Building bamboo envelopes is a good green building material and the technology to develop breathing buildings. It may seem an exotic technique but it is not. There are case studies also in Italy and, among these, in the Certosa Business District in Milan, the office building commissioned by STAM Europe in Goring&Straja. Since we continue to build reinforced concrete and steel buildings, we wonder why we should build in bamboo. Apart from the myth of bamboo, known as vegetable or natural steel, in green building bamboo is a green material that can be well used to build transpiring building envelopes or to create contemporary structures such as the Bamboo Roof. The fame of bamboo as vegetable steel is not undeserved. The bamboo, under certain conditions of diameter and length of the culm, can be more resistant than wood to the forces of tension and compression. The tensile strength of its fibers can reach up to 12000 kg / cm2, almost twice that of steel, while compression strength exceeds that of concrete. With these characteristics, bamboo turns out to be a perfect green building material for houses built using green building techniques, in areas of high seismic risk. Japan is a nation that knows well the effects of earthquakes and natural disasters on human constructions and the formation of Japanese schools of architecture focuses particular attention on the theme of anti-seismic architecture of which bamboo is a building material essential.
The bamboo envelope in green building material
In addition to this type of application, in our climate bamboo is an excellent material for creating breathing buildings for sustainable architecture. An energy-saving breathing building is able to control the internal / external microclimate and “sweat” to emit internal heat and cool naturally. One of these techniques is taken from Japanese natural architecture.
In some areas of Japan, the most sun-exposed façades of buildings were covered with an outer shell of bamboo canes. Later, water was poured into the pipes which, by evaporating, allowed the temperature to drop even inside the structure. This technique was used by the Japanese studio Nikken Sekkei with the project of Bioskin of the Sony City Osaky in Tokyo, 2012. The bamboo canes that define the envelope were replaced by thin ceramic pipes, which converge in a collection system of the rain water. The system allows to lower the temperature inside the building by 2 ° C, with a consequent reduction in CO2 emissions due to a reduced use of air conditioning systems. A relevant case of how contemporary architectures are able to reread the local building tradition in an innovative way is represented by the Bamboo Roof. This is an installation carried out in Houston, Texas in 2002 for the Rice University Art Gallery, designed by the Japanese architect Shigeru Ban . Shigeru Ban has developed a promising method of construction in terms of sustainability and efficiency. It uses bamboo and cardboard tubes for its constructions, both residential dwellings, buildings for emergency situations, and large tensile structures made with unconventional materials.
The Bamboo Roof is characterized by a free-form roof structure that develops with unlimited geometric possibilities. The concept is both simple and complex. The structure is created by interlocking a series of units of parts, each one made up of four bamboo boards connected together by metal pins. The undulating roof is finally supported by metal supports. Bamboo Roof transmits a great sense of lightness and transparency, so much so that one has the perception of being under the roof of a forest.
Resilient architecture techniques for bio-buildings. Stam Europe of Goring & Straja, in Milan
With resilient architecture techniques, bio-buildings are designed with the idea of making them as energy self-sufficient as possible, starting from the shape. Before building a house, depending on the construction area, it is essential to study the climate, then the sun’s exposure to the house and identify the direction of the winds to which it is exposed. The Sony City Osaky in Tokyo, for example, was built taking into account the exposure of the winds blowing over Tokyo Bay. So, in the direction of the winds, the sides of the building are thinner and tend to stretch on the opposite sides. The photovoltaic lamellas, on the other hand, are on the south façade to collect more solar rays but their purpose, besides producing energy, is to shield the rooms that face this side of the building that is notoriously warmer. The same shielding system from sunlight has been used in Milan. The facade of the Stam Europe Green Place is characterized by an envelope with a facade completely covered with a bamboo brise soleil. Bamboo creates a filter between the outside and the inside. The Green Place on Viale Certosa in Milan remains “covered” by bamboo canes, to achieve a green effect and shield it in the parts most exposed to the sun.
The building was designed to obtain LEED Gold certification. Stam Europe is a 4-level building with approximately 7,400 square meters of underground parking lots and 15,400 square meters outside with an internal green area. The ground floors of the building complex are intended for laboratories, entrances and a showroom. The other floors are all intended for offices. Furthermore, it is characterized by the widespread use of glass, aluminum, cement and bamboo string-course structures for shielding systems on the east and west fronts. The shielding system is a bamboo brise soleil, which incorporates heterogeneous sunshine. The bamboo brise soleil thins out, thickens, adjusts according to the inclination and the solar radiation, creating a game of density and rarefactions that makes the façades vibrant and changeable.