A methodology for estimating the life-cycle carbon efficiency of a residential building

Residential buildings account for a large share of global carbon emission, while they play important roles in economic growth and social development at the same time. Therefore, the appropriate evolution routes of residential buildings need balancing their carbon emission and value creation, which is realized in this paper by creating a new concept of life-cycle carbon efficiency and its relative methodology. First, the life-cycle carbon efficiency of a residential building is defined as the ratio of its life-cycle value to carbon emission, and the life-cycle of a residential building is divided into five stages, including construction materials preparation, building construction, building operation, building demolition, and construction & demolition wastes disposal. Second, the life-cycle carbon emission of a residential building is estimated through calculating the carbon emission at each stage based on its consumed energy and resources. Third, the product of the service life span of a residential building (in year), its building area (m2) and its storey height (m) is recommended to represent its life-cycle value, since this product is a physical measure and more useful to develop action plans to improve its performance. In the end, the proposed methodology is exemplified in estimating the life-cycle carbon efficiency of a five-storey brick-concrete residential building in Nanjing city (China) at its design phase. Possible measures to enhance the estimated carbon efficiency are further put forward, such as prolonging the service life span, enhancing 3R (reduce, reuse and recycle) principles of cement and rolled steel, saving electricity and natural gas at the stage of building operation.