June 15, 2023
Graduate School of Frontier Sciences, The University of Tokyo
Musashino University
Sumitomo Realty & Development Co., Ltd.
Promoting Decarbonization and Achieving Green Transition through Renovations of Detached Houses

Joint Research on Decarbonization Through Renovations
by The University of Tokyo, Musashino University, and Sumitomo Realty
Verifying the adoption of ZEH and achievement of life cycle carbon neutrality through renovations
Since December 2021, Professor Tsuyoshi Seike from the Graduate School of Frontier Sciences at The
University of Tokyo, Lecturer Takayuki Isobe from the Department of Sustainability Studies at Musashino
University, and Sumitomo Realty & Development Co., Ltd. (President: Kojun Nishima) have been conducting
joint research, aiming at establishing an environmental evaluation method for the renovations of existing
detached houses towards the realization of a decarbonized and circular society.
As an interim target towards carbon neutrality by 2050, the household sector is urgently required to reduce
CO2 emissions by 66% compared to fiscal 2013 by 2030. While discussions on environmental performancemeasures and government subsidy schemes for newly constructed houses are progressing, little progresshas been made in discussion toward promoting energy savings or decarbonization for existing houses, mostof which have inferior energy efficiency performance to newly constructed houses.
Following last fiscal year’s announcement, we are pleased to announce the verification results on theeffects of renovation for extending useful lives of existing detached houses, as well as the adoption of ZEH
and achievement of life cycle carbon neutrality through renovations measured using the Building Life Cycle
Assessment method*.
* Building Life Cycle Assessment method: A method of evaluating the total environmental impact over the lifespan of a building byconsidering the environmental load at each stage, from construction and residency to disposal.

Structural frame being reused

BIM 3D Model of a sample house◆ Key Points of the Research Findings•

A prototype of a quantitative evaluation tool has been completed for measuring the resource
recycling and decarbonization effects of housing renovations.

•

The research has demonstrated that through renovation, improving insulation and equipment
performance as well as installing solar power generation equipment, the adoption of ZEH (Net
Zero Energy House) and life cycle carbon neutrality could be achieved without the need forspecial construction work.

•

The research has demonstrated that through renovation, which is more resource-saving andlow on CO2 emissions compared to rebuilding, life cycle carbon neutrality could be achieved
more rapidly than through rebuilding.

•

By tracing the past construction cases of “Shinchiku Sokkurisan,” which has conducted morethan 160,000 renovation projects over the 27 years since 1996, the research confirmed thelifespan extension effects of renovated houses.

■ Background and Purpose of the Joint Research
For decarbonization in the household sector to achieve carbon neutrality by 2050, effective approaches areneeded not only for newly constructed houses but also for existing houses, most of which have inferior energy
efficiency. However, there have been few studies quantifying the contribution to decarbonization through therenovation of existing houses, and there has been a strong demand for establishing an environmental
evaluation framework for the renovation of existing houses based on scientific methods, from the perspectiveof policy and system formulation.*
Under such circumstances, the University of Tokyo Graduate School and Musashino University requested
research cooperation from Sumitomo Realty, which has a broad-ranging track record from partial to full
remodeling. With our full cooperation in performing studies at our worksites and data provision, researchbegan in December 2021.
In this research, under industry-academia collaboration, we aim to develop a method for evaluating theenvironmental contribution of renovations, which will serve as the basis for a system to promote thedecarbonization of existing detached houses, a social issue, and to establish an evaluation framework.
* Government’s Initiatives Towards Decarbonization of Existing Houses (Examples)•••Three ministries, the Ministry of Economy, Trade and Industry, the Ministry of Land, Infrastructure, Transport and Tourism, and theMinistry of the Environment, together formulated the approach for energy-saving measures, etc. in housing and buildings towards a
decarbonized society. It outlines the national decarbonization policy for buildings and explicitly states the need to develop methods
and evaluation techniques for rationally and efficiently assessing energy efficiency performance before and after renovation.
Government projects were set up to provide subsidies for partial improvements in energy efficiency, such as equipment updates andheat insulation on exterior walls and windows.
Our project to establish a CO2 evaluation system for existing detached houses (for renovation) has been selected for a subsidy by
the Ministry of Land, Infrastructure, Transport and Tourism's as part of their program to promote innovation in housing production
technology.

Since renovating existinghouses promotes resource
circulation, it has the potential
to contribute to decarbonization

However, little research has
been conducted to evaluate thedecarbonization effects ofrenovation, and there are noframeworks for quantifying its
contributions

It is urgent to establish
quantitative methods forevaluating resource circulationand decarbonization effects◆ Three-phase Verification of Issues
Phase 1

Verify the CO2 emissions reduction effects of existing detached house renovations

Phase 2

Verify the building lifespan extension effects of existing detached house renovations

Phase 3

Verify the adoption of ZEH and achievement of life cycle carbon neutrality through existing detachedhouse renovations

Phase 1 (Research findings announced in June 2022)
Comparison of CO2 emissions from rebuilding andrenovation, related to the amount of construction
resources and waste disposal from existing detachedhouses➡ CO2 emissions from renovation were 47% lower thanemissions from rebuilding(ton-CO2)

Demolition and waste disposal
60.0Interiors, equipment, etc.

Foundation, structural materials,
external walls, etc.
Construction, etc.

(47%)

50.0
40.0

Phase 2 and 3(Research findings announced in June
2023, details are on the next page)

Verify the building lifespan extension effects ofexisting detached house through renovations• Verify the adoption of ZEH and achievement of life
cycle carbon neutrality through renovations➡ Life cycle carbon neutrality can be achieved throughfull renovations (with improved energy efficiency) inroughly 35 years, which is faster than through rebuilding•

Achievement of life cycle carbon neutrality

30.0
20.0
10.0
0.0

建替
Rebuilding

Full renovation
改修* Measurements performed on houses constructed or renovated by Sumitomo Realty(Reference: News Release) The University of Tokyo, Musashino University, and Sumitomo Realty Announce the Results of Their Research on
Decarbonization Through "Shinchiku Sokkurisan" Building Renovation (June 16, 2022)

■ Life Cycle Carbon Neutrality through Renovations◇ Cases Compared◆ Structure of Life Cycle Carbon Neutrality
I. CO2 emissions during renovation work … (1)(renovation work + demolition work)

II. CO2 emissions during residency(during residency)… (2), (3)III. Life Cycle CO2 emissions… (4)IV. Life Cycle Carbon Neutrality… (5)(renovation work + demolition work
+ during residency)(renovation work + demolition work
+ during residency - power generation effect)A) Full Renovation (with unchanged energy
efficiency)
The existing house is stripped down to its main frame
and renovated into a house equipped with:• Unchanged level of insulation and energy
efficiency• Approximately 7.5kW solar panels
B) Full Renovation (with improved energy
efficiency)
The existing house is stripped down to its main
frame and renovated into a house equipped with:• Grade 4 insulation, energy efficiency equivalent
to ZEH• Approximately 7.5kW solar panels
C) Rebuilding
The existing house is dismantled down to an empty lot,
and a new house is built equipped with:• Insulation and energy efficiency equivalent to ZEH• Approximately 7.5kW solar panels(1) CO2 Emissions During Renovation Work (from the FY2021 research results)
The amount of CO2 emissions from renovation and demolition work depends on the amount of new materials
used and waste generated. Therefore, "Full Renovation (with improved energy efficiency)" emits less CO2 than
"Rebuilding," and even with the addition of energy efficiency improvements equivalent to a newly constructedhouse such as improved insulation and equipment performance, CO2 emissions can be reduced by 47%.
■Foundation & structure ■Exterior walls & roof ■Windows & doors ■Insulation material ■Interior ■Others ■Equipment■Balcony ■Common expenses ■Demolition & disposal
Full Renovation(with unchangedenergy efficiency)

４７％削減
47% Reduction

Full Renovation(with improved
energy efficiency)

Rebuilding(ton-CO2)(2) CO2 Emissions During Residency
The amount of CO2 emissions generated
during residency can be significantly
reduced by improving insulation andequipment performance.
Compared to "Full Renovation (withunchanged energy efficiency)", "Full
Renovation (with improved energy
efficiency)" can reduce CO2 emissions by
about 34% by improving energy efficiency
to the level of newly constructed house,
and affects the CO2 emissions duringresidency over the long term.

■Heating ■Cooling ■Ventilation ■Hot water supply■Lighting

Full Renovation(with unchangedenergy efficiency)
Full Renovation(with improved
energy efficiency)

Rebuilding(ton-CO2)

34%

34％削減
Reduction

(3) Extending Useful Lives of Existing Houses through Renovations
By replacing aging components throughrenovation, the building performance suchas seismic resistance improves, and its
useful life is extended. When considering
the life cycle CO2 of renovated houses, theextended useful life contributes to theoverall reduction of CO2 emissions.
Through this research, we confirmed thatthe majority of the houses renovated morethan 20 years ago are still standing atpresent. Of those no longer standing, it isassumed that demolition due to aging islimited, as the samples are in Tokyo where
many houses are demolished in theprocess of urban development such as
condominium development.

Study Samples

Study Method

Out of the 160,000 houses werenovated in the past, 3,702 that
underwent full renovation morethan 20 years ago were chosen.
Of these, nearly 500, which
accounts for the total number
within the top five wards in Tokyoin terms of construction number,were selected as samples andstudied.

The building useful life
extension effect was verified
following two studies
described below:(i) Document study(ii) Exterior study◇ Sampling Conditions• Renovation completed
before 2001
• Detached house• Fully renovated• The property address
can be obtained(4) Life cycle CO2 Emissions
By summing up the emissions from (1)and (2), and comparing the life cycle CO2
emissions of a house under the premise of(3), "Full Renovation (with unchangedenergy efficiency)" which has the least
CO2 emissions at the time of construction,emits the least CO2 for the first 10 years
following the renovation. On the other
hand, after 10 years, "Full Renovation(with improved energy efficiency)" whichemits less CO2 at the time of construction
than "Rebuilding" and improves insulation
performance to the level comparable to a
newly constructed house, resulted inemitting the least CO2.

◆ Comparison of Life Cycle CO2 Emissions
Full Renovation(ton-CO2)(with improved
energy efficiency)

Rebuilding

Full Renovation(with unchangedenergy efficiency)

リフォーム竣工時点

At the time ofrenovation

25

46

12

10 years
10年目時点52

72

52

20 years
20年目時点

84

102

98

30年目時点30 years

117

132

143

(5) Achievement of Life Cycle Carbon Neutrality
When the effect of solar power generation isadded to (4), in houses with high energy
efficiency, the amount of energy generated islarger than the amount of energy consumed
during residency, and the annual CO2
emissions becomes negative.
As a result, the CO2 emissions from
"Rebuilding" and "Full Renovation (withimproved energy efficiency)" decrease, while
the CO2 emissions from "Full Renovation(with unchanged energy efficiency)," which
has inferior insulation and energy efficiency,
increase over the long term. When all factors
are considered, "Full Renovation (withimproved energy efficiency)" can achieve life
cycle carbon neutrality earlier than the othertwo.

Achievement of life cycle carbon neutrality

■ Joint Researchers
Tsuyoshi Seike – Professor, Graduate School of Frontier Sciencesat The University of Tokyo
Tsuyoshi Seike graduated from the Department of Architecture in the Facultyof Engineering at The University of Tokyo in 1987. He worked as a Research
Associate in the Department of Architecture before joining the Graduate
School of Frontier Sciences in 1999.
He engages in research in renovation/demolition technologies, recycling
technologies, and environmental evaluation systems, from the viewpoints ofbuilding production and the environment.
He is the development leader for CASBEE for Detached Houses, and playsa central role in creating health checklists and resilient house checklists.
His publications include Sustainable Housing (editorial supervisor and cowriter), Creating Facades (co-writer), and Rethinking Living Environments From Smart to Healthy (co-writer).

Takayuki Isobe – Lecturer, Department of Sustainability Studies
in the Faculty of Engineering at Musashino University
Takayuki Isobe received his Doctorate from the Graduate School of Frontier
Sciences at The University of Tokyo in 2015. In 2016, he was appointed to
the Department of Environmental Systems Sciences in the Faculty ofEngineering at Musashino University.
He was appointed to the Department of Sustainability Studies in the
Faculty of Engineering at Musashino University from 2023.
His research has focused primarily on environmental evaluation systems
that relate to the recycling of construction materials and building life cycle(construction, usage, and disposal) environments.
He served as the director of the LCA Subcommittee within the ResearchCommittee on Global Environment in the Architectural Institute of Japan
until March 2023.
He is currently the organizer of the same committee.

Sumitomo Realty & Development Co., Ltd.
Sumitomo Realty has been working to solve social issues through its
business activities under its fundamental mission to "Create even bettersocial assets for the next generation."
Going forward, the Company will further contribute to realizing asustainable society by creating high-value social assets with environmentand social awareness.
◆ Sumitomo Realty’s initiatives on ESG and SDGs
https://www.sumitomo-rd.co.jp/english/sustainability/* The initiatives related to this release contribute to
the following SDGs objectives:
Goal 3: Good health and well-being
Goal 7: Affordable and clean energy
Goal 9: Industry, innovation and infrastructure
Goal 11: Sustainable cities and communities
Goal 12: Responsible consumption and production
Goal 13: Climate action
Goal 15: Life on land

<Reference> "Shinchiku Sokkurisan" Remodeling by Sumitomo Realty
In response to the devastating Great Hanshin-Awaji Earthquake of
1995, the Shinchiku Sokkurisan remodeling business was launchedwith the desire to find a way to renovate detached houses to makethem earthquake resistant without the high cost of rebuilding. Basedon our concept of providing safe and secure housing, we haveestablished a groundbreaking business model in the industry, offering
full remodeling at 50-70% of the price of rebuilding, featuring seismic
reinforcement and a fixed price system free of additional costs.
By leaving main structural components intact and utilizing existing materials such as foundations
and main frames, we have been able to reduce construction costs, reinforce seismic resistanceand thermal insulation, and enhance safety and comfort. We have handled more than 160,000
units (as of the end of March 2023) of such "full remodeling."

BeforeDuring renovation work

(Interior stripped down to its main frame)

After

We are also actively working to further promote decarbonization of existing houses. In December
2021, we began offering "High-Thermal Insulation Remodeling Plan" to improve energy-saving ofexisting houses, and in April 2022, we started offering "SUMIFU x ENEKARI," which enables
customers to install solar panels and storage batteries at zero initial cost, together with renovation.

<Related News Releases>■Remodeling to Meet Energy Conservation Standards for Newly-Built Houses High Thermal Insulation Remodeling Plan by
Shinchiku Sokkurisan Launched Nationwide (December 10, 2021)■Shinchiku Sokkurisan Remodeling Business to Start Offering SUMIFU x ENEKARI, a Solar Power Generation Service that
Delivers Continuous Peace of Mind (April 4, 2022)

<Reference> Initiatives of the “Shinchiku Sokkurisan” Business