Kitagata Town is located in the southwestern part of Gifu Prefecture, and although it is the smallest town in the prefecture, it has the highest population density (population: about 18,300). Around the site, there are prefectural northern housing, a lifelong learning center, the Kitagata Town Library, and Enkyoji Temple. In addition, there are public infrastructures such as the northern bus terminal and a disaster prevention park.
In consideration of cooperation with these surrounding facilities, the sketch of the design proposal depicts an open government building where people gather under a large roof floating at the center of the site among discretely planted trees. The building has a clear three-story structure: the first floor is a multipurpose space with uniquely characterized areas named "Ikoi," "Gathering," and "Manabi" squares; the second floor contains the mayor’s office, a disaster prevention office, and conference rooms; and the third floor consists of the assembly hall, a large conference hall, and the staff cafeteria. The first floor is an open space with high ceilings and excellent visibility, while the second and third floors are placed beneath the large roof, with each room having its own terrace to create a bright and comfortable indoor environment.
The starting point for the large roof was an exploration of Kitagata Town’s unique identity, referencing elements such as the portable shrines of the Northern Festival and Enkyoji Temple. Beyond this, the design seeks the potential of a large roof that creates a bright, comfortable interior environment through a simple and rational form informed by Japan’s climate and natural conditions. The deep eaves block the strong summer sun and allow natural ventilation even on rainy days, but they also result in a dark interior on the first floor.
To address this, a portion of the mountain-like roof was carved out like a valley, creating four deep “valley terraces.” These terraces allow light and wind to enter the first floor through the atrium via high windows facing the terraces, realizing a bright and comfortable interior space. For the roof finish, sheet metal with a deliberately low heat-shielding effect was selected to collect solar heat within the hollow layer of the large roof. In winter, this warm air is used as part of the HVAC system to save energy, and in summer, excess heat is exhausted through a rooftop vent. The cut-out portions beneath the eaves and the large roof itself function as an environmental double skin, while the diagonal interior walls act as reflectors that guide natural light into the building.
Because the interior spaces beneath the large roof inevitably include slanted walls along the outer edges, the small rooms on the second and third floors differ from the homogeneous spaces commonly found in typical office buildings. Instead, they are defined by diagonally shaped walls that emphasize the floor surfaces. We hope that the Kitagata Town Hall, crowned by this 21st-century large roof, will become a place where townspeople and staff alike feel comfortable and can foster diverse activities.