Japanese building claims world's lowest CO2 emissions

One of Japan's largest construction companies is making a bold claim. Shimizu Corp believes its new Tokyo headquarters emits less carbon dioxide per square meter than any other building in the world.

Thanks to a myriad energy-efficiency technologies and renewable energy installations, the building uses only 38 kilograms per square meter of CO2 annually, estimates Shimizu. That's 62 percent less than the average emissions of most Tokyo office buildings, says the company.

The 22-storey reinforced concrete building, which includes three lower ground floors, has a total floor area of 51,355 square meters. It employs a number of technologies and best practices developed by Shimizu itself to help squeeze out emissions. Among the key elements low energy/low emission elements are:

• Air-conditioning technology that uses radiant heat principles: The system works by absorbing the heat of people working in the office, through a water cooling system. The approach can help cut carbon dioxide emissions 30 percent compared with conventional systems.
• LED lighting, powered by solar: Controlled by motion and occupancy sensors, the energy needed to run the lights during the day comes from solar PV panels placed on the outside walls. The panels will generate an estimated 84,000 kwh of electricity annually.
• Automatic window shades: The angles of the shades shift automatically in order to let in sunlight, optimizing natural lighting for the building's occupants.

Taken together, the lighting innovations reduce carbon emissions by 90 percent compared with traditional approaches, says Shimuzu.

The company 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. It will offset the remainder of its emissions by buying renewable energy credits, making it a net-zero emission building.

In the European Union, near zero-energy buildings are mandated for public buildings by 2019 and for all construction by 2021. Similar regulations are being considered in the US and in Japan.

There is as yet no certification standard for zero-energy buildings, which will make it difficult to verify Shimizu’s claims, according to Eric Bloom, a senior research analyst at Pike Research. Zero-energy buildings are an emerging area and still a small piece of the total global building industry, he said.

“I see zero-energy buildings following a similar path as green building certifications. 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,” said Bloom.