Mitsui Home Begins Construction of "Akiya Hayama International School"

Mitsui Home Co., Ltd. (Headquarters: Koto-ku, Tokyo; President: Hidetoshi Nojima; hereinafter "the Company") is pleased to announce that construction has commenced on the "Akiya Hayama International School," for which the Company is responsible for the wooden frame and double-floor construction. This facility will serve as the campus for an international school scheduled to open in Shonan International Village, Yokosuka City, Kanagawa Prefecture, in August 2027. In this project, which involves a mix of traditional wooden post-and-beam construction and platform framing, the Company will be responsible for the integrated construction of all five wooden buildings.

Key Highlights of This Release:

* Adoption of a wooden truss with a maximum span of approximately 28m (Note 1) for the gymnasium, a first for Mitsui Home, realizing a large space filled with the warmth of wood. * A large-scale wooden educational facility that achieves a high level of environmental performance and design aesthetics through Mitsui Home's wooden construction technology.

Akiya Hayama International School (Image)

The Akiya Hayama International School is set to open as an international school aiming to foster individuals who can thrive globally, adopting an international standard educational curriculum. The planned campus will consist of five buildings: the gymnasium, a small hall/atelier building, a lower elementary school building, a cafe building, and an upper elementary school building (second phase construction). All five buildings will feature exposed wooden structures and are planned to incorporate a next-generation solar power system (solar panel integrated roof (Note 2)). Furthermore, the adoption of a truss with a span of approximately 28m, a first for the Company, will create an open gymnasium that allows visitors to feel the warmth of wood. This initiative not only contributes to decarbonization but also aims to promote the relocation of families with children and address regional population decline and revitalization by harmonizing with the rich natural environment of Shonan International Village and regenerating it as an educational hub.

Since its founding, the Company has contributed to the realization of affluent lifestyles and a sustainable society through its home-building expertise utilizing "wood." Moving forward, the Company will continue to explore the potential of "wood," promote the creation of environmentally conscious spaces based on wooden construction technology, actively engage in the construction of educational facilities, and contribute to the realization of a decarbonized society.

Adoption of a wooden truss with a maximum span of approximately 28m for the gymnasium, a first for Mitsui Home, realizing a large space filled with the warmth of wood

The construction of the Akiya Hayama International School gymnasium will feature a wooden truss with a span of approximately 28m, a first for the Company. This will create a spacious, large area while conveying the warmth and texture of wood, along with high seismic performance. Additionally, by using standard lumber instead of engineered lumber for the truss, costs have been successfully reduced.

As the approximately 28m span wooden truss is an unprecedented undertaking, structural analysis was conducted in advance, and verification tests were carried out with the cooperation of Akita Prefectural University, with whom the Company has jointly researched wooden truss structures. From December 2024 to December 2025, within the university campus, a "creep test (Note 3)" to measure deformation under long-term load and "construction lifting verification" were performed, completing thorough verification of both structural strength and construction safety.

A large-scale wooden educational facility that achieves a high level of environmental performance and design aesthetics through Mitsui Home's wooden construction technology

This project encapsulates the wooden construction technologies and know-how cultivated by the Company. From the load-bearing walls applied with technology from the single-story wooden warehouse "Smart Warehouse (Note 4)" to the high-strength insulation structural material "Double Shield Panel (Note 5)" used for the roof, excellent insulation performance and design aesthetics have been achieved. Furthermore, the school buildings are unified with an exposed wood design and incorporate a next-generation solar power system (solar panel integrated roof (Note 2)), contributing to a sustainable society through high environmental performance.

Facility Overview

Facility Name: Akiya Hayama International School

Construction Site: Part of 2-2388-63, 2388-64, 3194-2, 3210-10, Shonan International Village, Yokosuka City, Kanagawa Prefecture

Design and Supervision: Erika Nakagawa Architects & Associates Co., Ltd.

Contractor: KIKUSHIMA Corporation

Wooden Frame and Double Floor Construction: Mitsui Home Co., Ltd.

Site Area: 26929.14m2

Building Area: 3243.19m2

Total Floor Area: 3280.80m2

Scale and Structure: Gymnasium Building (Single-story, Platform Framing)

Small Hall/Atelier Building / Lower Elementary School Building (Two-story, Post-and-Beam Construction)

Cafe Building / Guardhouse (Single-story, Post-and-Beam Construction)

Construction Period: May 2026 - July 2027

Scene from the Groundbreaking Ceremony held on April 19, 2026

(Note 1): A truss is a structural form composed of triangles as basic units. It is characterized by its ability to create a strong structure by combining relatively slender members.

(Note 2): A solar panel integrated roof is a system where roofing material and solar panels are combined into one. The Roof-1 developed by Monochrome Inc. is planned to be installed (https://www.monochrome.so/roof)

(Note 3): In construction, a creep test is a test that measures the degree of deformation over time by continuously applying a constant load to materials such as concrete and wood for an extended period. It provides essential data for safe design to prevent long-term sagging and deformation of buildings.

(Note 4): "Smart Warehouse" is a single-story, simple wooden post-and-beam warehouse using environmentally friendly lumber (lumber for platform framing that meets general distribution standards). (https://www.mokuken.mitsuihome.co.jp/products/smartsouko)

(Note 5): Double Shield Panel is a structural insulation panel with expanded polystyrene (EPS) as the core material, sandwiched between structural panels (OSB) made of integrated hardwood chips. It has excellent structural strength and is widely used in large-scale buildings. (https://www.mokuken.mitsuihome.co.jp/products/dsp)

Mitsui Home Promotes MOCX Green Project

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

The MOCX Green Project is a project through which Mitsui Home, having built over 250,000 wooden structures, expands the possibilities of wooden construction and contributes to decarbonization through various initiatives.

Sustainability of the Mitsui Fudosan Group

Based on the "& mark" philosophy of "creating new value through coexistence, mutual existence, and co-creation, and continuing to take on challenges to do so," the Mitsui Fudosan Group views "creation of social value" and "creation of economic value" as two wheels of a cart. The Group believes that creating social value leads to the creation of economic value, which in turn enables the creation of even greater social value. Upon the establishment of the new Group Management Philosophy in April 2024, the following six items were identified as "GROUP MATERIALITY (Issues to Focus On)": "1. Contribution to Industrial Competitiveness," "2. Coexistence with the Environment," "3. Health and Vitality," "4. Safety and Security," "5. Diversity & Inclusion," and "6. Compliance and Governance." The Group will address these materialities through its core business and contribute to sustainability.

[Reference]

* "Group Long-Term Management Policy" 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 formulated the "&EARTH for Nature" declaration for environmental coexistence in town development, viewing "environment" as an integration of nature, people, and the community, and promoting town development that expands a rich "environment" and passes it on to future generations. The five priority issues in this declaration are: "Protecting and Nurturing Greenery," "Leveraging the Appeal of Water," "Enriching Ecosystems," "Connecting Community Sentiments," and "Circulating Natural Resources." The initiatives in this release contribute to two of the priority issues in "&EARTH for Nature."