) of

garage. The total area of the building is 16,387 (176,304 ft^). During

the design stage GSA established an energy consumption goal of 625 MJ/(m2xyear)

(55 X 10^ Btu/(f t^xyear ) ) for this building and for other energy conserving

buildings to follow.

Table 11 lists the annual energy consumption per unit equivalent gross floor area predicted for the building as a result of the five computer simulations.

Also listed are the values of actual energy consumption of the building since

occupancy in September 1976. The "as-designed" simulation prediction exceeds

the GSA goal by nine percent. However, when the solar sub-system is added,

the simulation prediction is 2 percent less than the goal. The "as-operated"

simulation prediction is 12 percent higher than the goal. The "design alternative" simulation results in a value which is eight percent above the GSA

goal.

The "as-operated" simulation was intended to represent the actual operation

of the building during the recent past. At the time that the simulations

were performed, the operation of the building during the third calendar

year (1979) was used as a basis for selecting "as-operated" case inputs.

It is important to remember that the "as-operated" simulation could not

exactly simulate the actual building operation because some manual control

has been used by the operator during the three years of operation, and

62
various operational schemes have been used for time periods shorter than

a year. It is impossible to accurately simulate a mechanical system when

human judgement has been used to control the operation of the equipment.

Including the qualifications given, the simulation predicted a total energy

consumption 14 percent greater than the third calendar year consumption.

The modifications to the "as-operated" simulation resulted in an annual

reduction in energy consumption of about 6 percent. A summary of the

major modifications causing the energy reduction are given in table 12.

Heating and Cooling Energy Requirements ; The monthly heating and cooling

energy requirements, or the energy delivered to or removed from the air side

of the mechanical systems, were available from the simulation output. Monthly

heating energy requirements per unit area for the "as-operated" case are shown

in figure 35. In the figure, the results for the core and perimeter have been

combined. The most apparent characteristic of this plot is that the requirements for the first three floors are much larger than the requirements for

the other floors. This is due to a higher infiltration rate on these three

floors compared to the other floors. Since the thermal design of the building facade is of high quality, loads due to infiltration tend to dominate.

Also the heating capacity of the heat pump system on the lower three floors

is higher than for the central system on the other floors. Higher capacity

results in less time in which the air-side system cannot satisfy the load.

Since in the simulation it was found that the air-side systems were not able

to meet the load on many occasions, the lower capacity of the equipment on the upper four floors results in less energy delivered to the upper four

floors by the air-side systems than if all loads had been satisfied. The

figure shows the effect of an increase in air infiltration rate from 0.75

to 1.0 air change per hour. The higher rate represents the value measured

in the air exchange tests made on the first three floors before the building

facade was caulked. The dotted line representing the requirements for the

higher air change rate is approximately 25 percent higher than for the lower

air change rate (solid line). In the "as-operated" case the lower three

floors have higher energy requirements than the upper floors. The greater

requirements result from a higher rate of constant infiltration. Higher

infiltration rates flush more heat out of the building during moderate

weather thus reducing cooling requirements.

The effect of infiltration rate on the cooling energy requirements for the

"as-operated" case can be observed in figure 36. For the lower floor zones,

the increase in infiltration rate lowers the cooling requirements. In this

figure, the fifth floor stands above the other floors. This is a result of

the redistribution of the lighting loads to reflect the tenant requirements.

The fifth floor in the simulation has a higher internal gain from lighting

than the fourth floor, which is otherwise similar.

Heating and cooling energy requirements for the "design alternative" case

are shown in figures 37 and 38. In this case there are only three major

zones. One zone represents an area on the first floor occupied 24 hours

63
Table 12, Summary of effects of modifications made to the

"as-operated" simulation

MODIFICATIONS

1. Cycle heat pump fans

2. Raise cooling coil

discharge temperature

of VAV

3. Raise heat pump loop

temperature

4. Lower central chiller

condenser water temperature and sequence

chillers; electric

chiller first,

absorption last

EFFECT

Save 45,000 kWh

Reduce cooling

requirements

18 percent

Save 5000 kWh

Save 54,415 kWh

absorption chiller

seldom used

PERCENT REDUCTION IN

TOTAL ENERGY CONSUMPTION

1.3%

1.2%

0.3%

2.5%

64
X1—o

o

10.0

8.0 —

6.0 —

4.0 —

2.0 —

0.0

1- ^1 1st 3 floors,

infiltration 1 ac/h

1 1 1st 3 floors,

infiltration 0.75 ac/h

tth floor

Dth floor

3th and 7th floors

-e^

~ 100.0

- 80.0

- 60.0

- 40.0

20.0

0.0

I—o

JAN FEB MAR APR MAY JUN JUL AUG SEP OCT NOV DEC

CALENDAR YEAR 1962

Figure 35. Monthly total heating requirements per unit area for the

Norris Cotton Federal Office Building as predicted by the

"as-operated" simulation

z

o

m

o

4.0

3.0 —

2.0 —

1.0 —

0.0 JAN FEB MAR APR MAY JUN JUL AUG SEP OCT NOV DEC

CALENDAR YEAR 1962

Figure 36. Monthly total cooling requirements per unit area for the

Norris Cotton Federal Office Building as predicted by the

"as-operated" simulation

65
10.0

8.0

6.0

GZ3 4.0 m

O

2.0

0.0

-1 24 hr zone, 1st

-P Perimeter zone

-e Core zone

- 100.0

- 80.0

- 60.0

- 40.0

- 20.0

I—z

o

0.0

Figure 37.

—I ' 1 I _ . _ , JAN FEB MAR APR MAY JUN JUL AUG SEP OCT NOV DEC

CALENDAR YEAR 1962

Monthly total heating requirements per unit area for the

Norris Cotton Federal Office Building as predicted by the

"design alternative" simulation

4.0

3.0

2.0

mtoo'- 1.0 \—

0.0

P^-P 24 hr zone, 1st

G—G Perimeter zone

1—1 Core zone

- 40.0

- 30.0 I

- 20.0 £

10.0

Figure 38.

-t 0.0 JAN FEB MAR APR MAY JUN JUL AUG SEP OCT NOV DEC

CALENDAR YEAR 1962

Monthly total cooling requirements per unit area for the

Norris Cotton Federal Office Building as predicted by

the "design alternative" simulation

66
per day as a guard office. The heating requirements are slightly higher

and the cooling requirements are definitely higher than in the other cases. The higher cooling requirements result from greater internal gains and from

solar gain. The high cooling requirements in the perimeter zone relative

to the core zone result from solar gains. For comparison, the total monthly

heating and cooling energy requirements for all cases are shown in figure 39.

Load Components ; One type of output data available from the ERE program is a summation of load components such as transmission losses and internal gains.

The information is output as a yearly total. This means that the summation of,

for example, transmission losses, includes losses during the summer as well

as the winter. This limits the value of the data but it is still possible to

gain insight into the building performance by looking at these components.

Figure 40 shows the components for all cases in bar chart form. Infiltration

and transmission gains are not shown since these are very small relative to

the corresponding type of losses. The figure shows that the heating energy

requirements for all cases are very similar although the cooling energy

requirements differ. All of the simulation cases result in approximately

the same infiltration losses. The internal gains differ somewhat, the gains

being higher in the "design alternative" case and lower in the "as-designed"

case. However, the most striking difference is for transmission losses where

the "design alternative" values are much larger than for the other cases. It

might seem that this would cause the "design alternative" to have higher heating energy requirements. However, examination of the solar gain data shows a much higher solar gain in the "design alternative" than in the other cases

(where gain is zero because of the very small window area). This solar gain,

together with the higher internal gains, is the cause of the higher cooling

requirements in the "design alternative" case. However, the higher solar and

internal gains offset the larger transmission losses in the "design alternative" so that for all the cases, the heating requirements are approximately

the same. The conclusion is that smaller window areas in the actual building do decrease transmission losses but also reduce beneficial winter solar

gain. In general, the solar gain, transmission loss, and internal gains

should be carefully balanced in any design to minimize energy usage or cost.

Fuel Energy Use for Meeting Heating and Cooling Requirements : In order to

meet heating and cooling energy requirements, fuel must be used. Besides

oil and gas, fuel is also considered to include the electric energy used by

compressors in the heat pumps and chillers. Total fuel use can be plotted

versus the ambient temperature. The value of such a plot is that actual

fuel consumption data are available for the building and a comparison with

the simulation results can be made. For the actual data, fan energy cannot

be separated from the fuel use. Figure 41 shows the fuel plus fan energy

versus monthly average ambient temperature for all the simulation cases and

actual data. The lines shown represent a third order (cubic) fit of the

data. Residual standard deviations (standard deviation between values predicted by the fitted curve and the original data) for the simulation data

range from 16 to 21 GJ (15 to 20 x 10^ Btu) and for the actual data the

residual standard deviation is 51 GJ (48 x 10^ Btu). The fit is approximately

67
500.0

400.0

2: 300.0 o

OQ 200.0 —

£>O

100.0

0.0

O As—designed

A As—operated

As-operated with modifications

-|- Design alternative

Heating requirements

Cooling requirements

- 500.0

400.0

- 300.0

- 200.0 O

- 100.0

^ ^ 0.0 JAN FEB MAR APR MAY JUN JUL AUG SEP OCT NOV DEC

CALENDAR YEAR 1962

Figure 39. Monthly total heating and cooling requirements for the Norris

Cotton Federal Office Building as predicted by all simulations

<

L±J

moO

50.0

45,0

40.0

35.0

30.0

25.0

20.0

15.0

10.0

5.0

0.0

Heating req.

IVN As—designed

^§ Design alternative

I I As—operated

V7\ As—operated with modifications

Fuel use

Transmission loss

Cooling req.

7}

Internal gain

Infiltration loss

So I 0 r go i n

550.0

500,0

450.0

400,0

350,0

300,0

(

250.0

200.0

150.0

100.0

50,0

0.0

<

UJ

Figure 40. Comparison of heating and cooling requirement components for the

Norris Cotton Federal Office Building as predicted by simulation

68
X

I—o

<

U-+

"C

-10.0 -5.0 0.0 5.0 10.0 15.0 20.0 25.0 800.0 ....

700.0

Zi 600.0

I—m

2 500.0

>-^ 400.0

300.0 -

200.0

100.0 -

0.0

ocxx)o As—designed

AAAAA As-operated

ooooo As—operated with modifications

% ++++ Design alternative

f8Sg/>^ "ox* Actual data (Sep 1978-Aug 1979)

Q

'Or." *8t>o -

0"

e

T—n—I 'I I I I 0.0

10.0 20.0 30.0 40.0 50.0 60.0 70.0 80.0 MONTHLY AVERAGE AMBIENT TEMPERATURE, V

Figure 41. Third order least squares fit of predicted and actual fuel use

plus fan energy for the Norris Cotton Federal Office Building

versus monthly average ambient temperature

100.0 0.0 100.0

__i 200.0

I GJ/MONTH

300.0 400.0

I 500.0 u

90.0 -

0.0 100.0 200.0 300.0 400.0 500.0 HEATING REQUIREMENTS, 10^ BTU/MONTH

Figure 42. Fuel use efficiency for the Norris Cotton Federal

Office Building as predicted by simulations

69
a "U" shaped curve with a minimum at an ambient temperature of approximately

16°C (60°F). Energy use to the left of the minimum is predominantly for

heating; to the right is predominantly for cooling. The actual data compare

well with the simulation data although the actual data are somewhat lower

than the "as-operated" simulation data. This figure also shows that fuel use

for heating is higher for the "design alternative" case than for the other

simulation cases.

The figures presented to this point have described overall building performance. The performance of the mechanical equipment may be represented by the

ratio of heating and cooling requirements to the fuel (plus fan) energy con- sumed for each month. For heating, such a ratio may be termed the fuel use efficiency. Least squares fits of the monthly calculated fuel use efficiency

for heating are plotted versus heating requirements in figure 42. The energy

necessary to meet the requirements was observed to be roughly a linear function of the requirements and thus the efficiency curves are of the form:

e = R/(AR + B)

where A and B are constants, R is heating (or cooling) requirements, and e is

efficiency. Residual standard deviations for the fits are less than nine

percentage points of efficiency. In general the efficiency decreases with

decreasing load on the mechanical equipment and approaches a full load efficiency at high loads. The "as-designed," "as-operated," and "as-operated

with modifications" curves approach efficiencies of 79 percent. At low

requirements the "as-operated with modifications" curve is higher because

fan energy is reduced in this case. The "design alternative" curve is lower

than the other curves, approaching only 66 percent efficiency.

For cooling, the ratio of cooling requirements to fuel plus fan energy may be

termed the cooling performance factor. Figure 43 shows least squares fits of

cooling performance factor versus requirements. Residual standard deviations

range from 1 to 15 percentage points. The "as-operated with modifications"

case shows the highest performance factors and the "as-designed" case the

lowest. The low "as-designed" curve is due to the use of natural gas as the primary cooling fuel for the central system.

Figures 41 through 43 used fuel consumption as the major dependent variable.

In any building, equipment is used to heat and cool the building space and to

supply required ventilation. Such equipment, which includes pumps, controls,

and fans, requires energy to operate. Such energy usage may be termed energy

distribution energy or operating energy. It is important to consider both

the operating energy and the fuel energy use in designing and analyzing the

performance of large buildings. Figure 44 is similar to figure 41 except

that total HVAC energy (fuel and operating energy) is plotted versus the

ambient temperature. This plot is also a third order fit of the data and

residual standard deviations are 18 to 22 GJ (17 to 21 x 10^ Btu) f or the

simulation data and 67.5 GJ (64 x 10^ Btu) for the actual measured data.

70
GJ/MONTH

0.0 50.0 100.0 150.0 200.0 250.0 300.0

COOLING REQUIREMENTS, 10 BTU/MONTH

Figure 43. Cooling performance factor for the Norrls Cotton Federal

Office building as predicted by simulations

o

m

>-o

en

LJ

800.0

700.0 -

600.0

500.0 -

400.0

£^ 300.0 o

200.0

100.0 -

0.0

-10.0 -5.0

I I 0.0 5.0 10.0 15.0 20.0 25.0

ooooo As—designed

***** As—operated

00000 As-operated with modifications

jJa Design alternative

• Actual data (Sep 1978-Aug 1979)

I I I I "

I I I I ^ I I I I

^

I I t I

^

I I I I ^ 1 I I I

^ I I I

800.0

700.0

600.0

500.0

- 400.0

- 300.0

200.0

100.0

0.0

o

10.0 20.0 30.0 40.0 50.0 60.0 70.0 80.0 MONTHLY AVERAGE AMBIENT TEMPERATURE, V

Figure 44. Third order least squares fit of predicted and actual total energy

used for HVAC at the Norrls Cotton Federal Office building

71
The curves in figure 44 lie closer together than the curves in figure 41 and

the actual data curve is in better agreement with the "as-operated" simulation data curve than in figure 41. There is a distinct difference between

the simulation and the actual data curves for cooling, the actual being lower

than the predicted. This discrepancy is due to differences in the operation

of the building cooling systems in actual practice compared to what was assumed in the simulations. For example, the strategy of flushing the building with outside air in the early morning by manual control was used during

the third year of operation but not simulated in any of the cases.

In figure 44, the position of the "design alternative" curve relative to

the other curves in the figure is different than the corresponding position

in figure 41. In figure 44, the "design alternative" curve is in roughly

the same position for heating as the other curves. In the plot of figure 41,

the "design alternative" curve is distinctly above the other curves. This

indicates that the operating energy is lower for the "design alternative"

compared to the other cases.

A total heating efficiency may be defined as the heating requirements divided

by the total energy for heating (fuel plus operating energy). Figure 45 is a plot of least squares fitted curves of total heating efficiency versus heating requirements. Residual standard deviations are all low, less than two

percentage points. At high loads all curves approach 64 percent efficiency.

The "design alternative" curve is in the same region of the plot as the other

curves while in the fuel use efficiency plot, figure 42, it was lower. This

is due to the addition of the operating energy to fuel energy.

Least squares fits of calculated total cooling factors (cooling requirements

divided by the sum of operating and fuel energy for cooling) are plotted in

figure 46. Residual standard deviations are less than 14 percentage points.

Due to the inclusion of operating energy in the total cooling factor the

"design alternative" cooling factors are higher than for the other simulation

cases.

Plotting HVAC energy versus energy requirements from the various simulation

cases allows a comparison to be made of the two major systems in this building, the heat pump and central systems. A plot of the total heating energy

(fuel and operating) versus the heating requirement is shown in figure 47

with a different symbol for each of the two systems. It appears that the

central system uses a slightly larger amount of energy to meet a given load

than does the heat pump system, but there are not enough points for a strong

preference for either of the systems. Data for the cooling season is shown

in figure 48 and again the central system appears to use a slight amount

more energy than the heat pump system. A complete comparison of the systems

should use a life cycle cost analysis (as in Chapter 6) including effects of

fuel and equipment cost.

Components of Fuel Energy Use at the Building ; The output data from the

simulation program allow the amount of energy being used by the major pieces

72
GJ/MONTH

0.0 100.0 200.0 300.0 400.0 500,0 ^ 80.0

I

1 ' ' ' ' c

o

i- 70.0 -

Figure 45. Total heating efficiency for the Norris Cotton Federal

Office Building as predicted by simulations

GJ/MONTH

0.0 50.0 100.0 150.0 200.0 250.0 300.0

- o—o As—designed

Figure 46. Total cooling factor for the Norris Cotton Federal

Office Building as predicted by simulations

73
0.0 G J/ MONTH

I—2

O

\ID

I—m

o

o

z

I—<

UJX

oro

>-o

a:

500.0

400.0

300.0

200.0

100.0

0.0

50.0 _i100.0 150.0

I —200.0 250.0

I 1 —300.0 350.0

'

O Central system

ir Heat pump system

I I I I

'

I I I I I 0.0 50.0 100.0 T—

^

I I t I

^ I r I r

^ I 200.0 . 250.0

- 500.0

I- 400.0

X

I- 300.0 z

o

- 200.0 O

- 100.0

150.0

I I I

I I I I ' 0.0 300.0 350.0 HEATING REQUIREMENTS, 10 BTU/MONTH

Figure 47. Total energy for heating versus heating requirements for the

central and heat pump mechanical subsystems at the Norris Cotton

Federal Office Building as predicted by the "as-operated"

simulation

G J/ MONTH

0.0 20.0 40.0 60.0 80.0 100.0 120.0 X

(—

z

o

I—m

O

O

O

O

o

cro

>-o

cr

ui

125.0

100.0

75.0 .

50.0

25.0

0.0

O Central system

ie Heat pump system

- 125.0

- 100.0

- 75.0

- 50.0

25.0

O

\—5o

0.0

Figure 48.

—I

' 1 ' I ' 1 ' 1 0.0 20.0 40.0 60.0 80.0 100.0 120.0 COOLING REQUIREMENTS. 10 BTU/MONTH

Total energy for cooling versus cooling requirements for the

central and heat pump mechanical subsystems at the Norris Cotton

Federal Office Building as predicted by the "as-operated"

simulation

74
of equipment such as the boilers, chillers, heat pumps, and engine-generator

to be determined, as well as the amount of energy delivered to areas with

heating loads and extracted from area with cooling loads. This does not

include auxiliary energy to operate the major pieces of equipment and to

operate pumps, fans, controls, and other devices used to transport fluids

throughout the building.

Actual measured energy data collected at the building was available for

comparison with the simulation energy data. The actual data consists of fuel

input to boilers, fuel input to the domestic hot water heater, electric input

to heat pumps, fuel input to the boilers used to heat water for the absorption chiller, and electric chiller input. No actual energy requirements or load data was available and therefore nothing can be said about the actual

energy conversion efficiency of the equipment. It is possible to compare the

actual fuel energy data with the analogous simulation data and this is done

in figures 49, 50, and 51. There are differences between the "as-operated"

simulation data and the actual data.

Figure 49 compares measured boiler input (gas and oil) and simulation

predicted boiler input. The actual input to the boilers is lower than the

simulated input at low ambient temperatures. Figure 50 shows the comparison

for heat pump electric input and service hot water heating (purchased energy

only). The actual data for the heat pumps include fans in the heat pump

units, while the simulated data are for compressor input only (total heat

pump system fan input in the simulation is one the order of 22 GJ/month (20

X 10^ Btu/month). The actual electric input to the heat pumps in winter is

lower than in the simulation, especially when fan energy is added to the

simulation data. However, the actual summer heat pump electric consumption

is slightly higher even when fan energy is added to the simulation data.

The simulated and actual service hot water heater inputs are similar although

in the actual case all requirements for service water heating are met by

solar energy during summer months. A comparison of actual and simulation

data for the chillers is given in figure 51. Actual input to the electric

chiller is slightly lower than predicted. Figure 51 also shows that the

pattern of use for the absorption chiller that is simulated is very different

from the actual use pattern. The simulation is based on parallel operation

of the chillers. In actuality, the absorption chiller can be and was used

independently of the electric chiller via manual control.

Components of Total Energy Use at the Building; Total energy use can be

divided into two broad categories, lighting-miscellaneous and HVAC. HVAC

energy is used to provide all heating, cooling, ventilation and service hot

water. Lighting-miscellaneous energy is used to provide all other functions

of the building such as lights, elevators, and electric receptacles for

operating typewriters, copiers, and other equipment. HVAC energy can be

further broken down into fuel and operating energy.

Operating energy can be subdivided into energy to operate fans and energy

to operate pumps, controls, and miscellaneous HVAC equipment. Table 13

75
500.0

400.0

300.0

CD 200.0

100.0

O O Simulated boiler input

Q O Measured boiler ini

- 500.0

- 400.0

- 300.0

31

I—Z

o

- 200.0 O

- 100.0

Figure 49.

0.0 '

1

1 ,

1——I ~«r , 1

, 1 0.0 JAN FEB MAR APR MAY JUN JUL AUG SEP OCT NOV DEC

CALENDAR MONTH

(SIMULATIONS, 1962; ACTUAL. NOV 1978-OCT 1979)

Comparison of actual and predicted boiler fuel input at the

Norris Cotton Federal Office Building using "as-operated"

simulation data

m

Figure 50.

140.0 -

120.0 -

100.0 —

80.0 -

60.0-

40.0-

20.0-

0.0

O—O Simulated heat pump electric

input (without fans)

G O Measured heat pump electric

input(with fans)

Simulated service water

heater input

& Measured service water

heater input

- 140.0

- 120.0

100.0

80.0 2

O

- 60.0 O

- 40.0

- 20.0

0.0 JAN FEB MAR APR MAY JUN JUL AUG SEP OCT NOV DEC

CALENDAR MONTH

(SIMULATIONS. 1962; ACTUAL. NOV 1978-OCT 1979)

Comparison of actual and predicted heat pump and service hot

water input at the Norris Cotton Federal Office Building

using "as-operated" simulation data

76
I—z

o

\

I—m

O

Figure 51.

80.0

70.0 -

60.0 —

50.0 -

40.0

«o 30.0

20.0

10.0

0.0

Simulated

Measured

ELECTRIC CHILLER INPUT

FUEL OIL FOR

ABSORPTION CHILLER

- 80.0

- 70.0

- 60.0

- 50.0

- 40.0

- 30.0

- 20.0

- 10.0

9—a- 0.0 JAN MAR MAY JUL SEP NOV MAY JUL SEP NOV

CALENDAR MONTH

(SIMULATIONS, 1962; ACTUAL, NOV 1978-OCT 1979)

Comparison of actual and predicted energy to central chillers

at the Norris Cotton Federal Office Building using "as-operated'

simulation data

100.0

90.0 -

80.0 -

70.0 -

60.0 -

50.0

40.0 -

30.0

20.0

10.0

0.0

59.3 60.2

I I Operating energy-fan energy ^

P'an energy + fuel

V7\ Fan energy

IS Fuel use ^ Lights and miscellaneous

61.8

58.1 54.0 56.2(1978-79)

DESIGN ALTER. AS-OESIGNEO AS-DES/SOLAR MODIFIED AS-OPERATED ACTUAL

h 100.0

90.0

h 80.0

70.0

I- 60.0

50.0

h 40.0

30.0

h 20.0

lO.O

0.0

<

UJ

>-

Z)I—

CD

toO

Figure 52. Energy use components and total energy use per year at the

Norris Cotton Federal Office Building using simulation

results and measured data from September 1978 to August 1979

77
contains data on a monthly basis for the "as-operated" simulation results.

At the bottom of the table are annual totals and the percentage of the total

for each category. The table shows that lighting-miscellaneous energy

accounts for 35 percent of the total usage. Fuel energy makes up 39 percent

while operating energy consumes a surprisingly large fraction of the total,

26 percent.

Actual measured data from the building for the period from November 1978 to

October 1979 is given in table 14 and is broken down into categories similar

to those used in the table for the simulation results. In order to compare

the results on an annual basis for the simulations and the actual data,

figure 52 has been prepared in bar chart form with the quantity of energy

for each end use shown as different regions of the bars. Using the actual

data, the energy for fuel and energy to operate fans cannot be separated

due to the fact that the heat pump units do not have separate meters for

the compressors and the integral fans. Thus, for the actual data, fan and

fuel energy have been combined.

In the "as-operated" case, while the energy predicted for lights and

miscellaneous was the same relative to the "as-designed" case, fuel use decreases and operating energy goes up to approximately 26 percent of the

total. The operating energy is larger in the "as-operated" case because

several pumps in the actual building operate around the clock but were

assumed ,to operate only when heating or cooling loads existed in the "asdesigned" case. Also, some equipment was added to the building after the

original design, most notably an air conditioner for the elevator machine

room to cool the solid state controls.

The "as-operated with modifications" case shows a reduction in HVAC energy,

both in the fuel and the operating energy categories. Operating energy for

this case is approximately 25 percent of the total and HVAC energy makes up

63 percent.

The energy use profile for the "design alternative" looks very different from

the uses for the other cases. The lighting-miscellaneous increases to about

41 percent of the total and fuel use increases to 51 percent of the total.

However, the operating energy is much less than in other cases, accounting

for only 8 percent of the total energy usage. The energy to operate fans

is 4 to 6 percent of the total in all cases. If the fan energy is subtracted from the operating energy for the "design alternative", the remainder

is 2 percent for pumps, controls and other HVAC equipment compared to 16 to

21 percent of the total in the other simulation cases. Much of the equipment

used in the "design alternative" is more distributed throughout the building

and less efficient than the equipment in the actual building but requires

less supporting equipment and less operating energy. The fact that the

Norris Cotton Building is an experimental building also has an effect on operating energy. The multiple systems in the building require much more

operating energy than if a single type of mechanical system were used.

78
Table 13. Energy use components for the "as-operated" simulation

Month Lights + HVAC Direct Operating Fans Pumps, controls

(1962) misc. kWh kWh fuel energy kWh + misc. Total

kWh kWh kVh

1 64138 213986 162945

2 56585 203955 156895

3 62592 143437 95618

4 61620 76416 32489

5 64138 59245 18753

6 61620 70555 27562

7 62592 73100 28992

8 65685 84367 37656

9 58530 49320 10263

10 64138 71847 26328

11 61620 131514 86413

12 61046 203890 152804

nual 744308 1381632 836718

% of total

energy 35 65 39

51041 11676 39365 278124

47060 10749 36311 260540

47819 10924 36895 206029

43927 9597 34330 138036

40492 9886 30606 123383

42993 10186 32807 132175

44108 10414 33692 135695

46712 10856 35856 150052

39057 9205 29852 107850

45519 9864 35655 135985

45101 10157 34944 193134

51086 11610 39476 264936

544915 125124 419791 2125940

26 6 20

Table 14. Energy use components from actual data

Month Total Lights + HVAC Direct fuel Pumps, controls

(1978-79) energy misc. kWh kWh and fans + misc.

kWh kWh kWh

1 262943 60149

2 256124 53576

3 172472 62367

4 135282 57227

5 108612 55405

6 113981 55450

7 151981 58840

8 135853 60074

9 108498 56012

10 120062 59150

11 142696 53981

12 212201 53197

Annual 1920705 685428

% of total

energy 100 36

202794 162002 40793

202548 169060 33488

110105 82476 27630

78055 51995 26060

53207 23454 29753

58531 25543 32988

93141 58684 34457

75779 36373 39405

52486 26305 26181

60912 33670 27242

88715 60884 27831

159004 120383 38621 1235277 850828 384449

64 44 20

79
The "as-operated" case shows an operating energy use 9 percent greater than

the actual building data indicates, a lighting-miscellaneous 9 percent greater

than actual, and a fuel plus fan energy use which is 12 percent greater than

the actual. Fuel plus fan energy for the simulation and measured data were compared on a monthly basis in figure 41. After plotting the fuel data versus ambient temperature, the "as-operated" curve fitted through the data was higher than the measured data curve. Some of the difference may be due to

weather differences. The lights plus miscellaneous energy and operating

energy may be compared on a monthly basis in figure 53. The lights plus

miscellaneous energy is higher for the simulation than for the measured data

and the difference is approximately constant through the year. However, the

difference between predicted and measured operating energy varies as a function of the month. The actual operating energy dips to lower values during

spring and fall compared to the "as-operated" simulation results.

80.0

70.0- LIGHTS AND MISCELLANEOUS

20.0 —

Simulation data

Measured data

10.0 -

0.0 I

1

1 ,

1

1

1 ,

1

, '

I ' JAN FEB MAR APR MAY JUN JUL AUG SEP OCT NOV DEC

CALENDAR nONTH

(SmULATIONS, 1962; ACTUAL, NOU 78-OCT 79)

Figure 53. Comparison of actual and predicted lighting-miscellaneous and

operating energy at the Norris Cotton Federal Office Building

using "as-operated" simulation data.

Facing page:

Lobby of the fourth floor at the Norris

Cotton Federal Office Building . Sodium

vapor lighting is used on this floor.

80
4. PERFORMANCE OF THE LIGHTING SYSTEMS

Measurements of the performance characteristics of the lighting systems at

the Norris Cotton Federal Office building were made during the first 3 years

of operation.

4.1 LIGHTING SYSTEMS

The Norris Cotton Federal Office Building has six different illumination

systems, all having approximately the same connected electric power per unit

81
floor area. The lumlnaires installed in the building are listed in table

15. Note that for all floors with fluorescent lighting systems, the lamp

distribution is four lamps per 9,3 m^ (100 ft^). All lamps with single lamp

luminaires are in two-lamp series circuits. Therefore, the connected power

densities for all floors with the fluorescent lighting systems are 19,8 W/m^

(1,84 W/ft^). On the fourth floor, the power density for the high pressure

sodium lamps is 18.3 W/m^ (1.7 W/ft^). The power density for the fifth floor

is not fixed, but is dependent on the density of the work modules. At the

time of measurements of lighting characteristics made at the building, the

power density for the fifth floor was obtained by actual count of the number

of working modules in the space and found to be 26.2 W/m^ (2.43 W/ft^).

The first and third floors have identical luminaires, but differ in the type

of installed lenses. The first floor has prismatic lenses and the third

polarized lenses. The second and sixth floors have identical lighting systems, but differ in the amount of fenestration, and therefore the amount of

potential contribution from daylight. The window area on the second floor,

comprising 12 percent of the east, west and south facades, is approximately

2h times larger than on the other floors. All windows are double glazed

with a Venetian blind between the two glazings. The slats of the blinds were

in s horizontal position when measurements of lighting performance were being

made.

4.2 EVALUATION PROCEDURE

A basic quantitative performance measure of a lighting system is the amount

of light it directs toward the task, that is, the illuminance, denoted by E

and in units of lumens per unit area. However, the effectiveness of the

illumination for visual task performance will vary depending on the geometry

of the light flux reaching the task surface. A common method used to assess

the geometric effectiveness of a lighting system is to compare its performance

to that of a reference lighting system by means of the contrast rendition

factor, (CRF), defined as:

where C is contrast and the subscripts t and r refer to test and reference

lighting systems, respectively. Contrast is defined as:

where L]^ is the luminance (in lumens) of the background and is the lumin- ance of the task detail.

Effective Illuminance, Egf, can be defined as

CRF = C|-/Cr (1)

C = (Lb - Ld)/Lb (2)

Egf = CRF X E (3)

82
Table 15.

Floor

1

2

3

4

Lighting systems installed in the Norris Cotton Federal Office Buildinj

Light Luminaires per

distribution

Direct

Direct

Direct

Direct

Luminaire

lense

Prismatic

Twin beam

Polarized

Prismatic

Luminaires pei

9.3m2(100 ftO

Lamps per

luminaire

2

1

2

1

Indirect

Direct

Direct

Direct

Task-lit

systems

furniture

Twin beam

Prismatic

Floor

1

2

3

4

Lamps per

9.3m2(100 ft^)

4

4

4

1

Lamp Type Watts

Fluorescent 40

Fluorescent 40

Fluorescent 40

High-pressure

sodium 150

Metal Halide 250

Fluorescent 20

Fluorescent 40

Fluorescent 40

Power density

W/m2(W/ft2)

(inc. ballast)

19.8 (1.84)

19.8 (1.84)

19.8 (1.84)

18.3 (1.70)

19.8 (1.84)

19.8 (1.84)

* depends on furniture density.

83
where E is the illuminance at the task surface. That is, the luminous flux

falling on the task surface is weighted by a factor, CRF, that "weights" the

luminous flux in terms of how well it makes the task detail stand out from

the background.

In terms of energy usage and system effectiveness, the most relevant performance measure was felt to be one relating the "amount of useful light" to

the input power density. Luminous efficacy (of a system) is defined as:

luminous efficacy = Egf/P^ (4)

where is the input power per unit area.

Equivalent sphere illumination (ESI) is often used in the literature as a measure of system effectiveness. Briefly, ESI assigns different weights to

the same CRF, depending on the absolute luminance level. As indicated in

Equation (3), the treatment of system efficiency used in this study did not

weight the CRF differentially for luminance levels. Since the contrast is

the same regardless of the luminance level, and since efficiency is determined by the geometry of the flux distribution, no rationale could be justified for differential weighting of the luminance levels.

In order to complete the measurements and determine luminous efficacy for

each of the lighting systems in accordance with Equation (4), a reference

lighting system and a reference task had to be used.

4.3 REFERENCE LIGHTING SYSTEM

A reference lighting system is a system in which light flux is incident on

the task equally from all directions. The reference lighting system used

for this study was designed and constructed at NBS as is shown schematically

in figure 54. The projector, P, produced a homogeneous beam over the entire

face of the diffusing plastic, D. The light was diffused while passing

through the plastic plate and fell on the hemisphere wall, H. The hemisphere

was coated with halon and thus light incident on the hemisphere was diffusely

reflected. That portion of the light incident on the plastic after reflection

from the hemisphere wall was either transmitted to the outside or was diffusely

reflected back to the hemisphere, since the inner surface of the plastic had a finely ground finish. The target holder, C, was placed in the center of the

plate, D. The target was viewed through an aperture. A, located at =v = 25

degrees from the center of the hemisphere.

Calibration of the hemisphere was accomplished by inserting a small acceptance

angle fiber optic in the center of the target holder with the fiber aperture

near the target plane. The fiber optic was aimed toward the hemisphere wall

and luminance readings taken. Readings were taken every 15 degrees along the

polar axis and at four azimuth angles. The readings are given in table 16.

As table 16 indicates, the flux reflected from the hemisphere wall which fell

on the task was homogeneous to within plus or minus 2 percent.

84
Figure 54. Reference hemispherical lighting system used in lighting

measurements for the Norris Cotton Federal Office Building

Table 16. Luminance (cd/m^) of hemisphere wall

with center of task area as the viewing point

Polar Azimuth angle

angle 0 90 180 270

0 65 65 65 65

15 66 66 66 65

30

64 65 65 65

45

60 65 65 65 64

75 65 65 65 64

85
The Illumination Engineering Society (lES) recommends that body shadow be

excluded from the hemispherical contribution to task lighting. In the

measurements to be reported in this study, this exclusion was not observed.

A body shadow inclusion is relevant, in that the body occludes all flux

directed to the task from behind the body. But due to variation in the

reflectance of the clothing worn by the worker, the light flux reflected

off the clothing and directed toward the task surface cannot be easily

determined. It could be substantial for a worker wearing a white shirt,

but insignificant for a worker wearing dark clothing. Since the reference

lighting system was an arbitrary one chosen primarily for its simple and

consistent geometric properties, the inclusion of a body shadow with its

size and reflectance variabilities and the resulting complexities were not

felt warranted. The primary requirement was that consistent conditions be

utilized.

4.4 REFERENCE TASK

The reference task used was a thin line drawn with a no. 2 pencil on bond

paper. The contrast under hemispherical lighting was 0.426. The task used

in evaluating the CRF is an important variable. It is theoretically possible

to have CRF = 1,0 for all lighting systems, by using a reference task in

which both the detail and background are complete diffusers. At the other

extreme, it is possible to have a task with a mirror finish (highly specular)

such that CRF is influenced only by rays near the specular angle, i.e.,

incident angle equals the observing angle and viewing direction is 180° from

the incident direction. The above considerations played an important role in

the choice of the task used in the set of measurements made.

4.5 MEASUREMENT LOCATIONS

Since the aspect of the lighting system effectiveness that was being evaluated in this study was the geometric properties of the installed luminaires

and reflectance characteristics of the spaces, the location where the measurements were taken was an important variable. There were infinitely many locations in the spaces that could have been used. For simplicity, measurement

locations were restricted to two broad categories, beneath and between luminaires, as shown in figure 55, For the three types of luminaire spacing in

the building, continuous rows (R), symmetrical (S), and checkerboard (C), the

two categories are indicated in figure 55 as 1 for beneath the luminaires

and 2-3 for between the luminaires.

The quantity of interest in contrast rendition is the luminous flux reaching

the eye after being reflected off the task surface. Therefore, at a specific

location, the direction of view and viewing angle had to be considered. The

viewing angle, 6, was fixed at 25 degrees (see figure 56). That is, the

angle between the line of sight of the photometer, P, and the normal to the

task plane, T, was fixed at 25 degrees. For a specific task location, there

were four primary directions pointing toward the task that could be represented

by the four compass points: north, east, south, and west. Each of these

86
1 1 1 r 1 1 1 1 1

• R-3a

I I I I I—I—+-H—I—I—

R.l

CONTINUOUS ROWS

i—I—4—I

] —I 1—I

1 OF LUMINAIRES

•R-3

I I I I I \—\—\ h—f—

SYMMETRICALLY S-1 S-3 H • SPACED

S-2 LUMINAIRES

C-i Q.2 CHECKERBOARD

a • PATTERN

LUMINAIRES

55. Lighting system test measurement locations shown relative

to lumlnaire orientation and location in the Norris Cotton

Federal Office Building

87
Figure 56. Viewing angle for contrast measurements at the

Norris Cotton Federal Office Building

Figure 57. Diagram showing the three measurement directions for the same observing spot when making contrast measurements in

the Norris Cotton Federal Office Building

88
compass points was appropriate for evaluating lighting system effectiveness

for the condition where the task was directly in front of the worker.

Measurements were made at two additional directions for each compass point.

These directions were intended to represent the conditions where the worker

turned his head to look at a task located off center.

For these conditions, the task was moved 45 degrees to the left, E^, or right, on an arc formed with the center of curvature at the location

of the photometer, P (see figure 57). Therefore at a given task location,

measurements were made in 4 x 3 = 12 directions of view.

For the special case of the task-lit furniture on floor 5, the direction of

view was fixed. Therefore, for this case, measurements were made at only one compass point with its right and left viewing directions, giving 1x3=

3 measurements.

4.6 RESULTS

The illuminance values were obtained with a color-and-cosine-corrected illuminometer, calibrated against a 500 W, T-20 inside-frosted 2856 K working

standard, and were measured with the photometer in place for contrast

measurements. The results are given in table 17 and figure 58. The N

and D in the location column refer to night and day, respectively. The

rest of the alphanumeric code describes the location relative to the

luminaires as shown in figure 55.

The bars in figure 58 give an indication of the variability of illuminances

as a function of the direction of view at a given location. The numbers at

the top of the columns designate the floor in the building. The ends of

the vertical bars give the extreme range of illuminances. The rectangular

area filled with diagonal lines includes the range for the middle 50 percent,

i.e., with the highest and lowest 25 percent of the values excluded. Therefore, the vertical lines connecting the rectangular areas and the upper and

lower horizontal bars give the range of the upper and lower 25 percent

illuminance values. Figure 58 shows that the variation in the level of

illuminance was largest for the fourth floor.

The illuminances for the first and fourth floors were much higher than those

measured for the remaining floors. Day and night readings were taken at the same locations on the second floor. The day readings for floor 2 were generally higher than those obtained at night, the difference indicating the effect

of the larger window area on the second floor.

The results of the contrast rendition factor measurements are given in table

18 and figure 59. Each value is the arithmetic average of 3 measurements.

The importance of direction of view in making contrast measurements is indicated by the range of CRF ' s found at the same location. For example, on the

fourth floor at location N3, when facing south with the task located to the

left, the CRF was 1.057. At this same location when the task was straight

89
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93
ahead, the CRF was 0.510. In other words, when facing left the task contrast was better than that under hemispherical lighting, but when sitting in the same position and facing straight ahead, the task contrast was considerably

lower than under hemispherical lighting. There was no obvious difference in

CRF values between floors. CRF's on floor 3 were slightly higher and on floor 5 slightly lower than the average, but the differences were not marked.

The effective illuminance per unit power input density or luminous efficacy

values are given in table 19 and figure 60. The results indicate that some systems were definitely more effective that others. As can be seen, the

visual performance and efficiency of the fourth floor system was high. However, other factors resulted in this system being unsatisfactory to a large

number of workers. This will be discussed in Chapter 5. Excluding the

fourth floor system, the system on the first floor had higher luminous

efficacy values than the systems on the other floors.

Figure 61 shows measurement results to indicate the effect of day lighting.

Measurements were made on the second floor during a sunny day (2D) and also

at the same locations at night (2N). As can be seen, the illuminance values

were consistently higher during the day. Measurements were made on the sixth

floor only during the day; however, a comparison of illuminance values

between 2N and 6D indicate small but consistently higher illuminances during

the day. The effect of the larger glazed area on the second floor can be seen by comparing results 2D and 6D. Both measurements were made during the

day and the results show a larger difference than between results 2N and 6D.

For location 1, the contribution of daylighting was sufficient to bring the

illuminance level from below the design level, 54 dekalux, to above it. The

CRF values that were obtained on the second floor under daylight conditions

(2D) were also generally higher than during the night (2N). Obviously, if

illuminance and CRF values were higher during the day, then the product of

these two, effective lumens per watt, was also higher as shown at the bottom

of the figure.

94
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and luminous efficacy in the Norris Cotton Federal Office Building

97
Facing page

View of open plan office on second

floor of Norris Cotton Building

showing the different window style

on this floor.

98
5. OCCUPANT RESPONSE

>\ Occupant response to the Norris Cotton Building was assessed In two ways.

First, observations were made and personal Interviews conducted In various

government agencies prior to their relocation to the Norris Cotton Building.

Second, two questionnaires — one six months after occupancy, the other

eight months later — were distributed to all occupants of the building.

This chapter will summarize the results of that work. Reference [23]

includes an in-depth analysis of the occupant response study Including its

relationship to similar studies conducted in other buildings.

99
5.1 INTERIOR SPACE OCCUPANCY AND DESIGN

Most of the energy conserving features of the building that would be expected

to affect occupant response have been described in other chapters of this

report. These include the lighting systems, windows, and heating, ventilating, and air conditioning systems. An additional feature that will be

described here is the interior space occupancy and design.

The building is occupied by various Federal agencies with a total of approximately 400 employees. The first floor is occupied by the Social Security

Administration with approximately 25 employees; the second and third floors

by the Veterans Administration (VA) with a total of about 90 employees; the

fourth floor by the Armed Forces Examining Station (AFES) with about 40

employees; the fifth floor by the Department of Housing and Urban Development

(HUD) with about 70 employees; the sixth floor by the Internal Revenue Service

(IRS) with about 60 employees; and finally the seventh floor has two senators'

offices, a congressional representative's office, and several agencies with

a small number of employees.

Most areas in the building consist of open-plan offices with a minimum number

of ceiling-high partitions. An exception is the fourth floor, occupied by

AFES, which has been subdivided into medical examination rooms, laboratory

space, testing rooms, private offices, and conference rooms. The seventh

floor also has been subdivided since several groups are located there.

5.2 RESEARCH APPROACH — INTERVIEWS AND QUESTIONNAIRES

Interviews were conducted in August 1976 in three agencies (IRS, VA, and

AFES) prior to their relocation to the Norris Cotton Building. The interviews covered employee reaction to their then current environment, impressions about the Norris Cotton Building, and attitudes toward the upcoming move

(see Reference [23] for a discussion of the results of these interviews).

The insights gained in this phase served as a reference for the interpretation

of the responses to the Norris Cotton Building.

In March 1977, a questionnaire was distributed to every employee in the

Norris Cotton Building. By March, the employees had been in the building 6

months and had experienced a winter in their new offices. Of 390 questionnaires distributed, 292 completed questionnaires were returned, a return

rate of 75 percent.

The questionnaire had 47 questions and required between 10 and 20 minutes to

complete. It began with questions concerning the occupants' general impressions of the building. For example: "Is there anything you particularly

like about the Norris Cotton Federal Office Building?" "Would you like to

change your present office in any way? If yes, how?" These early questions

tended to be open-ended and general in order to elicit opinions from the

occupants without drawing attention to specific environmental attributes.

Questions were then asked about more specific topics such as the lighting;

100
noise, particularly as it related to the open-plan offices; the thermal

environment; and the windows, especially their size and the view from them.

The questionnaire concluded with information such as floor number, sex, age

category, and general job category.

After the employees has occupied the building for a little over a year and

had experienced both winter and summer operating conditions, the questionnaire was readministered. The second questionnaire was distributed to the

employees in mid-November 1977, This questionnaire was essentially the same

as the first, A few questions were eliminated, for example, those asking

the employees to compare the Norris Cotton Building with their previous

office, and some questions were consolidated. As a result of response to

the open-ended questions on the first questionnaire, a question was added

about satisfaction with parking, elevators, eating facilities, and exterior

appearance. Sixty percent (230) of questionnaires were returned.

5,3 QUESTIONNAIRE RESULTS

General Response to the Norris Cotton Building ; Table 20 presents a summary

of the major employee "likes" in the building. As table 20 shows, the result

of the two questionnaires were essentially the same. Approximately two-third

of the occupants named at least one aspect of the building that they liked.

Location ranked first, being cited as "convenient," "downtown," and "central.

Appearance and related aspects such as "newness" and "cleanness" were other

positive attributes.

The major "dislikes" are summarized in table 21. On the first questionnaire,

83 percent named at least one aspect of the building they disliked and on the

second questionnaire, 79 percent named at least one. The main problems

identified by the building's occupants were:

" The temperature was considered to be too cold and too variable.

" The elevators were too slow and unreliable.

** The amount of parking space available was inadequate.

" The windows were too small, there were too few of them, and they could

not be opened.

° The amount of ventilation was excessive during the heating season and

inadequate during the cooling season.

° The building had no cafeteria.

° The front entrance doors were too difficult to open, particularly for

the handicapped and elderly people who often visited the Social Security Administration offices in the building.

" The lighting on the fourth floor distorted colors, caused annoying

glare, and provided illumination levels which were perceived to be too

low.

Most respondents said they would like to change one or more aspects of their

offices. On both questionnaires, the most often mentioned desired changes

were better temperature regulation, more privacy (especially on the second

101
Table 20. Summary of occupant "likes" in the Norris Cotton Federal Office Building

First questionnaire Number % Second questionnaire

/•vr _ 9 1 "1 \ Number %

Location 55 21 Location 60 28

Appearance 38 14 Appearance 29 14

Newness 24 9 Newness 16 8

Cleanness 18 7 Lighting 15 7

Atmosphere 17 6 Atmosphere 13 6

Design 11 4 Cleanness 12 6

Table 21. Summary of occupant "dislikes' in the Norris Cotton Federal Office Building

First questionnaire

('K^ — 0 ^ Number % Second questionnaire

(N = 213)

Number %

Temperature 85 32 Temperature 105 49

Elevators 70 26 Elevators 39 18

Parking 48 18 Parking 37 17

Windows 47 18 Ventilation 31 14

Ventilation 45 17 Windows 26 12

Lack of cafeteria 35 13 Lighting 23 11

Heavy front doors 30 11 Lack of cafeteria 21 10

Lighting 29 11 Heavy front doors 16 7

102
and fifth floors), and greater window area. Other changes desired were better lighting (on the fourth floor), more space, and less noise. "Comfortable temperature" and "good light" were felt to be the two most Important

physical features that determine the quality of the office environment.

All other features named, such as privacy and window area, were considered

much less important.

Response to Specific Design Features ; Response to six features — lighting,

noise, odor, ventilation, temperature, and windows — was examined in detail.

The results are described in this section.

On both questionnaires, lighting was the most satisfactory design feature in

the building. In addition, there was a statistically significant increase

in the number of persons who were satisfied* with the lighting on the second

questionnaire (73 percent) as compared with the number satisfied on the first

questionnaire given eight months earlier (62 percent). Follow-up questions

on light levels, color rendition, and glare also yielded generally favorable

opinions on both questionnaires, with no statistically significant shifts in

response over the eight-month interval between the questionnaires. There was,

however, an obvious lack of satisfaction with the high pressure sodium lighting system as it was installed on the fourth floor. Despite the fact that

the illumination levels on the fourth floor were among the highest in the

building, most persons there felt they had "too little light" to work by.

By contrast, occupants of other floors where the illumination levels were generally much lower perceived the amount of light as "about right." Many

people also felt that the high pressure sodium system distorted colors and

caused annoying glare. There were some unusually low contrast rendition

factors measured on the fourth floor, which could be expected to produce

complaints of poor task visibility if the placement of work stations was

not carefully considered. More fourth floor occupants complained of headaches and eyestrain than did occupants of other floors.

Response to the first and second floor lighting systems was consistently

quite positive. On both questionnaries over 80 percent of the respondents

on these two floors were satisfied with the lighting. Both floors have

uniformly spaced fluorescent lighting, with added daylight on the second

floor.

The fifth floor has task lighting built into each work station, thereby

concentrating light in those areas where it is needed. Despite the fact

that this system is quite different from those installed on the other

* A five-point rating scale was used to assess satisfaction: very satisfied, somewhat satisfied, indifferent, somewhat dissatisfied, and very

dissatisfied. "Percent satisfied" is the percent of respondents who were either "very satisfied" or "somewhat satisfied" with the particular

design feature.

103
floors, user satisfaction with the lighting was neither unusually high

nor low compared with the other systems in the building.

Two other comparisons between systems were made. The second and the sixth

floors have identical lighting systems, with the exception that on the second

floor horizontal windows near the ceiling provide more daylight. Statistical

analyses revealed that on both questionnaires the second floor system was significantly more satisfactory (about 90 percent satisfied) than the sixth

floor system (about 60 percent satisfied).

The first and third floors have identical luminaires but different lenses

(originally prismatic on the first floor, polarized on the third). In

June 1977, the lenses were interchanged in order to determine whether the

polarized lenses had been responsible for the lower level of satisfaction

initially observed on the third floor. On the second questionnaire, administered in November 1977, satisfaction increased substantially on both the

first and third floors. Thus no conclusions can be made about the relative

acceptability of the prismatic and polarized lenses based on these data.

With respect to noise, 50 percent of the respondents on the first questionnaire were satisfied with the noise level in their offices, and 42 percent

were dissatisfied. On the second questionnaire, 53 percent were satisfied

and 35 percent were dissatisfied. On both questionnaires more than 60

percent said their offices were never too noisy to work in, although 39

percent thought there was more noise in their present office than in others

they had worked in, while only 26 percent thought there was less. Voices

were the most "noticeable" type of noise and the most "bothersome." Telephones and office machines ranked second and third.

A comparison of the noise climate in the open-plan and partitioned offices

revealed statistically significant differences in user response in terms

of both the level of noise and its distractiveness. On the first questionnaire, employees in open-plan offices were more dissatisfied with the noise

level and had experienced more difficulty in working because of noise.

Although there was not a statistically significant difference in satisfaction

with the noise level on the second questionnaire, the difference in the

extent of work disruption due to noise persisted.

In contrast to most of the floors, the sixth floor response to noise was very

negative. On both questionnaires, less than 20 percent of the sixth floor

occupants were satisfied with the noise level. Nearly 90 percent said their

current office was noisier than the last one they had; no one found it quiete

Employees stated that the source of the noise problem was "white noise" or "ventilation system noise."

On two floors there was a statistically significant change in satisfaction

with noise level between the first and second questionnaires. On the fifth

floor, it increased from 29 percent to 53 percent; on the second floor, it

decreased from 64 percent to 45 percent. The reasons for these shifts are

104
not clear, but may be related to the fact that white noise generators were

initially installed on both of these floors, as on the sixth floor, but were

turned off on all but the east side of the second floor because of complaints

by the occupants.

The response to odor was characterized by both satisfaction and indifference.

While slightly more than half of the employees were "very" or "somewhat"

satisfied with the odor in their offices, about one-third were "indifferent."

Only 10 percent on the first questionnaire were dissatisfied, and 15 percent on the second. On the second questionnaire, there was an increase in the

number of persons who "often" or "sometimes" noticed unpleasant odors in

their offices; however, odor remained a relatively minor problem.

On both questionnaires, there was a statistically significant difference

between floors 1 through 3, outfitted with heat pump HVAC systems, and floors

4 through 7, serviced by central equipment systems, in terms of satisfaction

with odor. In both instances, respondents on floors 1 through 3 reported

relatively more "very satisfied" and "somewhat satisfied" responses and fewer

"indifferent" responses. Satisfaction was particularly low on the sixth and

seventh floors. These findings are explainable in light of the physical

measurements of air leakage in the building made in February 1977, which

showed that the rate at which air (and hence odor) was expelled from the

building and replaced by fresh air from the outside was much higher on floors 1 through 3 than on floors 4 through 7.

On the first questionnaire, response to ventilation was mixed, with nearly

equal amounts of positive and negative sentiment (41 percent satisfied, 43

percent dissatisfied). Following the summer months, however, there was a general decline in satisfaction (34 percent satisfied, 53 percent dissatisfied), and an increase in the number of persons who "often" felt "uncomfortably stuffy" from 22 percent to 32 percent. The decrease in satisfaction on

the second questionnaire was found in varying degrees on all floors. Some

individuals mentioned that there was poor air circulation in the building

during the summer. Many respondents were also bothered by cold drafts from

the ventilation system, particularly during the winter months on the second

and third floors.

A statistical comparison of the response on floors 1 through 3 with the

response on floors 4 through 7 revealed no difference in satisfaction with

ventilation on either questionnaire. On the second questionnaire, however,

after summer conditions had been experienced, feelings of stuffiness were

significantly more common on floors 4 through 7 than on floors 1 through

3. These data, like the odor data, are in agreement with the physical data

on air leakage.

Occupant response to temperature in the building was extremely negative on both questionnaires and on all floors. On the first questionnaire, 75

percent were dissatisfied with the temperature of their offices; on the

second questionnaire, 83 percent. The main reason for this widespread

105
dissatisfaction appears to be that temperatures were felt to be too cold.

This particular complaint was almost twice as common as any other concerning the temperature. Over 80 percent on both questionnaires reported that

they were "often" or "sometimes" uncomfortably cold. (At the time of the

first survey in March 1977, Federal guidelines were in effect which specified that thermostat settings not exceed 20°C (68°F).) Persons on floors

1 through 3 were more often bothered by cold temperatures than persons on

floors 4 through 7. This was especially a problem for occupants on the

second and third floors. Overheating was also a problem, particularly

during the summer on the fourth through the seventh floors. Some persons were bothered by fluctuations in temperature during the course of the day,

while others noted variations depending on the location within an office.

The latter complaint was most common on the first three floors, where cold

drafts near windows were a problem. These results are consistent with the

results of the thermographic measurements of the building, which showed

more cold surfaces on the first three floors than on the other floors,

particularly on the east and west exterior walls.

The windows were also a very negatively perceived building feature. Only

12 percent of the respondents on the first questionnaire and 17 percent on

the second were satisfied with the size of their windows. More than 80

percent thought the 0.4 m x 1.6 m (1.2 ft x 5.3 ft) windows were too small

and that they offered an insufficient view of the outside world. The windows

were perceived as being "poorly proportioned," "narrow," and "irregular."

Cold drafts near windows were "often" a problem for 30 percent of the respondents on the first questionnaire and 25 percent on the second. Very few

people had experienced problems with glare, overheating, or outside noise

from their windows.

From a design standpoint, a comparison of the response on the second floor

with that on the others is of interest, in order to assess the effect of its

larger window area (12 percent of the east, west, and south exterior walls,

as compared with six percent on the other floors) on user satisfaction.

Satisfaction with the size of the windows on the second floor was greater than

the average for the other six floors but was exceeded by the first floor on

the first questionnaire and the fourth floor on the second one. Floor-byfloor analysis of related questions on both questionnaires showed that the

second floor ranked highest by a slight margin on providing a good view of

the outside world and on having windows that are "about right" in size.

Despite the slightly higher level of satisfaction with the windows on the

second floor, however, the majority of persons on that floor still considered

the windows to be inadequate.

Facing page:

Four natural gas modular boilers in

the mechanical penthouse provide

heating at the Norris Cotton Building

106
6. COST ANALYSIS

The purpose of this chapter is to present an example of life-cycle cost

analysis of the investments made in the energy conserving techniques used at

the Norris Cotton Federal Office Building in Manchester, New Hampshire.

This analysis addresses the question of whether additional construction

costs incurred in order to reduce the energy consumption of the building are adequately offset by the value of the resulting annual energy savings. An

example is also given of analysis involving two buildings which offer

different quality of construction.

107
In this chapter, the construction costs of the Norris Cotton Federal Office

Building (NCFOB), an Equivalent Conventional Building (ECB) and a Design

Alternative Building (DAB) are combined with the corresponsing annual energy

consumption in a present value format for a maximum lifespan of 30 years. The

ECB design represented what might have been built by the government if energy

conservation had not been stressed and its size and shape, quality of material

and construction, and occupancy requirements were approximately equal to those

of the NCFOB. The DAB selected was intended to represent an ordinary commercial speculative office building of similar size to the NCFOB but not con- structed to Government specifications or standards required for a building

such as a corporate headquarters. The life-cycle costs resulting from initial

construction and annual energy use are calculated for the three buildings and

serve as the basis for the economic evaluation.

The actual energy consumption data for the year spanning from September 1978

to August 1979 are used in conjunction with the actual construction cost of

the NCFOB to compute the life-cycle cost of the building as a whole. The

building construction costs for the ECB are estimated in accordance with the

GSA Design Handbook of 1969, and energy consumption is calculated by simulation [2, 25]. The building represented by the DAB is the same as the "design

alternative" simulation case described in section 3.5.

Since no meaningful data on operation and maintenance costs (except energy

cost) are available to be included in the economic analysis at this time, this

report includes only the building construction costs and yearly energy costs

of the NCFOB, ECB and DAB in the^economic evaluation. A complete evaluation

would take into account equipment repair and replacement costs and manpower

requirements for building operation. In addition, the effect of local and

Federal income taxes on the building owner would have to be included.

6.1 BUILDING CONSTRUCTION COSTS

The construction costs developed for the NCFOB, ECB, and DAB do not include the

following cost items: Site acquisition cost; architecture and engineering

design fees; furniture and furnishing cost; and relocation cost. These cost

items are excluded from the economic comparison because they are considered

to be equal for the three buildings and therefore will not affect the outcome

of the cost comparison of these buildings.

The NCFOB construction cost represents the original contract price given in

the spring of 1974 to be fully paid for in the fall of 1976. All contract

change orders made during the construction period were adjusted so that the

resulting figures represent the dollar values as of the start of construction.

The sum of the original contract price and the adjusted change order prices

is used here as the total NCFOB construction cost incurred at the end of 1976.

The ECB construction cost was estimated and component costs given in a previous report [25]. The DAB construction cost was obtained by modifying

the estimates of electrical, lighting, and air conditioning costs for the

108
construction of the ECB. The construction costs assumed for all three

buildings are shown in table 22.

6.2 ANNUAL ENERGY CONSUMPTION

Annual energy consumption data for the NCFOB, ECB, and DAB are summarized in

tables 23 and 24. The NCFOB and DAB simulation estimates were obtained by a system computer simulation as described in section 3.5. The energy consumption estimates for the ECB were obtained by a load prediction computer program

[2, 25].

6.3 LIFE-CYCLE COST MODEL

There are several methods to express the combined cost of an initial investment and associated recurring costs for energy consumption, operation, and

maintenance associated with a building. One method is to transform the initial investment cost into an equivalent yearly uniform capital recovery payment over the life and then combine this yearly payment with the corresponding

recurring costs associated with operation, maintenance and energy consumption

Table 22. Building construction costs in 1976 dollars

BUILDINGS

Building NCFOB ECB DAB

Architectural/ Structural $6,147 ,122 $5,706,361 $5,706,361

Mechanical 1,195,731 944,028 907,028

Electrical 576,181 698,698 642,698

Subtotal 7,919,034 7,349,087 7,256,087

GC Overhead/Profit 601,847 558,531 551,463

TOTAL 8,520,881 7,907,620 7,807,550

Less Extras for non-building

items^ -285.765 None None

Comparable cost $8,235,116 $7,907,620 $7,807,550

^ This figure represents the "Demonstration" items as explained in Appendix A

of reference [25].

109
Table 23. Annual energy consumption in 10^ Btu

NCFOB NCFOB ECB DAB

Energy 1979* 1962 1962 1962

type Actual Simulated Simulated Simulated

Electricity 4,810 4,986 7,277 3,846

Fuel oil 292 242 0 0

Natural gas 1,578 2,022 4,983 3,115

TOTAL 6,680 7,250 12,250 6,961

Table 24. Cost of annual energy consumption in 1979 dollars

NCFOB NCFOB ECB DAB

Energy 1979 1962 1962 1962

type Actual Simulated Simulated Simulated

Electricity 77,973 80,973 117,955 62,323

Fuel oil 853 707 0 0

Natural gas 7,417 9,503 23,420 14,641

TOTAL 86,243 91,003 141,375 76,964

* September 1978 - August 1979

110
over the life of the building. Another method Is to transform both the

initial building Investment cost and the recurring costs to a single capital

recovery amount occurring at the end of the lifespan. The third method Is

to bring the stream of recurring costs back to the same period In which the

initial building Investment was made and then combine these transformed

recurring costs with the initial Investment to arrive at the present value

cost of owning and operating a building throughout its life. This present

value cost method will be used for the economic evaluation of both buildings.

Equation (5) is the general expression used to obtain present value costs

over a building lifetime.

L

PVC = C + Z (1+D)~^(E.+M. ) - (1+D)"^*S , (5)

1=1

where

PVC = Present value cost

C = Construction cost

D = Discount rate

Ei = Annual energy cost in period 1

Mj^ = Annual operation and maintenance cost (excluding energy cost)

L = Lifespan of the building in years

S = Salvage value at the end of lifespan.

With the exception of energy cost, no meaningful physical and cost data for

building operation and maintenance are available. Until operation and maintenance data become available, it is assumed that these costs would be similar

for the three buildings. The most significant difference between the non- energy costs for these buildings would be for equipment service and replacement costs, especially because the DAB uses mechanical equipment with a shorter expected lifetime. Since equipment service lives are not available

this time, the replacement costs due to aging for the DAB are not Included

in this study. Also, for all practical purposes the salvage values for the

three buildings are considered equal and negligible, given the relatively

long expected life of a building.

Therefore, equation (5) can be simplified to

L

PVC = C + S (l+D)"^*Ej^ (6)

1=1

Equation (6) will be used for the calculation of present value costs of the

NCFOB, ECB, and DAB. In equation (6), D is assumed to be 10 percent and

is obtained by multiplying the annual energy costs with the following

corresponding escalating rates [26] shown in table 25.

Ill
Table 25

Annual percentage change of energy escalating rate

Year Electricity Natural gas Distilate

1980-1985 2.51

1986-1990 -1.28

1991-beyond -0.45

-4.39 1.32

3.42 3.39

1.95 2.46

The results of calculating present value costs for all years from 1976 through

2006 for the three buildings are presented in table 26. The present value

costs and present value savings for the NCFOB over the other alternatives are summarized for three building lifespans in table 27.

Several noteworthy conclusions can be drawn from an examination of tables 26

and 27. Most importantly, the present value savings for the NCFOB over the

ECB are $46,000 in 15 years and $141,000 in 30 years. These positive present

value savings indicate that the additional investment in energy conservation

when the NCFOB is built rather than a building such as the ECB is more than

compensated by the value of the energy savings over the 30 year and 15 year

lifespans assumed. In other words, the NCFOB is economically more attractive

than the ECB for all lifespans over 12 years. In addition to the present

value saving, it is possible to calculate the discounted payback period for

the additional investment made on the energy conserving features of the NCFOB.

The discounted payback period is defined as the number of years required for

the additional investment in a building to be fully paid for with the present

value savings produced by the energy conservation features, taking into

account the time value of money. A discounted payback period of 11.8 years

is illustrated in figure 62 for the energy conservation investment made in

the NCFOB compared with the ECB. The present value savings of the NCFOB over

the ECB for all given lifetimes of up to 30 years can also be determined by

measuring the distance between the two curves shown on figure 62.

Based on the 1979 actual energy consumption for the NCFOB, the present value

cost for the period ending in 1991, a 15 year lifespan, is $8,882,000 as com- pared to $8,916,000 when the simulation predicted energy consumption for the

NCFOB with 1962 weather is used for same lifespan. The difference of $34,000

represents only a 0.4% decrease of the present value cost based on 1962

weather condition. Similarly, at the 30 year lifespan, the difference of

$44,000 in present value cost represents only a 0.5% decrease based on the

simulation using 1962 weather.

112
Table 26

Present value cost at year ending ($1000) for three

buildings for the period ending in a given year

Ending NCFOB NCFOB ECB DAB

year of 1979 1962 1962 1962

period Actual Simulated Simulated Simulated

1976 8235 8235 7908 7808

1977 8290 8294 8004 7861

1978 8348 8355 8098 7912

1979 8413 8423 8204 7970

1980 8473 8487 8302 8023

1981 8528 8545 8392 8072

1982 8580 8599 8476 8117

1983 8628 8650 8552 8158

1984 8672 8696 8623 8197

1985 8712 8738 8688 8232

1986 8748 8776 8745 8263

1987 8781 8810 8798 8292

1988 8810 8841 8845 8317

1989 8836 8868 8888 8340

1990 8860 8894 8926 8362

1991 8882 8916 8962 8381

1992 8901 8937 8994 8398

1993 8919 8956 9023 8414

1994 8935 8973 9049 8428

1995 8950 8988 9073 8441

1996 8963 9002 9095 8453

1997 8975 9015 9115 8464

1998 8986 9027 9133 8474

1999 8996 9037 9149 8483

2000 9005 9047 9164 8491

2001 9013 9055 9177 8498

2002 9021 9063 9190 8505

2003 9027 9070 9201 8511

2004 9034 9077 9211 8517

2005 9039 9083 9220 8522

2006 9044 9088 9229 8526

113
Table 27

Present value costs and calculation of present value savings^ ($1000)

BUILDING LIFESPAN

0 Years 15 Years 30 Years

Cost Saving Cost Saving Cost Saving

NCFOB 8235 8,916 9,088

ECB 7908 (327) 8,962 46 9,229 141

DAB 7808 (427) 8,381 (535) 8,526 (562)

^/ Present value savings of the NCFOB over the ECB and DAB. Savings in

parenthesis indicate negative savings, or more costly expenditures.

As mentioned, the NCFOB and DAB are designed to different criteria and a com- parison is difficult because the benefits from the two buildings are different.

The DAB type is intended to have a low first cost. The present value cost of

the DAB from table 27 is $427,000, at the end of 0 years (or completion of

construction), which is less than the equivalent present value cost of the

NCFOB. The DAB would probably be used for rental and sold after a short time

period to maximize tax benefits. On the other hand, the NCFOB type is designed

to provide a location to house government agencies for the life of the building

and mechanical systems are designed to meet criteria for reliability and maintenance. Figure 62 shows that for all lifetimes of the NCFOB up to 30 years,

the present value cost is lower for the DAB. The major factors not taken into

account in the cost analysis are as follows:

a) Sixty-three percent of the air-conditioning requirement in the DAB

is furnished by through-the-wall units. According to the ASHRAE

Journal [27], the median service life of through-the-wall units is

10 years and the median service life of central units such as those

used in the NCFOB and the ECB is 20 years. The replacement costs

due to aging equipment have not been included in the calculations.

b) Operation and maintenance costs (including manpower requirements) are

not included in the calculations and the DAB is apparently not

designed to GSA's standards for operation and maintenance.

114
9300.0 -

to

os: 9100.0

<

o

o

00

o

o

LJ

0-

8900.0

8700.0 -

8500.0 -

8300.0 -

8100.0 -

7900.0 -

7700.0 -f

NCFOB, simulated

0.0

NCFOB, actual

DAB

Discounted payback period

for additional investment

in NCFOB over ECB

5.0 10.0 15.0 20.0

LIFESPAN, YEARS

25.0 30.0

^ Present value cost is assumed to include Building Construction Cost,

Energy Cost as computed for 1962 consumption and DoE estimates for

annual energy price increases.

Figure 62. Present value cost^ vs lifespan for NCFOB, ECB & DAB

115
c) The NCFOB was built as an experimental building and contains

redundancies in equipment which would not be found in a non-experimental building.

This example shows the danger involved in comparing buildings built to

different criteria.

Facing page

A computerized monitoring and supervisory

control system is based in an operations

room at the Norris Cotton Building

,

116
7. CONCLUSIONS AND RECOMMENDATIONS

Over the 3 years that the Norris Cotton Federal Office Building has been in

operation, several experiments have been performed which have resulted in some valuable conclusions. In addition, three years of experience in operating the building have been accumulated and lessons have been learned when

problems with the building have been corrected or circumvented by the building operator. A number of conclusions concerning design and operation of an energy-conserving building have resulted from the study of the building.

117
After 3 years of operation, the building, although operated differently

than originally intended, now performs reasonably well and proves that:

1. It is possible to design, construct, and operate a medium-sized office

building in a northern climate to use no more than 625 MJ/(m^xyear)

(55 kBtu/(ft2xyear)).

The performance of the building and the benefits from the study of the building would have been improved if certain lessons had been learned before the

conception of the project:

2. Designing a building as an experimental laboratory to compare the performance of a variety of energy conserving concepts is in general not

compatible with an objective of designing a building for low energy use. In this building, a number of different energy conserving subsystems

are installed and interconnected in such a way that the overall mechanical system is complex and difficult to control.

3. When unusual construction details exist, it is important that building

designers, construction firms, and inspectors use extra care to guard

against unintentional thermal bridges and air leakage paths.

The addition of a solar system to the building allowed a number of lessons

to be learned with regard to design and operation of a solar system on a commercial building:

4. Problems have been experienced in this building with retrofitting a solar subsystem to a mechanical system that was not originally designed

for it.

5. Thermal storage capacity in solar systems should be carefully sized

relative to load and solar collector capacity. The storage tanks in

this building are far oversized and under-insulated and prevent temperatures in the tanks from reaching design levels.

6. The design strategy for solar energy use in this building was to increase

the amount of energy in storage up to a usable temperature level before

transferring any collected energy to the building heating and cooling

systems. Excess storage capacity and storage standby losses have

prevented effective use of the collected energy. A strategy to use the

collected energy directly to meet a load and store it only if collected

energy exceeds the load should be a much more effective strategy.

7. Four different flat-plate collector types are used on this building.

They range from a double-glazed collector with a selective-surface on

the absorber to a single-glazed collector with a flat-black surface.

The use of such a range of collectors in one array both degrades the performance of the more efficient collectors and creates difficulties in

flow balancing. Each type of collector has a different design flow rate.

118
8, The original solar system control scheme was found to be ineffective,

because it relied on solar irradiance levels to actuate collectors

without regard to ambient temperature or load.

9, Unless a solar system control scheme has been used previously in a similar application, an innovative mechanical system including solar

should always include a control system whose logic can be altered by

system operators. In this building, an inflexible control scheme

produced undesirable sequences of equipment operation; as a result

automatic control had to be abandoned and manual control used,

10, When variable speed pumps are employed in a solar installation, the

speed of the pumps should not be a simple function of collector inlet

and outlet temperatures. Under certain conditions, such control can result in collector stagnation and boiling of the heat transfer fluid

under high irradiation conditions,

11, Changing the tilt angle of the large collector array on this building

twice a year was found to be ineffective when the cost of the tilting

mechanism and difficulty of tilting the arrays was taken into account.

Changing the tilt of stationary south-facing collectors provides little

advantage for space heating and domestic hot water heating applications.

12, Solar collector arrays designed for cooling in conjunction with absorption chillers should be able to supply heated fluid at the absorption

unit rated input temperature during substantial portions of the cooling

season, not just under peak conditions.

In addition to findings from the operation of a solar system, the application

of energy-conservation and heat recovery concepts in this building has

resulted in valuable experience which can be summarized in the following

findings:

13, The use of chilled water storage to reduce peak cooling loads in this

building has been found ineffective due to chiller safety interlocks

cycling the chiller off before design storage temperatures are reached,

heat gain through tanks and long piping runs, insufficient storage capacity to meet building peak loads, and inability to automatically remove

the chilled water tank from the chilled water loop when it is no longer

useful.

14, When a heat recovery chiller (energy recovery from the condenser) is

designed into a mechanical system, there must be a heating load which

can be met while the chiller is required to operate and the load must

be satisfied by the fluid temperature level and flow rate from the

chiller condenser. In this building, heating and cooling loads are simultaneous only for brief periods in the spring or fall. However,

during those periods, the small heating loads can be met by the solar

system.

119
15. The use of a natural gas engine-generator to drive an electric chiller

and use of the engine waste heat to drive an absorption chiller is a possible method to extract more energy from natural gas than by con- ventional means. However, such a system must be very carefully designed

and critical factors such as the maximum temperature level deliverable

to the absorption chiller at maximum engine operating temperatures after

heat exchanger losses have been considered, and the relative rates of

engine heat recovery and absorption machine input energy under all con- ditions of loading must be considered.

16. The engine-generator, electric chiller, and absorption chiller set has

been found to not function well as a secondary chilled water source when

used in an intermittent fashion.

17. The temperature set point of the hot water heating system should have

been automatically adjustable as a function of load (or outside air

temperature) to allow solar heated water to be used most effectively.

18. Special care must be taken when using water-to-air-coil systems with

water temperatures below 41**C (105°F). Unless air registers are properly designed with diffusers to limit air velocity in the space,

space occupants will feel discomfort from the relatively cool air

blowing into the room.

19. Even operating the ventilation system in this building in a complete

recirculation mode (no outside air), CO2 levels were found to be less

than the levels implied by the ventilation rates recommended for office

space in ASHRAE Standard 62-73 (0.0118-0.0071 m^/sec* person or 15-25

cfm/person).

20. Flushing the building with outside air and cooling the building spaces

below thermostat settings in the summer prior to switching the building

into the occupied mode has been found to be effective in reducing startup cooling load and lengthening the time before mechanical cooling is

required. This strategy was not in the original design.

The study of the Norris Cotton Building involved performing simulations with

a building simulation computer program. The following conclusions were drawn

from the analysis of the simulation results:

21. Actual total energy consumption per year measured at the building for the

calendar year 1979 was within 14 percent of the predicted value using the

Ross Meriwether Energy System Analysis computer program for 1962 weather.

22. The simulation of the building in the "as-designed with solar" case with

the computer program resulted in a prediction of total energy consumption

per year which was within 2 percent of the original design goal of 625

MJ/m^» year (55 kBtu/(ft2.year)).

120
23. Actual energy consumption for lights and non-HVAC purposes at the

building for the third year of operation was within 8 percent of the

predicted value from the "as-operated" simulation case.

24. Actual energy consumption for fuel and fan energy at the building for

the third year of operation was within 12 percent of the predicted

value for the "as-operated" simulation case using 1962 weather data.

25. Actual energy consumption for operating energy at the building for the

third year of operation was within 9 percent of the predicted value

from the "as-operated" simulation case using 1962 weather data.

26. As a result of modeling the mechanical systems in the building, a maximum efficiency of approximately 64 percent was predicted for meeting the

heating loads in the building when heating requirements approached 470

GJ/month (500 x 10^ Btu/month). For cooling, an overall coefficient of

performance for the building was predicted to approach 0.75 as cooling

requirements approached 285 GJ/month (300 x 10^ Btu/month) for the "asoperated" case. These values include the operating energy for the

mechanical system as well as fuel consumption.

27. Based on a comparison of the performance predicted by the simulation of

the two major mechanical systems, the heat pump system on floors 1-3 and

the central system on floors 4-7, they were found to use approximately

the same amount of energy to meet a given load for the range of heating

and cooling loads occurring in the building. However, the heat pump

system used more costly electric energy.

28. A "design alternative" was simulated which had approximately twice the

lighting per unit area, five times more window area, one-third the insulation value in the roof and walls, and a much simpler mechanical system

than the present building. The yearly heating energy requirement or heating load was predicted to be similar to that of the present building.

The additional transmission losses in the "design alternative" were offset by increased solar gains and higher internal loads.

29. When the simulation results for the "design alternative" to the building

were compared to the results for the other simulation cases, the predicted

operating energy for the "design alternative" with its less complex and

less efficient mechanical systems was approximately two percent of the

total energy consumption of the building. This is in comparison to the

16-21 percent for the "actual design" case.

30. Selected modifications to the building as currently operated were predicted by simulation to reduce total energy consumption by six percent

if implemented.

A comparative study of lighting in the building led to the conclusion

that:

121
31. Based on physical measurements to determine lighting system efficacy,

the fluorescent system on the first floor and the high pressure sodium

system on floor 4 were found to be the most effective. The differences

between the other systems were not significant. However, the task

lighting system on floor 5 was found to be the least effective.

Surveys of the attitudes and feelings of the occupants of the building

resulted in important conclusions about the response of the occupants to

energy-conserving features of the building:

32. The most positive design feature of the building as determined by surveying the occupants with two detailed questionnaires was the lighting.

However, the reaction to the high pressure sodium system on floor 4 was strongly negative. Illumination level alone was found not to be

a good predictor of occupant response. There was some indication that

color rendition, glare, and amount of daylight affect satisfaction.

33. Reaction to the thermal environment was extremely negative throughout

the building. Ventilation levels in the building were considerably in

excess of ASHRAE recommendations and may have exaggerated the effects

of low temperatures during the winter months. Lower ventilation levels

on the upper four floors were associated with more complaints of

stuffiness, particularly during the summer.

34. Opinion on noise levels and disturbances was slightly more positive than

negative overall, but about evenly divided in the open-plan offices.

Response was very negative on the sixth floor possibly due to the use of

white noise generators. Voices were the most disturbing source of noise.

35. Most occupants were dissatisfied with the small windows in the building.

The windows were also perceived to be too narrow to provide a sufficient

view. The increased window area on the second floor did not substantially

improve opinion.

Finally, examples of life cycle cost analysis for this energy-conserving

building design were performed. Based on the results:

36. The construction of a building such as the Norris Cotton Federal Office

Building was determined to be feasible when such a building is constructed

as an alternative to a Federal office building not incorporating energy

conserving design features. With the assumptions made in this report,

the discounted payback period was determined to be approximately 12 years

for a thirty year building lifetime.

37. It is important to consider parameters other than annual energy cost and

construction cost when comparing buildings built to different criteria.

Maintenance costs, equipment replacement costs and benefits from differences in building quality should also be considered.

122
8. REFERENCES

1. Hill, J. E. and Kusuda T. , "Manchester's New Federal Building: An Energy

Conservation Project," ASHRAE Journal , August 1975.

2. Kusuda, T. , Hill, J. E. , Liu, S. T. , Barnett, J. P., and Bean, J. W,

"Pre-Design Analysis of Energy Conservation Options for a Multi-Story

Demonstration Office Building," NBS Building Science Series 78 , November

1975.

3. Kusuda, T. , "Energy Instrumentation and Supervisory Control System in the

GSA/Manchester Federal Office Building," Letter Report to GSA, April 1975.

4. ASHRAE Handbook of Fundamentals , American Society of Heating, Refrigerating, and Air Conditioning Engineers, 345 East 47th Street, New York, NY

10017, 1977.

5. May, Jr., W. B. , "Analysis of Data from the Energy Monitoring and Control

System at the Norris Cotton Federal Office Building," NBSIR in preparation, June 1981.

6. Hill, J. E. and Richtmyer, T. E., "Thermography Measurements in the

Norris Cotton Federal Office Building in Manchester, New Hampshire,"

Letter Report to DoE, August 1977.

7. Hunt, C. M. , "Air Exchange and Ventilation System Measurements in the

Norris Cotton Federal Office Building in Manchester, New Hampshire,

Letter Report to DoE, May 1977.

8. Hunt, C. M. , "Ventilation Measurements in the Norris Cotton Federal

Office Building in Manchester, NH," ASHRAE Transaction , Vol. 85, Part I,

1979.

9. Hunt, C. M. and Richtmyer, T. E. , "Remeasurement of Air Exchange Rates

in the Norris Cotton Federal Office Building After Retrofitting to

Reduce Leakage," Letter Report to DoE, April 1979.

10. Harrje, D. T. , et al., "Automated Instrumentation for Air Infiltration

Measurements in Buildings," Center for Environmental Studies, Princeton,

New Jersey, Report No. 13, April 1975.

11. Hunt, C. M. and Treado, S. J., "A Prototype Semi-Automatic System for

Measuring Air Infiltration in Buildings Using Sulfur Hexafluoride as

a Tracer," NBS Technical Note 898, March 1976.

12. ASHRAE Standard 62-73 , "Standards for Natural and Mechanical Ventilation,"

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

Inc., 345 East 47th Street, New York, NY 10017, 1973.

13. "Shelter Design and Analysis - Environmental Engineering for Shelters,"

TR 20, Vol. 3, Office of Civil Defense, May 1969.

123
14. ASHRAE Standard 93-77 , "Methods of Testing to Determine the Thermal

Performance of Solar Collectors," American Society for Heating,

Refrigerating, and Air Conditioning Engineers, 345 East 47th Street,

New York, NY 10017, 1978.

15. "Solar Collector Performance Tests," Desert Sunshine Exposure Tests,

Inc. Report No. 78SA0524, August 1978.

16. "Solar Collector Test Report," Desert Sunshine Exposure Tests, Inc.

Report No. 79S0130-31, February 1979.

17. May, W. B. , "Options for Solar System Improvement at the Norris Cotton

Federal Office Building in Manchester, New Hampshire, Letter Report to

GSA, January 3, 1980.

18. Klein, S. A., "Calculation of Flat-Plate Collector Utillzability ,

Solar Energy , Vol. 21, pp. 393-402, 1978.

19. "DOE-2 Reference Manual," Los Alamos Scientific Laboratory, document No.

LA-7689-M or Lawrence Berkeley Laboratory document No. LBL-8706, April

1979.

20. Hittle, D. C. , "The Building Loads Analysis System Thermodynamics (BLAST)

Program, Version 2.0: Users Manual, Volume I," U.S. Army Construction

Engineering Research Laboratory, Champagne, IL, NTIS Report CERL-TR-E-153,

June 1979.

21. May, W. B. and Spielvogel, L. G. , "Analysis of Computer-Simulated Thermal

Performance of the Norris Cotton Federal Office Building," NBSIR-80-2093,

March 1980.

22. "Energy Conservation Design Guidelines for New Office Buildings," General

Services Administration/Public Buildings Service, 2nd Edition, 324 pages,

1977.

23. Elder, J. and Tibbott, R. L. , "User Acceptance of an Energy Efficient

Office Building - A Study of the Norris Cotton Federal Office Building,"

NBS Building Science Series 130 , January 1981.

24. Gagge, A. P. and Nevins, R. G. , "Effect of Energy Conservation Guidelines

on Comfort, Acceptability, and Health," Final Report, Contract No. CO-04-

51891-00, Federal Energy Administration, March 1976.

25. Chen, P. T. , "Economic Analysis of the Norris Cotton Federal Office

Building," NBS Report NBSIR 78-1568, November 1978.

26. The National Archives of the United States, "Methodology and Procedures

for Life Cycle Cost Analysis," Federal Register , Vol. 45, No. 16, January 23, 1980.

27. Akalin, M. T. , "Equipment Life and Maintenance Cost Survey," ASHRAE Journal , October 1978.

124
9. BIBLIOGRAPHY

1. Issak, N. and Isaak, A., "Designing an Energy Efficient Building,"

published by the General Services Administration/ Public Buildings

Service, September 1975.

2. Kusuda, T. , Liu, S. T. , Bean, J. W. , and Barnett, J. P., "Analysis of

the Solar Energy System for the GSA Demonstration Office Building in

Manchester, New Hampshire," NBS Report NBSIR 76-1056, March 1976.

3. Murdoch, J. P. , "A Simplified Procedure for Calculating the Direct

Components of Contract Rendition Factor and Equivalent Illumination,"

NBS Report NBSIR 77-1303, November 1977.

4. Chen, P. T. , "Economic Analysis of the Norris Cotton Federal Office

Building," Letter Report to DoE, February 1978.

5. Elder, J., "Norris Cotton Federal Building — User Acceptance," Letter

Report to DoE, February 1978.

6. Elder, J. , "Norris Cotton Federal Building User Acceptance — Results of

the Second Questionnaire," Letter Report to DoE, March 1978.

7. Rensberger, R. A. , "The Norris Cotton Building - A Living Laboratory in

Energy Conservation," brochure, March 1978.

8. Yonemura, G. T. , Hattenburg, A. T. , and Tibbott, R. L. , "Luminous Efficacy of Lighting Systems Installed in the Norris Cotton Federal Office

Building, Manchester, New Hampshire, Letter Report to DoE, April 1978.

9. Richtmyer, T. E., "The Use of Computer-Controlled Data Acquisition

Systems in Determining Solar Heating and Cooling System Performance,"

Proceedings of the Conference on Performance Monitoring Techniques for

Evaluation of Solar Heating and Cooling Systems , held in Washington,

D.C., April 1978.

10. Richtmyer, T. E. , May, W. B. , Hunt, C. M. , and Hill, J. E. , "Thermal

Performance of the Norris Cotton Federal Office Building in Manchester,

New Hampshire," Proceedings of the DoE/ASHRAE Conference on Thermal

Performance of Exterior Envelopes of Buildings , Orlando, Florida,

December 3-5, 1979.

125
NBS-n4A IREV. 2-80) U.S. DEPT. OF COMM. BIBLIOGRAPHIC DATA

SHEET (See instructions)

1. PUBLICATION OR

REPORT NO. NBS BSS 133

2. Performing Organ. Report No, 3. Publication Date

August 1981

4. TITLE AND SUBTITLE

Performance of the Norrls Cotton Federal Office Building

for the First 3 Years of Operation

5. AUTHOR(S) James E. Hill, William B. May, Jr., Thomas E. Richtmyer, Jacqueline Elder,

Robert L. Tibbott, Gary T. Yonemura, Charles M. Hunt, and Phillip T. Chen

6. PERFORMING ORGANIZATION (If joint or other than NBS. see instructions)

NATIONAL BUREAU OF STANDARDS

DEPARTMENT OF COMMERCE

WASHINGTON, D.C. 20234

7. Contract/Grant No.

8. Type of Report & Period Covered

Final

9. SPONSORING ORGANIZATION NAME AND COMPLETE ADDRESS (Street. City, State. ZIP)

Architecture and Engineering Systems Branch Buildings Division

Office of Buildings and Community Systems

Department of Energy

Washington, DC 205A5

10. SUPPLEMENTARY NOTES

Library of Congress Catalog Card Number: 81-600082

I I Document describes a computer program; SF-185, FIPS Software Summary, is attached.

11. ABSTRACT (A 200-word or less factual summary of most significant information. If document includes a significant

bibliography or literature survey, mention it here)

The Norris Cotton Federal Office Building is a medium-size seven-story Government

office building of approximately 11,000 m (117,000 ft ) total floor area. It is

located in Manchester, New Hampshire, and was designed to demonstrate a number of

energy saving concepts.

Some of the major energy conserving features of the building are the use of solar

collectors; heavy masonry construction with exterior insulation; small overall window

area; heat recovery from heat pumps, chillers, a natural gas-powered engine /generator

,

and the ventilation system; modular boilers; thermal storage tanks; and a variety of

energy conserving lighting systems.

A team from the Center for Building Technology, National Bureau of Standards (NBS),

has been monitoring the performance of the building since it was occupied in

September 1976. The project has involved not only an analysis of building energy

consumption, but also a study of the effectiveness of the various lighting systems, a determination of the response of the occupants to the building, and a cost analysis of

the construction and operation of an energy conserving building. This report will

describe the building's performance for the first 3 years of operation.

12. KEY WORDS (Six to twelve entries; alphabetical order; capitalize only proper names; and separate key words by semicolons)

Building models, computer; energy conservation, user acceptance; energy conservation in

commercial buildings; lighting measurements; performance data for commercial office

buildings in New England; solar energy in commercial buildings.

13. AVAILABILITY

pQ^ Unlimited

I I For Official Distribution. Do Not Release to NTIS

pS| Order From Superintendent of Documents, U.S. Government Printing Office, Washington, D.C. 20402.

Order From National Technical Information Service (NTIS), Springfield, VA. 22161

14. NO. OF

PRINTED PAGES

lAO

15. Price

$5.50

<tU.S. GOVERNMENT PRINTING OFFICCi 1981-340-997/1767

USCOMM-DC 8043-P80

II

I 0 1
NBS TECHNICAL PUBLICATIONS

PERIODICALS

JOURNAL OF RESEARCH—The Journal of Research of ihe National Bureau of Standards reports NBS research and develop- ment in those disciplines of the physical and engineering sciences in which the Bureau is active. These include physics, chemistry,

engineering, mathematics, and computer sciences. Papers cover a broad range of subjects, with major emphasis on measurement

methodology and the basic technology underlying standardization. Also included from time to time are survey articles on topics

closely related to the Bureau's technical and scientific programs. As a special service to subscribers each issue contains complete

citations to all recent Bureau publications in both NBS and non- NBS media. Issued si.x times a year. Annual subscription: domestic

$13; foreign Sid. 25. Single cop>. %} domestic: S3, 75 !oreign. NOTE: The Journal was formerly published in two sections: Section A "Physics and Chemistry" and Section B "Mathematical

Sciences." DIMENSIONS/NBS—This monthly magazine is published to in- form scientists, engineers, business and industry leaders, teachers, students, and consumers of the latest advances in science and

technology, with primary emphasis on work at NBS. The magazine

highlights and reviews such issues as energy research, fire protection, building technology, metric conversion, pollution abatement,

health and safety, and consumer product performance. In addition, it reports the results of Bureau programs in measurement

standards and techniques, properties of matter and materials, engineering standards and services, instrumentation, and

automatic data processing. Annual subscription: domestic $11;

foreign $13.75. NONPERIODICALS

Monographs—Major contributions to the technical literature on

various subjects related to the Bureau's scientific and technical activities. Handbooks—Recommended codes of engineering and industrial practice (including safety codes) developed in cooperation with in- terested industries, professional organizations, and regulatory

bodies. Special Publications—include proceedings of conferences sponsored by NBS, NBS annual reports, and other special publications

appropriate to this grouping such as wall charts, pocket cards, and

bibliographies. Applied Mathematics Series—Mathematical tables, manuals, and

studies of special interest to physicists, engineers, chemists,

biologists, mathematicians, computer programmers, and others engaged in scientific and technical work.

National Standard Reference Data Series—Provides quantitative data on the physical and chemical properties of materials, compiled from the world's literature and critically evaluated. Developed under a worldwide program coordinated by NBS under

the authority of the National Standard Data Acl (Public Law

90-3%).

NOTE: The principal publication outlet lor the foregoing data is the Journal of Physical and Chemical Reference Data (JPCRD)

published quarterly for NBS bv the American Chemical Society

(ACS) and the American Institute of Physics (AlP). Subscriptions,

reprints, and supplements available from ACS. I 155 Sixteenth St., NW. Washington, DC 20056.

Building Science Series—Disseminates technical information

develofied at the Bureau on building materials, components,

systems, and whole structures. The series presents research results,

test methods, and performance criteria related to the structural and

environmental functions and the durability and safely characteristics of building elements and systems.

Technical Notes—Studies or reports which are complete in themselves but restrictive in their treatment of a subject. Analogous to monographs but not so comprehensive in scope or definitive in treatment of the subject area. Often serve as a vehicle for final reports of work performed at NBS under the sponsorship of other government agencies.

Voluntary Product Standards—Developed under procedures

published by the Department of Commerce in Part 10, Title 15, of

the Code of Federal Regulations. The standards establish nationally recognized requirements for products, and provide ail concerned interests with a basis for common understanding of the

characteristics of the products. NBS administers this program as a supplement to the activities of the private sector standardizing

organizations. Consumer Information Series—Practical information, based on NBS research and experience, covering areas of interest to the con- sumer. Easily understandable language and illustrations provide

useful background knowledge for shopping in today's technological marketplace. Order the above NBS publications from: Superinlendenl of Documenis, Governmeni Printing Office, Washington, DC 20402. Order the following ,\'BS publications—FIPS and NBSIR's—from

the National Technical Information Services. Springfield. VA 22161

Federal Information Processing Standards Publications (FIPS

PUB)—Publications in this series collectively constitute the Federal Information Processing Standards Register. The Register

serves as the official source of information in the Federal Govern- ment regarding standards issued by NBS pursuant to the Federal Property and Administrative Services Act of 1949 as amended.

Public Law 89-306 (79 Stat. 1127). and as implemented by Executive Order 1 1717 (38 FR 12315, dated Ma^ II, 1973) and Pai.6

of Title 15 CFR (Code of Federal Regulations).

NBS Interagency Reports (NBSIR)—.A special series of interim or

final reports on work performed by NBS for outside sponsors

(both government and non-government). In general, initial dis- tribution is handled by the sponsor; public distribution is by the National Technical Information Services, Springfield, VA 22161.

in paper copy or microfiche form.
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