REUSE SYSTEM OF INDUSTRIALIZED HOUSES (REUSED SYSTEM HOUSE)
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The 2005 World Sustainable Building Conference,
02-009 Tokyo, 27-29 September 2005 (SB05Tokyo)
“REUSE SYSTEM OF INDUSTRIALIZED HOUSES (REUSED SYSTEM HOUSE)”
1
Takumi IWAHARA
2
Yoshiyuki SUZUKI
1
2
Sekisui Chemical Co.,Ltd., 2-3-17 Toranomon,Minato-ku,Tokyo 105-8450,Japan :iwahara001@sekisui.jp
Sekisui Chemical Co.,Ltd., 2-3-17 Toranomon,Minato-ku,Tokyo 105-8450,Japan :suzuki028@sekisui.jp
Keywords: reuse, unit, environment, industrialized houses
Summary
We started our unit-housing business in 1970 with more than 80% of our houses being manufactured
under strict quality control on assembly lines in our plants, just as automobiles were assembled. The total
number of our houses in existence in Japan today is more than 400,000, so there are about 6,000,000
structural units. We endeavored to establish a “resource-recycling housing system” to effectively utilize the
units that were normally demolished when old houses were disassembled, resulting in the launch of our
“Reused System House” in 2002.
According to our survey, most of our customers rebuild their houses not because of the age or the
condition of the house, but because they desire new living arrangements. Therefore, old houses are
disassembled into units, which are returned to our plants, inspected, repaired as necessary, and sold to new
customers to be built on new sites. Interested customers can look at our website and select from a wide
range of houses that we offer. Such houses can be purchased at 60 to 70% of new-house prices. When one
house of an average size is demolished, it generates about 47 tons of waste. About 50% of the waste is from
the foundation and the other 50% from the house itself.
1. Introduction
The life cycle of a house is more than 50 years, from production of its parts, construction and use, to
dismantling. A house of average size has no less than 50 tons of material, and the environmental load
throughout its life cycle is enormous.
It is believed that the demand for rebuilding houses in Japan will not decrease drastically in the future, where
people are attached to the land on which they live. The recycling of certain materials such as concrete,
asphalt, lumber and so forth is regulated by the Construction Materials Recycling Act, which has been
enforced completely since 2002, and the effective utilization of building-waste materials is being promoted.
In May 2002, we introduced our rebuilding system whereby used houses are returned to our production
plants to be rebuilt instead of being demolished them. Through an integral assessment of the effect of each
environmental factor which is generated in the whole life cycle of a house, the effectiveness of the rebuilding
system has been realized. The outline of our Rebuilding System is explained in this paper.
2. The Housing Business of Sekisui Chemical Co., Ltd.
Our original concept is “to produce a living space on a production line in a plant, under strict quality control,
just as cars are produced.” In 1970 we started a unit-housing business based on this concept, whereby
more than 80% of an individual house is produced in our plant. We currently produce two kinds of units; steel
units and wooden frame units. A house of average size consists of a combination of 10 to 15 units. The total
stock of unit houses that our company has sold has exceeded 400,000, or more than 6,000,000 structural
units, which are distributed all over Japan.
Our company has a fundamental policy regarding the environment; “we contribute to society with our
environment-friendly residential houses that can be lived in safely and comfortably for at least 60 years.” In
order to realize the policy, we have been developing “a resource-recycling housing system”. The purpose of
this activity is to reduce the consumption of resources and energy during each phase; production of
components, assembly and construction, living, disassembly and demolition. Through this we carry out our
social responsibility as an enterprise in the long life-cycle of our houses.
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Tokyo, 27-29 September 2005 (SB05Tokyo)
Assembly/Construction Stage
Zero emissions in plants
Zero emissions on construction sites
Living
Production of
Long life Unit Technology components
Zero-energy cost house
Zero emissions household Use of parts cascade
Disassembly/ Demolition
Reused System House
Minimize waste by segregated collection
Figure 1 The Resource Recycling Housing System
3. Industrial Waste and the Construction Industry
About 400 million tons of industrial waste are generated annually in Japan, out of which about 20% is from
the construction industry, 40% is recycled or properly disposed of, and 60% is illegally disposed of.
On the other hand, according to an estimate of future waste generation from demolished buildings in Tokyo
and 8 prefectures, it is predicted that the waste from demolished buildings will increase more and more in the
future, as the construction of new buildings increased rapidly after 1965, meaning that these buildings are
approaching renewal time.
Construction Others
Others
Mining Emission
Wholesale 20
4% 15% volume
/Retail
23% 400 mil tons
Metal Final
/Non-iron 10% treatment
40
Publication 7% Agriculture 56 mil tons
/Printing 22%
Construction Illegal
60
19% disposal
0.4 mil tons
0% 50% 100%
Total: 406 million tons/year (2000) Prepared from Environmental White Paper and
White Paper on Land, Infrastructure and Transport
Figure 2 Ratio of waste generation according to industry
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Tokyo, 27-29 September 2005 (SB05Tokyo)
1995 1165 Non wooden Wooden
2000 2210
2005 3486
2010 4187
2015 4299
2020 4874
2025 5624
0 1000 2000 3000 4000 5000 6000
From the Report of the Society for the Study of Dismantling and Recycling System (October 1998)
Figure 3 Estimation of Future Waste Generation from Demolished Buildings in Tokyo
and 8 Prefectures
4. Waste Generated by the Housing Business of Sekisui Chemical Co., Ltd.
We have systematically and collectively promoted “Zero-emission 3R Activities” to enhance the effective
utilization of resources. These activities include our strict observance of all laws and regulations in the
treatment of waste, as well as the reduction of the volume of waste and the reuse and recycling of all waste
generated (Reduce, Reuse and Recycle).
We achieved zero emissions in all of our production plants in September 2001, and on all housing
construction sites in September 2003, thus attaining zero emissions from the point of production through
completion of construction. We will continue to promote the reduction of waste generation on housing
construction sites; in 2004 we began to promote zero emissions activities in our renovation sector.
Achieved zero emissions Achieved zero emissions
in Sept, 2001 in Sept, 2003
16 21 272
16
0 50 100 150 200 250 300 350
1,000ｔ/Y
Assembly Plants Construction Sites Renovation Disassembly
Figure 4 Amount of waste emission in the Housing Business of Sekisui Chemical Co.,Ltd.
Fig.4 shows the estimated volume of construction waste generated during each phase of our housing
business operations. It is clear that the volume of the construction waste at the phase of disassembly is
extremely large. We developed and implemented the Reused System House in May 2002, in order to reuse
our houses after disassembly.
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Tokyo, 27-29 September 2005 (SB05Tokyo)
5. Outline of Reused System House
We conducted a survey of the reasons that our customers rebuilt their houses, and in most of the cases they
had their houses demolished due to changing living requirements, or because of government-ordered
demolition for the purpose of land readjustment; not because of the structural condition of the house. After
learning this, we examined the possibility of reusing structural frames, and eventually launched our Reused
System House in May 2002.
In this system, an old house is separated into units, returned to our plants, inspected, repaired as necessary,
and is sold to a new customer to be built in a new place. Reused System Houses can be purchased at 60 to
70% of a new-house price. Moreover, owners of the original houses can reduce the volume of waste by
about half with this reuse system, as we purchase the original units.
Trade in Unit Trans- Inspection/ Trans- Completion
an old Separa- port to Repair port to of Rebuilt
house tion plant new site House
Figure 5 Flow of Reused System House
5.1 Reuse Ratio
A house of an average size generates 47 tons of building waste when it is demolished. About half, or 23 tons
are from its foundation, and 24 tons are from the house itself. We return the house itself to our plants where
we reuse as much of it as possible after inspection and repairs as necessary. The reused materials are its
structural frame and interior underlay materials. Equipment, fixtures, and interior finishing materials are
replaced with new ones. By this method, more than 85% in weight of the original house is reused, which
results in a great reduction of building waste.
In addition, surveys conducted tell us that owners of the original houses feel satisfied as their houses are
rebuilt into new houses instead of being demolished and disposed of.
Reuse Ratio by Weight Reuse Classification by Main Parts
Reused Parts Part Reuse New
Structural o
Frame
Building Structural Interior Walls o
Foundation Parts Frame
Floor o
49.8% 50.2% 85% Substrate
Interior/ Roofing o
Equipment
15% Bath/Wash o
Basin
New Parts Kitchen o
Interior o
Estimate from trial construction data in 2003. Finish
Figure 6 Reuse Ratio by Weight & Reuse Classification by Main Parts
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Tokyo, 27-29 September 2005 (SB05Tokyo)
5.2 Floor Plan
In order to maximize the material reuse ratio, we make it a principle to maintain the original floor plan as
much as possible. We have a website with a list of Reused System Houses for sale, making it possible for
potential home buyers to find a house of a suitable plan and design. Although our sales outlets only sell new
houses within their own regions, people can buy Reused System Houses from a much wider area.
Furthermore, we made it possible to increase or decrease the number of units of a particular house, which
gives more flexibility in creating a floor plan on the unit basis, keeping the reuse ratio high. More details are
explained by actual examples below.
5.2.1 Example 1: A Case of Unit Increase
3 new units were added to the original house of 10 units. The entrance unit (#01) was reversed and
moved from the east side to the west.
The floor plan of
the new house
G J G J
H K H Z3
I I K
2F 2F
A D Z1 D
B E B E
C F Z2 A
C F
1F 1F
Figure 7 A Case of Unit Increase
5.2.2 Example 2: A Case of Unit Decrease
This is an example of converting a house that was previously used as an office building to a residence,
by reducing the number of units. The floor plan was created around the original entrance unit and
staircase unit as they were before.
The floor plan of
13 the new house
10 14 13
11 15 10 15
12 16 12 16
2F 2F
05
01 06
02 07 05
03 08 01 08
04 09 04 09
1F 1F
Figure 8 A Case of of Unit Decrease
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5.2.3 Example 3: A Case of Combination
This is an example of combining two houses into one. This customer was looking for a large house,
but as there was no suitable one for his needs, we combined two houses to meet his requirements.
08 11 29 31
09 12 30 32
10 13 33
2F 2F
01 04 21 25
02 05 22 26
03 06 23 27
07 24 28
1F 1F
Figure 9 A Case of of Combination
5.3 Structural Durability and Quality Assurance
The basis of this rebuilding system is the structural durability of our units. In order to identify the structural
condition, we have established a simple non-destructive evaluation method. After each structural unit is
inspected for rust by this method, we choose the most appropriate repair method. In this way, our rebuilt
houses are certified as Degradation Control Measure: 2nd grade, under the Housing Quality Assurance Act.
With this designation, a house is expected to be able to be used continuously for more than 60 years.
Therefore, the same quality assurance which is applied to new houses is applied to our Reused System
Houses, including our 20 year long-term guarantee system and our long-term support system. Additionally,
the Housing Performance Indication System of the Ministry of Land, Infrastructure and Transport is applied
voluntarily as one of our standards, so that our customers can enjoy a safe and comfortable life in our
Reused System Houses.
Application of Housing Long-Term Support Long-Term Guarantee System
Performance Indication System of 20 Years
System
Stability of structure 6-month check 10-year check
Fire safety (Repair costs borne
by owner)
Reduction of degradation One year check
5-year extension of guarantee
Easy maintenance
Thermal environment 2-year check
15-year check
Indoor air environment (Repair costs borne
by owner)
Light/visual environment 5-year check
5-year extension of guarantee
Sound environment
Check every 5 years
Consideration for the thereafter
Elderly 20-year check
Figure 10 Quality Assurance
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Tokyo, 27-29 September 2005 (SB05Tokyo)
5.4 Expansion of Uses
Two and a half years have passed since we started marketing our Reused System House. We started with
detached two-story houses, and expanded to detached three-story houses and collective housing. A better
return of investment and an expansion of new sales areas was achieved, especially in the collective housing
market. consequently, a more effective utilization of units has been realized. We have also started marketing
on a unit basis for house additions.
Example 1: Collective housing rebuilt into collective housing
Example 2: Detached houses converted into terrace house
Figure 11 Method for expanding application of Reused System House
As a result, the reuse efficiency of units has increased, resulting in a higher number of sales contracts year
after year.
Unit
300
298
200
224
100
70
59
36
0
02 FH 02 SH 03 FH 03 SH 04 FH
Figure 12 Contracted number of units for reuse
5.5 Environmental Impact
We conducted an environmental impact evaluation by using LIME (Life-cycle Impact Assessment Method
Based on Endpoint Modeling) to identify the negative effects of rebuilding. As a result, it was determined
through a comparison of our houses that the cost of damage was reduced by 1.03 million yen by rebuilding.
- 1217 -The 2005 World Sustainable Building Conference,
Tokyo, 27-29 September 2005 (SB05Tokyo)
units of 10,000 yen
250 246 Reduction of damage
cost by 1.03 million yen
200
150 143
Biodiversity
Plant production
100
Social welfare
50 Human health
Quoted from JLCA-LA
0 data base:2004
New+New New+Rebuild
（0408:Computed by Yamamoto Lab., Institute of Industrial Science, University of Tokyo)
Figure 13 Environmental Impact
6. Conclusion
Replacing old houses with new ones helps customers realize their dreams, but at the same time this act has
a strong negative impact on the global environment.
When a house comes to be considered undesirable by its owner, for whatever reason, it is returned to our
plants and reused, instead of demolishing it. Through an integral evaluation of various factors, we have
determined that a large amount of external damage cost is reduced by this system in the Japanese housing
market, where people are firmly attached to their land.
We feel that housing manufacturers are responsible for taking back houses which they have sold when those
houses reach the end of their lives. It is also their duty to establish a system whereby reused materials can
be bought in an open market, as it is difficult for housing manufacturers to sell all of them through their own
sales networks within a closed market. We consider it an important role for housing manufacturers to
develop such a system in the future, in order to be able to contribute to local-community recycling efforts.
References
2004, Environmental White Paper, Ministry of the Environment
2000, White Paper on Land, Infrastructure and Transport, Ministry of Land, Infrastructure and Transport
1998, The Report of the Society for the Study of Dismantling and Recycling System
2004, Sekisui Chemical Co.,Ltd.,Environmental Report
2005, IBEC,”IBEC” No.146
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