CH-01.pdf

Jan F. Kreider “Introduction to the Buildings Sector”

Handbook of Heating, Ventilation, and Air Conditioning

Ed. Jan F. Kreider

Boca Raton, CRC Press LLC. 2001

Introduction to the

Buildings Sector

1.1 Energy Use Patterns in Buildings in the U.S

Jan F. Kreider

Commercial Buildings • Industrial Processes

and Buildings • Residential Buildings

Kreider

Associates, LLC

1.2 What Follows

Introduction

Buildings account for the largest sector of the U.S. economy. Construction, operation, and investment in

buildings are industries to which every person is exposed daily. One of the major expenditures in the life

cycle of a building is the operation of its space conditioning systems — heating, ventilation, and air

conditioning (HVAC) — dwarﬁng the initial cost of these systems or of even the entire building itself.

Therefore, it is important to use the best, most current knowledge from the design phase onward through

the building life cycle to minimize cost while maintaining a productive and comfortable indoor environment.

HVAC systems are energy conversion systems — electricity is converted to cooling or natural gas is

converted to heat. Because it is important to understand from the outset the nature of energy demands

placed on HVAC systems, that subject is discussed immediately below. The chapter closes with a short

outline of the rest of the book with its coverage of HVAC design, commissioning, operation, and

problem diagnosis.

1.1 Energy Use Patterns in Buildings in the U.S.

It is instructive to examine building energy use, sector by sector, to get an idea of the numbers and to

clarify the differences between large and small buildings as well as between industrial and ofﬁce buildings.

The next several sections discuss each.

1.1.1 Commercial Buildings

In 1997, there were 4.6 million commercial buildings, occupying 58.8 billion square feet of ﬂoor space

(PNNL, 1997). These buildings consumed 126.5 thousand Btu of delivered energy use (or 252.4 thousand

Btu of primary energy) per square foot of space. Figure 1.1 shows that of the four main census regions,

the South contains the highest percentage of commercial buildings, 38%, and the Northeast contains the

least, 16%.

Commercial Buildings Disaggregated by Floor Space

Sixty percent of U.S. commercial buildings range between 5,000 and 100,000 square feet, 82% range

between 1,000 and 200,000 square feet. The size class with the largest membership is the 10,000–25,000

square foot range. Table 1.1 shows the size distribution in the U.S.

Total Number of Buildings: 4.6 Million

Total Floor space: 58.8 Billion Square Feet

25 24

NORTHEAST

MIDWEST

21 20

WEST

Percent of Buildings

Percent of Floor space

SOUTH

FIGURE 1.1

Commercial building geographical distribution. (From the

1995 Commercial Buildings Energy Con-

sumption Survey

TABLE 1.1

Size Distribution of U.S. Commercial Building Space

Commercial Building Size as of 1995

(percent of total ﬂoor space)

Square Foot Range

Percent

1,001 to 5,000

10.80%

5,001 to 10,000

12.80%

10,001 to 25,000

19.80%

25,001 to 50,000

13.10%

50,001 to 100,000

13.60%

100,001 to 200,000

11.50%

200,001 to 500,000

9.40%

Over 500,000

9.00%

100%

Commercial Energy Consumption and Intensity by Square Footage (1995)

Total consumption is fairly evenly distributed across building size categories; only the largest size

category (over 500,000 square feet per building) showed a signiﬁcant difference from any of the other

categories. Buildings in the 10,001–25,000 square feet per building category have the lowest energy

intensity of all categories.

Commercial Buildings Disaggregated by Building Type and Floor Space

The usage to which building space is put is a key inﬂuence on the type and amount of energy needed.

Of the total square footage of commercial ofﬁce space, 67% is used for mercantile and service, ofﬁces,

warehouses and storage places, or educational facilities. The average square footage for all building types

ranges between 1,001 and 25,000 square feet. The largest building types, between 20,000 and 25,000 square

feet, are lodging and health care facilities. Medium sized building types, between 10,000 and 20,000

square feet, are public order and safety, ofﬁces, mercantile and service, and public assembly. Small building

types, less than 10,000 square feet, include warehouse and storage facilities, education facilities, food

service, and sales. Table 1.2 summarizes sector sizes and typical ﬂoor sizes.

Commercial End-Use Consumption

Mercantile and service, and ofﬁce buildings consume almost 40% of total commercial energy, in terms

of Btu per square foot. Education and health care facilities, lodging, and public assemblies also consume

Intensity Consumption

Over 500,000

200,001 to 500,000

100,001 to 200,000

50,001 to 100,000

25,001 to 50,000

10,001 to 25,000

5,001 to 10,000

1,001 to 5,000

120100 80 60 40 20 0 200 400 600 800

1,000 Btu/sq. ft.

Trillion Btu

FIGURE 1.2

Energy consumption and usage intensity for eight commercial building size categories. (From the

1995

Commercial Buildings Energy Consumption Survey.

)

TABLE 1.2

Commercial Building Sector Size and Typical Floor Area

1995 Average and Percent of Commercial Building by Principal Building Type (1)

Building Type

Floor Space

(%)

Average

Floor Space/Building

(SF)

Mercantile and Service

22%

11260

Ofﬁce

18%

12870

Warehouse/Storage

14%

6670

Education

13%

1770

Public Assembly

12110

Lodging

22900

Health Care

22220

Food Service

4750

Food Sales

4690

Public Order and Safety

14610

Vacant (2)

18480

Other

—

a large amount of energy, making up another 40% of total commercial energy consumption. Table 1.3

summarizes the energy use intensities for the 12 most important categories.

End Use Consumption by Task

Finally, one must know the end use category — space heating, cooling, water heating, and lighting. Space

heating and lighting are generally the largest energy loads in commercial ofﬁce buildings. In 1995, energy

consumed for lighting accounted for 31% of commercial energy loads. Space heating consumed 22%, and

space cooling consumed 15% of commercial energy loads. On average, water heating is not high at 7%;

actual load varies greatly according to building category. Health care facilities and lodging are unique in

their high water heating loads; however, ofﬁces, mercantile and service facilities, and warehouses require

minimal hot water. Figure 1.3 shows the distribution of energy end use by sector for 1995. Another way of

considering the data in Figure 1.3 is to consider the end uses aggregated over all buildings but further

disaggregated over the nine main end uses in commercial buildings. Figure 1.4 shows the data in this way.

Commercial Energy Consumption and Intensity by Principal Building Activity (1995)

Commercial buildings were distributed unevenly across the categories of most major building charac-

teristics. For example, in 1995, 63.0 percent of all buildings and 67.1 percent of all ﬂoor space were in

TABLE 1.3

End Use Consumption Intensity by Building Category

1995 Commercial Delivered End-Use Energy Consumption Intensities by Principal Building Type

(1000 Btu/SF)

Building Type

Space

Heating

Space

Cooling

Wa t e r

Heating

Lighting

Total

Percent of

Total

Consumption

Ofﬁce

24.3

9.1

8.7

28.1

97.2

19%

Mercantile and Service

30.6

5.8

5.1

23.4

76.4

18%

Education

32.8

4.8

17.4

15.8

79.3

12%

Health Care

55.2

9.9

39.3

240.4

11%

Lodging

22.7

8.1

51.4

23.2

127.3

Public Assembly

53.6

6.3

17.5

21.9

113.7

Food Service

30.9

19.5

27.5

245.5

Warehouse and Storage

15.7

0.9

9.8

38.3

Food Sales

27.5

13.4

9.1

33.9

213.5

Vacant

1.4

5.5

4.5

30.1

Public Order and Safety

27.8

6.1

23.4

16.4

97.2

Other

59.6

9.3

15.3

26.7

172.2

All Buildings

13.8

20.4

90.5

100%

Notes:

Parking garages and commercial buildings on multibuilding manufacturing facilities are excluded from CBECS 1995.

Includes all end-uses.

Includes vacant and religious worship.

Includes mixed uses, hangars, crematoriums, laboratories, and other.

Source:

EIA, Commercial Building Energy Consumption and Expenditures 1995, April 1998, Table EU-2, p. 311.

four building types: ofﬁce, mercantile and service, education, and warehouse. Total energy consumption

also varied by building type. Three of these — health care, food service, and food sales — had higher

energy intensity than the average of 90.5 thousand Btu per square foot for all commercial buildings.

Figure 1.5 shows the 13 principal building types and their total consumption and intensity.

Commercial Building Energy Consumption by Fuel Type

Five principal energy types are used in U.S. commercial buildings:

Natural gas

Fuel oil

Liqueﬁed petroleum gas (LPG)

Other and renewables

On-site electric

Table 1.4 s hows the relation between end use type in Figure 1.5 and the corresponding energy sources.

Space heating, lighting, and water heating are the three largest consumers of energy. Natural gas and

electricity directly competed in three of the major end uses — space heating, water heating, and cooking.

In each of these three, natural gas consumption greatly exceeded electricity consumption.

Table 1.5 shows expected commercial sector energy use growth in the U.S.

1.1.2 Industrial Processes and Buildings

The industrial sector consists of more than three million establishments engaged in manufacturing,

agriculture, forestry, ﬁshing, construction, and mining. In 1997, these buildings occupied 15.5 billion

square feet of ﬂoor space and 37% (34.8 quadrillion Btus) of total U.S. primary energy consumption.

After the transportation sector, the manufacturing sector consumes the most energy in the U.S. Of

the 37% of primary energy consumption in the industrial sector in 1997, 33% was used for manufacturing

purposes and 4% was used for nonmanufacturing purposes. Thus, manufacturing establishments con-

sume the majority of the energy in the industrial sector even though they are far outnumbered by

nonmanufacturing establishments. Because there is a lack of information regarding nonmanufacturing

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