Assessment of the circadian stimulus potential of an integrative lighting system in an office area

Abstract

Nowadays, people spend 90% of their time indoors, thus creating a healthy indoor environment for occupants is of great importance. Lighting in office spaces is an important aspect when it comes to occupant health and well-being. Research in the field of lighting has mostly been focusing on the visible light spectrum and image-forming (IF) processes. However, with the discovery of melanopsin containing intrinsically photosensitive Retinal Ganglion Cells (ipRGCs), non-visual effects of light such as circadian entrainment and alertness received more attention. Non-visual effects of light have previously been subject of research under laboratory conditions, yet, there are only few field studies that were conducted in office environments to evaluate these effects.
The present study was undertaken to fill that gap by investigating an integrative lighting system in an office building, The Spark, at Medicon Village in Lund, Sweden.
The study comprises of Technical Environment Assessments (TEAs) and Observed-based Environmental Assessments (OBEAs). TEAs include a series of photometric site measurements that were carried out for collecting information about the lighting system, calibration of the daylight model. Inputs used in simulations as well as sensor recordings were obtained by Movisens light and activity devices that were wrist-worn by the participants. OBEAs cover user assessment incorporating self-reported questionnaires and semi-structured interviews. Numerical modelling with the engine Radiance was used for photometric studies, and Adaptive Lighting for Alertness (ALFA) for circadian lighting potential. Lighting energy use of the building was calculated according to the standard EN 15193 since the building was completed in late 2019 and no full-cycle electricity bills were available at the time of the study.
The results showed that the integrative lighting system can steer equivalent melanopic lux (EML), especially in areas with less daylight intake, therefore affecting the human circadian system. Based on the self-reported questionnaire and sensor recordings of wrist-worn devices, alertness of most participants increased with higher values of arbitrary unit (CCT·lux), that combines Correlated Color Temperature (CCT) and illuminance level detected by the devices. Circadian lighting simulations in ALFA showed higher EML values than the measured ones, while the closest values were obtained under only electric lighting. Semi-structured interviews indicated that most of the participants were positive towards the lighting system. The integrative lighting system complies with the energy benchmarks designated for existing and direct lighting systems; however, the system was designed with most attention to health and well-being of the occupants and to promote their circadian rhythms, rather than maximizing the energy-efficiency.

Popular Abstract

Non-visual effects of a recently developed integrative lighting system on office workers were evaluated through a series of site measurements, computer simulations, user perspective assessments through questionnaires and interviews, and lighting energy use of the system was calculated based on European standards.

People spend most of their time indoors nowadays. Therefore, creating healthy indoor environments becomes an important issue. Lighting is one of the aspects that is taken into consideration while designing office spaces. Providing enough light in workplaces has been the focal point of the lighting research and applications. This practice that is related to visual effects of light has become mandatory due to building regulations and building certification schemes such as LEED, BREEAM and Miljöbyggnad. However, with the discovery of a new type of cell in the eye, it was seen that the lighting environment does not only influences our visual system but also has non-visual effects on the human body. Non-visual effects of light are found to be related with human health and circadian rhythm that has control over hormones and sleep/wake cycle. There have been recent developments in lighting systems that can mimic the daylight to improve health and well-being of the occupants. These lighting systems change the color and intensity of the light throughout the day and provide blue and brighter light in the morning and red and less bright in the afternoon. There have been laboratory studies that investigate the effects of similar dynamic lighting systems, however, there is a need for field studies that are conducted in uncontrolled office environments. This study examines the non-visual effects of the integrative lighting system in an office building, The Spark, at Medicon Village in Lund, Sweden in terms of site measurements, simulations, and user perspective assessment of five participants. In addition, lighting energy use calculations were carried out.
The results of the study showed that the integrative lighting system has non-visual effects on the office workers, and it influences one’s sleepiness and alertness. Therefore, more attention must be paid when designing the lighting systems in office environments, especially in the offices that do not have openings directly to outside and are lit by electric lighting only or in the offices with less daylight intake. When daylight was prominent in a space, these effects were dominated by the daylight itself rather than the electric lighting. It was also seen that most of the participants were less sleepy under bright blue light that appeared in the morning. When the light provided less lighting level with a light color closer to red in the afternoon, they reported more sleepiness. User assessment showed that most participants were satisfied with the lighting system and preferred using the automatic mode in the lighting system. Simulations to assess the effects of the lighting system showed that the results resembled to the ones that were measured on site. However, simulation results provided larger effects on the non-visual system of the participants compared to the measurements. Lighting energy calculations presented that the lighting system has high energy consumption, however, it was also observed that the system provides higher illuminance levels compared to traditional lighting systems. Further studies should be carried out to design a similar system that can have positive impacts on occupant well-being but have lower energy use.
Four office spaces were investigated by a series of site measurements and computer simulations, and five people that work in the building were assigned as participants for user assessment perspective. Participants were given devices that they wore on their wrists for three weeks and answered questionnaires three times a day for this period. The devices recorded data about their lighting conditions. At the end of three weeks, interview with the participants were conducted for a better understanding of their perception of the lighting system. Computer simulations in ALFA were carried out in terms of non-visual effects and the results were compared to the measurements that were taken in the offices of four participants. Lighting energy use of the system was calculated according to the European Standard EN 15193.

• author: Yilmaz, Elif Ceren and Abdulhaq, Rawan
• supervisor: Niko Gentile; Thorbjörn Laike
• organization: Division of Energy and Building Design; Department of Architecture and Built Environment
• course: AEBM01 20201
• year: 2020
• type: H2 - Master's Degree (Two Years)
• subject: Technology and Engineering
• keywords: Alertness, Circadian Rhythm, Circadian light effect, Daylighting, Energy efficiency, Entrainment, Health, Intrinsically photosensitive retinal ganglion cells, Light response, Melanopsin, Melatonin suppression, Photometric, Sleep quality, spectral sensitivity, Wavelength.
• language: English
• id: 9016391
• date added to LUP: 2020-06-11 16:37:33
• date last changed: 2020-06-12 10:24:27