2019 - Daylight Symposium
"Using Virtual Reality to Validate New Metrics for Prediction" by Steffen Petersen
Engineering expert & associate professor
Department of Architectural and Civil Engineering, Aarhus University
The spatial quality of indoor environments is a subjective human conviction based on a multi-sensory experience of the space. Many architectural theoreticians have articulated various phenomena that seems to affect the ‘quality experience’ of indoor environments. Some describes phenomena using terms such as ‘bodily identification’, ‘spatial juxtaposition and interpenetration’, and ‘enclosure, demarcation, texture’ but refrains from establishing any explicit rules or recommendations on how to obtain a perception of quality regarding these phenomena. Others describes desirable traits of indoor spaces and formulates descriptive guidelines for obtaining these traits. Such explicit guidelines are interesting from a practical point of view where prediction of spatial quality e.g. in a design situation often is desirable.
Guidelines can also be used as inspiration for empirical investigations of relations between physical quantities and phenomena affecting spatial quality. This type of investigations are often employed in building engineering. An example is investigations of the relation between indoor temperature (physical quantity) and thermal discomfort (phenomenon affecting spatial quality). The results from such an investigation can be used to establish an explicit parametric model for discomfort prediction in the design stage; now the risk of thermal discomfort in a certain building design can be derived from computer simulations of the indoor temperature. The same principle could maybe be applied to derive useful prediction models of how physical quantities relates to other phenomena affecting spatial quality. It is practically self-explanatory that windows governs many phenomena that affects the perception of spatial quality. For example, the phenomena view-out and privacy are completely governed by the number, size, placement, and transparency of windows. These design variables also have significant influence on other important aspects affecting spatial quality such as subjective perception of lighting, noise, thermal comfort, and air quality – aspects that already can be explicitly predicted during the design stage based on the calculation of a physical quantity (e.g. luminance, illuminance, temperature, and decibel). However, the phenomena view-out and privacy does currently not have any calculable physical quantity which is why recent research have proposed metrics that includes quantities that can be used to make explicit models of the phenomena view-out quality and privacy.
The quantities defining these metrics are factors that express the relative subjective desirability of view to elements in the surroundings of a building on a scale from 0-1. For example, the desirability in terms of view-out quality could be 1.0 for a nearby group of trees, 0.8 for the sky, and 0.1 for a neighboring building. The metric can then be calculated as the area-weighted desirability when looking at the surroundings through a window from a certain point in the room. It is then the assumption that this average corresponds to the average subjective vote of a group of people assessing the overall view-out quality from this specific point on a scale from 0-1. However, this assumption has not been validated; in this paper, we present a validation study of the proposed view-out quality and privacy metrics under a certain daylight condition using virtual reality. A total of 90 people evaluated the view-out quality and privacy from two different points in a room situated in a total of three different surroundings.
Evaluations were made for two different window sizes leading to a total of 12 evaluations per person. The results showed that there were no statistical significant difference between the calculated metric and the average of the subjective vote suggesting that the proposed metrics and its physical quantities can be used to predict the spatial quality phenomena view-out quality and privacy e.g. during design. Results also suggests that there is a certain trade-off between the daytime view-out quality and privacy when it comes to the size of glazing areas.
Steffen Petersen is an engineering expert in building physics with substantial experience in research, teaching and practice. He is currently associate professor at the Department of Architectural and Civil Engineering, Aarhus University, Denmark, where he is leading the research group ‘Indoor Climate and Energy’. His passion is collaborative research and development of methods and technologies for realization of sustainable, healthy, comfortable, and productive indoor environments.