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Project Details

Fabric 1

Fluon ETFE 250 HJ
Producer/Manufacturer: AGC Inc.
Primary Use: Main Fabric

Engineer Company 1
Taiyo Kogyo Corporation

Architect Company
KOMPAS

Fabrication Company
Taiyo Kogyo Corporation

Project Manager Company
TSP TAIYO Inc.

Installation Company
Taiyo Kogyo Corporation

Please describe the project specifications

The sauna facility “TAIYO TSUBOMI” was developed for Expo 2025 Osaka, Kansai, Japan, as part of a series of experiential attractions designed to engage and inspire visitors. In line with the Expo’s event concept, “SynaeEARTH: Connect with the Earth. Connect with the Future,” the client sought to create a transcendent, nature-integrated experience that would foster a deep sensory connection between people and the environment. The result is a striking sauna structure that incorporates ETFE film cushions for insulation, enabling a light-filled, ethereal atmosphere that departs from conventional sauna design.

What makes this project unique is its innovative use of ETFE film cushions to form the walls and roof of the sauna and adjacent facilities. These air-inflated cushions, arranged in modular tetra units, achieve both functional performance and sculptural beauty. With a high light transmission rate of 90%, the ETFE surface gently diffuses glare-free natural light into the space while maintaining user privacy. As daylight shifts—from sunrise to sunset and into the night—the translucent interior subtly transforms in tone, offering a meditative, immersive experience.

Each unit for the sauna stands approximately 2 meters wide and 8 meters tall. Ten of these units are seamlessly connected with minimal gaps to achieve a high level of insulation, crucial for creating an effective sauna environment. While the sauna area maximizes thermal retention, the water bath and the lounge are intentionally designed with greater spacing between units to encourage natural airflow. Structurally, the design minimizes the use of aluminum extrusion, placing visual and spatial emphasis on the soft, curved form of the cushions.

The project successfully delivered a new kind of value by combining wellness, architecture, and material innovation, specifically through the creative use of ETFE film. The unique modular structure, made entirely of membrane units, also demonstrated a key benefit of membrane architecture: adaptability. After the Expo, the structure can be deflated, compactly folded, and relocated for continued use elsewhere. This mobility echoes the origins of membrane structures, such as nomadic tents, and reflects a sustainable approach to temporary architecture. Given the high durability of the materials, the units can be reused without waste, aligning with environmentally conscious design principles.

Upon the opening of the EXPO, the sauna “TAIYO TSUBOMI” was met with overwhelming popularity and demand. Visitors described it as one of the most memorable and futuristic experiences at Expo 2025.

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