Ishioka City is believed to have been the site of the capital of Hitachi Province in ancient times, and is associated with an image of the prosperous country of ancient Japan known as the "tokoyo no kuni," a land of eternal youth. The region is also rich in nature, as seen in the Yago area, and Mt. Tsukuba, one of the 100 most famous mountains in Japan, is the symbol of the region. In response to the rich history of Ishioka and the natural beauty of Mt. Tsukuba, we created a city hall based on the concept of a city hall with a dynamic form that will become part of the cityscape of Ishioka.
Based on the experience of the disaster caused by the Great East Japan Earthquake, we aimed to create a disaster-resistant LCB (Life Continuity Building) city hall anticipating unexpected disasters. The "LCB city hall" refers to a city hall that further advances the concept of (Business Continuity Plan) and realizes a building that is more than just safe and secure, capable of sustaining human life, providing disaster relief activities, and protecting the lives of citizens. In addition to countermeasures against earthquakes, we have developed countermeasures against fires and floods as well as countermeasures against secondary damage and guarantee the safety in the building by preventing interior finishes from falling, providing safety in the building. We have also developed a "self-sustaining lifeline system" that supports independent operations in the event of an infrastructure failure, as well as a disaster relief function that allows for quick functional conversion to a disaster operation base in the event of a disaster. Taking advantage of the difference in elevation of the site, a multi-story seismic isolation structure was adopted. A pre-stressed concrete structure with reverse beams was adopted to realize a large office space. By adopting subfloor air conditioning systems, we were able to eliminate suspended ceilings and ceiling-mounted equipment.
We realized a city hall conveying a sense of the city of Ishioka surrounded by abundant nature by creating large spaces with symbolic forms using a wooden honeycomb unit structure for the city council chamber and multipurpose hall, and by using wood to build the roof and louvers.
The wood honeycomb unit structure of the roof is made of common, inexpensive wood, and is based on a cross-sectional configuration with flanges made of cedar and webs made of structural plywood. In addition, by actively incorporating wooden elements, including ribbed louvers that serve as sound-absorbing walls made of locally produced wood and randomly placed Japanese hardwood flooring, we were able to create a space that reflects the abundant nature of Ishioka.
We achieved a "city hall that leads the city" that serves as a model of the city's approach to environmental initiatives by realizing an advanced ecological city hall with the best environmental performance (CASBEE certification S-rating), which actively incorporates energy conservation methods that take advantage of the climate of Ishioka. One of the most noteworthy features is the use of a roof-type solar energy system for the large surface. By creating an air layer that also serves as attic ventilation using double folded plates and efficiently using the heat from the air layer heated by solar heat for air conditioning energy, and by sending fresh air to the desiccant air conditioner and outside air conditioner, we were able to significantly reduce the thermal load from outside air.