What do persons mean by cold or warm? A qualitative approach to the ASHRAE-scale

Karin Schakib-Ekbatan (Heidelberg Academy of Sciences and Humanities)

Against the background of climate change, the quality of indoor climate in office buildings becomes highly relevant in terms of appropriate room conditioning and user satisfaction. As part of post-occupancy evaluation the ASHRAE-scale is often applied in the field of thermal comfort in order to evaluate occupants’ perception of the built environment. Responses are assumed as being comparable, based on the assumptions that differences between neighbouring labels of the scale are perceptually equidistant and participants have the same association with individual labels. Because of the complexity of perception, it is worthwhile to scrutinize the scale.

Within an interdisciplinary experimental study with the objective to get insights into participants’ associations and concepts related to the ASHRAE-scale labels a free-positioning task combined with the think-aloud-method was used to gather qualitative data. In the free-positioning task, the 61 participants (32 females, 29 males) ad libitum positioned the verbal anchors of the ASHRAE-scale on a horizontal line. Comments regarding the positioning and associations with the verbal anchors were gathered by the think-aloud-method: participants were asked to mention whatever comes to their mind.

Results demonstrate that the positioning of verbal anchors varied greatly across participants: 54% drew and rated the labels of the scale as not equidistant. Most deviations from an equidistant distribution of neighbouring labels were related to the end points of the scale. Also the marked areas on the scale for the comfort zone varied greatly. Additionally, the participants experienced difficulties in defining the middle label ‘neutral’.

The results indicate that neglecting the variation of peoples’ associations with a scale might bear the risk of drawing wrong conclusions with regard to room conditioning.