The environmental impact of an office building throughout its life cycle

摘要

This dissertation quantifies and compares the potential environmental impact caused by an office building during its life cycle, i.e. from the extraction of raw materials to disposal of waste. Using both a multiple-case study method and life-cycle assessment (LCA) the study determines the life-cycle phases and elements contributing most to a building's life-cycle impact. Furthermore, the study performed a sensitivity assessment to evaluate the effects of possible changes during the long service life, fifty years, of a building.In the study, corresponding life-cycle phases were found to contribute similarly to the environmental impact of the office buildings studied, with building operations (electricity, heating and other services) dominating the climate change, acidification and eutrophication categories, while building material manufacturing (in construction and maintenance) dominated those of summer smog and heavy metals. The key environmental issues found for the buildings were: electricity use in the outlets, HVAC and lighting, heat in ventilation and conduction, materials used in internal surfaces and HVAC services, and the use of water and wastewater, which were quite dominant in that they, as 20 % of all life-cycle elements, caused 45-75 % of the average life-cycle impact of the buildings studied and 60-75 % of the cumulative range.The sensitivity analysis indicated important issues. Firstly, it is ill-advised to use weight related cutoff criteria in the inventory analysis, because even very small flows of material can have a noticeable life-cycle effect. Secondly, although local conditions can have a clear influence on the degree of life-cycle impact, local conditions seemed to have less impact on the contribution made by different life-cycle phases. Finally, the traditional life-cycle phase approach in analyzing the result seems to produce a somewhat different conclusion than the system approach.As a whole, the findings of the study would suggest that within the limitations of both the electricity mix used and the obsolescence (economic life cycle), the life-cycle impact of a typical contemporary office building would follow a similar pattern. Practical applications of the study could be in the conscious design and facilities management of office buildings based on the determined environmentally significant issues and the possibilities of influencing same.