Green Roof Case Study

This paper reports a feasibility study of constructing an extensive green roof on a future multi-storey carpark building in Singapore. In-depth technical analysis on each layer of the green roof, benefits analysis on society, environment and economy and financial analysis have been performed. Research on the contractor company to build this carpark in Singapore is also identified together with the local incentive schemes that support this green structure. Throughout the analyses, a conclusion based on cost-benefit analysis has been drawn which concludes that an extensive green roof on a carpark building will be a good investment.

The term ‘green roof ‘ is defined as a rooftop garden which provides both environmental and economic benefits to the building. Green roof consists of soil and vegetation that are planted over a waterproof membrane material. There are two different types of green roofs which are extensive green roof and intensive green roof. An extensive green roof system has an overall depth of 3 to 5 inches and is used as a living machine with restricted access to the public except for maintenance purpose (Green Roof Technology). The weight of an extensive green roof is about 60kg to 150kg per square metre (International Green Roof Association, 2014). On the other hand, an intensive green roof system has an overall depth of 7 to 24 inches and is best suited for being used as a garden or park for the consumers (Green Roof Technology). The weight of an intensive green roof is about 180kg to 500kg per square metre (International Green Roof Association, 2014).

UNLV Carpark which is about 1,600 square metres per level, will be built opposite National Library Board that is located in Bugis, Singapore. Because of the country...

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...180 for monthly season parking fee, the carpark will earn an estimate of about S$933,120 annually.

Highest Return of Investment Ratio Annually

= [(Earnings – Initial Investment)/Initial Investment]

= [(S$933,120 - S$156,000)/S$156,000]

= 4.98

Lowest Return of Investment Ratio Annually

= [(Earnings – Initial Investment)/Initial Investment]

= [(S$933,120 - S$216,000)/S$216,000]

= 3.32

The calculated return of investment ratio ranges from 3.32 to 4.98 which is considered quite ideal for the application of UNLV Carpark.

Although the initial cost in building the extensive green roof is much higher than building a bare roof, the social, environmental and long-term economic benefits are greatly observed. Using the cost-benefit analysis, the extent of benefits outweighs the increase in initial cost, hence it is cost effective to build green roof in UNLV Carpark.