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Comparison of Static and Ambulatory Measurements of Illuminance and Spectral Composition That Can Be Used for Assessing Light Exposure in Real Working Environments
Jönköping University, School of Engineering, JTH, Civil Engineeering and Lighting Science.
Department of Architecture and Built Environment, Lund University, Lund, Sweden.
Department of Environmental Science, Fukuoka Women’s University, Higashi-Ku, Fukuoka, Japan.
2019 (English)In: LEUKOS The Journal of the Illuminating Engineering Society of North America, ISSN 1550-2724, E-ISSN 1550-2716, Vol. 15, no 2-3, p. 181-194Article in journal (Refereed) Published
Abstract [en]

Reliable measurements are of utmost importance when investigating the relationship between light and human reactions. The aim of the present study was to compare two methods for measuring light exposure in real working environments. Ambulatory recordings of illuminance and irradiance were compared with static field measurements of horizontal illuminance at the normal working position, average horizontal illuminance in the room, vertical illuminance at the position of the eye in the normal angle of gaze, and spectral composition of the light radiation at the normal working position and at the position of the eye in the normal angle of gaze. The ambulatory measurements were carried out during a 3-day experimental period and were repeated monthly throughout the year. The static field measurements in the subjects’ offices were conducted five times during the year, in the morning and afternoon during one day. The relationship between the illuminances and irradiances measured with the portable instruments and the static measurements was statistically analyzed. Results from the analyses revealed that more than one third of the static measurements of vertical illuminances recorded were below 200 lx, and only 7% of the measurements exceeded 1000 lx. Measurements of the spectral composition of the light radiation in the rooms suggested that the light, although at a fairly low intensity, included relatively much radiation that can have a non-image forming effect. Furthermore, only a small number of significant correlations between the ambulatory and static measurements were found. Results from the t-tests showed that there were no differences between ambulatory measurements, and static measurements of horizontal illuminance at the normal position, average illuminance in the room and vertical illuminance at the position of the eye during three, five, and seven of the 10 measurements, respectively. There is a need to define appropriate parameters in order to describe the quality of a lit environment with respect to the non-image-forming effects of light radiation.

Place, publisher, year, edition, pages
Taylor & Francis, 2019. Vol. 15, no 2-3, p. 181-194
Keywords [en]
Indoor lighting, measurement, nonvisual effects, Radiation effects, Ambulatory measurement, Indoor lightings, Non visuals, Portable instrument, Reliable measurement, Spectral composition, Static measurements, Working environment, Lighting
National Category
Architectural Engineering
Identifiers
URN: urn:nbn:se:hj:diva-38822DOI: 10.1080/15502724.2017.1391101ISI: 000472454300008Scopus ID: 2-s2.0-85041096579Local ID: HOA JTH 2019;JTHByggnadsteknikISOAI: oai:DiVA.org:hj-38822DiVA, id: diva2:1182371
Available from: 2018-02-13 Created: 2018-02-13 Last updated: 2019-08-19Bibliographically approved
In thesis
1. Non-image-forming effects of light: Implications for the design of living and working environments
Open this publication in new window or tab >>Non-image-forming effects of light: Implications for the design of living and working environments
2018 (English)Doctoral thesis, comprehensive summary (Other academic)
Abstract [en]

Seasonal variation in mood and subjective well-being are common at geographical locations further away from the equator. The 24-h light-dark cycle is the main time cue for synchronizing the human circadian clock to the external day and night.

Nowadays, people spend more of their waking day indoors, with less exposure to the natural daylight cycle, relying on artificial lighting which differs to daylight in a number of aspects, including intensity, spectral composition and light exposure pattern.

In parallel with the technology development that has been mainly driven by energy-saving reasons, it is important to investigate the non-image-forming effects of different properties of the daily and seasonal light exposure.

The overall aim of the thesis was to identify characteristics of the daily light exposure that are important to support physiological and psychological needs of humans. To achieve this objective a number of research questions were posed concerning daily and seasonal light exposure, seasonal variation in physiological processes and psychological parameters, and evaluation of light exposure with respect to non-image-forming effects. The research questions were investigated in a longitudinal research design with measurements conducted each month during the year at a high latitude with large seasonal variation in day lengths.

Self-report diaries and instruments for ambulatory- and static measurements were used to examine daily and seasonal light exposure in the working and living environments and for investigating the relationship between different parameters that can be used for evaluating light exposure according to non-image-forming effects of light. Seasonal variation in daily light exposure and regarding the pattern of light exposure was observed. Also, the results indicate a seasonal variation concerning the quality (i.e. spectral composition of the visible radiation) of the exposing light.

Two biological markers, melatonin and cortisol, were used for investigating seasonal variation in physiological processes relating to the circadian clock. The results showed higher morning melatonin concentrations and peak level of melatonin during the winter although no seasonal change was observed concerning the phase position of the melatonin rhythm.

Seasonal differences in mood and sleep-activity were studied by means of selfreport diaries and questionnaires. Seasonal variations were observed for both parameters. The results showed higher ratings of mood in the summer, particularly 6 in the evening, and a relationship between bedtime and evening light exposure and photoperiod length. Furthermore, longer sleep times was observed in the winter.

Appraisal of lighting conditions in the offices during the year was rated by the use of a questionnaire. The results showed some seasonal differences concerning the perceived qualities of the light and some associations between characteristics of the lit environments and positive affect were found.

Two methods, static- and ambulatory measurements, were used for recording lighting conditions in the working environments. Taken together, the results showed weak associations between the two methods.

Research have demonstrated an increased need for taking non-image-forming effects into consideration when designing working and living environments, especially at geographical locations with large variations in day length where people are exposed to much of the daily light exposure at the workplace. Laboratory research has provided a good understanding of the basic concepts. However, more field research is needed. Also, current research has demonstrated that new methods of measuring and evaluating lighting conditions are needed.

Place, publisher, year, edition, pages
Lund: Department of Architecture and Built Environment, Faculty of Engineering, Lund University, 2018. p. 67
Keywords
circadian rhythms, circannual, light exposure, melatonin, cortisol, sleep-wake behavior, perception, mood, spectral composition, measurement
National Category
Architectural Engineering
Identifiers
urn:nbn:se:hj:diva-43220 (URN)978-91-7740-112-4 (ISBN)978-91-7740-113-1 (ISBN)
Opponent
Supervisors
Available from: 2019-02-28 Created: 2019-02-28 Last updated: 2019-02-28Bibliographically approved

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