Expo Sauna “Sun Buds” Update

(Tokyo headquarters: Setagaya-ku, Tokyo; Osaka headquarters: Yodogawa-ku, Osaka; President: Yumi Nomura; hereafter “Taiyo Kogyo”), a manufacturer of large membrane structures (tent structures), civil engineering and logistics materials, is sponsoring the Japan International Exposition 2025 (Osaka/Kansai Expo) as a Silver Partner in the organizers’ event The Expo sauna “Sun Buds” is steadily being prepared to welcome visitors to the Expo in preparation for the opening of the Expo. From design, architecture, and construction to operation, Taiyo Group’s solutions will be brought together and deployed in unison.

The “Sun Bud” is a sauna that allows visitors to experience the theme of the Osaka-Kansai Expo, “Designing a Future Society where Life Shines Brightly. It is characterized by a beautiful, life-like shape of petal-like air membrane cushions that gather to form a single bud, stretching toward the sun. The sun’s energy descends on the “sun buds,” which are covered with the air of the sea, plants, and trees. The space created by the delicate and strong membrane is filled with the energy of nature, and is intended to harmonize our body and soul, and to bring us back to our origins as humans.

In the “Sun Buds,” approximately 15,000 people will be able to enjoy a sauna in their swimsuits during the period of the project in a space covered with ETFE film* membrane material that allows natural light to penetrate. Pioneering buildings utilizing ETFE film have been built in the past, such as the Mercedes-Benz Stadium (Atlanta, Georgia, U.S.A.), but the frame of “The Sun Bud” consists of a minimal aluminum frame that also serves as the structure, ETFE film (0.25 mm thick, weighing 440 g) and air only. The tetra-shaped unit is the first of its kind to be used in the “buds” structure. The tetra shape enables the maximum volume of air to be encapsulated with the minimum number of components, and the soft design unique to the lightweight yet heat-insulating membrane is realized. The use of pear-shaped ETFE, which diffuses light, reflects the sun’s rays brilliantly, allowing you to feel the energy of nature even from inside the sauna. The “Sun Buds” consists of three tetra-shaped units: a sauna that traps the heat inside like a bud, a lounge that is tinted with light and breezes out, and a water bath made with 3D printing technology. The sauna is a completely new type of sauna that combines the delicate and powerful membrane technology with the power of nature.

The unit-type structure, which can be compactly stored when deflated, and the foundation structure, which can be easily relocated, make it possible to reconfigure and reuse the sauna in a new location after Expo 2010 Osaka/Kansai is closed.

*ETFE Film: Highly functional fluoropolymer rolled into film form. With its light weight, high durability and transparency, it is attracting attention as a material that can replace glass for new architectural expression. Despite its thickness of 0.25 mm, it is durable for more than 20 years and has fire retardant properties.

Daisuke Akiyama, who is known as a “sauna master” for his efforts to promote sauna culture, including the establishment of the “Sauna Society of Japan” to advance research on sauna and clarify its medical benefits, is in charge of producing the “sun buds”.

We have been exploring the possibilities of membranes and how they can contribute to world peace at the Expo, a gathering place for people from all over the world. Now, through the membrane sauna “Sun Buds,” we are offering three experiences that will help you relax your mind and body and lead to a “future society where life shines brightly.

First, to be enveloped by the warmth of the sauna, to release oneself in deep relaxation, and to connect with one’s true self.

Second, to experience a special space with people from all over the world and to connect beyond cultural and regional boundaries.

Third, to sharpen our senses, to experience synesthesia with the various colors, sounds, and scents of nature, and to connect with the earth.

By expanding these three connections, we hope to enrich and nurture the “soft and warm society” that the Taiyo Group is aiming for. We hope that as many people as possible will enjoy this special experience.

In 1970, Japan’s first World Exposition was held in Osaka under the theme of “Progress and Harmony of Mankind. Taiyo Kogyo was the first company in the world to realize a giant air membrane structure with a low-rise system, the principle of which was also used in the Tokyo Dome, in the “American Pavilion” at this Expo. At the time, Taiyo Kogyo was responsible for approximately 90% of the tent structures at the venue, and this was the first time that tents were recognized around the world as a new type of structure, rather than simply being used as sunshades. While Taiyo Kogyo is supporting the construction of tent structures for various facilities at this year’s Osaka-Kansai Expo, the “Sun Buds” project is the first project that Taiyo Kogyo is supporting.

Project name	Expo ’70 Osaka-Kansai Organizer’s Event Expo Sauna “TAIYO TSUBOMI” (English name: EXPO SAUNA “TAIYO TSUBOMI”)
URL	https://www.taiyo-tsubomi.jp
Location	Green World in the Expo site
Organized by	Japan Association for the 2025 International Exposition, Inc.
Supported by	Taiyo Kogyo Corporation
DESIGN	KOMPAS
Produced by	Daisuke Akiyama /TTNE Corporation
Period	April 13, 2025 – October 13, 2025
Expected visitors	Approx. 15,000 visitors
Scale	(Building area): 179.43 m2 (Total floor area): 160.83 m2
Structure	Administration building, rest area S construction, sauna building, water bath building, relax lounge building AL construction
Designed by.	KOMPAS, TSP Taiyo Corporation, Taiyo Kogyo Co.
Construction	TSP Taiyo Corporation, Taiyo Kogyo Corporation
Management	Actio Corporation

Reference: Past press releases related to this matter (our website)]
・Cosponsorship of Expo ’70 Sauna “Sun Buds” Project (September 24, 2024)
https://www.taiyokogyo.co.jp/news/65155/

Taiyo Kogyo is a leading manufacturer of large membrane surface structures that are economical, easy to install, translucent, and well designed. Under the corporate philosophy of “Unlocking the infinite possibilities of membranes to deliver inspiring and comfortable environments to our customers,” Taiyo Kogyo is also expanding its business into the environmental field and other fields. Under our corporate philosophy of “Delivering a comfortable and inspiring environment to our customers by exploiting the infinite possibilities of membranes,” we are also expanding our business into environmental fields and other areas to support the safety and security of society.

Taiyo Kogyo Corporation, TSP Taiyo Corporation, and Actio Corporation.

The Taiyo Group was founded in 1922 as Nomura Tent Shokai, and later restarted with a single sewing machine and a pair of scissors amidst the burnt ruins of the postwar period. Since its foundation, the company has been introducing unique products that take advantage of the characteristics of “membrane” materials, based on the desire to “contribute to society, even if only a little, and to deliver excitement to as many people as possible. Based on membrane technology, TSP Taiyo and Actio were born while undertaking the construction and operation of the large-scale pavilion at the 1970 Osaka World’s Fair, and the three companies of today’s group, which originated with Nomura Tent Shokai, were formed. On the occasion of the 100th anniversary of the group’s founding, we will continue to pursue the possibilities of membranes, spaces, and experiences while enhancing synergy among the three group companies. We aim to “make the world softer and the future warmer. We aim to “make the world softer and the future warmer”.