BUILDING RESEARCH INSTITUTE

Building the BRI’s
Ideal HomeThis month’s installment of our series introducing the varied activities of Japan’s Building Research Institute(BRI) focuses on the Institute’s proposals for emissions reductions in housing. The article looks in particular at
the BRI’s seminal Design Guidelines, which specify the different approaches required to design low-energy
residential buildings, and at the Life Cycle Carbon Minus (LCCM) house, a proposal for housing thatminimizes CO2 emissions at the construction stage.

It is generally understood that globalwarming results mainly from an increase in carbon dioxide and othergreenhouse gases due to huge consumption of fossil fuels. In view of that,
the Intergovernmental Panel on Climate
Change (IPCC), the International Energy
Agency (IEA) and other internationalorganizations stress the importance of
reducing carbon dioxide emissions fromthe residential sector.
Figure 1 shows the trend in carbon
dioxide emissions by sector in Japan. It
reveals that carbon dioxide emissions
from the industries sector, the largest
emitter in Japan, steadily declined to alevel that is 13% below the 1990 level,

whereas emissions from the residential,commercial and other sectors continued
to rise until finally beginning to drop in
2008, when the emissions level was
30–40% higher than in 1990. In response, the Japanese government announced a New Growth Strategy, which
was adopted by the Cabinet on July 18,
2010. It sets a long-term target of cutting greenhouse gas emissions by 25
percent from 1990 levels by 2020. The
Ministry of Land, Infrastructure,Transport and Tourism expressed theimportance of introducing an obligation
to comply with the energy conservation
criteria in a bid for energy conservationin all new residential and other build-

1990
1991
1992
1993
1994
1995
1996
1997
1998
1999
2000
2001
2002
2003
2004
2005
2006
2007
2008

Percent change from reference year

Figure 1: Trend in Carbon Dioxide Emissions by Sector

Source: Based on data from the National Institute for Environmental Studies

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ings and commenced a study on imposing the obligation.
Low Energy Housing with Validated
EffectivenessInvolved in research on energy conservation methods in residential houses, theBuilding Research Institute compiled
the research findings to draw up theDesign Guidelines for Low Energy
Housing with Validated Effectiveness.
Targeting Japanese regions with ar e l a tively mild climate, including
Tokyo, the Guidelines specify the different approaches required to design lowenergy residential buildings and facilitate estimationof the energy
conservation
effect expected
The figures in parentheses indicate
from a combithe emissions in 2008.
nation of theseapproaches.
The degree to
Residential sector(172 million metric tons)
which energy
consumption
Commercial & other sectors(232 million metric tons)
i s reduced isbased on thevalue of theeffect observedin a test carried
Transport sector
out with actual(236 million metric tons)
use of different
facilities andequipment.
The approaches
Industries sector
suggested cor(420 million metric tons)
respond to thirteen basic(fiscal year)
technologies
listed below.

Figure 2: Covers of the Guidelines

1. Use and control of wind
2. Daylight utilization (Sunlight utilization 1)
3. Photovoltaic power generation(Sunlight utilization 2)
4. Solar radiation heat utilization (Solarheat utilization 1)
5. Solar water heating (Solar heat utilization 2)
6. Insulated building envelope planning
7. Solar shading method
8. Heating and cooling system planning
9. Ventilation system planning
10. Domestic hot water system planning
11. Lighting system planning
12. Introduction of high-efficiency consumer electronics
13. Treatment and efficient use of waterand kitchen waste
They also show the ratio of energy
consumption reduction by each approach. For instance, ventilation system
planning is expected to cut ventilationenergy consumption by 30% to 60% by:
1. optimizing the duct diameter andthe layout for minimizing a pressure
loss in the duct ventilation;2. introducing high efficiency motorand fan; and3. a d o p t i n g a h y b r i d v e n t i l a t i o nsystem that capitalizes on thedifference between indoor and outdoor temperatures.
A large number of seminars havealready taken place with the use of these
Guidelines mainly in target regions withmild climates. More than 10,000 people
have to date participated in the seminars.
After some called for guidelines forother regions, the Building ResearchInstitute created a version for hot re-gions including Okinawa Prefecture,
called the Hot Humid Region Edition.
The climate in the region targeted bythis edition is comparable with that ofSoutheast Asia. The version for regions
where the climate is colder than inTokyo and Osaka is being prepared.
Foreign language versions of theGuidelines have also been created:
specifically, a Chinese version of themild region edition.
Energy Conservation Criteria for
Residential Houses

residential houses in eight cities
in Japan. It is
common in thiscountry to heator cool a room
only while theresident is present, except inregions withvery cold climates like
Sapporo. Thismeans that energy consumption
for heating and cooling is lower inJapan than in the West, where it is normal to constantly heat or cool the entire
building. According to the diagram, energy consumption for heating is huge in
Sapporo, accounting for more than halfof the total energy used. In this city, theclimate is so close to that in Canadaand Scandinavia that uninterrupted
heating of the whole house is widelypracticed. In other regions, the share ofenergy consumption for heating is as
small as about 25%. This implies thatfor the purpose of cutting energy consumption for an entire house in Japan itis necessary not only to lower the airconditioning load by improving theheat insulation properties, as prescribedin the Act on the Rational Use ofEnergy, but also to increase the efficiency of air conditioning equipment
for dealing with the load and to use
high-efficiency devices for hot water

Figure 3 shows the standard values of
the coefficient of heat loss for different
regions according to Japan’s Act on theRational Use of Energy. A smaller
value for this coefficient means a higher level of heat insulation efficiency,
and a region with a colder climate
needs greater heat insulation. The diagram demonstrates that theFigure 3: Standard Value of the Coefficient ofstandard value
Heat Lossof the heatloss coefficient has been
lowered eachtime the criteria are updated
in order tograduallyraise the insulation level ofresidentialhouses. Figure
5 shows thebreakdown ofenergy consumption insingle-family

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BUILDING RESEARCH INSTITUTE
GJ per household
140

Lightingand others

Cooking

Hot water
supplyCoolingHeating

120

100

80

60

40

200oropp
Sa
Zone with 4,500 heating
degree days or greater
Zone IaindSetagaNii

kyoToyagoNaotoKyaokkuFuhaNa

Figure 5: Current Status of Energy Consumption in theResidential Sector:
Comparison in single-family houses in eight cities

Zone II
Zone III
Zone IV
Zone V
Zone VI

Figure 4: Zone Classification under the Act on theRational Use of Energy

Lightingand
othersCookinglation properties
Hot water
supplyo f t h e house.
Specifically, theCoolingassessment is
Heating
done by comparing the energy
consumption for
air conditioning,
ventilation, hot
Figure 6: Energy Balance of the LCCM House
water supply andlighting in thehouse with the standard value, which is neighboring conditions and the lifedetermined at 90% of the energy con- styles of dwellers such as air conditionsumption anticipated at the time of in- ing durations and hot water demand are
troducing air conditioning, venti- determined and adopted as given condilation, hot water supply and tions. However, attention is paid to thelighting equipment considered climatic conditions depending on thenormal as of 2008 to a residential building region. A schedule for calcuConventional housebuilding with heat insulation lating energy consumption according
performance equivalent to the to different settings and conditions has
1999 standard value shown in been prepared. While it is possible touse this schedule, there is also a program
Figure 3. For equipment that has
LCCM house
yet to be installed at the time of for detailed calculation.
In the course of developing thishandover, the value for equipAge
ment that is considered to have assessment approach, much of thebeen commonly used in 2008 basic data studied for drawing up theapplies. As standard conditions Design Guidelines for Low Energyfor estimation purposes, housing Housing with Validated Effectiveness
Figure 7: Schematic of CO2 Balance throughattributes such as the form and were utilized.
out the Life Cycle
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Re
novation(2)Constru
ction
Re
nova
tion(1)CO2 balance [CO2-t]

supply, lighting and other purposes involving energy consumption.
Applying to businesses that build apredetermined number of houses ormore per year, the criteria for homebuilding businesses under the Act on theRational Use of Energy took effect in2009. In light of the point discussedabove, they stipulate that pre-installed
air conditioning, ventilation, hot watersupply, lighting and co-generation systems, and solar power generation equipment shall be assessed at the time ofcompletion in addition to the heat insu-

total of
CO2 emissions fromconstruction and others
the initial
350t
Power generation
CO2 emisInitial CO2
volume300t
sions andenergy
250t
consumption for
200t
operation
after ap150t
proxi100t
matelyt h i r t y
50t
years ofuse and to0t
achieve
30 yrs
40 yrs
50 yrs
60 yrs
70 yrs
80 yrs
90 yrsPeriod of usethe LCCM
Figure 8: Trend in CO2 Emissions and Power Generation Volumeobjective.
(Under the condition with the use of a solar thermal hot water
Longersystem with natural refrigerant and with the unit CO2 emissions
use willof 0.418 kg-CO2/kWh on average for all power sources)
result ina greater
amount of surplus energy.
the LCCM technology. An LCCM house
Accurate initial CO2 emissions from evaluation tool that covers various cliconstruction will be calculated with the mate conditions and lifestyles in Japanuse of measured data on the amount of will be developed with the use of thewaste emitted from the construction site findings of this examination. In addition,of the demonstration LCCM house. the results will be used to authenticate
Simulated living in this house will be LCCM houses with a view to acceleratcarried out to measure the energy con- ing the adoption of this energy-saving
sumption for operation and to examine housing solution.
CO2 emissions from construction and others & energy consumption
and power generation volume in CO2 equivalents

LCCM Houses

A Life Cycle Carbon Minus (LCCM)
house has been proposed as a house forminimizing CO2 emissions at the stagesof construction, operation and scrapping in its long life span and forachieving a negative life-time CO2 balance, including CO 2 emissions frombuilding it, by making active use of renewable energy produced by solar andother power generation.
Specifically, energy consumption
for operation will be slashed and solar
power generation that exceeds the consumption will be introduced so that surplus energy for operation may be used
for other houses. Power supply companies will minimize CO2 emissions frompower generation. This will counterbalance the CO2 emissions in construction
and other phases (see Figures 6 and 7).
However, a drastic cut in energy consumption for operation will degrade
health, safety, comfort and convenienceand impair effectiveness. For theLCCM house to achieve widespread
adoption, it is necessary to retain theseelements to the maximum degree. As isshown in Figure 7, CO2 emissions fromconventional houses growthe longer they are operated.
In contrast, CO 2 emissions
The Demonstrative LCCM House in Tsukuba
from LCCM houses fall withthe surplus energy for operaSolar panels andsolar collector panels
tion and decline below zeroafter the lapse of a certain
number of years, although
Large openings on thethey do rise slightly at thesouthern side to maximize
the direct gain in wintertime of renovation.
Based on this concept, ademonstration LCCM house
A parabolic wall for
capturing light and wind
was erected in the premises ofthe Building Research Institutein the city of Tsukuba, inIbaraki Prefecture.
The potential of theUse of local lumber andLCCM technology wasother materials
studied on the basis of theinitial CO2 emissions of thisUse of blast-furnace
cement and concrete
house at the time of conWin
terstruction and energy conSum
sumption for equipment opmereration (Figure 8). As far as
this demonstration LCCM
Winterhouse is concerned, solar
Windows are closed to provide asunroom-like space.
power generation volume
is estimated to surpass theFigure 9: Overview of the Demonstrative LCCM House

Roof ventilators thatcreate air flows

A dispersed layout ofmultiple LED light sources

Partial intermittent
heating and cooling witha high efficiency heatpump air conditioner

Wooden louvers forshielding the sunlightA high efficiency hotwater supply system- Fuel cells, etc.

SummerWindows are opened to use the engawa, orthe Japanese-style veranda, as a roofed
outdoor space.

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