energy efficiency and energy savings in japanese residential buildings—research methodology and...

Energy efficiency and energy savings in Japanese residential

buildings—research methodology and surveyed results

Luis Lopes a,*, Shuichi Hokoi a, Hisashi Miura a, Kondo Shuhei b

a Department of Architecture and Environmental Design, Faculty of Engineering, Kyoto University,

Yoshida-Honmachi, Sakyo-ku, 606-8501 Kyoto, Japanb Energy Use R&D Center, Kansai Electric Power Company Inc., 661-0974 Amagasaki, Japan

Received 15 June 2004; received in revised form 15 September 2004; accepted 15 September 2004

Abstract

Worldwide energy consumption has risen 30% in the last 25 years. Fossil fuels exploitation is causing depletion of resources and serious

environmental problems. Energy efficiency improvement and energy savings are important targets to be achieved on every society as a whole

and in residential buildings in particular. In this article, results of a survey and questionnaire on energy consumption and thermal environment

held in Kansai area, Japan are reported. Energy savings potential was analyzed for the surveyed 13 houses focusing on certain electrical

appliances e.g. TV, rice cooker and refrigerator. Residents’ environmental awareness towards energy consumption was clarified through

questionnaire. An energy information session towards residents was held, and the resulting changes in lifestyle and their implications on

energy consumption were evaluated.

# 2004 Elsevier B.V. All rights reserved.

Keywords: Energy savings; Energy efficiency; Residential buildings; Lifestyle

www.elsevier.com/locate/enbuild

Energy and Buildings 37 (2005) 698–706

1. Introduction

1.1. Energy consumption

Worldwide energy consumption has risen 30% in the last

25 years. Industrialized countries consume ca. four times

more than the world average. As economic growth is being

pursued in countries such as China, India and Brazil, the

energy consumption is expected to increase further. In this

scenario, improvements in energy efficiency are regarded

as the guarantor of economic growth, without increasing the

energy consumption further.

In that context, the Japanese economy is the most energy

efficient in the industrialized world as can be seen in Fig. 1.

It has faced an urgent need for the improvement of its overall

efficiency at the time of oil shocks in 1970s. Energy savings

regulations for the industry were extremely important to

achieve that aim, which enabled the Japanese industry to

* Corresponding author. Tel.: +81 75 7534796.

E-mail addresses: [email protected] (L. Lopes),

[email protected] (S. Hokoi).

0378-7788/$ – see front matter # 2004 Elsevier B.V. All rights reserved.

doi:10.1016/j.enbuild.2004.09.019

increase its output 40% by spending the same energy in 2001

as in 1973 [2].

On the other hand, the residential sector has shown an

opposite trend, thus, energy savings achieved at industry

level may be surpassed by the households spending.

Therefore, energy efficiency/savings in the residential sector

is strongly required in Japan. Moreover, a specific approach

will be necessary since it has specific problems, namely the

willingness of residents to achieve energy savings or not,

their environmental consciousness and their ability to

understand the close relationship between energy and

environmental issues.

1.2. Energy conservation programs and energy labeling

Since the first oil shock in 1973, several measures like

improving the building/equipment standards or marketing

solutions with higher energy efficiency have been taken

worldwide. In order to promote energy conservation and to

provide consumers with information about energy effi-

ciency, energy labels have been proposed. There are two

L. Lopes et al. / Energy and Buildings 37 (2005) 698–706 699

Fig. 1. GDP vs. energy consumption per capita [1].

Fig. 2. Japanese Energy savings label.

Fig. 3. Environment, Residents and Technology interrelationship: ‘3-star’

concept.

main types: endorsement labels, which simply identify

appliances that are particularly energy efficient (e.g. ‘Energy

Star’), and comparison labels, which provide information

that enables consumers to compare the energy efficiency of a

specific product with the rest of appliances within the same

category. Some examples of comparison labels are the

Australian ‘Energy Rating’, the US ‘Energy Guide’ and the

European ‘Energy label’. ‘Energy label’ is conceived for a

variety of electrical appliances, like refrigerators/freezers,

washing machines, dish washers and lamps.

In Japan, a specific energy conservation program was

introduced, the ‘Top-Runner Program’ [3]. Parallel to the

program, a voluntary energy-saving labeling system has also

been developed for five household appliances categories:

refrigerators, freezers, AC, TV and fluorescent lamps. The

label specifies the equipment’s energy-saving standard

achievement ratio as a percentage (e.g. refrigerator;

Fig. 2) thus helping consumers select products with high-

energy conservation performance.

1.3. Global environmental issues and awareness of

residents

In the 1970s, CFCs emitted to the atmosphere were found

to be destructing the ozone layer at an accelerated rate. After

years of research, an international agreement on the phase

out of substances that deplete the ozone layer, known as

‘Montreal Protocol’, was adopted in September 1987. After

implementation, CFCs production was reduced to one-tenth

in 10 years. In 1997, climatic changes related to the

emissions of the so-called greenhouse gases, led to a new

agreement on the reduction in emissions of greenhouse

gases, the Kyoto Protocol. Electricity production, mainly if

generated in thermal power plants, presents a significant

environmental burden. However, residents do not necessa-

rily associate the use of electricity to the pollution it stands

for, since there are no perceptible emissions when using

electricity in opposition to the emissions of their private cars.

Hence, awareness to the close link between environmental

problems and energy issues should be raised among

dwellers.

2. Research approach

When analyzing energy consumption in housing, several

factors are interrelated. In this research, a graphical way, the

‘3-star’ concept is proposed (Fig. 3). It presents three main

axes, representing the surrounding environment, resident’s

action and technology matters.

Axis 1 corresponds to the environment where a house is

built. The surrounding environment is very important since it

is possible to design a house that interacts better with its

surroundings by taking into account the natural air, water

and energy flows. The focus is put on achieving a suitable

thermal environment by using local resources, e.g. use of

locally available building materials, implementation of

heating and cooling passive strategies, hence reducing the

energy input needs. Axis 2 corresponds to occupants’

interaction with housing. The way people use the house can

have a significant influence on its energy consumption. Just

to mention a few examples: use of curtains to reduce heat

load, making use of natural ventilation, appliance usage

among others. The usage depends on the number of

dwellers, their income, age and even on their culture.

Economic issues and regulations regarding energy con-

sumption are aspects included in axis 2 since they influence

directly the residents’ way of spending energy at home.

Axis 3 corresponds to the technical features, that is, the

characteristics of the housing materials and of the equipment

installed. Improved characteristics mean that the input of

external work/energy will be smaller for the same service

L. Lopes et al. / Energy and Buildings 37 (2005) 698–706700

Fig. 4. Base scenario and improvement along axes 1 and 3.

provided. In this case are included the envelope building

materials (walls, insulation, windows) that influence indoor

environment and the performance of the equipments (stoves,

fans, TV, washing machine) installed at home.

These three axes are scaled from 0 to 1. Using this scale,

the household energy consumption can be given by the area

delimited by the values of each axis. To illustrate this

concept, an example will be given. Suppose that the cooling

load of a building is being evaluated. The base situation is

that the building receives direct solar radiation, leading to a

thermal condition out of comfort zone. Thus, many residents

will tend to use HVAC systems to cool it down. The

consumed energy corresponding to this situation is

represented by grey area in Fig. 4a.

Considering that there are trees and plants around the

house that shade it properly, total heat gains will be reduced

for the same typical day. In this case, an improvement along

axis 1 is registered so that A* becomes A** as in Fig. 4b.

Through this measure, total energy consumption decreases

for the same comfort level. On the other hand, an

improvement on the cooling device can be achieved (e.g.

HVAC or fan) either by regular maintenance or through

buying a device with better performance, then C* becomes

Table 1

Characteristics of surveyed houses

House Location Building year House type

A Nara 2000 Detached

B Kyoto 2000 Detached

C Osaka 1998 Detached

D Hyogo 2000 Detached

E Hyogo 2001 Detached

F Shiga 1990 Detached

G Osaka 1991 Detached

H Osaka 1984 Detached

I Nara 1999 Detached

J Nara 1997 Flat

K Nara 1995 Flat

L Nara 1996 Flat

M Osaka 2000 Flat

Note: Ad.—adults and Ch.—children.

C**. Since resident’s actions influence consumption on

three axes, resident’s awareness is a major concern.

Improvements for decreasing total energy consumption

in residential buildings can be introduced in any of three

axes. Thus, the strategy is towards the minimization of the

total energy consumption within the comfort limits, and the

way of achieving those energy savings along axes 1, 2 and 3.

The first step is to know the actual base scenario

accurately. For that purpose an extensive survey in

residential houses was performed.

3. Outline of research

The present research was performed under three main

approaches: survey, questionnaire and simulation of energy

savings potential.

3.1. Survey on energy consumption

The survey was carried out in Kansai area (Osaka, Kyoto,

Nara), Japan for 18 months starting in October 2002. This

survey aimed to characterize in detail the real energy

Area (m2) Number of floors Number of residents

143.6 2 2Ad. + 3Ch.

118.0 2 2Ad. + 2Ch.

111.5 2 2Ad. + 2Ch.

97.0 2 3Ad. + 2Ch.

158.8 2 2Ad. + 3Ch.

115.2 2 4Ad.

124.8 3 3Ad.

129.0 2 2Ad.

125.8 2 2Ad. + 2Ch.

125.7 1 (5th out 5) 2Ad. + 2Ch.

84.9 1 (2nd out 5) 2Ad. + 2Ch.

76.2 1 (2nd out11) 2Ad. + 2Ch.

88.4 1 (5th out 10) 2Ad.


Fig. 5. Measuring apparatus (left: electricity; right: gas).

Fig. 6. Measuring apparatus (WHM and temperature/humidity).

Fig. 8. Building envelope characteristics.

consumption and the thermal environment in 13 houses

throughout the different periods of the year (heating, cooling

season, etc.). The characteristics of the surveyed houses are

described in Table 1. With the collected data the energy

consumption baseline scenario defined in Fig. 4a was

determined.

In order to characterize the global energy consumption as

well as thermal environment, electricity data was registered

every minute, gas and kerosene every 5 min, while

temperature (air and water) and humidity were registered

every 15 min (Figs. 5–7).

The electricity data was collected in two ways. First,

measuring the current intensity of 13 channels in the main

breaker and second, installing Watt Hour Meter (WHM)

between certain appliances plug (refrigerator, washing

machine, etc.) and the consent (Figs. 5 and 6). Gas

consumption was measured using an apparatus that reads the

gas counter display visually.

Fig. 7. Measuring apparatus (kerosene).

Data concerning the house characteristics (insulation, air

tightness) was also collected, examining housing plans and

performing an air tightness test.

Analyzing the house characteristics and considering the

building year, a trend is visible in the reduction of the heat

transfer coefficient (Kglobal) and air tightness ratio (Aratio)

(Fig. 8).

3.2. Questionnaire and energy information session

To understand energy consumption issues, the lifestyle

pattern of each family should be analyzed. In order to

understand the way of living, two questionnaires were held

both concerning summer and winter conditions. Among

other issues, the following issues were asked: mechanical

versus natural ventilation, number of rooms using AC and

their set temperature, thermal comfort, taking shower versus

hot bath, usage of blinds and curtains, appliance usage and

energy costs. Complementary, after analyzing the data on

energy consumption for every family, an energy information

session was held in 11 of the 13 surveyed houses. It was held

toward the residents in person for about 30 min. It took place

in September–October 2003 after one year of survey had

been completed, so that the typical annual consumption

pattern could be characterized. The main aim of this session

was:

� P
resent residents with energy consumption data (monthly
consumption; comparison with other houses), so that they

can understand better how energy is spent, thus raising

awareness.

Examples of data presented to residents are shown in

Figs. 9 and 10.

In three of the houses where the energy data was shown,

there was little interest on the information given. In eight of

houses there was an active interest, thus a small discussion

was held focusing:

� L
ifestyle and daily life situations related to energy
consumption;


Fig. 9. Energy consumption data shown to residents (e.g. House A).

Fig. 10. Data shown to residents (comparison between houses).

� I
nformation where possible energy savings could be
achieved was provided to residents.

Analyzing the surveyed data, some appliances were id-

entified to be consuming more than the average, and thus

were selected to have potential for energy savings. That

information was shown to residents in the session held.

Details of changes occurred after energy sessions are rep-

orted elsewhere [4].

Fig. 11. Data ana

3.3. Simulation of energy savings potential

An evaluation of the energy savings potential corre-

sponding to an hypothetical improvement along axis 3 and

axis 2 of Fig. 3 was made, that is, energy savings either by

improving equipment efficiency (e.g. reduction in the power

input for the same output) or by simulating changes in the

way that residents use appliances (e.g. reduction in stand-by

time) [4].

4. Data analysis

Energy consumption, especially in heating and cooling is

closely related to the weather conditions. Furthermore, other

relevant information concerning energy use and resident’s

lifestyle pattern e.g. bathing habits, gas end use, was

obtained by analyzing thermal environmental data. The

tasks performed are shown in Fig. 11.

4.1. Electricity and gas data; end use categories

Concerning the electricity data, the power consumption

per minute was analyzed in detail. Knowing the rated power

lysis tasks.


Table 2

End use categories in data analysis

End use category Detailed

Air conditioning Cooling

Heating

Ventilation

Hot water Hot water (bath)

Hot water (cooking)

Other

Illumination Illumination

Cooking Cooking

Cooking related

Information/leisure Information

Leisure

Security

Household/Hygiene Household

Hygiene

Unknown Unknown

Fig. 13. Electricity data divided into end use categories (House K).

Table 3

Characteristics of rice cooker (example: House H)

Characteristics Characteristic value

Power used during normal functioning period (W) 550

Power used out of normal functioning period (W) 18

Average usage length (min) 35

Total power consumed per usage (Wh) 170

and the power consumption characteristics of different

appliances, it was possible to divide the total consumption of

living room, kitchen, etc. into end use categories described

in Table 2, as shown in example of Fig. 12.

With the data processed for every division in the house, it

was compiled per end use categories, and then plotted

minute by minute, as in Fig. 13. Then, the gas data was

analyzed together with thermal environmental data and

finally, the daily energy consumption per end use was plotted

as in Fig. 14. In the example shown, hot water represents

36% of total consumption, which is a quite significant figure.

Fig. 12. Power consumption in dining room (House K).

4.2. Main program for data analysis

Analyzing the electricity data, the characteristics of

different appliances were studied in order to built up a

program that could handle any household appliance data.

The important characteristics identified were:

� P
ower used during normal functioning period;
� P
ower used out of normal functioning period (e.g. stand-
by power);

� A
verage length of usage; frequency of usage;
� T
otal power consumed per usage.
With the main characteristics identified for every appl-

iance as shown in Table 3 for the case of one rice cooker, a

program that divides energy consumption data into different

modes depending on the use given, was made (e.g. Figs. 15

and 16). Mode 1 corresponds to the period when device is

used in full. Mode 2 corresponds to some secondary use,

common in devices that have the function ‘keep warm’.

Mode 3 corresponds to a marginal consumption usually

associated with ‘stand-by’ power. Mode 4 means zero co-

nsumption. Depending on device, the meaning of the modes

changes as in Table 4.

To implement this task, border values that make the

division into different operation modes were estimated. For

Fig. 14. Daily energy consumption per end use (House E, 2003).


Fig. 15. Data handling program (e.g. heat pump).

Fig. 17. Yearly energy consumption (November 2002–October 2003).Table 4

Modes defined for each appliance

Rice cooker;

hot pot

Microwave;

toaster

TV Refrigerator

Mode1 Boiling Cook; warm up On Compressor

on cycle

Mode 2 Keeping

warm

– – Defrost

Mode 3 Stand-by Stand-by Stand-by Off cycle

Mode 4 Off Off Off Off

some appliances, ‘mode 2’ was not defined, hence, just one

border value was used as an input by the program. Since

electrical appliances do not have a constant consumption

even within one functioning mode, one extra variable was

necessary to be defined, ‘hold time’, which holds the

consumption for a certain time whenever there is a transition

between modes, checking if the transition is temporary or

not.

The output values of the program are the modes, the

initial and final use times, time used, energy consumption,

frequency of use, and the initial and final temperature/

humidity in the case of heating/cooling devices.

The yearly energy consumption is shown in Fig. 17. Total

consumption ranged between 30 GJ in a two-residents flat

(House M), to 84 GJ for a five-residents house (House A)

Fig. 16. Data handling program (e.g. rice cooker).

that has a gas heat pump used both for cooling/heating.

House K, a flat, had the highest consumption per square

meter (0.73 GJ/m2). Concerning electricity consumption,

House I, where more energy savings measures are

implemented, consumed the lowest electricity (7.8 GJ) of

all.

After processing the surveyed data, yearly electricity

consumption per appliance was obtained as shown in

Fig. 18. As expected, refrigerator consumption represents

the biggest share in all surveyed houses, representing a share

of 10% in House E and 25% in House I. TV and video

consumption varied from 100 to 500 kWh/year from house

to house. The highest consumption was registered in Houses

C, H, K and L where residents are usually at home the whole

day. The hot pot consumption varied between 150 and

400 kWh/year, while washing machine consumed 20–

50 kWh/year.

‘Washlet and warmlet’ used to heat up the toilet seat, used

ca. 150–200 kWh/year/unit, with the maximum consump-

tion of 450 kWh registered in House D, corresponding to

2 unit, which were turned off just for 3 days during

the summer period. It represented a significant average

monthly consumption of 38.7 kWh more than the 20.6 kWh

consumed by TV. On the other hand, in House A the

Fig. 18. Yearly energy consumption per appliance.


Table 5

Yearly energy consumption (kWh/month) per appliance/mode (monthly average)

House TV ‘Washlet/Warmlet’ Rice cooker Hot pot

Mode1 Mode3 Total Mode1 Mode 2 + 3 Mode1 Mode 2 + 3

A 9.7 5.4 25.2b 6.7 2.6 5.1 22.9

B 25.5 6.9 19.6 5.1 8.9 – –

C 24.5 2.8 – 8.5 1.2 – –

D 14.8 5.8 38.7a 3.0 1.0

E 31.2 0.1 9.0 7.5 3.1 – –

F 18.1 2.1 16.9 4.4 3.3 – –

G 13.4 4.8 12.0 – – 3.5 9.5

H 18.2 6.2 10.8 1.6 0.1 13.2 19.0

I 6.7 0.1 1.3 5.8 0.9 – –

J 4.0 2.7 12.9 5.4 0.7 – –

K 45.1 3.0 – – – 3.9 31.6

L 18.5 1.1 – – – – –

M 17.3 0.4 0.7 1.2 0.4 – –

a 2 ‘Washlet’ units used.b 1 ‘Washlet’ unit + 1 ‘warmlet’ unit used.

‘washlet’ was disconnected for 7 weeks (25.2 kWh) while in

House B (19.6 kWh) it was off for 15 weeks.

With the output of the data analysis program, the yearly

frequency of usage, using the set on time throughout the day

was plotted as in Fig. 19. The frequency of watching TV

during the day in Houses G and J is quite low since in

daytime there is no one at home. Analyzing similar graphs

for other appliances, like rice cooker, washing machine,

‘washlet’, the lifestyle pattern was characterized for each

family.

Processing the surveyed data with the program described

in the previous section, the electricity consumption per mode

per month was obtained as shown in Table 5.

Several valuable information is presented in Table 5.

Concerning the TV, Houses like E, I, L and M usually do not

let it in ‘stand-by’ mode, thus, consumption is low compared

with 6.9 kWh of House B or 6.2 kWh of House H. This

corresponds to ca. 80 kWh/year. Some houses use multi-

type switch consent to reduce ‘stand-by’ consumption.

Concerning the rice cooker, in Houses A, B, E and F, the

‘keep warm’ mode is very frequently used, even during the

whole night in the case of House B. This means that more

Fig. 19. Yearly frequency usage throughout day (TV).

energy is spent in that function than in cooking the rice itself.

Also the hot pot spends a significant amount of energy in the

‘keep warm’ mode, being the case of houses A, H and K that

have it often switched on the whole day.

Performing this kind of analysis, targets for energy

savings were identified and information was given to

residents in an energy information session [4]. The main

issue concerning its implementation is the intrinsic value

residents give to secondary functions. Some residents

consider it to be convenient and almost indispensable,

others are able to cut that consumption share.

5. Conclusions

In order to understand energy consumption issues in

residential sector, a detailed survey was held. Analyzing the

data from our survey, the following conclusions were made:

� E
nergy consumption is closely related to the resident’s
life style, thus energy savings can be implemented or not

depending on the resident’s receptivity.

� S
econdary modes like ‘keep warm’ function represent a
significant consumption (up to 8.9 kWh/month for the rice

cooker) sometimes surpassing the consumption of the

main function.

� F
rom the surveyed data, some appliances were identified
to have a high-energy savings potential, namely the

‘washlet/warmlet’ (up to 200 kWh/year), hot pot (up to

240 kWh/year) and rice cooker (up to100 kWh/year).

� ‘
Stand-by’ power consumption was identified to
represent a significant share of total consumption (8–

10%). Awareness of residents is normally just towards

long absent periods. Easy to implement solutions like

multi-type switch consent are popular, however, their

effectiveness depends much on the use given by

residents.


� E
nergy cost is the main priority even for residents
enthusiastic about energy savings. In second place comes

the concern on environmental issues and only afterwards

energy efficiency/savings issues.

� A
wareness should be raised, towards a closer association
between electricity production and its environmental

burden. Nowadays, since energy cost is the main factor

affecting energy consumption, any successful energy

savings policy should consider raising energy cost, which

currently represents 2–4% of the income.

Showing detailed energy consumption by appliance to

dwellers is one possible approach to raise awareness towards

energy issues, leading to energy savings especially with

residents already motivated.

Acknowledgements

This research is a part of the survey by the special

research committee on ‘‘Energy consumption of residen-

tial buildings’’ working group (Chairman: Prof. Shuzo

Murakami, Faculty of Science and Technology, Keio

University) belonging to the scientific committee of the

Architectural Institute of Japan. This special committee is

supported by the Ministry of Land, Infrastructure and

Transport, as well as Tokyo Electric Power Co., Kansai

Electric Power Co., Chubu Electric Power Co. and Kyushu

Electric Power Co.

References

[1] J. Browne et al., BP Review of World Energy 2002, June 2003.

[2] Agency for Natural Resources and Energy, January 2004, http://www.

enecho.meti.go.jp.

[3] Japanese Energy Conservation Center, January 2004, http://www.eccj.

or.jp.

[4] L. Lopes, Energy Efficiency, Energy Savings and Thermal Environment

in Residential Buildings. Master Thesis. Kyoto University, 2004.

http://www.enecho.meti.go.jp/

http://www.enecho.meti.go.jp/

http://www.eccj.or.jp/

http://www.eccj.or.jp/

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