Expo Sauna “Sun Buds” Recognized by Guinness World Records™.
Tallest Membrane Structure Sauna Building Official Certificate Awarding Ceremony Held on October 8 at the Expo site in Japan
2025.10.08
Taiyo Kogyo Corporation (Tokyo headquarters: Setagaya-ku, Tokyo; Osaka headquarters: Yodogawa-ku, Osaka; President: Yumi Nomura; hereafter “Taiyo Kogyo”), a company involved in large-scale membrane structures (tent structures) and civil engineering and logistics materials, has been selected as a Silver Partner of the organizers of the Japan International Exposition, Expo ‘2025 in Osaka, Kansai. The Expo sauna “Taiyo no Tsubomi” was certified by Guinness World Records™ as the Tallest membrane-structure sauna building on Wednesday, October 8, 2025. The official certificate awarding ceremony was held on the same day in the presence of the certifying official.
Taiyo no Tsubomi” is a sauna facility designed and constructed using the membrane structure technology that Taiyo Kogyo has cultivated over the years. Visitors can enjoy a sauna while feeling the energy of nature in a space covered with ETFE film membrane material that allows natural light to penetrate. It consists of a minimal aluminum frame that also serves as the structure, ETFE film* (0.25 mm thick, 440 g in weight), and a tetra-shaped unit composed only of air. The tetra shape allows the maximum amount of air to be encapsulated with the minimum amount of components, resulting in a lightweight, yet insulating, soft design that is unique to membranes. The sauna building reaches a height of 8.4 m, which was recognized as the “tallest membrane-structured sauna building.
*ETFE film: High-performance 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.
Comments from Yumi Nomura, President and Representative Director, Taiyo Kogyo Corporation
We are proud to announce that the “Sun Bud” has been certified by Guinness World Records as the tallest membrane-structured sauna building. It is a very gratifying achievement to see the challenges and innovations of our employees take shape in the wonderful setting of the Expo.
Sun Buds” is not just a sauna for toto. It is a place where visitors can feel connected to themselves, to others, and to the earth, based on the concept of “synergy with the earth. We believe that saunas have the power to connect people and bring peace to the world. This certification is a testament to our conceptual and technical capabilities, and gives us great confidence to support future challenges.
We are also considering the possibility of relocating the “Sun Buds” after the closing of the exhibition so that more people can experience them. We will continue to challenge new ideas and designs with an eye to the future, and while drawing out the infinite possibilities of membranes, we will give shape to the soft and warm society that the Taiyo Group is aiming for.
Guinness World Records™ Certification Overview
Official English record name: Tallest membrane-structure sauna building
・Official Japanese record name: Tallest membrane-structure sauna building
・Building of record: Expo sauna “Taiyo no Tsubomi”
・Certified height: 8.4m
Official Guinness World Record Certificate Awarding Ceremony for the Great Roofing Ring at Osaka Expo '70, Osaka, Japan
| Implementation Date and Time | Wednesday, October 8, 2025 at 9:00 a.m. |
| Venue | Osaka, Kansai Expo Expo Sauna “Sun Buds” (Future Life Zone) |
| Certification Awarding Ceremony Attendees | Mr. Jun Takashina, Deputy Secretary General, Japan Association for the International Exposition, 2025 Mr. Kenji Kobashi, Event Producer, Japan Association for the International Exposition, 2025 Mr. Yumi Nomura, President, Taiyo Kogyo Corporation (Sponsor) Ms. Mai Komuro, KOMPAS (Facility Design) Mr. Daisuke Akiyama, TTNE (Sauna Producer) |
Expo Sauna "Sun Buds" Overview
| Project name | Expo ’70 Osaka-Kansai Organizer’s Event Expo Sauna “Sun Buds |
| URL | https://www.taiyo-tsubomi.jp |
| Location | Future Life Zone at the Expo site |
| Organized by | Japan Association for the 2025 International Exposition, Inc. |
| Supported by | Taiyo Kogyo Corporation |
| Design | Mai Komuro /KOMPAS |
| Produced by | Daisuke Akiyama /TTNE Corporation |
| 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)
・Sponsored Expo sauna “Sun Buds” project (September 24, 2024)
https://www.taiyokogyo.co.jp/news/65155/
・Published latest information on Expo sauna “Sun Buds” (March 7, 2025)
https://www.taiyokogyo. co.jp/news/66300/
・Hosting Expo sauna “Taiyo no Tsubomi” international exchange event (September 19, 2025)
https://www.taiyokogyo.co.jp/news/68618/
About Taiyo Kogyo Corporation
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 an inspiring and comfortable environment to our customers. Under the corporate philosophy of “We will bring excitement and a comfortable environment to our customers by exploiting the infinite possibilities of membranes,” TSP Taiyo has been supporting the safety and security of society by utilizing the characteristics of light and strong materials to expand its business in various fields including construction, as symbolized by the roof of the giant dome, civil engineering, logistics, and environmental fields.
Together with group companies such as TSP Taiyo Corporation, which provides event consulting services, and ACTIO Corporation, which manages facilities, we are working to “make the world softer and the future warmer. We aim to “make the world soft and the future warm. We aim to “soften the world and warm the future.