A STUDY OF THE RELATIONSHIP BETWEEN GREENERY AND WHITE PAINT ON THE EXTENT OF SURFACE TEMPERATURE REDUCTION OF CONCRETE WALLS

Abstract

Urbanization and urban development have been the main causes of the increased ambient temperature and other environmental issues around the world. The most prominent and concerned climate change in Singapore is the increase in air temperature. Being a tropical country, Singapore already experience hot and humid climate throughout the year. Hence, a large part of the total energy consumption is used to cool buildings’ interior. The best way to reduce energy consumption of cooling devices in buildings is to minimize the need for cooling. Due to the land scarcity in Singapore, majority of the building structures are high-rise buildings and thus, the surface area of walls is considerably larger than that of the roof area. As such, reducing the amount of heat transfer through building walls becomes a critical factor to bring down the energy consumption of cooling devices. The usage of light coloured external paint and concrete walls are the most common passive cooling methods in Singapore due to their effectiveness and relatively cheap cost. Greenery such as the green façade and living walls has also been increasingly popular as an effective alternative strategy to reduce heat transfer into the building. However, the significantly higher cost of installation and maintenance of greenery are two main factors of considerations deterring building owners to implement it. Thus, it will be beneficial to have an optimum system combining all the 3 cooling systems, which can not only balance the cost of installation and maintenance, yet providing the required efficiency in mitigating the heat transfer into buildings by reducing the surface temperature of external walls. Research has been done on the relationship between greenery and white paint, and their impact on the extent of surface temperature reduction of concrete walls. An experiment has also been conducted to determine the optimum ratio of greenery and white paint to achieve the most effective system in terms of surface temperature reduction and cost. Due to the arrangement of the greenery and white painted areas in each system, the increased in percentage of plant coverage is not proportional to the degree of surface temperature reduction. With strategic shading from the plants, a system with 30% lesser plant coverage is able to achieve a similar surface temperature reduction. From the experiment, the system of 50% greenery and 50% white paint is found to be the most efficient and cost effective in reducing cooling energy consumption. White paint is found to have a lower ability to reduce surface temperature of concrete than green plants. It has a limit as to how much solar energy it can reflect whereas, greenery can not only provide shading from direct sunlight, it can also lower the ambient air temperature in its surrounding, proving to be a better cooling means. Due to the vast difference in cost of painting and construction of a living wall, a combined system will not only help neutralize the cost factor and yet, achieve the cooling results desired.

However, this research is not without its limitation. The most concerned limitation being that due to time and resource constraints, only limited variables are used for the experiment. Although the external façade of buildings are made up of many different materials and different shades of colours, only white paint and concrete were chosen to be examined for this research as they have already been proven by previous research for their cooling properties. In addition, the objective of the experiment was to examine the extent of surface temperature reduction by greenery and white paint. However, due to weather constraints, where there were rain and drizzles on 3 of the 5 observation days, the rain water has helped to cool the concrete surface temperature, instead of the sole intended greenery and white paint.