Ten questions concerning the usage of subjective assessment scales in research on indoor environmental quality

The usage of scales to assess subjective ratings related to indoor environmental quality (IEQ) is ubiquitous in built-environmental research. Despite their importance, research and discussions on the scales themselves are scarce and the number of variations in the field is huge, which is reducing the potential for cumulative research. Motivated by the increasing interdisciplinary exposures of the authors, this 10 questions-paper addresses ten key issues related to the current and potential future usage of subjective rating scales in built environment research. These issues are particularly relevant in the context of multi-domain research, where an increasing number of papers have revealed differences between IEQ-domains like thermal and visual aspects. The first question sets the basis for the following discussion by giving a brief summary of the history of scales’ development. Questions 2 to 6 start with addressing specific challenges related to language and multi-domain applications and then broaden the scope to more general issues like the type and variation of scales and potential biases through their application. The third block of questions (Questions 7 and 8) discusses alternatives to scales like physiological signals and observing behavioural reactions. With the last two questions we ask ourselves and the community to what extend a fit-for-purpose approach to the use of scales would be beneficial, and what steps could lead to improving the use of scales in the future. We conclude by acknowledging the central role of questionnaires in advancing knowledge about IEQ and support their continued use with increased reliability and interpretability.