The Effects of Surrounding Vegetation, Building Construction and Human Factors on the Thermal Performance of Housing in a Tropical Environment

Abstract

Increasing energy consumption is having a detrimental effect on the environment. This issue combined with rising energy costs, is motivating people to reduce energy consumption. Moderating a building’s surrounding microclimate naturally through strategic landscaping has the potential to benefit the environment, save energy, save money and provide comfortable living environments.

The urban heat island effect is a well documented phenomenon, which influences the climate of most of the major cities around the world. It occurs when the air temperature in densely built urban areas is higher by 2°C to 8°C compared to the temperature of the surrounding rural environment. This issue is of particular concern in tropical areas, which experience high temperatures and humidity all year round. In these areas, solar heat passes through a building’s envelope via glazed windows and the walls and roofs resulting in uncomfortable interior spaces. The increased purchasing power of the population has resulted in greater use of air-conditioners to create and maintain a comfortable indoor temperature. This study found that the average household uses up to 37% of their electricity consumption for cooling. Careful planning of exterior spaces can help reduce energy consumption for cooling by reducing the adverse impact of some climatic factors. Strategically placed vegetation around a building has long been recognised as a means of cooling. It can reduce temperatures and humidity through shading, evapotranspiration and wind channelling.

The aim of this study was to examine and quantify the relationship between surrounding vegetation, and the thermal performance of housing in a hot-humid tropical environment. The primary objective was to determine the energy saving potential of vegetation for the tropical residence. The secondary objective was to investigate the effect of vegetation on modifying the outdoor temperature around a single-family house in a hot-humid climate.

Monitoring of household electricity use in the two Malaysian cities, Shah Alam and Putrajaya, has shown that at night time, when families are at home, is when airconditioning is used the most. Building surfaces on the east and west side are most affected by the sun, gaining and storing heat throughout the day until night time, when it is released into the house as the outdoor temperatures cool. Planting the right species, size and shape of trees, shrubs, vines, groundcover, and turf in strategic positions around a garden can greatly reduce the temperature around buildings. This in turn reduces the energy used for air conditioning. This study found that strategic landscaping, which resulted in shading and encouraged evapotranspiration and wind channelling, could reduce electricity use and costs by as much as 20%. The physical characteristics of buildings including their construction, size and age, combined with their landscape designs were looked at in 50 private houses in Malaysia. Measurements were taken from several outdoor and indoor locations around the houses. The findings showed that strategic design of landscaping could reduce heat build-up in a house, by shading, evapotranspiration and wind channelling by as much as 4°C for the exterior and 3°C for the interior spaces.

These results demonstrate how strategic landscaping can assist in creating a favourable microclimate in a house, which will help reduce energy consumption. Its effect can extend beyond the residential to have a positive influence on an area’s macroclimate and at a regional scale.