Probabilistic cost-benefit analysis of installing extensive green roof in Malaysia

Abstract

Green roofs have been known as an environmentally friendly application and a sustainable approach in the developed countries such as: Germany, United States and Canada. Although environmental cost-benefits related issues of green roofs are already proven by many researchers in developed countries, it is not used widely in developing countries like Malaysia. It is estimated that the market at first focuses on extensive green roof due to the lower initial and maintenance costs; as a result, a probabilistic cost-benefit analysis for extensive green roof is conducted in this study. Installation, maintenance, and disposal costs of extensive green roof system are compared with the related private and social benefits (increase of property value, savings for air conditioning, longevity, air quality improvement, carbon reduction, etc.), determining two indicators: the Net Present Value (NPV) and the Pay Back Period (PBP), using Monte Carlo simulation. The analysis demonstrated that green roofs are not long-term investments in terms of net returns. In general, installing extensive green roof is a low risk investment. Furthermore, the probability of profits out of this application is much higher than the potential financial losses.