Unique Homes in Japan: Living “inside” a mountain in Kagawa Prefecture

Literally buried at the foot of Mineyama mountain, in Takamatsu, Kagawa prefecture, is a small and unique residential complex called Miyawaki Gurindo. It is a good example of how Japanese developers and architects deal with building structures in a country where 75% of the land area is covered by mountains.

Miyawaki Gurindo is a multi-family residential rental complex comprised of five floors buried into the foot of a small mountain. Viewed from the side, the floors seem to connected by the steps of its undulating roof. The roof of the first floor also serves as the garden for the second floor, and so on.

Miyawaki Gurindo
Miyawaki Gurindo

Natural Insulation and Geothermal Temperature Control

Keita Nagata, of Keita Nagata Architectural Elements, is the architect behind the building’s design. He came up with the idea to “gently build into the slope” itself, rather than trying to level the site area and adding a retaining wall. This more traditional method would have added significant cost to the project and would not have been as aesthetically pleasing, according to the architects.

The outside walls of the building are constructed of steel-reinforced concrete, which is generally considered the safest material for minimizing earthquake damage. There is also an insulating layer of air between the inner wall, as well as the ceiling and floors, which prevents heat movement by convection, similar to the way a thermos bottle works.

Also, almost every part of the building is in contact with the soil, so the inside air temperature is stablized by geothermal heat, which causes the average indoor temperature to stabilize around 15 degrees Celcius. There are also heating and cooling tubes which capture fresh air through an air-supply tower. Air is pumped underground to ducts below the units and fed into the rooms to regulate the temperature as needed.

Miyawaki Gurindo was only recently completed. The entire construction process took about two and half years, which is longer than the usual time needed for a project of this size. An important part of the plan also calls for seedlings of various oak varieties to be planted on the site; and according to the architects, these seedlings are not expected to mature for another ten years, so the building will continue to “grow” as it ages.

Side view of Miyawaki Gurindo showing air ducts.
Side view of Miyawaki Gurindo showing air ducts.

There are seven units in Miyawaki Gurindo. The bottom two floors are each divided into two units, named Moku (木) or tree, for a total of four units. These 1LKs (1 Room, plus a Living room and Kitchen) have about 30 square meters of living space and are designed for single people. The third and fourth floors are named Rin (林) or grove, and are designed for families. They have about 75 square meters of living space. The top floor is a “maisonette-type” apartment, which means that it has two floors. It also has about 75 square meters of living space. The top floor apartment is dubbed Shin (森) or forest. All of the apartments, except for the first-floor units, come with a yard, which is essentially your downstairs neighbor’s roof.

The apartments rent from between 66,000yen for the smaller units to 135,000yen for the top-floor maisonette unit.

Miyawaki Gurindo Floorplans
Miyawaki Gurindo Floorplans

Source: Green-do (in Japanese)

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