How, exactly, do you design the world’s least C02-emitting building? By incorporating a whole host of green features, apparently, as Shimizu Corporation has with its new headquarters building in Tokyo. The building, which officially opened yesterday, is said to emit only 38 kilograms per square meter of CO2 peryear, 62 percent less than your average Tokyo building.

Shimizu has both developed and adopted the technologies it used to reduce the carbon footprint of this building. One such technology is its air conditioning system, which makes use of radiant heat. In a neat reverse of an in-floor radiant heating system, this air conditioning system employs water hoses that run under ceiling boards like capillary vessels. By controlling the temperature of the water circulating in the hoses, the temperature of the celling board surface is controlled. As per high school physics, heat rises, and — in this case — chills out when it reaches the cool air near the ceiling. A surface temperature of about 20 degrees at the ceiling absorbs the heat of people working in the office through a radiant effect, reducing CO2 emissions by 30 percent as compared with conventional AC.

Shimizu headquarters, Tokyo
image via Shimizu Corporation

Energy efficient LED lighting throughout the facility has been made further efficient through the use of motion-sensor controls. What energy is needed to run these lights during the day is provided via photovoltaic panels housed in the building’s outer walls. (The solar array generates around 84,000 kilowatt hours of power on an annual basis.) Window shades control the amount of sunlight that enters the building, helping to reduce unwanted solar gain. (The angle of these shades changes automatically throughout the day to follow the path of the sun.) All told, these elements reduce the CO2 emissions associated with the building’s lighting systems by 90 percent over conventional systems.

By the end of the year 2015, Shimizu plans to further  reduce the amount of CO2 emissions produced by its headquarters by fine tuning its air conditioning and lighting facilities, as well as by adopting other (as yet unnamed) energy saving systems. The target is 70 percent emissions reduction — at that time, Shimizu will offset the remaining emissions by purchasing offsets, achieving net zero status.

With this move, Shimizu now joins the list of Japanese businesses that have made energy efficiency and renewable energy a priority in the wake of the 2011 Tōhoku earthquake tsunami disaster. The disaster shut down of all of Japan’s nuclear reactors, which has led the Japanese government to set regional energy reduction targets to help the country meet its electricity demands with reduced generating capacity.

Hence, Kyocera has implemented energy efficient lighting in all of its buildings, installed green “curtains” to shield buildings from the sun during the summer months, and even gone so far as to relax the dress code at work to accommodate reduced AC. The advertising agency known as TBWA\HAKUHODO, with its finger on the pulse of public sentiment, weighed in on the public desire for efficiency and resilience with MIRAI NIHON, the portable off-grid house it designed with the help of big players like Nissan and Altima Corporation. And now, it seems, one of Japan’s largest building contractors is getting in the game.

Shimizu notes that, since Japan has few natural resources such as oil or gas and has faced energy crises more than once, its buildings are already designed to conserve energy. By raising the bar on efficiency for Tokyo with its new headquarters building, the construction company is likely to position itself well for clients seeking to build similar buildings.

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