Energy Saving and Environmental Benefit Assessment for Corporate Green Roof

• Main Authors: Chou, Cheng-Lung, 周政隆
• Other Authors: Kao, Jehng-Jung
• Format: Others
• Language: zh-TW
• Published: 2013
• Online Access: http://ndltd.ncl.edu.tw/handle/gm23cu

碩士 === 國立交通大學 === 工學院永續環境科技學程 === 101 === Green roof technology has the functions of roof insulation, room temperature decreasing, and rainwater runoff detention, corporate green roof (CGR) establishment is thus widely promoted in many countries and is regarded as an appropriate approach for demonstrating the corporate social responsibility in energy conservation, carbon-emission reduction and landscape aesthetics. However, the method for evaluating the cost-benefit of domestic CGRs is so far not available. This study was thus initiated to develop a cost-benefit analysis method to evaluate major benefits of CGRs including the heat reduction for energy saving, carbon-emission reduction and rainwater runoff detention for a local corporate building. The eQUEST simulation program and thermal conductivity coefficient (U-value) method are applied to estimate the energy savings of CGRs, with consideration of different CGR type and thickness of soil medium. The environmental benefits of CGRs are mainly carbon-emission reduction and rainwater runoff detention. The carbon emission reduction is approximated based on the avoided emission from energy saving and the amount of carbon sequestrated by CGRs. The rainwater detention of CGRs is calculated by an experimental equation. The benefits are estimated based on the local electricity fee, a suggested carbon tax, and a stormwater charge. A case study for a corporate office building was implemented for both extensive and intensive CGRs. The proposed benefit-cost analysis method was applied to estimate the potential benefits and costs of CGRs, and compared with the conventional roof with a life span of 10, 15, or 20 years. The annual costs for extensive and intensive CGRs are 212 and 301 NT$/m2-yr, while the costs for the conventional roof for different life spans are 241, 182, and 134 NT$/m2-yr, respectively. The results show that the intensive CGR is not cost effective due to its high initial installation cost. Although the extensive CGR is more expensive than the conventional roof with a life span of 15 or 20 years, it is superior to the latter with a life span of 10 years. The CGR will be more cost effective if the electricity rate increases and other benefits such as heat island mitigation are also considered. This study has demonstrated the applicability of the proposed CGR cost-benefit analysis method, and the results are expected to facilitate related decision-making analyses for a company to install CGRs.