Shirasu

Shirasu

Premio Architettura Sostenibile

Year of entry: 2015

Crediti

Cliente

Ijichi Hisashi

Collaboratori

tmsd & takashi manda structural design

Autori

ARAY Architecture

There were no other houses in the neighborhood that would block insolation, since the site was located in the south western corner of a slightly inclined land. Therefore the house is exposed to abundant sunshine during the day. On the other hand, land and sea breeze blowing in the northwest contributes to a fine wind circulating condition.

Disegni tecnici:

Report esteso:

SHIRASU -Eco- House by Volcanic soil brickwork

The residents wished to realize a new ecological life having a stronger connection with the surrounding environment without relying on artificial energy, even in the hot and humid climate of southern Kyushu. They hoped to feel the wind, use rain water, and touch the soil everyday; a thoroughly local and natural way of living. Their house was to be built in a residential area near the center of Kagoshima city, located on the unique Shirasu plateau. I intuitively came up with the idea to use the indigenous Shirasu soil as the main material so that the house matches the local environment.

Shirasu has the following unique characters: fire-resistant, high thermal insulation, high humidification, high heat reservation, and light weight.I decided to make use of the existing local technology of producing flat Shirasu blocks by adding high pressure, which had been originally developed for paving roads. I was the first in history that decided to use Shirasu blocks for buildings. The blocks for the outer walls were strengthened by adjusting the amount of Shirasu soil, and the blocks for the inner walls were encrusted with Shirasu ores. The property of Shirasu is expressed in the layers that represent passage of time. Since I adopted an inside-and-outside double layer wall with space of air in between, the entire building looks like a Shirasu cave.

By adopting a double layer wall, the thermal load towards the inside has been drastically reduced. Moreover, the inside wall surrounding every single room helps maintain appropriate humidity. In summertime the inside is kept cool whereas in winter it is quite warm, which indicates that comfortable temperature is maintained throughout the year. The nature of the soil is one of the most important factors that decides the climate and natural features of the area. My aim was to reproduce the energetic function of the local geological resource in order to realize a new environmentally circulating space.

Since the light-weighted Shirasu blocks that are embedded for roof greening functions like soil on the ground, they help reduce the load of the roof. They not only provide positive effect to the urban environment, but also improve energy efficiency. I am glad to hear that the residents who decided not to equip the house with air conditioning devices are now enjoying their new life closely attached to the local natural environment, leaving thermal control to the Shirasu block walls.

Sustainable material: Shirasu block

The “Shirasu block” is a sustainable material. The outer wall consists of Shirasu blocks made by mixing Shirasu and cement particles. The inner wall consists of a different type of Shirasu blocks that has been encrusted with Shirasu ores. “Shirasu” refers to soil that had piled up over the years, originating from ash and pyroclastic flow caused by the volcanic eruption of Sakurajima which occurred 25,000 years ago.