Mitsui Home Group Completes Its First Wooden Koban (Police Box)

Mitsui Home Co., Ltd. (Headquarters: Koto-ku, Tokyo; President and CEO: Hidetoshi Nojima; hereinafter "the Company") announces that its regional operating subsidiary, Mitsui Home Hokkaido Co., Ltd. (Headquarters: Kita-ku, Sapporo, Hokkaido; President and CEO: Kiyoshi Ito; hereinafter "Mitsui Home Hokkaido"), has completed the construction of five wooden koban (police boxes) across Hokkaido. This project involved building five new wooden koban in Sapporo City and Eniwa City. This marks the first time the Mitsui Home Group has constructed and completed wooden koban. By using cross-laminated timber (CLT) for the structural framework and adopting box-type units pre-assembled in a factory, the project achieved high-quality, efficient construction while prioritizing safety and environmental considerations—establishing police boxes as reliable hubs for community safety and security. Additionally, through the active use of locally sourced building materials from Hokkaido, the project contributes to building a sustainable local society.

Key Features of the Project

● First wooden koban construction by the Mitsui Home Group

● Achieved safety and environmental performance through CLT structural elements and factory-assembled box-type units

● Contributes to regional revitalization through active use of local materials and collaboration with local companies

● Contributes to a decarbonized society through improved thermal insulation performance and carbon storage inherent in wooden construction

Genmachi Koban

Asahikawa Koban

Hokuto Koban

Kitano Koban

Megumino Koban

Construction began in late December 2025 and all five buildings were completed by May 2026.

Since its founding, the Company has contributed to enriched living and sustainable societies through housing that makes full use of wood. Going forward, Mitsui Home will continue to explore the potential of wood, promoting wooden construction for medium- to large-scale buildings to contribute further to a decarbonized society.

Achieving Safety and Environmental Performance with CLT and Factory-Assembled Box Units

The construction of koban—vital hubs for residents' safety and security—requires not only high safety standards but also environmental responsibility and contributions to the local community. To meet these demands efficiently, the project used domestically produced Japanese cedar CLT, which offers excellent strength and rigidity, and adopted box-type units with primary structural components pre-assembled in a factory. This approach ensured high safety standards while enabling easy reuse in cases where relocation or transfer of the units becomes necessary.

CLT units being installed and joined during structural construction

Contributing to the Local Community through Use of Local Materials and Collaboration with Local Enterprises

This project actively utilized local Hokkaido materials: Hokkaido-grown Sakhalin fir for underlayment, Hokkaido-grown Japanese larch for structural plywood and structural LVL (Laminated Veneer Lumber), and Hokkaido-grown white birch for custom furniture such as counters and desks. White birch, in particular, is beloved by local residents, so the exterior of each koban features decorative accent louvers styled to resemble birch as an iconic design element. Additionally, structural construction was carried out by Nishijo Sangyo Co., Ltd. (Headquarters: Otaru, Hokkaido; President: Kimitoshi Nishijo), a local construction firm, with collaboration across design, construction, and quality control involving various companies within Hokkaido. These efforts contribute to promoting local production for local consumption and revitalizing the regional economy.

Example of exterior with wooden-style accent louvers Counter made from Hokkaido-grown white birch

Contributing to a Decarbonized Society through Enhanced Insulation and Carbon Storage

To maintain indoor temperatures at approximately 15°C or higher during winter in Hokkaido’s cold, snowy climate, the project adopted external insulation for exterior walls and resin-framed windows with triple-glazed insulated glass, achieving high thermal insulation performance (HEAT20: G2 level). Additionally, efficient indoor temperature control is supported by heat-exchange ventilation fans and high-efficiency air conditioning. Energy-saving features include LED lighting and water-saving faucets with eco-handles, further enhancing energy efficiency.

Wood absorbs CO2 during growth and continues to store carbon even after being processed into building materials. The total carbon storage across the five buildings amounts to 82 t-CO2 (equivalent to the carbon stored by 99 mature 50-year-old cedar trees). Furthermore, CLT offers excellent strength and rigidity, enabling wood to be used in medium- and large-scale buildings where it has traditionally been underutilized. This method is gaining attention as a key technology for decarbonization, with the Ministry of Land, Infrastructure, Transport and Tourism actively promoting its adoption. The use of wood also reduces CO2 emissions by minimizing transportation and construction vehicle usage through the utilization of locally sourced timber, further contributing to a decarbonized society.

(1) CLT (Cross-Laminated Timber): A large-scale wooden panel made by stacking layers of lumber with fibers oriented perpendicularly, then bonding and pressing them together. CLT offers high strength and rigidity and is used for structural components such as walls, floors, and roofs. It can achieve fire resistance depending on thickness and allows high-precision factory fabrication, making it increasingly suitable for medium- and large-scale buildings.

(2) A wholly owned subsidiary of Mitsui Home, operating direct sales and construction services with a focus on localized business and customer satisfaction tailored to regional needs.

(3) LVL (Laminated Veneer Lumber): A structural wood product made by stacking thin veneers with fibers aligned in the same direction and bonding them together.

(4) General Incorporated Association: Japan Research Group on High-Performance Insulated Housing for the Next 20 Years.

(5) Carbon storage volume calculated based on the "Guidelines for Indicating Carbon Storage in Wood Used in Buildings" published by the Forestry Agency. Equivalent cedar tree volume also calculated.

https://www.rinya.maff.go.jp/j/mokusan/mieruka.html

(6) Ministry of Land, Infrastructure, Transport and Tourism official website "Initiatives toward CLT Promotion": https://www.mlit.go.jp/jutakukentiku/house/jutakukentiku_house_tk4_000088.html

Project Overview

Client: Police Mutual Aid Association Hokkaido Branch

Project Name: FY2025 Purchased-Type Koban and Police Substation Development Project (First Phase)

Design and Supervision: Mitsui Home Hokkaido Co., Ltd.

Construction: Mitsui Home Hokkaido Co., Ltd.

Scale and Structure: Single-story and two-story buildings, five in total, wood construction (box-type CLT unit structure)

Construction Period: December 2025 – May 2026

Facility Details

1 Genmachi Koban

Facility Name: Higashi Police Station Genmachi Koban

Location: 15-19, Kita 24-jo Higashi 18-chome, Higashi-ku, Sapporo

Stories: Two-story

2 Asahikawa Koban

Facility Name: Kita Police Station Asahikawa Koban

Location: 335-5, Kita 39-jo Nishi 5-chome, Kita-ku, Sapporo

Stories: Two-story

3 Hokuto Koban

Facility Name: Shiroishi Police Station Hokuto Koban

Location: 11-2, 11-3, Kitago 4-jo 13-chome, Shiroishi-ku, Sapporo

Stories: Single-story

4 Kitano Koban

Facility Name: Toyohira Police Station Kitano Koban

Location: 354-17, Kita 4-jo 5-chome, Kiyota-ku, Sapporo

Stories: Single-story

5 Megumino Koban

Facility Name: Chitose Police Station Megumino Koban

Location: 23-6, 23-9, Megumino Nishi 1-chome, Eniwa City

Stories: Single-story

【Mitsui Home Promotes the MOCX Green Project】

https://www.mitsuihome.co.jp/company/mocx_green_project/

The MOCX Green Project is an initiative by Mitsui Home—having built over 250,000 wooden structures to date—to expand the possibilities of wooden construction and contribute to decarbonization through diverse initiatives.

Sustainability at the Mitsui Fudosan Group

The Mitsui Fudosan Group operates under the "& Mark" philosophy of "continuously challenging ourselves to create new value through coexistence, collaboration, and co-creation." The Group views "social value creation" and "economic value creation" as two wheels of a car—each driving the other. Creating social value leads to economic value, which in turn enables even greater social value. At the time of establishing its new Group Management Philosophy in April 2024, the Group identified six key material issues—"1. Contribution to Industrial Competitiveness," "2. Coexistence with the Environment," "3. Health and Vitality," "4. Safety and Security," "5. Diversity & Inclusion," and "6. Compliance & Governance." The Group is addressing these material issues through its core business to contribute to sustainability.

【References】

・"Group Long-Term Management Strategy": https://www.mitsuifudosan.co.jp/corporate/innovation2030/

・"Group Materiality": https://www.mitsuifudosan.co.jp/esg_csr/approach/materiality/

・"& EARTH for Nature": https://www.mitsuifudosan.co.jp/business/development/earth/for-nature/

In April 2025, the Group established "&EARTH for Nature," an environmental coexistence declaration for urban development, recognizing "environment" as the integration of nature, people, and communities. The initiative aims to expand rich environments and pass them on to future generations. Five priority areas have been defined under this declaration: "Protecting and Nurturing Green Spaces," "Enhancing the Appeal of Water," "Enriching Ecosystems," "Connecting Community Aspirations," and "Cycling Natural Resources." This project contributes to two of these priority areas under "&EARTH for Nature."