Managing Uncertainty in Environmental and Cost Life Cycle Studies of Building Design

Abstract: In order to mitigate global warming and address other pertinent environmental issues, it is important to reduce the environmental impact from the building stock. Emissions can be large for both operational energy consumption and production of materials. It is therefore important to find building design solutions that consider production, operation and maintenance in order to minimise the climate impact of a building during its entire lifetime. At the same time, the production of buildings has to be cost-efficient. In the design of buildings, both environmental impact and cost must be evaluated in order to make well-supported decisions. There are many uncertainties in the design phase of buildings. This study explored the uncertainties that occur when a life cycle perspective is adopted in building design decisions and developed an approach to manage them. Addressed issues were secondary effects of design changes, material data gaps and how subjective choices and parameter uncertainties can be managed in conjunction. This was done by developing the Effect and Consequences Evaluation (ECE) method and the Decision Choices Procedure (DCP), which were combined into a general approach. The presented approach will provide a structured means to set up system boundaries and manage uncertainties when life cycle studies are used as decision support for optimising building design. Several case studies were carried out to penetrate specific issues, and the final approach was demonstrated with a case study of selecting optimal insulation thickness when designing the building envelope. The results can be used to support decisions on where and how to effectively make improvements when subjective choices and parameter uncertainties are considered in the study. This will facilitate decisions on different building design solutions so that the option with the lowest total environmental impact and a reasonable cost can be chosen.