Research indicates that spectral distribution and the direction of the light received at the eye are relevant parameters in studies looking into non-image-forming effects. Nonetheless, lighting conditions are often described with vertical illuminance at the eye and correlated color temperature only, both of which are integral measurements that are not appropriate to give information about the spatial distribution of light and its spectrum. This article describes approaches for spatially and spectrally resolved measurements to properly quantify lighting conditions in research on non-image-forming effects. The overview of measuring methods indicates that the spectral irradiance, when combined with a luminance image of the lighting setting, is an adequate measure in a large number of research approaches. Nonetheless, lighting conditions in experimental setups with different light sources or various surface reflectances require a higher resolution of detail. Four examples of devices are presented that can be applied in different experimental setups or lighting settings. A decision scheme is included to support the selection of the most suitable measuring equipment. The article concludes with a proposal for analysis and representation of the measurements.

This paper presents selected results from the first stage of DAYKE (Daylight Knowledge in Europe), a 3-phase project that investigates the knowledge on daylighting in buildings among architecture students and practitioners across Europe. Subjective judgements from 561 students from 8 architecture universities in the EU, collected through two surveys in 2018. The key findings are: (i) the spatial distribution of comfort and mood in the classrooms varied depending on sky conditions and distance from windows; (ii) the average daylight factor DF_m showed a good agreement with subjective judgements on the amount of daylight in a space; (iii) experts and non-experts provided similar judgements on the perception of a daylit environment; (iv) a general lack of knowledge about daylighting metrics, regulations, assessment tools and software was highlighted. Furthermore a difficulty in implementing daylighting into the design practice is also identified.

Spectrally and spatially resolved information on daylight is critically important when planning for non-image forming (NIF) responses. Nevertheless, the availability of such data is scarce given the high initial costs and complex on-site maintenance of high-end spectral measurement devices. The CIE (Commission Internationale de l’Éclairage) reconstruction procedure allows for the derivation of the daylight spectral power distribution (SPD) from the chromaticity coordinates or the correlated color temperature ( $T_{cp}$). However, several studies have suggested that both the daylight locus and the reconstruction procedure are erroneous, and specifically SPDs with a higher $T_{cp}$ cannot be reproduced accurately. This paper studies the reconstruction accuracy of the SPD of daylight, and contextualizes the findings in relation to NIF effects. The analysis comprises a comparative study to determine the accuracy of the CIE procedure compared to two localized reconstruction procedures, and a sensitivity study to examine the impact of accuracy on the assessment of NIF responses, as represented by all five retinal photoreceptors and expressed in the α-opic efficacy of luminous radiation. The results indicated that a localized procedure, adjusting both the daylight locus and the PCA components of daylight, outperformed the CIE reconstruction method. However, improvement in the reconstruction accuracy had no effect on NIF assessment. The RSMPE for α-opic quantities did not exceed 4% for any procedure. In practical terms, this implies that cost-effective sensors and the representation of spectral properties in sky models with a single value – the correlated color temperature – can be used for NIF purposes. These findings bridge theory and practice by opening up new insights into the understanding of simplified methods used to determine NIF effects of daylight.

This paper summarises findings from two workshops evaluating a series of views in various settings by an interdisciplinary group of experts. In the first one (Trondheim, June 2022), ten experts visited and assessed views from nine rooms. In the second one (Lausanne, June 2023), eleven experts assessed window views from four spaces. The workshops’ main objective was to develop and test multi-method assessments of window views. During both workshops, participants completed a survey that included close and open-ended questions about the perceived quality of the room and the view. Participants also measured lux level, took photographs, made hand drawings of the view, and answered a questionnaire about their mood and the environmental conditions in the room. After the workshop, point-in-time daylight simulations were performed for the visited rooms. The paper describes, compares, and recommends the use of the aforementioned methods depending on the type and complexity of the view, and the space, the evaluators’ professional background, and the type of collected data. It also discusses the overlap of the methods and estimates the preparation time, time spent on site, and the amount of work after the visit. Finally, it recommends the use of the tested methods depending on the application.

Access to an unobstructed view of the outside through a window has been shown to play a critical role in supporting occupants’ visual comfort, psychological well-being, and cognitive performance, as it provides environmental connection and reduces stress. The aim of this study was to investigate how window view assessment ratings differ between “view owners” (individuals with long-term experience of the view) and “view observers” (those who view photos of a view). Findings from 12 in-person workshops on window view assessment are presented. The participants were 207 students from six European universities. Each participant presented their window view as “view owner”, while the remining students rated it on the 1–9 Likert scale as “view observers”. The ratings given by the “view owners” (prior to workshops) were significantly higher than those given by the “view observers”, showing the influence of familiarity and long-term experience. The additional contextual information about the interior and narrative descriptions provided orally by the “view owners” had a small positive effect. Night views were rated lower than day views by the “view observers”. The findings highlight the impact of long-term experience on the assessment of the window view and encourage the inclusion of night-view in recommendations.