THE ENERGY PERFORMANCE OF NEW ZEALAND'S BUILT ENVIRONMENT

THE ENERGY PERFORMANCE OF NEW ZEALAND'S BUILT ENVIRONMENT

G, Baird, M.R. Donn, Chan S.A. & F. Pool

School of Architecture Victoria University of Wellington Private Bag, Wellington, New Zealand

ABSTRACT

An indication is given of New Zealand's response to the energy problems of the early '70s, in particular the lack of basic data on energy use in the built environment. An outline is presented of the results of the major field studies and comparisons made with some North American work. The paper concludes with a brief description of the direction of future research in this area.

INTRODUCTION In most westernised countries, considerable quantities of energy are consumed within the built environment. New Zealand is no exception to this. With the domestic sector using 16 percent of the country's annual energy consumption, the commercial sector using 11 percent and an industrial sector which consumes over 35 percent all told (l) it can be seen that at least one-third of the energy use may be directly attributed to the built environment. Whilst the country's total consumption, at around 300 PJ per annum, is compara­ tively small, and many of the fuels are indigenous, the energy problems of the early '70s made a profound impact. From the point of view of the built environ­ ment, one of the more important measures that resulted was the setting up of the New Zealand Energy Research and Development Committee (NZER&DC). This body quickly established that among its top priorities was the determination of

613

current energy demand (2). As part of the research programme stemming from these priorities, the Committee undertook the sponsorship of a number of projects aimed at quantifying energy use in the transport, industrial, domestic and commercial sectors. Some groups, such as the New Zealand Electricity Department, had already become involved in studies of the domestic sector; others, such as the Ministry of Energy were to fund investigations of the commercial sector. What follows is an outline of some of the findings of the major field studies of New Zealand's built environment that have taken place during the last few years. The geographical areas covered

In these studies are indicated on Figure 1.

[THE AUCKLAND [REGION STUDY (700)

T H E WELLINGTON REGIONAL SCHOOLS STUDY (250)

100

200 k m

FIG 1 Location of Field Surveys of Energy Consumption 614

THE WELLINGTON CENTRAL BUSINESS DISTRICT The Victoria University of Wellington School of Architecture started investi­ gating energy use in the Wellington Central Business District (CBD) In 1977. The alms of the project were to elicit hard data on energy use within the CBD and to establish the factors upon which energy consumption depends ( 3 ) .

Commercial Sector Definitions and Overall

Consumption

From the start the study attempted to break the widely disparate activities encompassed by the label 'commercial' Into more specialised activity-related groups. The hypothesis under test was that the energy consumption pattern of a particular activity would be far more dependent on the activity Itself than on the building housing It. Thus, the commercial sector was sub-divided Into seventeen sub-categories within which the various physical parameters could be studied. The total energy consumption In the Wellington CBD was Just over 900 TJ In 1978. Of the sub-categories selected, six were significant CBD consumers using almost 90 percent of the total energy. These were: Accommodation ( 5 . 2 ^ ) Consultants ( ^ . 2 ^ ) , Technical Services ( 1 0 . 9 ^ ) , Administration ( 4 2 . U ) , Retail Trading (]β.5%) and Wholesale Trading ( 9 . 0 ^ ) . On the national scale, almost 3 . 6 percent of New Zealand's total commercial sector energy consumption occurs within the Central Business District of Wei 1Ington.

Energy Use by Particular Activities As an example, banks and consulting engineers' office premises were compared and found to consume energy that was far more dependent on the type of activity (whether it was banking or engineering) and the building HVAC system than on any other factor investigated. Banks and engineers' offices In similarly conditioned buildings consumed greatly different amounts of energy per unit floor area, ^ithin the banking activity itself, average energy use ranged from 655 MJ/g /yr for naturally ventilated premises with local electric heating to 1061 MJ/m /yr for those with a centralised air conditioning system. Restaurants and saunas were also examined. It was found that their intensity of energy use (Area Energy Use J_ndex) was much higher thag for banks and engineers' o f f i c e s and that their range (500 to 4000 MJ/m /yr for saunas; 800 to A2OO MJ/m /yr for restaurants) was considerably wider.

Energy Use in Individual

Buildings

As far as individual buildings were concerned, the study uncovered O f f i c e blocks' with AEUI's ranging from under 300 to over 3000 MJ/m /yr. After coming to terms with the act Ivlty/energy Interaction, other likely factors will be examined to see if they might account for this variation. Where the existing data allowed, a preliminary exploration of the energy use in individual buildings, and by individual tenants of these buildings, has been attempted. Table 1 presents the results from all the office buildings on one side of one street In Wellington. 615

TABLE 1 Energy Use in Individual Office Buildings, Wellington

BLDG NO

FLOOR AR|A m

CENTRAL AEUl (MJ/m /yr) Oil

Gas

-

-

TENANT^ AEUl (MJ/mVyr) Elec

Mean

Range

142

139

32-280

34

312

-

48

207

O'ALL AEUl

HVAC TYPE* Htg

Vtg

281

L

Ν

209-449

346

L

Ν

336

62-689

384

L

Μ

59

138

29-335

411

C

Ν

1

2250

2

4230

3

4180

k

24740

7

5

5080

307

-

188

NA

NA

495

C

Ν

6

3550

465

13

210

NA

NA

688

c

Ν

7

3770

422

-

80

153

41-279

615

c

Ν

8

2160

319

-

342

NA

NA

661

c

Μ

9

9360

-

477

470

NA

NA

947

10

23200

408

4

299

NA

NA

711

11

7490

61

1232

1444

NA

NA

2737

F

Α

c

C Μ

F

Α

C

* Principle of heating and ventilating L ... Local Heating ^ Ν ... Natural Ventilation C ... Central Heating Μ ... Mechanical Ventilation F A C ... Full air conditioning

While the overall AEUI's are too few for conclusive pronouncements to be made, it will be of interest to note that the three lowest values are for 'all electric' buildings. The lowest values are for buildings with local heating and natural ventilation; the mid range for those with central heating and natural ventilation; while the highest values are found In those buildings with mechanical ventilation or full air conditioning systems. These are expected to be useful lines of enquiry. As far as individual tenants of a single building were concerned, variations of the order of 10:1 were found in most cases where individual meters were fitted.

616

Figure 2 illustrates the AEUI's for each tenant for the five buildings examined in this way. The horizontal axis is scaled to represent floor area. The bottom "layer(s)" represent centrally metered energy, while the individual "bars" represent tenant metered energy (electricity in all the cases represented). In each case the horizontal scale represents the area occupied by tenant or by building, as appropriate; the vertical scale the corresponding AEUl. Thus the enclosed area is representative of the total energy used in each building. In addition, energy end-use can be inferred from Figure 2 .

AEUl MJ/m2/yr Tsor

500

25*

OL AEUl

BLDG 1 - 2250m2 BLDG 2 - 4230m2 (LN) (LN)

BL0G3 -4180 m2 (LM)

BLDG7-3770m2 (CN)

MJ/m2/yr

50o|250h

S L O G 4 - 24.740 m2 (CN) KEY:

•ELECTRICITY

EJOIL

OGAS

FIG 2 Energy Use in Five Office Buildings with Partial Tenant Metering

ANNUAL MONITORING OF WELLINGTON'S CBD The first stage of this study compared two years' energy use in the Wellington CBD ( 4 ) . It was found that consumption in 1978 was down by 5 percent on that of 1977. However, 1978 was 12 percent warmer than 1977, as indicated by degree day totals, so it seems unlikely that a permanent reduction was achieved. Figure 3 shows the modal split by fuel type for the two years.

617

ENERGY TJ 700

600

500

400

300

200

100

'

Individual

I-

'77 78 ELECTRICITY

77

-78

Μ

«77 «78 GAS OIL FIG 3 Modal Split of Energy Supplied to the Wellington CBD : Comparison of 1977 with 1978

Consumers

For individual consumers it was found that electricity and gas consumption was dependent on the monthly average of weekday hourly temperatures. It would also appear that a number of large consumers operate essentially independent of outside temperature. Overall, these large consumers dominate energy use in the CBD. Percentage energy reductions between 1978 and 1977 varied not only between large and small consumers, but also depended considerably on the predominant activity in the buildings. Some activity categories, such as consultants, showed reductions of 23 percent. This figure may well reflect the increasing cost of energy and opportunity for control of energy use in this group's premises. Other activities such as public and private administration, retail and wholesale trading, and restaurants show very little change. It must be recognised that the activity housed will affect the consumers' reaction to conservation measures. Oil Deliverles - 1977,

'78 & '79

There were 128 buildings in the Wellington CBD for which oil delivery information for the years 1977, 1978 and 1979 was available. The deliveries for these three years were 4 . 5 6 , 4 . 4 5 and 3-39 million litres respectively,

618

these figures indicate reductions of 3 percent and 2k percent between the successive years. An oil rationing scheme, that restricted deliveries to 80 percent of that for 1978, came into effect for commercial buildings in 1979. it is interesting that the sample of 128 buildings shows this target to have been met. For individual buildings, annual oil deliveries vary considerably between the three years. However, in 1979, the randomness of annual oil deliveries >is noticeably less. It is believed this indicates that a more conscious management effort has been applied to the oil supply problem. It was found that the most dramatic reductions occurred in the twelve buildings using greater than 9 0 , 0 0 0 litres/year, and these dominated the average oil delivery reduction of 2k per cent.

THE GREATER AUCKLAND STUDY This study consisted of a detailed field survey of 707 commercial buildings in the Greater Auckland Region ( 5 ) . These were selected to be a representative cross-section and amounted to a S-k percent sample of all the commercial buildings in that area. As in the Wellington CBD study, the Auckland researchers maintained the separation between building and tenant energy use in the design of their survey, in order to allow freedom for future analyses. They too employed use categories, though these tended to be broader than for the Wellington study. The total floor space of each sub-category was known from Valuation Department records. Thus the ratio of these areas to that sampled for a given use cate­ gory, was taken as the multiplier to extrapolate for the corresponding total energy consumption. Table 2 Indicates the extrapolated totals and modal splits of the fuels used, together with the total area of each use category from a building (as opposed to a tenant) viewpoint. Table 2 also lists the total (le, extrapolated) capacity of the energy consuming equipment Installed in the buildings of each use category. The wide range of energy use per unit capacity Is well worth noting here. The extremes are represented by educational uses on the one hand (mainly schools) and health and security (mainly hospitals) and commercial accommodation on the other. This seems to confirm the Importance of hours of occupancy as an important factor In assessing energy performance. One of the study's main conclusions was that use category is one of the most important determinants of energy use. This is demonstrated on Figure k which shows the average energy use per square metre per year for nine Mse categories. Analysis of the large amount of survey data is continuing, making use of the Automatic Interaction Detection method.

619

TABLE 2 Total Floor Area, Extrapolated Energy Consumption and Installed Equipment Capacity for the Auckland Commercial Sector

MAJOR USE CATEGORY

TOTAL FLOOR SPACE (m )

ENERGY USE Coal

Oil

Gas

EQUIP­ MENT CAPA­ Elec Total CITY (MW)

(TJ/yr)

ENERGY USE PER UNIT CAP. TiMWVr

Comme rc i a1 Offices

470,000

-

90

-

300

390

51

7.6

Retail and Services

480,000

-

120

20

220

360

73

4.9

Educational

900,000

85

30

-

60

175

84

2.1

Health and Securi ty

430,000

450

30

35

220

735

67.5

10.9

Recreational

240,000

-

30

5

40

75

16

4.7

Commercial Accommodat ion

480,000

-

110

40

110

260

29

9.0

Religious and Communi ty

520,000

-

-

10

90

100

30

3.3

1,790,000

-

30

70

435

535

83

6.4

570,000

-

-

15

50

65

22

3.0

Multi-Use Commercial

Mi seellaneous

620

AVERAGE AEUl MJ/m2/yr 2OO0L

1500

1000

500μ

OFFICES

SCHOOLS

RETAIL & SERV! C E S

Τ

RECREATION RELIGIOUS Z\ COMMUNITY

HEALTH & SECURITY

COMMERCIAL ACCOM' N.

MISC.

MULTI-USE COMMERCIAL

FIG k Average AEUI's for the Nine Activity Categories of the Auckland Commercial Sector

THE WELLINGTON REGION SCHOOLS A pilot study of the energy use in sixteen Wellington primary schools (6) was carried out in 1978. The results indicated a wide range in the annual energy consumption per unit area. The study was later extended to include all 247 of the Wellington Education Board's schools. They consisted mainly of light-weight siggle storey timberframed buildings and varied in size from about 50 to 3000m in area ( 1 - 2 5 classrooms).

Energy Consumption Data The energy consumption data was extracted from the electricity, gas, oil, coal and wood supply invoices which the Education Board systematically filed as part of their accounting system. Thus, although no deliberate attempt had been made to monitor the energy consumption, the amount used by each school could be deduced from the file records - given sufficient time and patience. Area Energy Use Indices (AEUI's) were calculated for the 1978 calendar year which is roughly equivalent to the school year in the southern hemisphere.

621

A preliminary analysis of the AEUI's based on building boundary energy use, indicated variations from about 50 to 1,250 MJ/m /yr, a ratio of 25. However, as shown2Ín Figure 5, the majority of the schools have AEUI's within the 100500 MJ/m /yr range. At the time of writing, no obvious reasons have emerged for this wide variation. Both large and small schools are included at2the extremities of the range (ie, less than 100, and greater than 500 MJ/m /yr) and all of the fuel types are represented. A further breakdown of the energy consumed each month for some selected schools showed that space heating consumed a major proportion of the total.

FREQUENCY (No. of S c h o o l s )

251-

20

LT

15

10

I Í I I I 1 I I I I I I I 250 500 750 AEUl

1000

1250

(MJ/m2/yr)

FIG 5 Frequency Distribution of AEUl Values for the Wellington Region Primary Schools

Case Study Analysis Te Aro is an example of ope of the older Wellington City schools. It has 11 classrooms totalling 792m and a roll of about 190 pupils. The buildings are single storey timber-framed classrooms, heated by gas and naturally ventilated. It has a fairly low AEUl, at about 120 MJ/m /yr, due possibly to its very good solar orientation.

622

When its energy use data were analysed in the manner suggested (7) by the British Property Services Agency (PSA) excellent correlation was obtained between average outside temperature and heating energy consumption. The coefficient of the 'performance line' was 0.95, a correlation sufficiently encouraging to warrant further tests of the PSA method. The performance line is shown graphically on Figure 6.

HEATING ENERGY CONSUMPTION MJ/day Τ Ε ARO SCHOOL WELLINGTON (Sept. 1977-Oct. 1976)

1000

P S A PERFORMANCE LINE (r= .0-95)

500

10

15

20

MEAN OUTSIDE TEMPERATURE FIG 6 Plot of Heating Energy Consumption vs. Mean Outside Temperature

(Each data point normally represents the average daily consumption and outside temperature over a period of around 20 working days - this corresponds to the interval between successive readings of the gas meters.)

SOME COMPARISON WITH INTERNATIONAL DATA These studies and similar ones in other parts of the globe are not yet fully completed. However it is instructive to attempt comparisons, even with the sparse amount of statistical data so far available.

623

As far as offices are concerned, two New York studies provide tiie most informa­ tion. Lawrence's study Í 8 ) of 86 large office buildings produced an average AEUl of about 2 , 4 0 0 MJ/m /yr. However, the more representative sample of the Syska and Hennessy/Tishman Research Corporation (9) study gave a rather lower figure, at around 1,300 MJ/m /yr. The comparable figure for the Auckland sample came out at 840 MJ/m /yr, while for Wellington the data of Table 1 average out around 750 MJ/m /yr. It would be foolhardy to speculate on the precise nature of the reasons for the differences found, but it seems reasonable that the more severe New York climate (wiηter/summer 99^ design range - 1 2 C / + 3 7 C) would result in higher rates of energv consumption relative to those in the North Island of New Zealand with a +3 C to 24 C range. The schools' data exhibits a similar pattern. Those in New York (10) and Ottawa (11) have AEl/l's around 1,450 MJ/m /yr. The Wellington schools average out around 300 MJ/m /yr while the Auckland sample gives a figure of 220 MJ/m /yr. In this case, both climatic differences and method of thermal environmental control are probably involved. Most New Zealand schools tend to be naturally ventilated, while in Ottawa and New York, a large number would be mechanically ven ti la ted. In the domestic sector^ the data from the Twin Rivers, New Jersey field survey (12) makes interesting comparison with that from New Zealand ( 1 3 ) . The annual average energy use of 248 two-storey, gas-heated, townhouses at Twin Rivers was 142 GJ/year (84 GJ of gas, 16,200 kWh of electricity). The roughly comparable figure for New Zealand, based on 123 all electric single family dwellings, was 43 GJ (approximately 12,000 k W h ) , of which about 40 percent was for heating. It is to be hoped that more data of this type will become available thus allow­ ing better international comparisons. At the present time, the amount of information is pitifully small, and a common basis for comparison is desperately needed. If w e are to learn from each other then more effort is needed in both areas.

CONCLUSIONS AND FUTURE DEVELOPMENTS There seems little doubt that much more field work of the type described is essential. World-wide, there is an almost total absence of useful data on the energy related performance of existing buildings. In retrospect, it seems incredible that such simple feedback is just not available in a form useful to building users, operators and designers. The benefits of such feedback would include: »

A better understanding of the effects of design, operational and management factors on building energy use, based on a large body of feedback from a wide range of existing buildings.

5^

The development of realistic operational energy targets for existing build­ ings and design energy targets for new ones.

"

The establishment of a proven set of energy consumption prediction methods.

"

Ultimately, a reduction in energy use in buildings together with a signifi­ cant improvement in the energy performance of the built environment. 624

As far as the New Zealand scene is concerned the studies described earlier are continuing and the full analysis will reveal many more interesting facts concerning energy use in buildings. In the commercial sector, continued monitoring of the Wellington CBD will demonstrate any variability in consumption with time and the effects of fiscal and other controls. A new and detailed study of the energy end-use and perform­ ance of selected buildings is expected to reveal many interesting facets of the problem. In addition, the energy use in the Christchurch commercial sector is to be the subject of a major field survey, similar to that conducted in Auckland. Institutional buildings are to be the subject of further investigation too. Energy conservation in government buildings is being studied with the aim of producing practical guidelines for energy management and energy auditing. The study of primary schools has already been extended to three further areas of the country and the results will give an indication of regional differences. In addition it is anticipated that a repeat study of energy use in the domestic sector will be undertaken in the near future. Thus New Zealand's energy conservation efforts and priorities in this sector will be firmly based on a knowledge of the actual patterns of energy use. It is anticipated that real knowledge of these patterns will lead to real and lasting improvements in the energy performance of New Zealand's built environment.

ACKNOWLEDGEMENTS The authors would like to thank the New Zealand Energy Research and Development Committee, the New Zealand Ministry of Energy and the Wellington Education Board for their assistance with the studies described; Rod Shaw and Vic Jowsey of Beca Carter Hollings and Ferner, Auckland, for permission to use data from their investigation of the Auckland commercial sector; Kay Paget for typing and RoDin Cresswel1 for graphics.

CONVERSION FACTORS IMJ (Mega Joule) = 10 J (Joules)

IMJ = 9 . 4 8 χ 10

ITJ (Tera Joule) = lO^^J

IMJ = 0.948 MBtu

IPJ (Peta Joule) = lO^^J

Im^ = 10.7b ft^

Btu

IMJ/mVyr = 88 Btu/ft^/yr

625

REFERENCES

1.

"Goals and Guidelines - an Energy Strategy for New Zealand" Ministry of Energy, Wellington, New Zealand (May 1978)

2.

"NZERSDC Newsletter No 4" New Zealand Energy Research and Committee, Auckland, New Zealand (April 1976)

3.

G. Baird, M.R, Donn, W.A. Porteous & G, Runeson "Energy Demand in the Wellington Central Business District - Stage 1 Report" New Zealand Energy Research and Development Committee, Auckland, New Zealand, Publication P2 (October 1978)

4.

M.R. Donn and F. Pool "Annual Building Energy Use Survey for the Wellington Central District - Data and Methodology for 1977 and 1978" Ministry of Energy, Wellington, New Zealand (May I98O)

Development

Business

5.

Beca Carter Hollings and Ferner in association with R.A. Shaw "Greater Auckland Commercial Sector - Energy Analysis" New Zealand Energy Research and Development Committee, Auckland, New Zealand, Publ ication 45 (1979)

6.

Energy in Architecture Class of 1978 "Energy Consumption in Wellington Primary Schools" New Zealand Energy Research and Development Committee, Auckland, New Zealand, Publication P I 6 (May 1979)

7.

A.W. Loten "Energy Conservation in the Property Services Agency" Building Services Engineer, Vol 4 3 , ρ 83 (Augubt 1975) and personal communication from H. Dixon (May 1978)

8.

C.W. Lawrence "Energy Use Patterns in Large Commercial Buildings" Department of Conferences, Continuing Education and Extension, University of Minnesota, USA (May 1973)

9.

"Energy Conservation in Existing Office Buildings : Phase 1 Volume 1" Syska and Hennessy/Tishman Research Corporation, New York (ERDA Contract No EY-76-C-O2-2799-OOO) (June 1977)

10.

R.G. Stein et al "Research, Design, Construction and Evaluation of a Low Energy Utilisation School - Research Phase 1" NSF/RANN Report 74-117 (NTIS Accession No 8 PB242 217) New York (1974)

11.

M.P. Graham and A.A. Bourassa "Variation in Energy Consumption of School Buildings" _m. ^Proceedings of the First Canadian Building Congress : Energy and Building' Toronto, Canada (1976)

12.

R.H. Socolaw "The Twin Rivers Program on Energy Conservation Conclus ions" Energy and Buildings, Vol 1, p234 (April 1978) 626

in Housing

: Highlights and

13.

P.W. Blakeley and D.C. Cook "Household Energy Consumption in New Zealand" Ninth World Energy Conference, Detroit (September

627

1974)