Many of developing cities in Asia are getting uniformed and losing its regional characteristics under the influence of the furious urban sprawl and commercialism. Increasing population is worsening the quality of life and decreasing green area. Ho Chi Minh City, the biggest city in Vietnam, is not an exception. Stacking Green, which was designed as a prototypical private house in the tropics, is a challenge to change this situation. There is still a remarkable custom among the people in Ho Chi Minh City: They love their life with a large variety of tropical plants and flowers around the streets. Even in the modernized city, people unconsciously desire the substitute of rampant tropical forest.
Stacking Green designed this custom onto its facades, which are composed of numerous planters like horizontal louvers. These green facades contribute not only to visual comfort for the inhabitants, but also to improving indoor thermal environment therefore saving energy. Furthermore, they enhance the biodiversity of the surrounding environment. The house was designed for a 30-year-old couple and their mother. They were not happy with a narrow and dimly lit tube house, a common residential design in Vietnam whose origin dates back more than 200 years ago. The earlier versions of tube house, "nha ong" in Vietnamese, had interior courtyards and light shafts, however, as the city grew up to be more crowded, the houses became smaller and their interiors dim and stuffy.
Stacking Green goes up on a typical plot for such a tube house with 4 metres wide and 20 metres deep, trying to combine the earlier spirit of tube house with modern architectural vocabulary. The house is 4-stories building with 220 square meters of gross floor area, containing a backyard and a light well inside of its tubular volume. The entry staircase to the upper floors and 70-year-old mother's room facing to the backyard are located on the ground floor. The first floor contains a living space with a kitchen and the second a master's bedroom: These two floors are connected vertically by the light well. A guest room, which will become the children's room in the future, is at the top of the house. All these spaces in the three upper floors are open to both the street side and the back side through the green facades. The front and back facades are entirely composed of the layers of concrete planters cantilevered from two sidewalls. The distance between each planters and its size are adjusted according to the height of the plants, which varies from 25 cm to 40 cm.
To water plants and for easy maintenance, the automatic irrigation pipes inside the planters were installed. This green facades and roof top garden protect its inhabitants from the direct sunlight, noise and pollution from the street. According to the post-occupancy measurement of the indoor environment, the porous facades and the two skylights with openings let the wind flow throughout the house and contribute to save a great amount of energy in a harsh climate in Ho Chi Minh City. This semi-open green facades also provide privacy and security of the house, which are important for residents in the city, not in combative but in friendly manner.
According to the latest statistics of the parks and greenery management office of the Department of Transport of Ho Chi Minh City in 2010, the whole area of parks, gardens and greenbelts are only about 535 hectares in the city, which has been decreasing by nearly 50 percent from 1998.
A private house with rampant greenery is profitable not only for its residents but also for the community. The facades are composed of 25 horizontal planters with different species, contributing to the biodiversity of neighbouring environment. Stacking green, whose green facades are quite visible from the street, is inspiring and encouraging people in the city to install more green onto their buildings. The house is being widely exposed through various media inside and outside of Vietnam, conveying its concept to the people.
In general, a double-skin facade is composed of two glass layers. However in a tropical climate, a closed cavity between the two layers is useless since there is no need to block out cold radiation nor enclose pre-heat air. The tropical double-skin facade shall consist of two different layers: green and glass. The outer green layer prevents hot radiation and shades a building from direct sunshine all year around, cooling the perimeter through transpiration of plants. It also enables natural ventilation due to its porosity. The inner glass screen enables to increase the efficiency of HVAC when it is closed. Thanks to plentiful rainfall and ideal temperature, it is quite easy to grow and maintain plants in a tropic city as Ho Chi Minh City. Stacking Green proves the effectiveness of this tropical double-skin facade - its electricity charges is just 20 EURO per month.
The flow of fresh wind is especially important in a tropical climate to save energy consumption and provide comfortable indoor environment. The porous green facades and the courtyards were designed to maximize the wind flow from outside into the house. In addition, continuous interior space with minimum partition also allows natural breezes to go through the house. One year after the completion, the wind flow inside of the house was measured to see the effectiveness of the building design. The wind speed was measured at 11 spots distributed in all rooms and courtyards, and then the data were compared to the wind speed at the relevant height outside of the house. The result was remarkable; average wind speed in the first to the third floor were from 0.15m/s (minimum value at 1F) to 0.53m/s (maximum value at 3F), which are to be compared to those of outside from 0.31m/s (value at 1F level) to 1.15m/s (value at 3F level).
The measurements reveals the fact that comfortable wind flows in the house, which has been proved by the behavior of the inhabitants; they has rarely used the lone air conditioner, thanks to the wind flow and other passive design methods. (average temperature of Ho Chi Minh City is 28 degrees Celcius.)