membrane structures shape experimental sauna complex by KOMPAS at expo 2025 osaka

Kompas unveils multisensory sauna experience at Expo 2025 Osaka

KOMPAS presents Taiyo Tsubomi, an experimental sauna complex at the 2025 World Exposition site in Osaka. Positioned along the western seafront of the Expo grounds, the project, whose name translates to Bud of the Sun, introduces a sauna experience that engages light, heat, sound, and scent while fostering a deeper connection with the surrounding natural landscape. At just 161 square meters, the installation transforms a compact footprint into a layered architectural exploration of translucency, material innovation, and ritualized engagement.

The design organizes three primary membrane volumes on an open platform. Taiyo Tsubomi envelops visitors in warmth in a comfort lounge flooded with natural light and wind, and also features a cold bath sheltered beneath a balloon-like canopy. Each unit interacts with its environment, swaying in the breeze, reflecting the sky, and glowing with sunset hues. These subtle gestures amplify the sensory impact of the sauna, supporting the project’s concept of resonance with nature and an awakening of synesthesia.

all images by Yohei Sasakura

tetrahedral air-membrane structures shape Taiyo Tsubomi

Japanese studio KOMPAS includes tetrahedral air-membrane structures made from lightweight aluminum frames and ETFE film. This system encloses large volumes of air for insulation and stability and maintains a minimal physical footprint. Frosted ETFE diffuses sunlight during the day and creates a luminous interior at night, replacing the wooden interiors associated with saunas using a translucent, adaptable envelope. Taiyo Tsubomi also uses concrete canvas, a fabric-like material that hardens when wet, and 3D printed concrete for the organic-shaped cold bath. The modular nature of the membranes allows the units to be deflated, relocated, and reused, aligning with the Expo’s broader exploration of sustainable and flexible design for future societies.

Central to the experience is a sequence of eleven curated sauna rituals, guided by an attendant, where participants navigate a progression of heat, light, sound, and scent, transforming physical immersion into a narrative exploration of sensory perception. 

KOMPAS presents Taiyo Tsubomi at Expo 2025 Osaka

an experimental sauna complex positioned along the western seafront of the Expo grounds

a sauna experience that engages light, heat, sound, and scent

the design organizes three primary membrane volumes on an open platform

the sauna envelops visitors in warmth

each unit interacts with its environment

swaying in the breeze, reflecting the sky, and glowing with sunset hues

KOMPAS includes tetrahedral air-membrane structures

made from lightweight aluminum frames and ETFE film

1/7

large volumes of air are used for insulation

frosted ETFE diffuses sunlight during the day

replacing the wooden interiors associated with saunas using a translucent, adaptable envelope

Taiyo Tsubomi also features concrete canvas, a fabric-like material that hardens when wet

3D printed concrete shapes the organic-shaped cold bath

the modular nature of the membranes allows the units to be deflated, relocated, and reused

a luminous interior at night

project info:

name: Taiyo Tsubomi

architect: KOMPAS | @kompas_arch, TSP Taiyo Inc., Taiyo Kogyo Corp.

location: Expo 2025 Osaka | @expo2025japan, Yumeshima, Konohana-ward, Osaka, Japan

area: 161 square meters

owner / design client: Taiyo Kogyo Corp.

sauna produce: TTNE Inc.

landscape: SORA BOTANICAL GARDEN Project Inc.

lighting: REALROCKDESIGN Inc.

sound: KISSonix, Inc.

construction: TSP Taiyo Inc., Taiyo Kogyo Corp.

photographer: Yohei Sasakura | @yoheisasakura