Ryonetsu Co., Ltd.
Japanese building-services engineering firm specializing in HVAC, plumbing, and fire-protection installation and maintenance, headquartered in Fukuoka.
Last updated September 29, 2026
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Overview
Ryonetsu Co., Ltd. (株式会社 菱熱) is a Japanese building-services engineering company headquartered in Hakata-ku, Fukuoka City. Founded in August 1959 as Kyushu Shinryo Reinetu Co., Ltd. (九州新菱冷熱株式会社), the company was renamed Ryonetsu Co., Ltd. in 1977. It designs, installs, and maintains mechanical building services — air-conditioning and ventilation, plumbing and sanitary, fire-protection, refrigeration, electrical and telecommunications, and machinery installation — for commercial, medical, hotel, logistics, and airport facilities. Its works list includes projects such as Yakuin3, the Fukuoka Airport facility hangar, the Heavy Industry Memorial Nagasaki Hospital, D-Marks Nishi-Shinjuku Tower, and the DHC Karatsu Seaside Hotel new east wing. The company operates primarily across Kyushu, with branches in Kitakyushu, Saga, Nagasaki, Oita, Kumamoto, Miyazaki, and Kagoshima, plus a Tokyo branch office and an Okinawa office. Its head office is in Fukuoka City. As of September 30, 2025, it employed 305 people. Its major shareholders are Mitsubishi Heavy Industries, Ltd. and Kyushu Electric Power Co., Inc.; in January 2023 it became a group company of Kyushu Electric Power. The company's corporate motto, "Research, Cooperation, Execution" (研究 協力 実行), dates from its founding in 1959. Ryonetsu's business spans design and construction, maintenance, renewal, and green innovation. It offers comprehensive facility maintenance services, consulting and renewal services, and equipment sales and installation, including the commercial EcoCute water heater "Cuteon." It is registered as a ZEB (Net Zero Energy Building) planner and ZEB leading owner, and completed the ZEB conversion of its head office building in February 2020. It holds ISO 14001 and ISO 9001 certifications and various construction business licenses from the Ministry of Land, Infrastructure, Transport and Tourism.
History
Ryonetsu Co., Ltd. was established in August 1959 as Kyushu Shinryo Reinetu Co., Ltd. (九州新菱冷熱株式会社) in Ishiro-cho, Fukuoka City, with the simultaneous opening of its Kitakyushu sales office. The company's founding corporate motto, "Research, Cooperation, Execution" (研究 協力 実行), was chosen at that time and remains its management philosophy; it was written by the then-chairman of Kyushu Electric Power, Mr. Kawarayashi, and is still displayed in the president's office. In April 1960, the Oita sales office opened, followed by the Nagasaki sales office in June 1964. In 1969, the company opened the Saga, Miyazaki, and Genkai offices and relocated its head office to its current location. The Kumamoto and Kagoshima sales offices opened in 1971. In 1977, the company relocated its Kitakyushu sales office to its current location, opened the Okinawa and Tokyo sales offices, and changed its name to Ryonetsu Co., Ltd. (株式会社 菱熱). The head office building was expanded in November 1979. In April 1982, the Oita sales office was rebuilt and relocated to its current location; the Nagasaki sales office followed in December 1988, and the Saga sales office in September 1989. In 1997, the Tokyo sales office was upgraded to a branch, and the Sendai office was opened. The Kitakyushu sales office was rebuilt in November 2001, and the current company building was completed in May 2003. In October 2004, the sales offices in Kitakyushu, Saga, Nagasaki, Oita, Kumamoto, Miyazaki, and Kagoshima were all upgraded to branches. The Nagasaki branch was rebuilt in September 2007, the Saga branch in September 2008, and the Tokyo branch was upgraded to a branch office in October 2008. In February 2018, Ryonetsu registered as a ZEB (Net Zero Energy Building) planner. In November 2019, it registered as a ZEB leading owner. In February 2020, the ZEB conversion of its head office building was completed. In January 2023, the company became a group company of Kyushu Electric Power Co., Inc. As of September 30, 2025, the company employed 305 people. Its major shareholders are Mitsubishi Heavy Industries, Ltd. and Kyushu Electric Power Co., Inc.
- 2023
Became a group company of Kyushu Electric Power Co., Inc.
- 2020
ZEB conversion of head office building completed.
- 2019
Registered as a ZEB leading owner.
- 2018
Registered as a ZEB planner.
- 2008
Saga branch rebuilt.
- 2008
Tokyo branch upgraded to branch office.
- 2007
Nagasaki branch rebuilt.
- 2004
Kitakyushu, Saga, Nagasaki, Oita, Kumamoto, Miyazaki, and Kagoshima sales offices upgraded to branches.
- 2003
Current company building completed.
- 2001
Kitakyushu sales office rebuilt.
Products and positioning
Regional building-services engineering specialist in Kyushu with a growing focus on energy-efficient and ZEB solutions, backed by Mitsubishi Heavy Industries and Kyushu Electric Power.
Air-conditioning and ventilation equipment installation
Plumbing and sanitary equipment installation
Fire-protection equipment installation
Refrigeration and cold-storage equipment installation
Electrical and telecommunications equipment installation
Machinery and equipment installation
Building construction
Comprehensive facility maintenance services
Consulting and renewal services
Equipment sales and installation (including commercial EcoCute "Cuteon")
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