Zero-Energy School Connects Students' Passion for the Environment
～Achieving ZEB (zero energy building) via smart design & student eco-activities

The project served as an opportunity for Nikken Sekkei to become re-acquainted with Mizunami City and its local climate and culture. Kenji Murai, a native of the region and an associate at the firm, headed the design team. The plan it developed was aimed at maximizing the power of nature.

As architecture serves to regulate airflow and temperature, designs for the zero energy building allowed for student comfort while minimizing the need for air conditioning equipment. The school building, which comprises the north, east, and south wings, as well as the gymnasium, is angled, with the gym’s curved wall allowing wind flow into the courtyard. Wind enters cool trenches and circulates to each classroom at a temperature of 22-24℃ in the summer. Extensive simulations helped to yield optimal design configurations.

Natural lighting was used as much as possible, and artificial light avoided. Regular classrooms are located on the top floor with the best view, and a sloped, wooden pitched roof is built north to south. The south side of the building has eaves to reduce direct light, while the north window allows soft skylight to enter. This design secures a standard desktop brightness of 500 lx from natural light alone.

In addition, the paneled, lower portion of the classroom walls and the gymnasium roof are composed of steel plated solar heat collection panels. These warm the air in the winter.

"Our first priority was to have students use the school building while thinking about the environment,” notes Mr. Murai.

While achieving zero energy consumption is important, student awareness of ecology and energy conservation is even more valuable, says Hiroaki Tanaka, the company’s Facilities Design Group Senior Director of Engineering. “That's why we came up with an air conditioning system that students can operate manually, rather than using automated controls,” he said. “In fact, the building was designed from the beginning to achieve zero energy consumption, including energy-saving activities, so the voluntary activities of the students are a very important factor.”

Ideas for this purpose are scattered throughout the building. Eco-monitors in each classroom can be manipulated to see the entire school’s real-time environmental conditions, as well as classroom temperature, humidity, and carbon dioxide concentration. By comparing the temperature in the classroom and the cool trench, students can decide whether or not to vent air into the classroom.

The system also displays the "energy saving ranking" of any one classroom vs. other classrooms, a good conservation motivator. Designers collaborated to determine what and how environmental data should be displayed. For example, touch panel icons are based on smartphones to ease understanding among the digitally fluent, adds Mr. Murai.

"Cool-warm lockers" are a unique, innovative ventilation feature in the school’s regular classrooms. A unit located in the rear wall of the classroom integrates lockers, natural ventilation and air conditioning. A slit at the top of the locker allows for blowing cool and warm air, and is flanked on either side by a set of fans. These circulate air from the cool trench in the basement and blow sunlight-warmed air on the classroom wall. A high performance air conditioner built into this wall blends seamlessly into the wood finish.

Other features include a glass floor that allows viewing temperature and airflow in the cool trench, as well as walls that afford a feel for insulation effects. Meanwhile, a ceiling sign in the science room shaped like a ruler displays solar altitude by reflecting natural light from the light shelf. From the design stage, teachers, architects and engineers held joint workshops on environmental learning. After the school opened, designers gave on-site classes on how to use school facilities.

According to one survey, more than 80% of students reported increased environmental awareness. Many students said this awareness received a boost at home as well. Further, they expressed confidence that manipulating environmental conditions while thinking for themselves would likely influence their community’s environmental behavior as well as that of the next generation.

A year of measurements showed that Mizunamikita Junior High School’s primary energy consumption was about 50% more efficient than baseline models suggested. In addition, the school cut its energy consumption by 72% by switching to solar and wind power, and to pellet stoves.

“When we talk about energy conservation, we tend to think that only mechanical and electrical engineers are doing it,” points out Mr. Tanaka. “But we cannot achieve zero energy unless we consider the shape and materials of the architecture together.” He adds that although energy savings at the Mizunamikita Junior High school building itself reached 50%, plans remain for an 80% reduction.

Architectural design is an important factor in energy creation, too; the area and shape of the roof plays a major role in the placement of solar panels. Furthermore, although not included in ZEB energy calculations, the transport of building materials is also a major factor in the lifecycle CO2 emissions of buildings. For flooring and wall materials, much local Gifu Prefecture cedar and cypress were used. Exterior walls were also made of tiles fired at a local factory using soil from the area around pottery-rich Mizunami City. In line with the zero energy consumption goal, the school created an educational space to raise environmental awareness among the children. Designers came up with ideas for an architecture rooted in the community.

The resulting building embodies Nikken Sekkei's vision of environmental architecture. In its essence, this does not mean painful endurance for the sake of energy conservation, but rather the creation of a comfortable environment for students enabled by an energy conservation system. It also inculcates further values such as the enjoyment of nature and its blessings as portrayed via natural light and education.