Takenaka Corp announced May 17, 2017, that the energy balance of its Minami-Kanto branch office (Chuo-ku, Chiba Prefecture) has become "positive" throughout the year.
The two-story office building was completed in 2003 with a site area of 1,432m2 and a total floor area of 1,318m2. Takenaka renovated the building to reduce its power consumption and installed a solar power generation system while the office was being in normal operation. The renovation period was from October 2015 to March 2016.
The full-scale operation of the system started in May 2016, and one year has passed since then. During the period, the amount of solar power generation exceeded the amount of power consumption.
This is the first time in Japan that an office building in operation has been renovated to realize a net zero energy building (ZEB), Takenaka said.
The annual primary energy consumption of the entire building became 403MJ/m2, which is more than 70% lower than before the renovation, due to (1) the exterior insulation improved by heat collection, (2) technology for fine environmental control and (3) reform of business style.
On the other hand, the amount of electricity generated by the solar power generation system was 417MJ/m2 in the year. The output of the system is about 40kW, and solar panels were installed on the roof of the building. While aiming at net zero energy, Takenaka minimized the total capacity of solar panels.