Takenaka Achieves Zero-Energy Retrofit on Own Building while in Operation, First in Japan

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Takenaka Corp., a leading Japanese construction company, announced on May 17, 2017, that it has become the first in Japan to successfully complete net zero-energy retrofitting work on its own office building without interrupting business operation. The building, the Higashi Kanto Branch located in Chiba City, Chiba Prefecture, ran on net zero energy in the first year after the work was completed.

The two-story reinforced concrete and steel structure with a floor area of 1,318 square meters went through the following refurbishment from October 2015 to March 2016:

• Improved thermal insulation on entire building exterior
• Optimized use of natural lighting and ventilation and LED lighting
• Downsizing of facilities and mechanicals by direct use of solar thermal and geothermal and reduced heating/cooling load
• Downsizing of PC and other devices

The renovated building's overall annual energy consumption shrank to 403 MJ/m2, a 71% reduction from pre-renovation. Moreover, its minimal solar power system generates 417 MJ/m2, exceeding energy consumption and thus achieving an energy surplus.

In order to cater to diverse customer needs, Takenaka plans to apply the know-how it gained in the project to different ZEB offerings, such as ZEB Ready, Nearly ZEB and Net ZEB.