Bronze Architecture, Building and Structure Design · 2026
Yoshinogawa Valley Headquarters Building Renovation
by Wataru Sato
- A' Design Award 2026 Bronze Winner in Architecture, Building and Structure Design
- Awarded April 15, 2026
- CLIENT: KITAOKA Group
- Estimated Number of Design Views: 7,194
- Verification code FE83265DFD · Verify this award
About Yoshinogawa Valley Headquarters Building Renovation
This project is a renovation of a 40-year-old prefabricated office building without demolition. A 50-meter linear void is inserted at the center of the existing structure, aligned with the east-west axis of the Yoshino River, reorganizing the building into two north-south wings. Named Yoshino River Valley, this spatial operation forms the backbone of the architecture. A north-oriented skylight provides stable daylight, while passive ventilation is generated through height and pressure differences. By reorganizing the building, the project avoids dividing the values it supports.
Wataru Sato's Yoshinogawa Valley Headquarters Building Renovation demonstrates a thoughtful synthesis of contemporary architectural language with responsive site-specific design strategies that honor both functional requirements and environmental context, situating this work within broader movements toward material authenticity and biophilic integration that have characterized progressive architectural practice across the early twenty-first century, the renovation engages traditions of modernist clarity wherein orthogonal geometries and restrained material palettes create legible spatial hierarchies while the generous overhangs and sheltering rooflines recall vernacular building wisdom responding to climatic conditions through passive design intelligence, the corrugated metal cladding system demonstrates technical sophistication through its dual performance as weather barrier and visual texture generator, the warm neutral coloration suggesting natural materials while maintaining the longevity and low maintenance characteristics of contemporary industrial fabrication, the compositional strategy reveals careful attention to proportional relationships wherein the two-story volume establishes vertical presence without overwhelming the domestic scale suggested by the horizontal lower wing that extends gracefully into the landscape creating transitional zones between built form and cultivated ground, the fenestration pattern exhibits disciplined restraint with glazing strategically positioned to capture views and natural light while maintaining privacy and thermal performance, the recessed entry portal framed by contrasting terracotta structural elements creates a moment of human-scale intimacy and threshold awareness that welcomes occupants through material and chromatic differentiation, the landscape design emerges as integral rather than supplementary to the architectural proposition with the flowing concrete hardscape establishing circulation patterns that encourage meandering exploration rather than rigid linear procession, the sculptural placement of weathered boulders introduces geological time and elemental presence into the composition connecting the built environment to broader natural processes while providing focal points that anchor the eye and invite contemplation, the selection of drought-tolerant ornamental grasses and bamboo demonstrates environmental stewardship and water-conscious planting strategies while the mature Japanese maple offers seasonal transformation and chromatic drama that will deepen the experiential richness of the space across yearly cycles, the presence of multiple generations occupying and activating the architecture speaks to the project's success in creating flexible resilient spaces that accommodate varied patterns of use from children's spontaneous play to adult observation and conversation, the photograph captures the building under soft atmospheric conditions where diffused light renders materials and colors with truthful clarity while the gentle sky and distant vegetation establish the structure within its broader environmental setting suggesting integration rather than isolation, this work invites consideration of how architectural renovation might balance respect for existing structures with contemporary performance expectations, how material selection communicates values of durability and authenticity, and how landscape integration transforms buildings from objects into inhabited ecosystems that support both human community and ecological health.
Press Kit
- Unique Properties
- Inspired by the Yoshinogawa River, the design translates the structure of a valley into architecture. By dividing the existing building into two volumes and inserting a linear void, a valley-like interior is created.
A 50-meter skylight brings daylight inside, while the void enables ventilation, greenery, and social interaction. This configuration integrates environmental elements into the workplace.
Through renovation, the design reinterprets an existing office and proposes a new spatial model. - Dimensions & Packaging
- A valley-like void and continuous skylight are introduced at the center of a 50-meter prefabricated office building. The two-story void brings daylight to the ground floor and enhances natural ventilation.
A 7-meter Benjamin fig tree is placed at the center, visible from both levels. Planting along the void forms a layered green environment connected to the exterior.
Existing structure and finishes are retained, creating a composition where old and new materials coexist. - Tags
- Prefabricated office renovation, open lounge, atrium and skylight, regional architecture, nature-inspired workspace, Yoshino River
- Production Technology
- The project renovates an existing prefabricated office building without demolition.
A central valley-like void integrates daylight, ventilation, and greenery. Continuous skylights provide stable north light, while passive ventilation is driven by height and pressure differences.
Spatial organization is redefined as an environmental system, reducing reliance on mechanical equipment. Existing structure and finishes are retained, forming a layered expression and a sustainable model for reuse. - Design Challenge
- The primary challenge was to renew the environmental and social value of a deteriorated prefabricated office without demolition or new construction.
Introducing a skylight and central void into an enclosed structure required coordination of structural, safety, and cost constraints.
Rather than relying on equipment, the design redefines spatial organization as an environmental system.
The project shows that architectural operations can generate new value within existing buildings. - Project Duration
- The project started in January 2023 in Miyoshi Town, Tokushima Prefecture, Japan, and was completed in August 2024.
- Operation Flow
- The building transforms a closed office into an open environment accessible to families and the local community.
The central valley acts as a social axis supporting movement, staying, and interaction. The ground floor serves as a shared space, while the upper floor provides flexible work areas.
Users are not assigned fixed workplaces but choose spaces as needed. Through everyday use, the project encourages informal encounters and redefines how work and social life coexist. - Research
- This research examines how renovation can achieve environmental performance comparable to new construction.
A skylight and central void introduce daylight and passive ventilation, reducing reliance on mechanical systems.
Monitoring shows that artificial lighting is unnecessary during daytime and HVAC demand is reduced. Annual energy decreased by about 73,000 kWh, with savings of 65% in lighting and 30% in air conditioning.
The project presents a replicable model for sustainable renovation. - Inspiration
- The project draws inspiration from the Yoshinogawa River, known as the Mother River of Tokushima.
Rather than referencing its form directly, the design interprets the river as a spatial structure.
By inserting a linear void through the existing building, the architecture transforms the logic of a valley into an interior condition, bringing light, wind, and greenery deep into the space, while also inviting relationships among people, families, and the local community. - Image Credits
- Image #1: Photographer Keita Yamamoto (Architectural Photography), Kitaoka Group Headquarters Renovation, 2024.
Image #2: Photographer Keita Yamamoto (Architectural Photography), Kitaoka Group Headquarters Renovation, 2024.
Image #3: Photographer Keita Yamamoto (Architectural Photography), Kitaoka Group Headquarters Renovation, 2024.
Image #4: Photographer Keita Yamamoto (Architectural Photography), Kitaoka Group Headquarters Renovation, 2024.
Image #5: Photographer Keita Yamamoto (Architectural Photography), Kitaoka Group Headquarters Renovation, 2024.
Colors of Yoshinogawa Valley Headquarters Building Renovation
Grand Interview about Yoshinogawa Valley Headquarters Building Renovation
When I first visited the building, what impressed me most was not the building itself, but the landscape of the Yoshino River stretching beyond it. In particular, I noticed that the river and the building were aligned along almost the same axis, and this observation became the starting point of the project.The Yoshino River and the surrounding valley are often referred to as the “mother river” of Tokushima Prefecture, having historically nurtured the region’s culture and industry. I wondered whether bringing the river’s axis of flow into the building as a linear void could generate new flows of people, culture, and activity within Kitaoka-group headquarters. To achieve this, we divided the building into two wings centered around the entrance and inserted a 50-meter-long linear void between them.We call this space the “Valley of Light.” By allowing light, wind, views, and human activity to pass through the building, we sought to bring the presence of the Yoshino River into the interior and transform it into a new organizing principle for the entire architecture.
In Japan, many anonymous existing buildings are replaced through a cycle of demolition and reconstruction. However, although this building was over forty years old, it had been built under post-1981 seismic regulations and its structural frame remained in excellent condition. We began the design process by asking a simple question: “Does it really need to be demolished?”Existing buildings accumulate layers of time, memory, and relationships with their communities—qualities that never appear on drawings. Rather than tearing the building down and starting over, we believed it was possible to create new value while preserving and activating those accumulated qualities.There are countless buildings of the same generation throughout Japan. Through this project, we wanted to propose the idea that such buildings are not only reusable, but can also be transformed into architecture with a level of originality that sometimes exceeds that of new construction.
Before improving mechanical systems, we first considered space itself as an environmental device.The central void and skylights bring natural daylight deep into the building, significantly reducing the need for artificial lighting during the day. At the same time, the vertical movement of air created by the void promotes natural ventilation and helps reduce cooling and heating loads.As a result, primary energy consumption was reduced by approximately 30 percent compared to the building before renovation. We believe environmental performance should not be something added afterward through equipment alone; it should emerge from the spatial composition itself. The form of architecture should generate environmental performance, and energy reduction should be a consequence of that design logic. This was the architectural approach we sought to realize.
The Yoshino River is more than a scenic landscape; it is an essential force that has supported the culture and industry of the region. Rather than imitating the physical form of the river, we sought to translate its behavior into architectural space.A river continuously gathers and carries people, goods, and information as it flows. Similarly, the central void was designed as a space that accommodates movement and interaction while connecting the entire building.For us, regional identity is not about applying local motifs or stylistic references. It is about understanding the forces, relationships, and dynamics inherent to a place and reconstructing them as a new architectural principle.
Excavating a 50-meter-long opening through the center of an existing building presented significant structural and fire-safety challenges.We repeatedly collaborated with structural engineers and contractors to verify the impact on the existing structure and ensure the safety of the large daylight openings. Throughout this process, the key was not to reject the existing building, but to intervene with a deep understanding of its characteristics and limitations.Ultimately, these constraints refined the design. They pushed us to uncover the latent potential of the existing structure while creating a completely new spatial experience.
The Benjamin tree was never intended as a decorative element.The central void is a place where not only light and wind, but also human activities intersect. By placing a tree at its center, we hoped to create a natural focal point that encourages people to gather, stay, and engage in conversation.Plants also grow and change over time. For us, the tree symbolizes an environment that continues to evolve through use, rather than a building that is considered complete at the moment of construction.
From the beginning, the team at Kitaokagumi had a clear vision of communicating new ways of working from a regional city to the wider world. Because of this, they strongly resonated with the idea of treating the office not merely as a workplace, but as a platform for experimenting with new forms of work and interaction.In regional areas of Japan, the relationship between family life and work tends to be closer than in large metropolitan cities. We sought to embrace this characteristic by proposing an environment where not only employees, but also their families and members of the local community could naturally engage with the space.Since completion, the building has hosted community events, welcomed visitors, and supported a variety of activities beyond conventional office functions. Seeing the architecture begin to operate as an interface connecting the company, the community, work, and everyday life has been one of the project’s most meaningful achievements.
Our practice is deeply interested in rediscovering and renewing existing value rather than simply creating something new.This award demonstrates that architecture does not need to begin from a blank slate. Even an anonymous prefabricated building in a regional city can become a source of new cultural value when its latent potential is carefully reinterpreted.We see this not merely as recognition of a single project, but as an acknowledgment of our broader design approach—one that focuses on editing, transforming, and reactivating what already exists.
Although working styles have changed dramatically in recent years, many offices still rely on desk-centered layouts.Through workplace research, observations of actual usage patterns, and interviews with employees, we came to believe that the key question is no longer where people work, but how they encounter one another.As a result, we designed an environment composed of diverse places to work and opportunities for spontaneous interaction rather than fixed seating arrangements. For us, flexibility is not simply a matter of layout freedom; it is a spatial strategy that supports organizational culture and collaboration.
We regard the existing building itself as a material, equal in importance to any new material introduced into the project.Throughout the design process, we carefully observed existing finishes, structural elements, and traces of past use, considering how they could be integrated with new interventions. Preserving existing elements was never about conserving the past for its own sake; it was a creative act aimed at generating new value.We believe that architecture is not only about creating value from nothing—from zero to one—but also about renewing value by reconnecting things that already exist. This project was an attempt to demonstrate the potential of that approach.