Setting contextual life-cycle objectives in urban design: requirements for a decision-support method

A variety of building labels and norms exist that set evermore-ambitious environmental and energy performance targets. In parallel, a growing number of building performance evaluation tools are adopting the life-cycle assessment (LCA) methodology to allow verifying if a project, based on its detailed description, reaches these targets. However, such norms and tools seem unsuited to the district scale, where environmental impact considerations are often left out of the urban planning and design process. There specifically appears to be a lack of decision-support instruments that can relate urban-scale performance targets to concrete design choices, taking into consideration the project’s specificities (e.g., climatic context), but without requesting design information that is not yet available. This paper presents the first phase of a collaborative research and development project, aiming at developing a novel decision-support method to integrate life-cycle objectives from the masterplanning stage. In this first phase, we investigate barriers and requirements from a practice-oriented perspective in the Swiss context by: (i) exploring urban-scale LCA-based methods and tools, and (ii) engaging with key stakeholders who hold complementary roles in a case study district project, which aims to be low-carbon. These exchanges are conducted in the form of a focus group and a questionnaire to gather qualitative and detailed information. Our findings notably highlight the mismatch between the ambitious objectives set by regulations and labels and the (lack of) means available to practitioners to support them in achieving these objectives. Specifications for a novel tool are derived from the practitioner’s feedback, as well as information on relevant design parameters and performance indicators.