Hikari-doma House (House with a dirt floor to let in light)

Concept:
This project is a renovation of a wooden house for a young couple in Osaka, Japan. While surrounding buildings were gradually being replaced with newer structures, this house was left unused, seemingly frozen in time. The project aims to restore and modernize this 86-year-old home, located in a densely built neighborhood where reconstruction is challenging. By incorporating open seismic retrofitting, additional insulation, and airtight improvements, the renovation bridges history and modernity, creating a functional, comfortable, and timeless living space. The result is a home that embraces the pure and simple beauty unique to renovation projects.
Approach and Floor Plan:
A narrow pathway connecting the house to the street was extended indoors, leading to openings around a light-filled earthen floor ("hikari-doma"). This design ensures natural light, ventilation, and privacy, even within the dense urban context, while establishing a serene, cave-like ambiance. Open steel braced walls were employed to maintain structural integrity, creating a unified and open space with gentle connections through a central atrium.
Section Plan:
Above the light-filled doma, an atrium and large openings were designed to bring natural light deep into the home. The flooring in the doma area is covered with small-cut “Sabi” granite, providing the interior with the tactile, natural texture of stone, fostering a harmonious connection with nature.
Energy Efficiency:
The original earthen walls were preserved while adding high-performance insulation to the exterior to address common issues of airtightness and thermal performance in wooden structures. This approach allows the preservation of the traditional "shin-kabe" (exposed frame) design, a hallmark of Japanese wooden construction. Inside the walls, wood-wool cement boards were used to enhance sound absorption, noise reduction, humidity control, and thermal mass. These elements together create an energy-efficient and comfortable space while maintaining the aesthetic and functional value of traditional architecture.
Interior Elements:
The interior design focuses on natural materials such as wood, stone, metal, and glass, celebrating their inherent textures and colors. This minimalist approach establishes a harmonious and organic space that balances modernity with timeless elegance.
project title: Hikari-doma House (House with a dirt floor to let in light)
Architecture Firm: KNOOOT Inc.
Architect: Yasuyuki Kitamura
Address: Osaka-shi , JAPAN Completion: Revamped 2024.07 (Built in 1963)
Total Area: 78.65㎡
Main materials:
Floor: granite (rust), cypress (solid wood), softwood plywood, tatami mats
Wall: Wooden cement plate, Thinly painted polished finish material (decolier)
Pillars: Old wood, Japanese cypress, stainless steel (bracing)
Ceiling: Old wood, deck plate base, wood hair cement board, lauan plywood
Stairs: Rubber (laminated wood), striped steel plate (hot-dip galvanized)
Door: FRP flat plate (clear) Handrail: Agricultural single pipe, track rope
Photo: Masashige Akeda