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PUBLICATIONS

NBSIR 80-2093

NAT'L INST. OF STAND

III I

TECH R.I.t.

A1110S 1S74L2

Analysis of Computer-Simulated

Thermal Performance of The Norris

Cotton Federal Office Building

William B. May, Jr.

Building Thermal Performance Division

Center for Building Technology

National Engineering Laboratory

National Bureau of Standards

U.S. Department of Commerce

Washington, DC 20234

and

Lawrence G. Spielvogel, P.E.

Lawrence G. Spielvogel, Inc. Consulting Engineers

Wyncote, PA 19095

November 1980

Sponsored by

QG"

' Department of Energy

lington, DC 20585

100

. U56

80-2093

1980

NBSIR 80-2093

ANAl YSIS OF COMPUTER-SIMULATED

THERMAL PERFORMANCE OF THE NORRIS

COTTON FEDERAL OFFICE BUILDING

Nttienal Bureau of Stswtanfe

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William B. May, Jr.

Building Thermal Performance Division

Center for Building Technology

National Engineering Laboratory

National Bureau of Standards

U.S. Department of Commerce

Washington, DC 20234

and

Lawrence G. Spielvogel, P.E.

Lawrence G. Spielvogel, Inc. Consulting Engineers

Wyncote, PA 1 9095

November 1 980

Sponsored by

The Department of Energy

Washington, DC 20585

U.S. DEPARTMENT OF COMMERCE, Philip M. Klutznick, Secretary

Luther H. Hodges, Jr., Deputy Secretary

Jordan J. Baruch, Assistant Secretary for Productivity. Technology, and Innovation

NATIONAL BUREAU OF STANDARDS, Ernest Ambler, Director
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ABSTRACT

Five computer-based energy simulations of the Norris Cotton Federal Office

Building (NCFOB) in Manchester, New Hampshire, were performed using the Ross

Meriwether Energy Systems Analysis Program. The NCFOB is a medium-size office

building, occupied in September 1976, designed to serve as a demonstration

of and feasibility test for energy-conserving building features. The

simulations included two in accordance with the original design, with and

without a solar system; a simulation of the building as actually operated; a simulation of the building with modifications to actual operation; and a simulation of an alternative building design. Results of the five simulations

are compared with each other and with actual measured data at several levels

of detail including total energy consumption, consumption by fuel type, and

heating and cooling requirements. Good agreement between the simulation and

actual data is demonstrated and consequences of design features are discussed.

Key Words: Building models; building performance data; computer simulations,

building; energy conservation in commercial buildings; heat pumps;

validation of computer models, 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 reported by DoE/NBS Task Order No. A 008-BCS under Interagency Agreement

No. EA 77 A 01 6010.
TABLE OF CONTENTS

Page

ABSTRACT iii

PREFACE iv

LIST OF TABLES vi

LIST OF FIGURES vii

1. INTRODUCTION 1

2. DESCRIPTION OF NORRIS COTTON FEDERAL OFFICE BUILDING 2

3. DESCRIPTION OF COMPUTER SIMULATIONS 4

4. OVERALL ENERGY CONSUMPTION 10

5. HEATING AND COOLING ENERGY REQUIREMENTS 14

6. COMPONENTS OF FUEL ENERGY USE AT THE NCFOB 19

7. COMPONENTS OF TOTAL ENERGY USE AT THE NCFOB 20

8. CONCLUSIONS 22

9. REFERENCES 24

v
LIST OF TABLES

Page

1. Important input parameters for ERE program, "as-designed"

simulation 25

2. Selected important input parameters for ERE program, "asoperated" simulation 25

3. Selected important input parameters for ERE program,

"design alternative" simulation . 26

4. Norris Cotton Federal Office Building annual energy

consumption 27

5. Summary of effects of modifications made to the "as-operated"

simulation 27

6. Fuel energy use components for the "as-designed" simulation . 28

7. Fuel energy use components for the "as-designed with solar"

simulation 29

8. Fuel energy use components for the "design alternative"

simulation 30

9. Fuel energy use components for the "as-operated" simulation . 31

10. Fuel energy use components for the "as-operated with

modifications" simulation 32

11. Partial fuel energy use components from actual data 33

12. Energy use components for the "as-designed" simulation 34

13. Energy use components for the "as-designed with solar"

simulation 34

14. Energy use components for the "as-operated" simulation 35

15. Energy use components for the "design alternative"

simulation 35

16. Energy use components for the "as-operated with

modifications" simulation 36

17. Energy use components from actual data 37

18. Comparison of components of annual operating energy for

actual data and for "as-operated" and "design alternative"

simulation cases 37

vi
LIST OF FIGURES

Page

1. Schematic diagram of Norris Cotton Federal Office Building

mechanical system 38

2. Total energy consumption of the NCFOB as predicted by

simulation 39

3. Electric energy consumption at the NCFOB as predicted by simulation 39

4. Natural gas consumption at the NCFOB as predicted by simulation 40

5. Fuel oil consumption at the NCFOB as predicted by simulation .. 40

6. Average monthly ambient temperatures for actual weather and

1962 weather used in the simulations 41

7. Total energy consumption at the NCFOB as predicted by the "asoperated" simulation compared with actual consumption for

three years 41

8. Monthly total heating requirements per unit area for the NCFOB

as predicted by the "as-designed" simulation 42

9. Monthly total cooling requirements per unit area for the NCFOB

as predicted by the "as-designed" simulation 42

10. Monthly total heating requirements per unit area for the NCFOB

as predicted by the "as-operated" simulation 43

11. Monthly total cooling requirements per unit area for the NCFOB

as predicted by the "as-operated" simulation 43

12. Monthly total heating requirements per unit area for the NCFOB

as predicted by the "design alternative" simulation 44

13. Monthly total cooling requirements per unit area for the NCFOB

as predicted by the "design alternative" simulation 44

14. Monthly total heating and cooling requirements for the NCFOB as predicted by all simulations 45

15. Comparison of heating and cooling requirement components for

the NCFOB as predicted by simulation 46

vii
LIST OF FIGURES (Continued)

Page

16. Least squares fit of NCFOB heating requirements predicted by

simulation versus monthly average ambient temperature 47

17. Least squares fit of NCFOB cooling requirements predicted by

simulation versus monthly average ambient temperature 47

18. Third order least squares fit of predicted and actual NCFOB

fuel use plus fan energy versus monthly average ambient

temperature 48

19. Fuel use efficiency versus heating requirements as predicted

by simulation for the NCFOB (least squares fits) 48

20. Cooling performance factor versus cooling requirements as predicted by simulations of the NCFOB (least squares fits) .... 49

21. Third order least squares fit of predicted and actual total

energy used for HVAC at the NCFOB versus monthly average

ambient temperature 49

22. Total heating efficiency versus heating requirements as predicted by simulations of NCFOB (least squares fits) 50

23. Total cooling factor versus cooling requirements as predicted by simulations of NCFOB (least squares fits) 50

24. Total energy for heating versus heating requirements for the

central and heat pump mechanical subsystems at the NCFOB as predicted by the "as-operated" simulation 51

25. Total energy for cooling versus cooling requirements for the

central and heat pump mechanical subsystems at the NCFOB as predicted by the "as-operated" simulation 51

26. Comparison of actual and predicted boiler fuel input at the

NCFOB using "as-operated" simulation data 52

27. Comparison of actual and predicted heat pump and service hot

water input at the NCFOB using "as-operated" simulation data .. 52

28. Comparison of actual and predicted energy to central chillers

at the NCFOB using "as-operated" simulation data 53

29. Comparison of actual and predicted lighting-miscellaneous and

operating energy at the NCFOB using "as-operated" simulation

data 53

30. Energy use components and total energy use per year at the

NCFOB using simulation results and measured data from September

1978 to 1979 54

viii
1

.

INTRODUCTION

The Norris Cotton Federal Office Building (NCFOB) is a seven-story government

office building located in Manchester, New Hampshire. This building, occupied

in September of 1976, was designed to serve as a demonstration and a feasibility test for a number of energy-conserving building features. Each floor

utilizes different types and arrangements of heating, ventilation, and air

conditioning (HVAC) equipment and lighting systems. The equipment in the

building includes heat pumps, fan coil units, variable volume air distribution systems, several heat recovery concepts, and a solar energy system.

The building envelope was designed to minimize wall and roof thermal losses

by making use of a cubical shape, minimum fenestration, massive construction,

and external wall and roof insulation.

The original design for the building was developed by an architect/engineering

firm under contract to the General Services Administration (GSA), the agency

responsible for Federal Buildings [1]. The National Bureau of Standards (NBS)

participated in the design stage by examining alternate design concepts with

the NBSLD computer program, which was developed at NBS to predict heating and

cooling loads in buildings [2, 3, 4, 5]. NBS has been under contract to the

Department of Energy (DoE) to collect and analyze energy consumption and performance data on the building. NBS subcontracted a consultant to simulate

the thermal performance of the building using a state-of-the-art hour-by-hour

computer program for the following reasons:

1. The original modeling of the building with NBSLD 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 kBtu/(f t^*year) ) )

.

2. Building energy consumption data from 98 kWh meters, six natural

gas meters, and two fuel oil meters is available for the NCFOB

over three years of operation. By comparison of actual data and

predicted data from a simulation of the building as it has been

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 actual 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 to conventional non-government criteria.

4. The model could also be used to examine possible improvements to

present building operation and to predict their effect on building

energy consumption.

1
The computer-based model chosen to accomplish the above objectives was the

Ross Meriwether Energy System Analysis Program*. This program was felt to

represent the state of the art in building load and mechanical systems

modeling. The popular public-domain programs such as DOE-2 and BLAST were

not generally available at the time this analysis was begun. Because they

are now available, consideration is being given to using them to replicate

some of the modeling reported here. If this proves to be desirable, the

results will be published later.

2. DESCRIPTION OF NORRIS COTTON FEDERAL OFFICE BUILDING

2.1 BUILDING ENVELOPE

The Norris Cotton Federal Office Building has an approximately cubical shape

to minimize surface area. The walls are of a massive masonry construction

with insulation installed on the exterior of the masonry and covered with a granite facade. The wall has an overall heat transfer coefficient (U-value)

of 0.34 W/(m^»°C) (0.06 Btu/h«f t^ • °F)) and a mass of approximately 390 kg/m^

(80 lb/ft^) of surface area. This wall design was intended to minimize

thermal transmission losses in the winter and thermal gains in the summer. To further assist in minimizing winter transmission losses and summer solar

gains, the window area averages only 6 percent of the total wall area and the

north building wall is completely windowless. The south, east and west walls

have approximately the same window area. Each window is double-glazed and

contains a set of adjustable louvers between the panes of glass. Overhangs

and fins surround the windows to maximize winter solar gain and minimize

summer solar gain.

2.2 MECHANICAL SYSTEMS

Due to the experimental nature of the NCFOB, the mechanical systems are more complex and include more redundant equipment than would be found in a typical

energy-conserving building. The mechanical systems at the NCFOB 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 having a combined capacity of 350 kW (1200 kBtu/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

* Identification of a proprietary computer program in no case implies

a recommendation or endorsement by the National Bureau of Standards.

2
for two below-grade parking levels and a mechanical equipment penthouse is

heated and ventilated. The NCFOB 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 accomplished 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 NCFOB 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 1 is a schematic of the energy conversion and supply

equipment. Four 55 kW(187 kBtu/h) natural gas modular boilers and two 108 kW

(370 kBtu/h) number 2 fuel oil modular boilers (not shown in figure 1) 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 enginegenerator set in the penthouse. Thermal energy for the absorption chiller

is supplied by the oil boilers or by recovery of waste heat from the engine

generator.

A solar energy system is installed on the NCFOB and includes 353 m^ (3800 ft^)

of liquid-type flat-plate collectors mounted on the roof of the building and

which may be tilted at angles of from 20 to 60 degrees. In the winter, the

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

fluid and a heat exchanger is used between 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 liter (10,000 gallon) storage tanks

located in the basement. Solar heated water was intended to fire the absorption chiller, to be used in the heating water system, and potentially could

be used in the heat pump system (the control system which existed during the

first three 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 heating water system by means of a double-bundle condenser. The other scheme was to operate the electric chiller as a heat pump

to produce hot water for the heating water system from low temperature water

3
stored in the tanks (false loading). These options have not proven to be feasible in the operation of the building because heating water system temperatures

have been elevated above maximum condenser operating temperatures (41°C) (105°F)

during mid-winter to ensure occupant comfort [6]. During mild weather, when

the heating water system temperature is lowered, the solar system can supply

energy to meet the heating requirements.

2.3 CONTROLS

The NCFOB has two distinct control systems for the mechanical equipment. A

pneumatic system provides basic control functions and device actuation. Tied

to the pneumatic system is a minicomputer. The minicomputer was 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.

3. DESCRIPTION OF COMPUTER SIMULATIONS

3.1 DESCRIPTION OF COMPUTER PROGRAM USED FOR SIMULATION

The Ross Meriwether Energy System Analysis program basically consists of a number of computer programs run in sequence, the output data generated by one program being used as input to the next. The building is divided into a number of zones, the number and size of the zones depending on the load resolution required, hours of operation, and the number of air-side HVAC and control systems in the building. Hourly heating, cooling, and electrical loads

for each zone are calculated by the Energy Requirements Estimate program

(ERE). The ERE program uses as input an hourly weather tape and design point

data describing the building envelope, the zone occupancy, zone base electric

loads, and the types of air-side HVAC and control systems in the zone. Hourly

loads calculated for individual zones by the ERE program are combined by the

Total Coincident Requirements program (TCR) to determine total and peak simultaneous loads for an entire mechanical subsystem. Using the ERE and TCR calculated loads and data describing the characteristics of the mechanical systems, the Equipment Energy Consumption program (EEC) simulates the performance

of the mechanical system components as they respond to loads imposed on them

by the building air-side systems, and determines the monthly input of all

energy forms to the building systems. The EEC program also computes operating

and full-load hours for each piece of equipment, heat recovery utilization,

and an energy use breakdown by categories.

For simulation of a solar energy system or solar heat gain, a program is used

which generates an ASHRAE solar table for the specific location and orientation

of any surfaces collecting solar energy [7]. This table gives the energy

striking a unit surface area after taking into account cosine effects and

optical losses. The EEC program can be used to model an actual solar array

by simulating a room with an "imaginary" chiller. Any net solar gain into the

room, which represents the collector array, is pumped into the building by the

chiller.

4
Five different simulation runs were made. The characteristics of the building

simulated by each run will be described in the next sections, followed by a presentation of the simulation results.

3.2 AS-DESIGNED SIMULATION

An "as-designed" simulation was intended to represent the NCFOB as it was originally designed, using the design plans and specifications for the

building as input to the program. A solar energy system was not originally

included in the 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 subsystems, the heat pump

system and the combined central systems. Each of the sub-buildings was further sub-divided into major zones, each of which required a separate

ERE program execution. 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

by the ERE program. 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 6pm

to 5am during the week and all day on weekends and holidays. Table 1 lists some important input parameters used by the ERE program. Other parameters

used as input data but not described here included base electric load for

lights, miscellaneous and fans, supply fan temperature rise, supply air flow,

hourly percentage variation profiles for base electric and internal loads,

maximum outside air flow, primary supply air temperature and humidity, air

system economizer temperatures, outside air-exhaust air heat recovery efficiency, and minimum variable volume air flow.

The TCR program was run to sum the loads calculated for individual major

zones by the ERE program into total hourly loads for the two sub-buildings,

the heat pump and central. The EEC program was used to predict the performance of the mechanical equipment as it supplied the load for the two main

types of air-side systems over a year. All of the equipment was described

in the EEC program input data by a full-load input and output rating together

with a part-load profile. The part-load profile allows the program to determine equipment energy consumption when the equipment is not delivering the

full rated load. The 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 to be supplied by the electjric chiller,

5
always driven by the engine-generator, as called for in the original design.

Waste heat from the engine generator was assumed to be 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 for the absorption chiller if no other

sources were available.

3.3 AS-DESIGNED WITH SOLAR SIMULATION

A second simulation was run using the final building design which included

a solar energy system added to the original design. This simulation used

the same ERE program inputs as the "as-designed" simulation. Besides the

addition of a solar system, the EEC (equipment) program inputs for this case were similar to the "as-designed" inputs with the exception that the

central electric chiller was assumed to always run on purchased power rather

than power produced by the engine-generator. The "with solar" design called

for the solar system to provide thermal energy to run the absorption chiller.

With the solar system, the engine-generator was designed to be operated and

the recovered heat to be used only if the solar 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 Ross Meriwether program had no provision for direct solar system simulation. The operation of the solar system

in the building was approximated by a room with south-facing windows simulated

by the ERE program. 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

for removing heat from the room was 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

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 system performance than might be expected from the actual design.

Prediction of the amount of solar energy entering the room was accomplished

by using a separate program to generate a table of solar heat gain values

for each hour of the day throughout the year. The regular function of this

program is to predict solar 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 a solar collector. This gives the same result as applying

a transmittance-absorptance product and an incident angle modifier to the

energy incident upon the solar panel. Energy loss from the solar collectors

by heat transfer to the environment was approximated by the transmission

6
loss through the walls of the solar room simulated by the ERE program.

Original design specifications for collector performance were used for the

collector simulation.

3.4 AS-OPERATED SIMULATION

Following building start-up in September 1976, differences between the design

predictions for the building and the actual operational performance became

apparent. The major problems with the building have been described in a previous paper [6]. 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". 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:

1. Different air infiltration rates were used. In the simulations,

infiltration is considered to be air leakage to or from outside

the building and is separate from mechanical ventilation. For the

"as-designed" simulation, 0.5 air changes per hour were used.

However, average rates of 0.75 air changes per hour were measured

initially after occupancy of the building [8]. After recaulking of

the building exterior, lower rates were measured (0.75 air changes

per hour on the first three floors and 0.39 on the upper four

floors or an average of 0.54 air changes per hour for the building). The lower rates were used in the "as-operated” simulation.

Table 2 lists ERE program inputs for the "as-operated" case. In the "as-designed" case, infiltration was assumed to be constant

on the first three floors and exist only on the upper floors when

the fans were off (a pressurized building). The air exchange

measurements showed that there is constant infiltration throughout

the building even when the fans are operating. Consequently the

infiltration rate for the "as-operated" case was not only higher

but was input as constant in all zones.

2. 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. 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.

3. 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.

7
4 . The building operators increased the heating water 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.

5. Recovered heat from the engine-generator has never successfully

driven the absorption chiller. When the engine-generator is

operated at maximum jacket water temperatures, water in the heat

recovery loop, after having passed through the jacket water heat

exchanger, seven stories of piping, and an oversized storage tank,

is at too low a temperature to drive 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 oilfired boilers. Also, the two other heat recovery options for the

electric chiller (double-bundle condenser and false loading) have never been used successfully. No heat recovery from the enginegenerator or electric chiller was simulated in the "as-operated"

case.

6. In the actual building, the solar array output is used only during

the spring and fall to provide energy for the heating water system. During mid-winter, the heating water system temperature is

raised to 60°C (140°F) and at this temperature the efficiency of

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 at 104°C (220°F), the temperature required

by the absorption chiller. Although the solar array can easily

produce energy at temperatures usable in the heat pump water loop,

problems with the valves and controls specified in the original

design have prevented solar-heated water from being used in the

heat pump system [6], To simulate this situation, the "as-operated" simulation allowed the solar array to provide energy for the

heating water 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 near the end of the third

operating year.

8. In the "as-operated" simulation the lighting loads were raised

slightly and redistributed to more accurately reflect the electric

energy requirements of the various agency tenants occupying different floors.

3.5 SIMULATION OF MODIFICATIONS TO EXISTING OPERATION

A simulation of the NCFOB was made to predict what the effect would be of

several easily implemented changes to the current operation of the building.

8
The "as-operated" simulation was taken as a baseline and several changes were made to the input data. The changes for this "as-operated with modifications

case 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 16°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 41°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.

3.6 DESIGN ALTERNATIVE SIMULATION

The final simulation run was intended to be a prediction of how a design

alternative to the NCFOB 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 a commercial building used

for rental of office space during the early 1970's. This type of building

might have been used if office space for government agencies had been rented

in a commercially owned building. Basically, 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. Table 3 describes ERE program input data. The

major differences between the "as-designed" and the "design alternative"

building were as follows:

1 . The alternative used more electricity for lighting per unit of

floor area and had higher internal gains.

2. The alternative had no solar system or heat recovery systems.

3. The overall wall U-value including the effect of windows was changed from 0.57 to 1.59 W/(m^*°C) (0.10 to 0.28 Btu/(h*ft^ # °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. The "design

alternative" simulation input data included a reference solar gain

9
since the window area was increased beyond the area in the original

design and no outside window shading "fins" were assumed (solar

gains were considered negligible in the "as-designed" case). A

shading coefficient of 0.5 was used to calculate solar gain for the

alternative

.

5. The wall and roof U-value was changed from 0.34 to 0.85 W/(m2 .°C)

(0.06 to 0.15 Btu/(h.ft 2 .°F)).

6. The design alternative used a hot water system for heating with

a central boiler and hot water coils on the perimeter. The

capacity per unit area was higher than for the "as-designed"

building.

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.

4. OVERALL ENERGY CONSUMPTION

Each of the simulation runs resulted in a prediction of the consumption of

various fuels and the overall building energy consumption, on a monthly

and annual basis. The following sections will describe the simulation

results.

4.1 TOTAL ENERGY CONSUMPTION

Total energy consumption predicted in each of the five simulation runs is

shown in Figure 2 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 keep in mind

that while different buildings may use the same amounts of energy at the

building boundary, the cost of the energy will differ between buildings using

different fuels and having different demand characteristics. In figure 2 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 result of a number of factors. The "asdesigned 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 "as-operated" 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 in 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 sections.

10
4.2 ELECTRIC ENERGY CONSUMPTION

The electric energy consumption per month predicted for the NCFOB is shown

in Figure 3. 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 system has little effect on the electric energy consumption 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 "asdesigned" case due to higher heating and cooling loads, greater energy use by

pumps, fans, controls, for 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 noticable 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.

4.3 NATURAL GAS CONSUMPTION

Predicted natural gas consumption is shown in Figure 4. 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,

because gas was used to heat water to fire the absorption chiller when the

solar system could 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 to be permitted to fire the absorption chiller. Thus, the summer gas use in Figure 4 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 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.

11
4.4. FUEL OIL CONSUMPTION

No fuel-oil-fired equipment was included in the original design and therefore

no oil consumption was predicted by 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 present. 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 in the "as-operated" cases,

more gas boiler capacity had to be included in the simulation than the building

actually has. The "as-operated" simulations predicted that the extra gas

boiler capacity was used, indicating that the actual 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 5 depicts use of fuel oil in the summer predicted by the simulation

cases. Piping was added to the original building so that the oil boilers

could be used to heat water to fire the absorption chiller. Figure 5 shows

a large use of oil for the absorption chiller for the "as-operated" case

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.

4.5 ACTUAL ENERGY CONSUMPTION COMPARED WITH PREDICTED CONSUMPTION

The simulation runs were all made using weather data for Concord, New Hampshire (which is 24 km (15 miles) away) for the calendar year 1962. The

monthly average dry-bulb temperatures for this particular year were found

to be very close to the thirty year norm values. In comparing actual energy

consumption data with the results of the simulations, it is important to con- sider 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 tapes were not obtainable. Figure 6 is a plot of the average

monthly ambient drybulb temperature in Concord for 1962 and for the three

years that the NCFOB has been in operation. The plot is based on the operating

year which is defined as being from September to August (the building was occupied in September 1976). It is obvious that the ambient temperatures

for all years are similar although there is an 8°C (15°F) variation in January

average temperature among the years.

A comparison of the overall building energy consumption for the "as-operated"

case and the actual consumption for the three years of building operation is

shown in Figure 7. The energy consumption for the first two 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 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

12
installed systems and equipment. The agreement between the actual energy

consumption and the "as-operated" simulation results is fairly close for the

third year.

4.6 ANNUAL TOTAL ENERGY CONSUMPTION PER UNIT AREA

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 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 [9]. 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 ft^) is used here. This includes 9072 m^ (97,648 ft^) of office

space, 643 m^ (6925 ft^) of mechanical space, and 6672 m^ (71,818 ft^) of

garage. The total area of the NCFOB is 16,387 m^ (176,394 ft^). During the

design stage GSA established an energy consumption goal of 625 MJ/(m^.year)

(55 kBtu/(ft^»year) ) (using EGFA) for the NCFOB and as a provisional goal for

other energy conserving buildings to follow.

Table 4 lists the annual energy consumption per equivalent gross floor area predicted for the NCFOB 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 9 percent. However, when the solar 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 8 percent above the GSA goal.

The reasons why the alternative building does not use much more energy than

the original design will be discussed in the following sections.

The actual operating data show that the annual energy consumption of the

NCFOB has been falling since the building was first occupied. Consumption

for the third year of operation (September 1978 to August 1979) was only

2 percent above the GSA goal and the consumption for the third calendar year

(ending December 1979) was 1 percent below the 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

13
year (1979) was used as a basis for selecting "as-operated" simulation

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 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 these

qualifications and the use of different weather data, the simulation predicts

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 5.

5. HEATING AND COOLING ENERGY REQUIREMENTS

5.1 ZONE 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. Heating requirements predicted for the "asdesigned" case are shown in Figure 8 per unit floor area for the major zones

for each month of the year. In the figure, the results for the core and

perimeter zones have been combined. The most apparent characteristic of

this plot is that the requirement for the first three floors is much larger

than the requirements for the other floors. This is due to the constant

infiltration component assumed on the lower three floors rather than the

infiltration occuring only with fans off on the upper 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 (confirming

actual experience in the building), the lower capacity of equipment on the

upper four floors results in less energy delivered to the upper four floors

by the air-side system than if all loads had been satisfied.

Figure 9 shows the cooling requirements for the same case. The cooling requirements for the lower three floors are less than the requirements for the upper

floors and this is again due to the difference in the assumptions concerning

air infiltration. Higher infiltration rates flush more heat out of the building

during moderate weather thus reducing cooling requirements. The figure also

shows the prediction of small cooling requirements in the winter months.

Heating energy requirements per unit area for the "as-operated" case are shown

in Figure 10. Extra runs of the ERE program were made for the perimeter and

core of the first three floors. These extra runs were made using a value for

the air infiltration rate which had been measured in tests made before the

14
building facade was caulked. The figure shows the effect of the increase in

air infiltration rate from 0.75 to 1.0 air changes per hour. 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, as was noted for the "as-designed" case, the lower

three floors have higher energy requirements than the upper floors. The

greater requirements are not due to a difference between constant and fansoff infiltration rates but result from a higher rate of constant infiltration

(see Table 2). Basically the heating requirements are similar for the two

cases, with the "as-operated" requirements being slightly higher.

The effect of infiltration rate on the cooling energy requirements for the

"as-operated" case can be observed in Figure 11. 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.

The heating and cooling energy requirements per unit area for the "asoperated with modifications" case are not shown since they are very similar

to the "as-operated" requirements. The cooling requirements for the "modifications" case are lowered slightly due to the supply air temperature reset on

the upper four floors.

Heating and cooling energy requirements for the "design alternative" case are shown in Figures 12 and 13. In this case there are only three major zones.

One zone represents an area on the first floor occupied 24 hours per day as a guard office. The requirements follow a pattern similar to the other cases.

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 14.

5.2 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 15 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.

15
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 loss where the "design alternative

value is much larger than for other cases. It might seem that this would

cause the "design alternative" to have higher heating energy requrements.

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.

5.3 HEATING AND COOLING ENERGY REQUIREMENTS VS AMBIENT TEMPERATURE

Figure 16 illustrates the result when the total monthly heating energy requirement is plotted against the average ambient temperature for the month. The curves in this figure are second order (quadratic) least squares fits of the

simulation output data and are nearly straight lines. The symbols on the

lines are identifiers and do not represent the actual points. The closeness

of the fitted line to the individual points can be described by a residual

standard deviation which is the standard deviation between values predicted

by the fitted curve and the original points. In figure 16 residual standard

deviations are less than 22 GJ (23 x 10^ Btu) for all curves. The value

of figure 16 is that it divorces the energy requirements data from the climate

to some extent and allows comparisons to be made between buildings in different climatic regions. The slope of the curve represents an overall heating

requirement factor. The curves from all simulation cases lie fairly close

together and approach zero between 13 and 18°C (55 and 65°F).

If the cooling energy requirements are plotted versus ambient temperature,

the result is Figure 17. Again, the curves in this plot are second order

least squares fits of the simulation output data. The curves are less significant than for heating since there are less months of cooling and thus less

data points. Residual standard deviations are less than 15 GJ (15 x 10^

Btu). The results differ between the cases, the "design alternative" data

lying well above the others as observed previously. Cooling requirements

tend to appear at ambient temperatures lower than 18°C (65°F) since during

spring and fall there may be times when heating and cooling energy requirements appear on the same day.

5. A FUEL USE VERSUS AMBIENT TEMPERATURE

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

16
plotted versus the ambient temperature. The value of such a plot is that

actual fuel consumption data are available for the NCFOB and a comparison

with the simulation results can be made. For the actual data, fan energy

cannot be separated from the fuel use. Figure 18 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 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 a "U" shaped

curve with the 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 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.

5.5 FUEL USE EFFICIENCY VERSUS HEATING AND COOLING ENERGY REQUIREMENTS

The figures presented to this point have described overall building performance. The performance of the mechanical equipment can be represented by

the ratio of heating or cooling requirements to the fuel (plus fan) energy

consumed 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 19.

The 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 9

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 20 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.

5.6 TOTAL HVAC ENERGY VS AMBIENT TEMPERATURE

Figures 18 through 20 used fuel consumption as the major dependent variable.

In any building, equipment is used to heat and cool the building space and to

17
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 21 is similar to Figure 18 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) for the simulation

and the actual measured data.

The curves in Figure 21 lie closer together than the curves in Figure 18 and

the actual data curve is ii\ better agreement with the "as-operated" simulation data curve than in Figure 18. 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 simulation. For example, the strategy of flushing the building

with the outside air in the early morning by manual control was used during

the third year of operation but was not simulated in any of the cases.

In Figure 21, the position of the "design alternative" curve relative to the

other curves in the figure is different than the corresponding position in

Figure 18. In Figure 21, the "design alternative" curve is in roughly the same position for heating as the other curves. In the plot of Figure 18, 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.

5.7 HVAC ENERGY USE EFFICIENCY VERSUS HEATING AND COOLING ENERGY REQUIREMENTS

A total heating efficiency may be defined as the heating requirements divided

by the total energy for heating (fuel plus operating energy). Figure 22 is a plot of least squares fitted curves of total heating efficiency versus heating

requirements. Residual standard deviations are all low, less than 2 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 19, 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 23. 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

.

5.8 COMPARISON OF SIMULATED SUBSYSTEMS - CENTRAL VERSUS HEAT PUMP

Plotting HVAC energy versus energy requirements from the various simulation

cases allows a comparison to be made of the two major subsystems in this

building, the heat pump and central system. A plot of the total heating

18
energy (fuel and operating) versus the heating requirement is shown in Figure

24 with a different symbol for each of the two subsystems. It appears that

the central system uses a slightly larger amount 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 subsystems. Data for the cooling season are shown in Figure 25 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 including effects of

fuel and equipment costs.

6. COMPONENTS OF FUEL ENERGY USE AT THE NCFOB

The output data from the EEC program allow the amounts of energy being used

by the major pieces of equipment such as the boilers, chillers, heat pumps

and engine-generator, as well as the amount of energy delivered to areas with heating loads and extracted from areas with cooling loads, to be determined. This fuel energy does not include auxiliary energy to operate the

major pieces of equipment and to operate pumps, fans, controls, and other

devices used to transport heat transfer fluids throughout the building. The

components of fuel energy use for the five simulation cases described here

are compiled in tables 6 through 10.

A limited amount of actual measured energy data collected at the NCFOB is

available for comparison with the simulation fuel energy components data.

The actual data is presented in Table 11 and 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

are available and therefore nothing can be said about the actual energy con- version 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 26, 27, and 28. The Figures show that at this level there are some differences between the "as-operated" simulation data and the actual data.

Figure 26 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 27 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 on 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 28. Actual input to the electric

chiller is slightly lower than predicted. Figure 28 also shows that the

pattern of use for the absorption chiller that is simulated is very different

19
from the actual use pattern. The simulation is based on parallel operation

of the chillers. In actuality, the absorption chiller can be used independently

of the electric chiller via manual control.

7. COMPONENTS OF TOTAL ENERGY USE AT THE NCFOB

Total energy use can be divided into two broad categories: lightingmiscellaneous and HVAC. HVAC energy is used to provide all heating, cooling,

control functions, ventilation, and service hot water. Lighting-miscellaneous

energy is used to provide power to lights, elevators, and electric receptacles

for operating typewriters, copiers, and other equipment. HVAC energy can be

divided 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 12 contains energy use component data on a monthly basis for the "as-designed" 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 36 percent of

the total usage. Fuel energy makes up 44 percent while operating energy consumes a suprisingly large fraction of the total, 20 percent.

Tables 13 through 16 show the components of total energy use as predicted for

the various building simulation cases. Actual measured data from the NCFOB

for the period from November 1978 to October 1979 is given in Table 17 and

is broken down into categories similar to those used in the tables for the

simulation results. Actual and simulated total energy components are compared

in Figure 29. In order to compare the results on an annual basis for the

simulations and the actual data, Figure 30 has been prepared in bar chart

form with the quantity of energy for each end use shown as different regions

of the bars. For the actual data, the fuel energy 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 Figure 30.

7.1 PREDICTED COMPONENTS OF TOTAL ENERGY USE

When the solar system is added to the "as-designed" case the effect on the

energy use is to decrease the fuel used; all other energy usages remain the same. This has the effect of increasing the percentage of energy used for

lighting-miscellaneous and for operating energy.

For the "as-operated" case, while the energy used for lights and miscellaneous remains the same relative to the "as-designed" case, the fuel use decreases and the operating energy goes up to approximately 26 percent of the

total. The operating energy increases 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 "as-designed" 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

.

20
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 components for the "design alternative" look

very different from the use components for the other cases. The lightingmiscellaneous increases to almost 41 percent of the total and fuel use increases

to 51 percent of the total. However, the operating energy is much less than in

the other cases, accounting for only 8 percent of the total energy usage.

The energy to operate fans is about 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 NCFOB 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.

7.2 ACTUAL ENERGY USE COMPONENTS VERSUS PREDICTED USE COMPONENTS

In Figure 30, the "as-operated” case shows an operating energy use 9 percent

greater than for the actual building, a lighting-miscellaneous which is 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 18. 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 discrepancy may be due to weather differences. The lighting-miscellaneous

energy and operating energy may be compared on a monthly basis in Figure 29.

The lighting-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.

Table 18 contains a comparison of the components of operating energy for the

"as-operated" case, the "design alternative" case, and the actual data. The

"as-operated" simulation overpredicts usage for various categories of equipment

in some cases and underpredicts in others. This type of energy consumption

is the most difficult to predict since estimated values for hourly consumption

of auxiliary equipment must be input on an item by item basis for equipment

which may operate under varying load and control conditions.

The "design alternative" does not contain as much mechanical equipment as in

the "as-operated" case and this explains much of the higher operating energy

consumption for the "as-operated" case. When the pieces of equipment exist

in both cases, the usage is similar.

21
8. CONCLUSIONS

8.1 VALIDATION OF SIMULATION

1. Actual total energy consumption per year measured at the NCFOB for

calendar year 1979 was within 1A percent of the predicted value using the

Ross Meriwether Energy System Analysis computer program for 1962 weather.

2. The simulation of the NCFOB 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/(ft^»year)).

3. Actual energy consumption for lights and non-HVAC purposes at the NCFOB

for the third year of operation was within 8 percent of the predicted value

from the "as-operated" simulation case.

A. Actual energy consumption for fuel and fan energy at the NCFOB for the

third year of operation was within 12 percent of the predicted value from the

"as operated" simulation case using 1962 weather data.

5. Actual energy consumption for operating energy at the NCFOB for the third

year of operation was within 9 percent of the predicted value from the

"as-operated" simulation case using 1962 weather data.

8.2 BUILDING DESIGN CONCLUSIONS

1. As a result of modeling the mechanical systems in the NCFOB, a maximum

efficiency of approximately 6A percent was predicted for meeting the heating

loads in the building when heating requirements approached a maximum of A70

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 a maximum of 285 GJ/month (300 x 10^ Btu/month) for the "as-operated"

case. These values include the operating energy for the mechanical system

as well as fuel consumption.

2. Based on a comparison of the performance predicted by the simulation of

the two major mechanical subsystems in the NCFOB, the heat pump system on floors 1-3 and the central system on floors A-7 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.

3. A "design alternative" was simulated which had approximately twice the

lighting per unit floor area, five times more window area, one-third the

insulation value in the roof and walls, and a much simpler mechanical system

than the NCFOB. The yearly heating energy requirement was predicted to be

similar to that of the NCFOB. The additional transmission losses in the

"design alternative" were offset by increased solar gains and higher internal

loads. However, cooling requirements were higher than for the NCFOB due to

solar and internal gains.

22
4. When the simulation results for the "design alternative” to the NCFOB

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 2 percent of the total energy

consumption of the building. This is in comparison to the 26 to 21 percent

for the "actual design" cases. The large operating energy was partially due

to the experimental nature of the building.

5. Selected modifications to the NCFOB as currently operated were predicted

by simulation to reduce total energy consumption by 6 percent if implemented.

A 2.5 percent reduction was due to lowering central chiller condenser water

temperature and minimizing use of the absorption chiller fired by fuel oil.

23
9 REFERENCES

1. Isaak, N. , and Isaak, A., "Designing An Energy Efficient Building,"

General Services Administration/Public Buildings Service, GSA DC 76-3360

(September, 1975).

2. Hill, J. E., and Kusuda, T., "Manchester's New Federal Building: An

Energy Conservation Project," ASHRAE Journal, (August, 1975).

3. 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 Bulding, "Nat. Bur. Stand. (U.S.), Bldg. Sci. Ser.

78, (November, 1975).

4. 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," Nat. Bur. Stand. (U. S.) Report NBSIR 76-1056,

(March, 1976).

5. Kusuda, T., "NBSLD, the Computer Program for Heating and Cooling Loads in

Buildings," Nat. Bur. Stand. (U. S.), Bldg. Sci. Ser. 69, (July, 1976).

6. Richtmyer, T. E., May, W. B., Hunt, C. M., Hill, J. E., "Thermal Performance of the Norris Cotton Federal Office Building in Manchester, New

Hampshire," DoE/ASHRAE Conference on Thermal Performance of Exterior

Envelopes of Buildings, Orlando, FL, (December, 1979).

7. ASHRAE Fundamentals Handbook, ASHRAE, New York, NY, (1977).

8. Hunt, C. M. , "Ventilation Measurements in the Norris Cotton Federal Office

Building in Manchester, New Hampshire," ASHRAE Transactions, Vol. 85,

Part 1, (1979).

9. General Services Administration/Public Buildings Service, "Energy Conservation Design Guidelines for New Office Buildings," 2nd ed. (1977).

24
Table 1.

Important

input

parameters

for

ERE

program,

"as-designed"

simulation

lO 4J d *H CM

•H o 4J H (I) o a d • o cfl u d CJ u pq

H

O eN

(Ji

H

N VO

m

m CO

LO

N 10

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N ro o CO CN rH M CO rH CM

>N

60 -u d *H CM . 4-) CJ

<d

cd a*

d

03 cd 4J &

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on cm on

H cm

m

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60 4-J rH ON

O o o CM

a •H ON rH fM vO in in co

•H CJ rH cd in CM

n

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>>, in

60 4-J ON CM rH ON uo NT d •H Mf 00 IM VO

•H

a o • 4-J cd O VO n 00 co

cd

a 3 . CO CM rH rH

03 cd Pd a CQ

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ZJ CM

60

d 4-J •H *H ^ 4H W Cd 3 . (U 00 iJ d O PQ ^ d

60 CO •H CO CO O D rH n

<de

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pq

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a> 1 d^ rH ^

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CM4-> 4-4 CO • • J4 ,C C 42

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p

n) -H 4-1 40H H 3o 0 4-1 •H " C 0 1*3

<dH >s 4-» 03 rH ^

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JJCM

Cd 4-J U 4-4 rH

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4-1O

ON

O

M On

N cO cO

n rH CO CO CO CM in

d

rH o o O rH

O o d

MC • o •H *H o o o o o o o •H co cd

d

u 03 60 4-J cd Q PQ d6

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Q,? »—1

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03 3

rH rH rH •»

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a -h 60

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rH rHV0 CO 00 oo ON

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03 o a a

cd

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<d co co co co

CO ^ d § §

CJ 4-4 t)_4 4-4 4-4 O $ S £ S

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n

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CM CM

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25
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CO CO d • CM CN o rH

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d a*' d 4-1 •H o d CN rH CM u is d cd QJ 4J • • • • QJ a •rH oo a pp rH rH rH o

4-1 rH CN

cd rH 4-4 cd 4H a d CO • 00 M - 4-1 .d m cn m CN

•H QJ d HU — CM cn CM m

CO X 4-1 *H oo d

• • • aj is d cd vH 4J o o O 00

TP a •H 00 rH PP rH i—

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s

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4-4 U 4-1 4H 4-4 cd O o O

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4-1 •rH cd cd cd

QJ 4-1 4-1 44 4-1 a

CO H D* & S M

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P4 4-1 r>. <*•

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4-1 4-4 a o o o o

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l_i V_j QJ cd TJ

i-i h cd

QJ O O w H

cd

QJ CN

00a

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rH

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26
Table 4: Norris Cotton Federal Office Building

annual energy consumption

SIMULATION CASES

2* Energy consumption in MJ/ (m •yr) (kBtu/ (ft 2 1yr))

(1962 weather data) 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(54.0) 174(15.3) 441(38.7) —

"As-operated" 705(61.8) 197(17.2) 442(38.8) 24(2.1)

"As-operated with modifications" 662(58.1) 194(17.0) 468(41.0) 1(0.1)

"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) 76(6.6)

January 1977-December 1977 813(71.3) 237(20.9) 514(45.1) 61(5.3)

September 1977-August 1978 758(66.5) 225(19.7) 498(43.7) 35(3.1)

January 1978-December 1978 730(64.0) 208(18.3) 495(43.4) 27(2.3)

September 1978-August 1979 641(56.2) 153(13.4) 459(40.3) 28(2.5)

January 1979'-December 1979 619(54.3) 141(12.3) 459(40.3) 19(1.7)

2 2 *equivalent gross floor area = 10,900 m (117334 ft )

Table 5. Summary of effects of modifications made to the "as-operated" simulation

MODIFICATIONS

1. Cycle heat pump fans

2. Raise copling coil discharge

temperature of VAV

EFFECT PERCENT REDUCTION IN TOTAL ENERGY CONSUMPTION

Saves 45 000 kWh for fans 1.3%

Reduce cooling requirements 18% 1.2%

3. Raise heat pump loop

temperature

Save 5000 kWh 0.3%

4. Lower central chiller Save 54 415 kWh condenser water temperature absorption chiller seldom used

and sequence chillers, electric

chiller first, absorption last

2.5%

27
Table

6.

Fuel

energy

use

components

for

the

"as-designed"

simulation

ft) pH 60 §

03 p p

P •H P pH 0 P O cr

ft) o ft) CJ a p

CO p

p

e* ft) & 0

p 60 0) cu p p

•H *H p rH P

cd O cr

ft) o ft) 33 CJ p

COcu1 60

Pd P

•H 60 P P P

cd cd Cl)

ft) ft) P

Pi 43 o

CO& 1 o S

•rH p p CU

4J O

U P p

CU 03

1—

1

ft) W 43

CO

i p cu

0)

1—

1

o p

•H p cd O cu

P cd

ft) p

pH O P

•H W C

o <uo

P

OP

(U cd c M 4J ^ •h a) d co oo p cu cd p a) a oo w oo -h

ft) 03 a ft) •h 43 >

u u

a) a; CO P

03s

P P

C1) 2

pH CU

•H P

O 3

PQ O

P

ft) P /-s pH P C/3 •H ft o3 o d M

43 CM P vO P ON O pH X ^

oovoosrcon<rcoNsr o|<r

CM <f* CO O <f CM IrH tH l<f

oooocmvovooocooo o|m H H N I vO

mcocon^oooo^M<r H Ch (Ti O sf CM 00 CO CTn CO M H H pH CM

OOOOpHvOI^pHpHOO o VO

CN OOCOCMCMmOOOvOv£>vO rl OV

on ov vo n h cm m o» n

|<3-

N LO vO

pH O CO

CM CM i—

I

COOOOOO'iVOC'O

CO pH in CM O

pH CM

nOpHM’M’ONpHpIpHM’OnvO vOlcM

00 Oh in CM pH CO I CM

OOinvDHONincO^CO

rH m cm co m vo cm o oo

loo Un

ONOONONOOCOONCOOO O I pH pH pH pH

m'v00cr>cMOOO<roocMON O ON on on M pH S- 00 CO M H pH CM

vOOMHinO OO ^COONCO

00 00 M- CM in i—I CJN i—I vD

on cn CM pH CM CO

HMOMinvONOOONOdCM

m

o

VOo

43

4Jpo

e

VOo

-a

a)

a)P&

ft)

ft) p

cd

28
Table 7. Fuel energy use components for the "as--designed with solar" simulation

Month Boiler Boiler Service Boiler Boiler Electric Heat pump

(1962) input output water to to to system

(gas) input central heat pumps heat pumps requirements

heat cool heat cool

1 330 260 11 43 217 98 0 315 0

2 329 257 9 52 205 93 0 298 0

3 195 153 10 15 136 62 0 198 0

4 93 73 9 0 71 32 0 103 0

5 44 34 9 0 33 15 1 42 2

6 28 21 8 0 0 0 6 0 16

7 27 21 8 0 0 0 7 0 16

8 35 27 10 0 0 0 11 0 28

9 21 5 8 0 10 6 1 20 3 10 77 60 10 0 59 26 0 85 0

11 176 139 10 13 126 56 0 182 0 12 321 253 10 50 203 91 0 294 0 Totals 1676 1303 112 173 1060 479 26 1537 62

Month Solar Solar Solar Auxiliary Electric Central Solar

(1962) to to to to chiller cooling energy

heat pumps central absorption absorption input requirements used

chiller chiller

1 0 43 0 0 0 0 43

2 0 39 0 0 0 0 39

3 0 39 0 2 0 6 39

4 0 24 4 2 1 20 28

5 0 9 16 1 5 44 25

6 0 1 22 21 13 78 23

7 0 1 24 21 14 83 25

8 0 1 27 27 18 104 28

9 0 4 16 5 6 48 20

10 0 19 8 1 2 27 27

11 0 33 0 0 0 4 33

12 0 36 0 0 0 0 36

itals 0 249 117 80 59 414 366

All quantities are expressed in 10^ Btu/month (106 Btu = 1.055 GJ)

.

29
Table 8. Fuel energy use components for the "design alternative" simulation

Month

(1962)

Boiler

input

(gas)

Boiler

toheating

Service

water heater

input

electric

to thru-wall

air conditioners

electric

to packaged

units

cooling

load

1 626 447 5 0 0 0

2 617 444 4 0 0 0

3 375 249 4 4 0 9 4 173 110 4 10 0 25

5 74 46 4 31 7 96

6 0 0 3 67 27 243

7 0

0 3 69 30 250

8 0 0 4 78 39 295

9 32 18 3 32 8 103

10 160 98 4 12 0 30

11 365 140 5 1 0 2 12 608 430 5 0 0 0 totals 3030 1982 48 304 111 1053

All quantities are expressed in 10^ Btu/month (10^ Btu = 1.055 GJ)

.

30
Table 9. Fuel energy use components for the "as -operated " simulation

Month Boiler Boiler Service Boiler Boiler Electric Heat pump

(1962) input output water to to to system

(gas & input central heat pumps heat pumps requirements

oil) heat cool heat cool

1 447 344 11 120 224 101 0 325 0

2 434 334 9 122 212 95 0 307 0

3 261 202 10 72 130 58 0 188 0

4 81 61 10 8 53 24 0 77 0

5 40 26 10 0 19 8 4 27 9 6 55 46 8 1 0 0 18 0 45

7 59 47 8 1 0 0 19 0 47

8 74 58 10 11 0 0 27 0 68

9 14 10 9 0 8 4 5 12 13

10 63 47 10 5 42 19 0 61 0 11 236 179 10 64 115 52 0 167 0 12 420 323 11 113 210 94 0 304 0 Totals 2184 1677 116 507 1013 455 73 1468 182

Month

(1962)

Solar

tocentral

Solar

toabsorption

chiller

Auxiliary

toabsorption

chiller

Electric

chiller

input

central

cooling

requirement

Solar

used

1 0 0 0 0 0 4

2 0 0 0 0 0 3

3 0 0 0 0 3 5 4 25 0 0 0 9 28

5 14 12 17 5 27 29

6 0 0 45 14 72 7

7 0 0 47 15 77 6

8 0 0 58 20 103 6

9 5 21 2 6 34

' 29 10 21 0 0 0 14 24

11 0 0 0 0 1 3 12 0 0 0 0 0 3 Totals 65 33 169 60 340 147

All quantities are expressed in 106 Btu/month (10 6 Btu = 1.055 GJ)

.

31.1
Table 10 Fuel energy use components for the "as-operated with modifications" simulation

Month

(1962)

Boiler

input

(gas & oil)

Boiler

output

Service

water-heater

input

Boiler

to central

Boiler to heat pumps

Electric to heat pumps

heat cool

Heat pump system

requirements

heat cool

1 444 348 11 119 229 96 0 325 0

2 432 339 9 122 217 90 0 307 0

3 257 202 10 69 133 55 0 188 0 4 77 59 10 5 54 23 0 77 0 5 5 4 10 4 0 8 4 27 9 6 0 0 8 0 0 0 19 0 45

7 0 0 8 0 0 0 20 0 47

8 0 0 10 0 0 0 29 0 68

9 1 1 9 1 0 3 6 11 13

„ 10 61 43 10 0 43 18 0 61 0 11 231 179 10 61 118 49 0 167 0

12 416 326 11 111 215 89 0 304 0 Totals 1924 1501 116 492 1009 431 78 1467 182

Month

(1962)

Solar

to central

Absorption

chiller

input

Electric chiller

input

Central cooling

requirement

Solar used

1 0 0 0 0 4

2 0 0 0 0 4

3 0 0 0 2 5 4 26 0 0 5 29

5 9 0 5 21 12

6 0 0 14 61 3

7 0 0 16 66 3

8 0 1 21 89 5

9 4 0 6 26 7 10 25 0 0 8 25 11 0 0 0 0 4 12 0 0 0 0 4 Totals 64 1 62 278 105

All quantities are expressed in 10^ Btu/month (10^ Btu = 1.055 GJ)

.

32
Table 11 Partial fuel energy use components from actual data

Calendar Oil & gas Gas to Electric to Oil to Electric

month boiler service heat pump boiler for chiller

input water heater (+ fans) absorption input

chiller

1 374 10 88 0 0

2 351 6 79 0 0

3 205 6 35 0 0

4 109 5 22 0 1

5 16 0 26 16 6

6 1 0 36 1 15

7 37 0 74 37 44

8 5 0 57 5 27

9 2 0 37 2 14

10 46 7 27 0 4 11 134 2 41 0 0 12 296 9 67 0 0 Totals 1576 45 589 61 111

All quantities are expressed in 10^ Btu/month (10^ Btu = 1.055 GJ).

Data are from the period from November 1978 to October 1979.

33
Table 12. Energy use components for the "as-designed simulation

Month

(1962)

Lights + misc.

kWh

HVAC

kWh

Direct

fuel

kWh

Operating

energy

kWh

Fans kWh

Pumps

,

controls + misc.

kWh

Total

1 64138 188841 144700 44140 10415 33725 252979

2 56585 183987 140863 43124 10261 32862 240572

3 62593 133413 93959 39453 9193 30260 196006

4 61620 82630 52154 30475 6648 23827 144250

5 64138 68125 38381 29744 6360 23384 132263

6 61620 72489 41998 30491 6068 24423 134109

7 62593 75326 43866 31460 6069 25391 137919

8 65683 85278 52233 33045 6685 26360 150961

9 58530 56031 28051 27980 5557 22423 114561

10 64138 79144 47605 31539 6863 24676 143282

11 61620 119146 83964 35182 8177 27005 180766

12 61047 182671 137509 45162 10602 34560 243718

Annual

% of total

744305 1327081 905576 421795 92898 328896 2071386

energy 36 64 44 20 4 16

Table 13. Energy use components for the ' 'as designed with solar" simulation

Month

(1962)

Lights + mi sc

.

kWh

HVAC

kWh

Direct

fuel

kWh

Operating

energy

kWh

Fans kWhPumps t controls + misc.

kWh

Total

1 64138 172663 128581 44082 10415 33667 236801

2 56585 169080 126210 42870 10261 32609 225665

3 62593 117646 78244 39402 9193 30209 180239

4 61620 69969 39598 30371 6648 23723 131589

5 64138 51332 21546 29786 6360 23426 115470

6 61620 46816 16250 30566 6068 24498 108436

7 62593 48188 16575 31613 6069 25544 110781

8 65683 55062 21806 33256 6685 26571 120745

9 58530 40528 12448 28080 5557 22523 99058

10 64138 65399 33853 31546 6863 24683 129537

11 61620 106017 71096 34921 8127 26794 167637

12 61047 168721 123735 44986 10602 34384 229768

Annual

% of total

774305 1111421 689942 421479 92898 328581 1185726

energy 40 60 37 23 5 18

34
Table 14 Energy use components for the "as-operated" simulation

Month Lights + IIVAC Direct Operating Fans Pumps, controls

(1962) misc. kWh kWh fuel

kWh

energy

kWh

kWh + misc.

kWh

Total

1 64138 213986 162945 51041 11676 39365 278124

2 56585 203955 156895 47060 10749 36311 260540

3 62592 143437 95618 47819 10924 36895 206029

A 61620 76416 32489 43927 9597 34330 138036

5 64138 59245 18753 40492 9886 30606 123383

6 61620 70555 27562 42993 10186 32807 132175

7 62592 73100 28992 44108 10414 33694 135692

8 65685 84367 37656 46712 10856 35856 150052

9 58530 49320 10263 39057 9205 29852 107850

10 64138 71847 26328 45519 9864 35655 135985

11 61620 131514 86413 45101 10157 34944 193134

12 61046 203890 152804 51086 11610 39476 264936

Annual 744308 1381632 836718 544915 125124 419791 2125940

% of

total

energy

35 65 39 26 6 20

Table 15. Energy use components for the "design alternative" simulation

Month Lights + HVAC Direct Operating Fans Pumps 5 controls Total

(1962) misc. kWh kWh fuel energy kWh + misc.

kWh kWh kWh

1 72271 203802 186100 17702 14255 3447 276073

2 63279 199606 182876 16729 13096 3633 262885

3 69976 126968 112981 13987 11262 2725 196944

4 69274 67004 55646 11358 9623 1735 136278

5 72271 47888 35049 12839 10073 2766 120159

6 69274 43265 29920 13345 9623 3722 112539

7 69976 44029 30511 13517 9643 3874 114005

8 74565 52042 36282 15759 10504 5255 126607

9 64685 34959 22935 12024 8762 3262 99644

10 72271 65472 52691 12781 10073 2708 137743

11 69274 122688 109531 13157 10501 2656 191962

12 67683 197546 180239 17308 14218 3090 265229

Annual 834802 1205269 1034761 170506 131633 38873 2040071

% of

total

energy

41 59 51 8 6 2

35
Table

16.

Energy

use

components

for

the

"as-operated

with

modifications"

simulation.

Cti U

oH

O' OH'JHH'<rONIvNrsiri conm<rriMnH(NONoo

00 O<J-Ov£>v0 <J-C0 rH 00 O<f

CM OOnoOH'sf^^ONON LOOCOOrHrHCMONCOOOm

CM CMCNlrHrHt—li—IH H H CM

vOO

CO

ON

ON

wa

£

o

Pu U £ X

C

o + o

o cm in

cm i—i co

CO CM 00

ON vO vO

CO CO CO

co h m

vo oo m n h <3- ON H

CO CM CO

on cm m cm co

co o oo

CM ^ 00

CO CO CM

h <r m ON CC CM m on <r m <r on

co co co

ONorH

CO

wC

r- co on VO

00 Mr

00 00

m c

vO CM <3

- on

r^- m

vo m

cm oo

CM iH vo

ON ON

r- o

cm oo

r- nvO CM CO

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rH

COvO

00

<r

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d a; 3

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co co vo <r

vo in oo vo cm on

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CM

COVO

+

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X £

oo m cm co oo on

rH m in sf vO CM

vo m vo

o oo o

CM CO CM

VO rH VO

rH rH

vO vO vO

cm m o ON 00 co m vo m

cm in oo

vo vo m

00 O VO

co CM H vO O *>3" rH rH vO vo vO

00oCO

<r co

X CM

4J vO C ON O rH 2

HMM^lfliONCOWOrl

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'—

1

U u

Cfl QJ 0 4H G

c o a) £

36
Table 17. Energy use components from actual data

Month Total Lights + HVAC Direct fuel Pumps, control

(1978-79) energy misc

.

kWh and fans + misc

.

kWh kWh kWh kWh

1 262943 60149 202794 162002 40793

2 256124 53576 202548 169060 33488

3 172472 62367 110105 82476 27630

4 135282 57227 78055 51995 26060

5 108612 55405 53207 23454 29753

6 113981 55450 58531 25543 32988

7 151981 58840 93141 58684 34457

8 135853 60074 75779 36374 39405

9 108498 56012 52486 26305 26181

10 120062 59150 60912 33670 27242

11 142696 53981 88715 60884 27831

12 212201 53197 159004 120383 38621

Annual 1920705 685428 1235277 850828 384449

% of

total 100 36 64 44 20

energy

Table 18. Comparison of components of annual operating energy

for actual data and for "as-operated" and "design alternative" simulation cases

Ac tual^

data

kWh

%

2 of

operat ing

energy

As-operated

simulation

data

kWh

%

2 of

operating

energy

Design

alternative

data

kWh

%

2 of

operating

energy

Operating energy -fans 384449 100 419791 100 38873 100

Abs. chill accessories 303 <1 2055 <1 - - Elec, chill accessories 4216 1 13974 3 3070 8 Solar pumps 3531 1 7788 2 - - Elev. rm. air conditioner 18411 5 21453 5 21203 55 Boiler accessories 11480 3 6709 2 4518 12 Cooling towers 30499 8 9597 2 412 \

HWS pump 12353 3 607 68 14 9792 25 CHWS pump 3607 1 6960 2 - - HPS pump 57524 15 65700 16 1

1

- Snow melting 28371 7 75520 18 - _ Other misc. 214154 56 148920 35 0 0

Components of other misc .

Telephone power 19051 5 Controls 38968 10

Computer & emergency 71646 19 Misc. pumps & motors 20135 5 Other misc

.

64354 17

1 Data are from the period from November 1578 through October 1979.

^ Does not add up to 100% due to rounding.

37
OJ

CD

38

Schematic

diagram

of

Norris

Cotton

Federal

Office

Building

mechanical

system
io

3

kwh/month

10

BTLJ /

M0NTH

1000.0

iOQ.O

&G0.0

700.0

600.0

500.0

4 00.0 O

300.0

200.0

100.0

0 0 JAN FEB MAR APR MAY JUN JUL AUG SEP OCT NOV DEC

CALENDAR YEAR 1962

Figure 2. Total energy consumption of the NCFOB as predicted by simulation

iuuu.

CALENDAR YEAR 1962

Figure 3. Electric energy consumption at the NCFOB as predicted by simu1 9 1 1 on

39

J/

MONTH
10

BTU/MONTH

800.0

700.0

600.0

500.0

400.0

300.0

200.0

- 100.0

0 0

CALENDAR YEAR 1962

Figure 4. Natural gas consumption at the NCFOB as predicted by simulation

EG.C

70.0

60.0

50.0

40.0

30.0

20.0

10.0

C.o

CALENDAR YEAR 1962

Figure 5. Fuel oil consumption at the NCFOB as predicted by simulation

40

J/

MONTH

GJ/

MONTH
MONTHLY

AVERAGE

TEMPERATURE

MONTHS AFTER OCCUPATION OF BUILDING

Figure 6. Average monthly ambient temperatures for actual weather and 1962

weather used in the simulations

1400.0

1200.0

1000.0

800.0

600.0

400.0

200.0

0.0

ZLo

o

Figure 7. Total energy consumption at the NCFOB as predicted by the "as- operated" simulation compared with actual consumption for three

years

41
io 3

btu/(ft

2

-month)

io 3

btu/(ft

2

-month)

10.0

8.0 —

6.0 —

4.0 —

2.0 —

0.0

- 100.0

80.0

- 60.0

- 40.0

- 20.0

O

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

CALENDAR YEAR 1962

0.0

Figure 8. Monthly total heating requirements per unit area for the NCFOB

as predicted by the "as -des i gned " simulation

40.0

30.0

O

20.0

10.0

0.0

CALENDAR YEAR 1962

Figure 9. Monthly total cooling requirements per unit area for the NCFOB

as predicted by the " a

s -des i gned " simulation

42
io

3

btu/(ft

2

-month)

io 3

btu/(ft

2

-month)

10.0

8.0 —

6.0 —

4.0

2.0 —

1-- --1 1st 3 floors,

infiltration 1 ao/h /

/ - 100.0 1——

1

1st 3 floors,

infiltration 0.75 ae/h

/1

/

/ 4-—A 4th floor /

/ / 5-—5 5th floor / / - 80.0

^

6-—6 6th and 7th floors / / i / JZ

h0.0 JAN FEB MAR APR MAY JUN JUL AUG SEP OCT NOV DEC

CALENDAR YEAR 1962

Figure 10. Monthly total heating requirements per unit area for the NCFOB

as predicted by the "as-operated" simulation

40.0

30.0 X

10.0

0.0

CALENDAR YEAR 1962

Figure 11. Monthly total cooling requirements per unit area for the NCFOB

as predicted by the "as-operated" simulation

43
io 3

btu/(ft

2

-month)

io 3

btu/

(ft

2

-month)

10.0

8.0

1 1 24 hr zone, 1st

P P Perimeter zone G G Core zone

100.0

CALENDAR YEAR 1962

Figure 12. Monthly total heating requirements per unit area for the NCFOB

as predicted by the "design alternative" simulation

40.0

30.

0

h-O

CN 20.0 O'

10.0

C 0

CALENDAR YEAR 1962

Figure 13. Monthly total cooling requirements per unit area for the NCFOB

as predicted by the "design alternative simulation

44
H1NQH /r 9

Cvl CD

cn

on<

LjJ >•

on<

Q

<

O

o

o

to o

o

o

o

to o

o

CM o

o

(/) fd CDO

<D sz

4->

S_o

4-

«/) +>C

O)E

<U

s_

C

r

at

SC7> c

o

0

a

T3C

fd01c

•r-

+-> fd

cu

fd

+-> O

+->

>>

+->c

o

<D

S-CD

HiNoi^/nia9

oi

45

predicted

by

all

simulations
(dVHA-w

o o o o o q o o

o o o o o o o o

LO o LO o LO O LO o

LO LO xh ro ro C\l CM

o

d

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o

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cd£

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<73 CD 03 V & a a ^500 73

73 0) 73 7) ^ q

p:

KXNSSSX

<D _C

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a)

a)

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r

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i.co

o

o

uO

c

03a>

4-> fD<u

c

o

to

SfOQE

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LO

a>

s-3

co O o o o o o O o o o o

o LO d id o id o id o id o

LO to ro CM CM

(yV 3 Az U)/fli 8

£

0 L

46

NCFOB

as

predicted

by

simulation
COOLING

10

BTU/MONTH

HEATING

10

BTU/MONTH

°C

Figure 16. Least squares fit of NC FOB heating requirements predicted by

simulation versus monthly average ambient temperature

°c

-10.0 -5.0 0.0 5.0 10.0 15.0 20.0

300.0

250.0

200.0

150.0

100.0

50.0

0.0 MONTHLY AVERAGE AMBIENT TEMPERATURE, °F

Figure 17. Least squares fit of NCFOB cooling requirements predicted by

simulation versus monthly average ambient temperature

47

GJ/

MONTH

GJ/

MONTH
FUEL

USE

EFFICIENCY,

percent

°C

-10.0 -5.0 0.0 5.0 10.0 15.0 20.0 25.0

800.0

700.0

600.0

500.0

400.0

300.0

200.0

100.0

0.0

Figure 18. Third order least squares fit of predicted and actual NCFOB

fuel use plus fan energy versus monthly average ambient temperature

GJ/MONTH

0.0 100.0 200.0 300.0 400.0 500.

0

Figure 19. Fuel use efficiency versus heating requirements as predicted

by simulation for the NCFOB (least squares fits)

48

GJ/MONTH
GJ/MONTH

Figure 20. Cooling performance factor versus cooling requirements as pre- dicted by simulations of the NCFOB (least squares fits)

oc

10.0 20.0 30.0 40.0 50.0 60.0 70.0 80.0

800.0

700.0

600.0

500.0

400.0

300.0

200.0

100.0

0.0 MONTHLY AVERAGE AMBIENT TEMPERATURE, °E Figure 21. Third order least squares fit of predicted and actual total

energy used for HVAC at the NCFOB versus monthly average

ambient temperature

49

GJ/MONTH
TOTAL

COOLING

FACTOR

TOTAL

HEATING

EFFICIENCY,

percent

GJ/MONTH

0.0 100.0 200.0 300.0 400.0 500.0

Figure 22. Total heating efficiency versus heating requirements as predicted by simulations of NCFOB (least squares fit)

GJ/MONTH

0.0 50.0 100.0 150.0 200.0 250.0 300.0

Figure 23. Total cooling factor versus cooling requirements as predicted

by simulations of NCFOB (least squares fit)

50
ENERGY

EOR

COOLING,

10 6

BTU/MONTH

ENERGY

FOR

HEATING,

10

BTU/MONTH

0.0 500.0

400.0 —

300.0 —

200.0 —

100.0 —

GJ/MONTH

50.0 100.0

j u

150.0

_L 200.0 250.0

J u

O Central system

Heat pump system

<P

eft

<tc

0.0 T I I 0.0 1

300.0 350.0

-I L

- 500.0

- 400.0

- 300.0

200.0

100.0

. "I 7 I ‘I

1 I i I *

I I I I

‘

I I I I

"

II I I i 1 I 0 0 50.0 100.0 150.0 200.0 250.0 300.0 350.0

HEATING REQUIREMENTS, 10

6 BTU/MONTH

Figure 24. Total energy for heating versus heating requirements for the

central and heat pump mechanical subsystems at the NCFOB as predicted by the "as-operated" simulation

GJ/MONTH

0.0 20.0 40.0 60.0 80.0 100.0 120.0

125.0

100.0

75.0

50.0 O

25.0

0.0 0.0 20.0 40.0 60.0 80.0 100.0 120.0 COOLING REQUIREMENTS, 10

6 BTU/MONTH

Figure 25. Total energy for cooling versus cooling requirements for the

central and heat pump mechanical subsystems at the NCFOB as predicted by the "as -operated" simulation

125.0

100.0 O Central system

Heat pump system

o

o

o

75.0 .

50.0

25.0

o

n n

51

J/MONTH

GJ/MONTH
10

BTU/MONTH

Figure 26. Comparison of actual and predicted boiler fuel input at the

NCFOB using " as -operated" simulation data

140.0 -

120.0 -

100.0 —

80.0

-

60.0

-

40.0

-

20.0 -

0.0

G G Simulated heat pump electricinput (without fans)

G G Measured heat pump electric

input(with fans)

G Simulated service water

heater input

a ej Measured service water

- 140.0

- 120.0

100.0

- 80.0

- 60.0

40.0

- 20.0

-t

*

1 * c & r o.o JAN FEB MAR APR MAY JUN JUL AUG SEP OCT NOV DEC: CALENDAR MONTH

(SIMULATIONS, 1962; ACTUAL, NOV 1978-OCT 1972)

Figure 27. Comparison of actual and predicted heat pump and service hot

water input at the NCFOB using "as-operated" simulation data

52

GJ/MONTH

GJ/MONTH
10

KWH/MONTH

10

BTU/MONTH

80.0

80.0

70.0

60.0

50.0

40.0

30.0

20.0

10.0

. . . . . . . _ ^ , . , . _ _ _ 0.0 JAN MAR MAY JUL SEP NOV MAY JUL ' SEP NOV

. CALENDAR MONTH

(SIMULATIONS, 1962; ACTUAL, NOV 1978-OCT 1979';

70.0 -

60.0 —

50.0 -

40.0 —

30.0 -

20.0

10.0 -

0.0

Simulated

Measured

FUEL OIL FOR

ABSORPTION CHILLER

ELECTRIC CHILLER INPUT

Figure 28. Comparison of actual and predicted energy to central chillers

at the NCFOB using " as - opera ted " simulation data

CALENDAR MONTH

(SIMULATIONS, 1962; ACTUAL, NOU 78-OCT 79)

Figure 29. Comparison of actual and predicted 1 i ghti ng-mi seel 1 aneous and

operating energy at the NCFOB using "as-operated" simulation

data

53

GJ/MONTH
av3A-z ju/nia £ oi

o

o

o O o o o o q o

o d o d o d o d

cn 00 to m 1-0 CM q

o

o

d

o q q o o O o q o q o

d d o d d d d d d d d

o cn 00 N CD in CM T—

av3A-z h/rn

54

DESIGN

ALTER.

AS-DESIGNED

AS-DES/SOLAR

MODIFIED

AS-OPERATED

ACTUAL

Figure

30.

Energy

use

components

and

total

energy

use

per

year

at

the

NCFOB

using

simulation

results

and

measured

data

from

September

1978

to

1979
'ft?

NBS-1 1 4A (REV. 9-78)

U.S. DEPT. OF COMM.

BIBLIOGRAPHIC DATA

SHEET

1. PUBLICATION OR REPORT NO. NBSIR 80-2093

2. Gov't Accession No. 3. Recipient's Accession No.

'

4. TITLE AND SUBTITLE

ANALYSIS OF COMPUTER-SIMULATED THERMAL PERFORMANCE

OF THE NORRIS COTTON FEDERAL OFFICE BUILDING

•

5. Publication Date November 1980

6. Performing Organization Code

742.02

j 7. AUTHOR(S)

William B. May, Jr. and Lawrence G. SpdeTvjexgel

8. Performing Organ. Report No.

9. PERFORMING ORGANIZATION NAME AND ADDRESS

NATIONAL BUREAU OF STANDARDS

DEPARTMENT OF COMMERCE

WASHINGTON, DC 20234

10. Project/Task/Work Unit No. 742 2411

11. Contract/Grant No.

12. SPONSORING ORGANIZATION NAME AND COMPLETE ADDRESS (Street, City, State. ZIP)

Buildings Division

Office of the Assistant Secretary for Conservation & Solar

Applications

Department of Energy, Washington, D.C. 20545

13. Type of Report & Period Covered

Final

14. Sponsoring Agency Code

15. SUPPLEMENTARY NOTES

[2] Document describes a computer program; SF-185, FIPS Software Summary, is attached.

16. ABSTRACT (A 200-word or less factual summary of most significant information. If document includes a significant bibliography or

literature survey, mention it here.)

Five computer-based simulations of the Norris Cotton Federal Office Building (NCFOB)

in Manchester, New Hampshire, were performed using the Ross Meriwether Energy Systems

Analysis Program. The NCFOB is a medium-size office building, occupied in September,

1976, designed to serve as a demonstration of and feasibility test for energy-conserving

building features. The simulations included two simulations in accordance with the

original design—with and without a solar system; a simulation of the building as actually

operated; a simulation of the building with modifications to actual operation; and a simulation of an alternative building design. Results of the five simulations are compared

with each other and with actual measured data at several levels of detail, including

total energy consumption, consumption by fuel type, and heating and cooling requirements.

Good agreement between the simulation and actual data is demonstrated, and consequences

of design features are discussed.

17. KEY WORDS (six to twelve entries; alphabetical order; capitalize only the first letter of the first key word unless a proper name;

separated by semicolons)

Building models; building performance data; computer simulations, building; energy

conservation in commercial buildings; heat pumps; validation of computer models,

buildings

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