The Shimizu headquarters, located in Kyobashi, Chuo-ward, Tokyo, emits 38 kg/sq m of CO2 per year, 62 percent less on average than conventional buildings in the city, the company said.
Shimizu says it has developed and adopted a variety of technologies in the building in an effort to improve efficiency, cut gas and oil use and reduce CO2 emissions. For example, the company uses an air conditioning systems that makes use of radiant heat. Water hoses are installed under ceiling boards, helping to control the temperature of the water circulating in the hoses and in turn, the ceiling board surface.
The surface temperature of about 20 degrees Celsius absorbs the heat of people working in the office through a radiant effect, and the system can reduce CO2 emissions by 30 percent compared with conventional air conditioning systems, Shimizu said.
The building is equipped with motion sensored LED lighting. Energy used for lighting during the day is generated by PV panels installed on the outer walls. The area of PV panels is about 2,000 sq m and is expected to generate 84,000 kWh of power annually. Shimizu also installed window shades, which angle automatically to follow the sun and optimize natural light.
Shimizu says that by 2015 it will reduce CO2 emissions down to 70 percent less than conventional buildings, by fine tuning the air conditioning and lighting equipment and adopting additional energy saving systems. The company will offset the remainder of its emissions by buying renewable energy credits.
There isn’t a clear certification standard for zero-energy buildings, which makes it difficult to verify this building’s claims, according to Eric Bloom, a senior research analyst at Pike Research. However, the building definitely uses a number of highly energy efficient and CO2-reducing features that aren’t commonly seen in large buildings, such as the radiant heating and even the solar installations, Bloom said.
Zero-energy buildings are an emerging area and still a small piece of the total global building industry, Bloom said.
“I see zero-energy buildings following a similar path as green building certifications,” Bloom said. “There was once a couple million square feet of building space LEED-certified each year. Now we’re seeing 1 billion square feet of buildings LEED-certified each year.”