The site of this building is located at Lake Chuzenji in Nikko city. Its lakeshore has been lined up with summer houses of foreign embassies since quite some time ago.The project is to pull down a 5-story recreational facility of a company and build a new, private summer house for an individual client. The building is built as close to the waterside of the lake as possible, while its height is kept low.
▼建筑外观，exterior view ©Harunori Noda [Gankosha]
▼屋顶视角，roof top view ©Koji Fujii [Nacasa & Partners]
▼螺旋状空间动线，sequential diagram ©Nikken Sekkei Ltd
A two-story building is placed at a location with inclined topography, where its height level goes down from a road to the lakeside in 7m. The circulation of this building is designed to be accessed from the road, to the 2nd floor level provided with a main dining space for welcoming guests, while the spiral configuration of the building gradually leads the guests to the 1st floor level with bedrooms. The 1st floor plan brings in the lake water to an inner garden by removing the shoreline protection work existed between the lake and the previous building. The scenery of the lake is framed by a 20m long, large spanned floor slab, which extends over the garden area.
▼大跨度屋盖框出一片如诗如画的湖景，the scenery of the lake is framed by a large spanned floor slab extending over the garden area ©Harunori Noda [Gankosha]
The structure design to provide the best vista to the lake
▼剖面图，section ©Nikken Sekkei Ltd
The porch area on the 2nd floor continues to the dining space covered with a steel frame cantilevered roof. Considering snowfall on the roof as much as 1.2m deep, the steal beam of the roof is cambered in advance, and sag rods (SUS13φ) are placed in 3m intervals at the roof tip for consistently adding tension to the roof. These structural designs prevent from the deformation of the roof at the time of heavy snowfall, as the tension to the roof is relieved by snow load. The reaction force of those sag rods are taken from the reversed beam of the steel reinforced concrete (SRC), which is utilized for making the eaves soffit of the 1st floor appear straight and flat–therefore those structural designs also reduce the deflection of the long-spanned floor slab at the same time.
By managing the deflection of the roof against snow load, it becomes possible to utilize large-sized sashless glasses to maximize the vista to the lake. The glass has the width of 10m for its dimension, while this is the maximum size to carry through the severely winding road of Iroha-zaka sloping road in Nikko city.
▼二楼门廊，the porch area on the 2nd floor ©Koji Fujii [Nacasa & Partners]
▼用餐空间，dining area ©Koji Fujii [Nacasa & Partners]
▼无边框大幅玻璃最大限度确保湖景视野，large-sized sashless glasses were used to maximize the vista to the lake ©Harunori Noda [Gankosha]
Study of visual sequence and thermal environment simulation using BIM model
▼BIM模型，BIM model ©Nikken Sekkei Ltd
During the design process, data of the topography and the mountain range around the site was entered to the BIM model in order to study and find the most suitable location of the building for getting the best vista of the surrounding scenery. This model was also used to study the balance of the scale of each room, and the shapes and the heights of the openings in consideration to the visual sequence along with the circulation inside of the building. During the execution design process, more in depth studies were made by using the BIM model for the details of each part of the building, finishing materials, and placement of furniture.
This BIM model was further and well utilized for examining the structure to control the roof deflection under snow fall, and studying the natural ventilation by making use of the continuous spiral space, and simulating the thermal environment of the heat produced by the fireplace in a lounge space with a bar corner.
▼酒吧和休息室，bar lounge ©Koji Fujii [Nacasa & Partners]
▼屋顶平台，roof terrace ©Harunori Noda [Gankosha] (below) ©Koji Fujii [Nacasa & Partners] (bottom)
A guesthouse promising a pleasant time by the water in the balmy summer weather
▼滨水环境在螺旋状空间中接连不断地呈现，the various lakeside environments are carried on into the spiral but non-uniform distribution of spaces ©Koji Fujii [Nacasa & Partners]
▼休闲室楼梯，stair to the lounge ©Koji Fujii [Nacasa & Partners]
▼客房浴室，bathroom ©Koji Fujii [Nacasa & Partners]
Situated alongside a lake, this guesthouse was designed as a continuous spiral space flowing from the approach to the bedrooms. Each step taken deeper inside the building reveals a changing lakefront view. The various lakeside environments, including the sound of ripples, light reflecting from the water surface, the humidity and thermal radiation, are also carried on into the spiral, but in a non-uniform distribution due to changes in physical distance from the water surface. Since the whole structure is an interconnected space with different elevations, there is no homogeneous environment—various areas present various thermal environments such as the fireplace warmth and the dryness of the air.
▼随步履轻移而变化万千的水景 ©Harunori Noda [Gankosha]
each step taken deeper inside the building reveals a changing lakefront view
▼从中庭望向湖景，view to the lake from the garden area ©Koji Fujii [Nacasa & Partners]
Guests wander around in this atmosphere, discovering and enjoying spots they find comfortable. Located in a natural environment that requires a bit of heating in the building even during the summer nights, one may find joy in the warmth near the fireplace, while another may relish the area’s tranquility and cold characteristic. The building is closed during the harsh winter season to prevent any wasteful investment of energy.
This is the kind of hospitality this guesthouse promises to deliver.
▼别墅夜景，night view ©Harunori Noda [Gankosha]
▼场地平面图，site plan ©Nikken Sekkei Ltd
▼一层和二层平面图，first and second floor plan ©Nikken Sekkei Ltd
用地面积 1,325.16 m²
建筑面积 751.92 m²
最高高度 7.33 m
Design Team: Tomohiko Yamanashi, Satoshi Onda, Hajime Aoyagi
Location: Tochigi, Japan
Site area: 1,325.16㎡
Building area: 640.50㎡
Total floor area: 751.92㎡
Building height: 7.33 m
Structural system: reinforced concrete