Week 10: The Scientific Vernacular (final)

To what extend bamboo is used as a façade treatment in tropical and subtropical climate? 

Introduction

Bamboo constructions are well known in various countries in Asia and South America. Several famous architects; for example, Vo Trong Nghia from Vietnam and Kengo Kuma from Japan; have explored the potential of bamboo to get inspired in their designs. They apply the inherent properties of the plant in their works based in tropical and subtropical (warm) climate. Bamboo is used in a refined architectural way in terms of façade treatment or building structure where sunlight is filtered by bamboo as sunshades and privacy is kept without preventing daylight to enter. According to Kengo Kuma; he explained the vertical bamboo poles of the façade seem to give a soft, airy feeling to the overall structure. The bamboo façade screens in the spaces to invite visitor in a pleasing and delicacy manner thus creates a design that stands in between Japanese and Western approaches (Figure 1).

Figure 1: Kengo Kuma's bamboo house

Bamboo Facade

The major feature of bamboo as a façade treatment is the fact that it is open to daylight and air; as a screen wall (Figure 2). The gap between each bamboo poles are very well ventilated; thus the rays of sunlight entering through the facade look nice but do not result in overheating the house. Bamboo facade is one of the important components of a building. Not only does it give an identity to a building but it also plays the vital role of acting as an interface between the interior space and the exterior. However, another factor that affects interior and exterior comfort of the bamboo building is the climate issue; for instance the solar heat or solar radiation, temperature, wind flows, rainfall and humidity. As a consequence, the façade and climate determine how a person feels about a building from the outside as well as a whole living experience within a building.

Figure 2: Bamboo as screen wall

Construction of bamboo facade

Bamboo screen walls are extremely durable and long lasting. It can also be used in multiple climates as the bamboo is resistant to rain, excessive heat and ultraviolet rays. It has excellent environmental benefits as bamboo reduces pollution by absorbing carbon dioxide and other toxic gases. Having a comparison between trees and bamboo; trees are allowed to be used once when it is being cut down whereas bamboo is allowed to be used repeatedly as the grass grows back after being harvested. The construction of bamboo screen wall is completed in multiple ways. The most popular method uses a row of bamboo poles to tie them together with twine. In a warm climate conditions, the walls can even be constructed as an ecological growing wall. Making the bamboo screen wall is not easy due to its uneven characters on the material. The craftsmen have to be very precise about the thickness of the base and the spacing of the poles. The one way of constructing the bamboo screen wall will be placing the bamboo poles horizontally between columns. In some part of the wall, bamboos are placed side by side with appropriate joinery creating a full bamboo façade on the external face.

Environmental Performance of bamboo facade

Tropical and subtropical climate has an average temperature and relative humidity between 30-33ᵒC and 70-86% per month. The primary concerns of the tropical and subtropical climate in the warm humid region are high temperature and humidity. To overcome it, the main strategies are to provide maximum ventilation and shading to avoid heat storage. Bamboo screen wall provides a unique screen that protects the building from intense sun. It is able to reduce the sunlight intensity by 10% compared to a reading that is gained in an open space under the daylight. The windows and bamboo screen walls are well insulated that allows heat to egress from the building through the gaps between the poles as the wind flows through the building. It also acts as a heat recovery ventilator and provides fresh air into the building. Besides that, the bamboo screen wall reduces the temperature differences between the exterior and the interior of a bamboo facade building by 4-5 degrees throughout the day and night. The differences between indoor and outdoor temperature decreases because heat evaporates as it starts to transmit internally into the bamboo pole.

The bamboo screen wall design proves that thermal comfort throughout the year by improving air movement within the building. High rate of natural ventilation will lead to a situation where the indoor humidity levels follow the outdoor condition. The gap between the bamboo screen walls manage to achieve a ventilation rate that is more than required by the standards, hence this criteria has been addressed adequately. Continuous air flow within the room should help achieve a reasonably good quality of air.

Conclusion

Bamboo as a local material, is known as a bioclimatic design because the properties of the bamboo response towards the local climate. The main objective of bioclimatic design is to provide ‘comfortable’ living conditions with a minimum reliance of artificial energy. It is obvious that keeping the building warm in the cold season and keeping the building cool in the hot season is the main design objective for comfortable buildings for tropical and subtropical climate conditions. In conclusion, bamboo; as an alternative building material has both economic and ecological advantages in comparison to concrete and steel constructions; thus provide aesthetic and thermal comfort to the users.