This is a building like inside and outside.
The project was planned on the site with Mt. Fuji rising closely in the south and the two sides facing the trunk roads.
This building seems to belong to such nature objects as mountains and clouds. It is made from soft geometry, which will not arise from the figures like quadrangles and circles. By continuously operating innumerable polygon mesh points, we have determined the shape that clears the conditions such as the consistency as shell construction and the undulations that ward off rainwater in spite of its free geometry. The RC shell with cubic surfaces creates such spaces as 530 square meters of seats, 140 square meters of kitchens, and 50 square meters of rest rooms, in such a manner that it envelops and opens them.
This building has no air conditioners. It is open to the air at most seasons, and people have a meal in the air like outside air. The curved acrylic sliding door is closed only during the strong wind and the coldest season. Giving 60 mm thick urethane insulation to the outside of the RC shell and keeping a stable RC temperature secures a stable temperature environment for the building like inside and outside, and also reduces the deformation volume due to the temperature of RC to make the building last longer. For the lighting plan, we have determined such illumination as makes people simply feel changes in the evening light and does not make insects gather around the lights. When it rains, rain comes in near windows and doors. In the spaces where rain does not come in, people enjoy the sound of raindrops. When it is foggy, the fog comes into the building. When it snows, it becomes a landscape buried in snow, and birds and animals will visit there. In this place like the middle between nature and art, people eat hoto rich in natural ingredients.
Structural Design Concept. In consideration of regionality at the foot of Mt. Fuji such as climate, heavy snow and seismic possibility etc, “Sandwich RC Shell Structure” was adopted integrated architectural form and highly structural, environmental, and lighting performance.
The sandwich skin consists of the main RC structure of 100mm thickness, sandwiched 60mm hard urethane for heat insulation and outer 15mm GRC (Glass fibre Reinforced Concrete) to prevent cracking and give high durability. This skin improved enhanced environmental performance, structural strength with light-weight skin and thus a long-lived shell structure has been achieved.
The free formed shape was calculated by “Form Finding Analysis” utilising Gaudi’s principle of reverse-hanging to minimise the strain energy in the shell plane and make a rational form structurally based on original architectural shape. In order to establish appropriate seismic load for the complicated shell structure, a dynamic response analysis was done by 3D FE Model using seismic waves considering site geological condition.
A major issue was the complex and extensive formwork required to support the wet concrete on site. To minimise the typical issue of shell structure, the solution adopted was to use “Truss Wall System (Pre-fabricated form work)”. Applox 200 units of 3D formed rebar truss were transported from a factory to site, and this construction method made possible high accuracy of site work, short construction period and reduction of complex formworks on site as much as possible.
Environmental Design Concept. The environmental design concept has been developed from the viewpoint of architectural and structural concepts to control the thermal comfort for the restaurant building minimizing the energy consumption.
The items listed below have been taken into account to make the restaurant space comfortable through the year;
– “thermal mass” to stabilize the internal surface temperature
– minimal openings to protect form the summer direct solar radiation and to introduce required daylight into the indoor space
– outer layer insulation with optimised thickness
– adopt sphere shape to maximise volume and minimise external surface area
– white painted external surface to reflect the direct solar radiation
MRT (Mean Radiant Temperature) is stable through the year in the building due to the effect of “thermal mass” so that cooling device would not be required in summer and minimal heating device could control the indoor thermal condition. The visual comfort could be controlled with securing daylight factor to enjoy “HOTO” by the white coloured internal surface reflecting the daylight entering from outdoor.
The quantitative studies for thermal and visual comfort have been conducted by simulation software and it has been concluded that the distribution of PMV (Predicted Mean Vote) and daylight factor would be acceptable for the restaurant space.
Architect: Takeshi Hosaka / Takeshi Hosaka Architects
Structural Engineers: Ove Arup & Partners Japan Ltd/Hitoshi Yonamine
Location: Yamanashi, Japan
Site: 2493.82 m2
Building area: 733.98 m2
Floor area ratio: 726.30 m2
Building height: 7460 mm
No. of floors: 1F
Building function: A local traditional food restaurant
Design: Feb.2008 – March 2009
Planning start (M/Y): February 2008
Beginning of construction: March 2009
Completion: December 2009
Photographer: Koji Fujii / Nacasa&Pertners Inc.