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Person: Mehlika Inanici

Multispectral lighting simulation approaches for predicting opsin-driven metrics and their application in a neonatal intensive care unit

Jung, B., Cheng, Z., Brennan, M., Inanici, M. (2023). Multispectral lighting simulation approaches for predicting opsin-driven metrics and their application in a neonatal intensive care unit. Proceedings of Building Simulation 2023: 18th Conference of IBPSA. https://doi.org/10.26868/25222708.2023.1446.

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Abstract

Design decisions affect the duration, intensity, and spectra of light exposure in built environments. Therefore, it is necessary to quantify and visualize the interaction of light and biology to inform design decisions that can improve health outcomes. This paper explains the addition of new features in a multispectral lighting simulation tool. Sample workflows are demonstrated through a neonatal intensive care unit (NICU) design. State-of-the-art NICUs have complex lighting designs that provide full-spectrum lighting that changes its spectra and intensity in 24-hour cycles. Prescription of healthy light recipes through thoughtful design decisions and dynamic commissioning practices of shading and programmable electric light systems are discussed.

Keywords

Daylighting; Circadian Rhythms; Non-image forming Ocular Photoreceptors, NICU.

Tri-stimulus Color Accuracy in Image-based Sky Models: Simulating the Impact of Color Distributions throughout the Sky Dome on Daylit Interiors with Different Orientations

Inanici, M. (2019). Tri-stimulus Color Accuracy in Image-based Sky Models: Simulating the Impact of Color Distributions throughout the Sky Dome on Daylit Interiors with Different Orientations. Proceedings of Building Simulation 2019: 16th Conference of IBPSA. https://doi.org/10.26868/25222708.2019.210585.

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Abstract

Spectral properties of daylight surpasses any other light source. Its dynamic intensity and spectra across the full spectrum facilitates sustainable daylighting practices, produces best color rendition, and regulates circadian rhythms in all living beings. However, simulation models do not typically include spectral variability; daylight is modelled as a uniform, equal energy white source. In this paper, tristimulus calibration procedures are utilized to create spectrally accurate High Dynamic Range (HDR) photographs. HDR photographs of skies are collected and utilized as an input to image based lighting (IBL) simulations. The impact of color variations across the sky dome and between different sky conditions are studied. Per-pixel photopic luminances, tri-stimulus chromatic distributions, Correlated Color Temperatures (CCT) and circadian luminance and illuminance values are quantified for image-based daylighting simulations, and compared with standard colorless Perez skies.

Keywords

color based skies; image based lighting; daylight simulations; high dynamic range imagery; color calibration

Our skies are too grey: Where is the colour?

Knoop, M., Balakrishnan, P., Bellia, L., Błaszczak, U., Diakite-Kortlever, A., Dumortier, D., Hernández-Andrés, J., Inanici, M., Kenny, P., Kobav, M., Liang, S., Luo, T., Maskarenj, M., O’Mahoney, P., Pierson, C., Thorseth, A., & Xue, P. (2025). Our skies are too grey: Where is the colour? Lighting Research & Technology (London, England : 2001). https://doi.org/10.1177/14771535251322618.

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Abstract

The Daylight Illuminant D65, a standardised reference light source in design and research with a colour temperature of 6500 K, is often used to describe the colour of the daylight. However, it represents the colour of an overcast sky, failing to capture the variability and richness of actual daylight, particularly the blue of clear skies. Recent research shows that both sunlight and skylight significantly influence our mood, perception and physiological responses. The colour of daylight is influenced by factors like sun position, weather conditions, as well as geographical location. To address these variations, researchers are collecting worldwide spectral daylight measurements, emphasising the need for localised spectral reference data to appropriately represent daylight in different locations.

Methodology to modify and adapt the standardised spectral power distributions for daylight to account for geographical, seasonal and diurnal variations for practical applications

Knoop, M., Balakrishnan, P., Błaszczak, U., Diakite-Kortlever, A., Dumortier, D., Hernández-Andrés, J., Inanici, M., Kenny, P., Maskarenj, M., O’Mahoney, P., Pierson, C., Rudawski, F., & Thorseth, A. (2025). Methodology to modify and adapt the standardised spectral power distributions for daylight to account for geographical, seasonal and diurnal variations for practical applications. Lighting Research & Technology (London, England : 2001). https://doi.org/10.1177/14771535251322386.

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Abstract

In recent years, the spectral properties of solar radiation and daylight have become increasingly important in lighting design and research, and various approaches to implement these have been applied. This paper proposes to modify and adapt the CIE reconstruction method, a procedure developed in the early 1960s to define standardised spectral power distributions (SPDs) of daylight, for this purpose. The CIE D Illuminants resulting from the reconstruction procedure are widely used for standardisation purposes but are based on a smaller number of measurements and do not consider geographical, seasonal and diurnal variations. In order to be able to use the CIE reconstruction method specifically in daylight planning, research and application, a technical committee of the CIE has launched a worldwide measurement campaign to collect spectral daylight measurements. The aim of the committee is to formulate a customised reconstruction method that more accurately reflects the local SPDs of daylight. This paper contributes to the discourse on the improvement of daylight estimation methods and emphasises the importance of accurate daylight data in various scientific and practical contexts.

Research Methods in Daylighting and Electric Lighting

Inanici, M. (2021). Research Methods in Daylighting and Electric Lighting. In: Azari, R., Rashed-Ali, H. (eds) Research Methods in Building Science and Technology. Springer, Cham. https://doi.org/10.1007/978-3-030-73692-7_4

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Abstract

Research in daylighting and electric lighting focuses on the physical quantity of light, physiological response to the physical stimuli, and the resulting visual perception. This chapter starts with an overview of the measurement and simulation-based research approaches used in understanding and quantifying the lighting availability and variability in the luminous environment. Field and laboratory measurements are discussed along with computational techniques. The rest of the chapter focuses on psychophysical research methods that aim to quantify the human physiological and psychological responses to the quantity and distribution of light.

Keywords

Daylighting; Electric lighting; Visual comfort; Visual performance; Visual perception; Energy efficiency; Circadian lighting

A Critical Investigation of Common Lighting Design Metrics for Predicting Human Visual Comfort in Offices with Daylight

Van Den Wymelenberg, K., & Inanici, M. (2014). A Critical Investigation of Common Lighting Design Metrics for Predicting Human Visual Comfort in Offices with Daylight. Leukos, 10(3), 145–164. https://doi.org/10.1080/15502724.2014.881720

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Abstract

Existing visual comfort metrics are reviewed and critiqued based upon their ability to explain the variability in human subjective responses in a daylit private office laboratory environment. Participants (n = 48) evaluated visual comfort and preference factors, totaling 1488 discreet appraisals, and luminance-based metrics were captured with high dynamic range images and illuminance-based metrics were recorded. Vertical illuminance outperformed all commonly referenced visual comfort metrics including horizontal illuminance, IES luminance ratios, daylight glare probability (DGP), and daylight glare index (DGI). The bounded borderline between comfort and discomfort is introduced, and preliminary visual comfort design criteria are proposed for several existing metrics. Fundamental limitations of glare indices are documented, and the implications of inconsistent application of luminance ratio calculation methods are quantified. Future research is detailed.

Keywords

daylight glare; daylight metrics; luminance ratio; vertical illuminance; visual comfort

Non-ionizing radiation modeling to predict ambient irradiance in work areas at an indoor cannabis farm

Chmielinski, M., Yost, M. G., Cohen, M., Inanici, M., & Simpson, C. D. (2023). Non-ionizing radiation modeling to predict ambient irradiance in work areas at an indoor cannabis farm. Annals of Work Exposures and Health. https://doi.org/10.1093/annweh/wxad048

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Abstract

Agricultural workers frequently experience potentially hazardous exposure to non-ionizing radiation from both solar and artificial sources, and measurement of this exposure can be expensive and impractical for large populations. This project develops and evaluates a vegetative radiative transfer model (VRTM) to predict irradiance in a grow room of an indoor cannabis farm. The model uses morphological characteristics of the crop, manufacturer provided lamp emissions data, and dimensional measurements of the grow room and cannabis hedgerows to predict irradiance. A linear regression comparing model predictions with the measurements taken by a visible light spectroradiometer had slopes within 23% of unity and R2 values above 0.88 for visible (400–700 nm), blue (400–500 nm), green (500–600 nm), and red (600–700 nm) wavelength bands. The excellent agreement between the model and the measured irradiance in the cannabis farm grow room supports the potential of using VRTMs to predict irradiance and worker exposure in agricultural settings. Because there is no mechanistic difference between visible and other non-ionizing wavelengths of radiation in regards to mechanisms of radiative transfer, the model developed herein for visible wavelengths of radiation should be generalizable to other radiation bands including infrared and ultraviolet radiation.

Keywords

horticulture; indoor; Marijuana; non-ionizing radiation; radiative transfer; UV

Window View Quality: Why It Matters and What We Should Do

Ko, W. H., Schiavon, S., Altomonte, S., Andersen, M., Batool, A., Browning, W., Burrell, G., Chamilothori, K., Chan, Y.-C., Chinazzo, G., Christoffersen, J., Clanton, N., Connock, C., Dogan, T., Faircloth, B., Fernandes, L., Heschong, L., Houser, K. W., Inanici, M., … Kent, M. (2022). Window View Quality: Why It Matters and What We Should Do. Leukos, 18(3), 259–267. https://doi.org/10.1080/15502724.2022.2055428

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Human-Centric Lighting Performance of Shading Panels in Architecture: A Benchmarking Study with Lab Scale Physical Models Under Real Skies

Parsaee, Mojtaba; Demers, Claude M. H.; Lalonde, Jean-francois; Potvin, Andre; Inanici, Mehlika; Hebert, Marc. (2020). Human-Centric Lighting Performance of Shading Panels in Architecture: A Benchmarking Study with Lab Scale Physical Models Under Real Skies. Solar Energy, 204, 354 – 368.

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Abstract

This study investigates shading panels' (SPs) impacts on daylighting features in a lab scale model in terms of parameters representing potential human eyes' biological responses identified as image forming (IF) and non-image forming (NIF). IF responses enable vision and NIF responses regulate internal body clocks known as circadian clocks. Human-centric lighting evaluates photopic units, representing IF responses, and melanopic units representing NIF responses, combined with correlated color temperature (CCT) of light for potential biological effects. SPs' impacts on such parameters of daylighting have not yet been studied. Previous research mostly studied panels' impacts on visual comfort and glare related to IF responses. This research explores the impact of SPs' color, reflectance, orientation, and openness on photopic and melanopic units and CCT of daylighting inside a 1:50 physical scale model of a space. Approximately 40 prototypes of SPs were evaluated. An experimental setup was designed under outdoor daylighting conditions to capture high dynamic range (HDR) images inside the model. HDR images were post processed to calculate and render the distribution of photopic and melanopic units, melanopic/photopic (M/P) ratios and CCTs in the captured viewpoint of the model. Results reveal the behavior of SPs' color, reflectance, orientation, and openness in modifying daylighting parameters related to biological responses. Bluish panels, in particular, increase daylighting melanopic units and CCTs whereas reddish panels increase photopic units and reduce CCTs. The research results were discussed to provide an outline for future developments of panels to adapt daylighting to occupants' IF and NIF responses.

Keywords

Models & Modelmaking; Shades & Shadows; Daylighting; Color Temperature; Benchmarking (management); Ecological Houses; Eye Tracking; Circadian Rhythms; Adaptive Design; Healthy Lighting; High Performance Façade; Photobiology; Responsive Building; Design; Sensitivity; Illuminance; Systems; Spaces; Impact; Glare; High Performance Facade; Reflectance; Scale Models; Biological Effects; Human Performance; Prototypes; Parameter Modification; Lighting; Shading; Eye (anatomy); Color; Parameter Identification; Light Effects; Panels; Mathematical Models; Images; Biological Clocks; Orientation

Syncing with the Sky: Daylight-Driven Circadian Lighting Design

Altenberg Vaz, Nathan; Inanici, Mehlika. (2021). Syncing with the Sky: Daylight-Driven Circadian Lighting Design. Leukos, 17(3), 291 – 309.

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Abstract

The use of daylight in the built environment is often preferred to artificial light sources as its successful application can provide visual comfort and satisfaction along with the potential for significant energy savings. Exposure to daylight is also the primary source for stimulus that establishes a healthy day/night cycle in all living organisms. This is known as circadian rhythm. Newly discovered photoreceptors (intrinsically photosensitive retinal ganglion cells - ipRGC) within the mammalian eye, including humans, are specifically linked to the portion of the brain responsible for maintaining a healthy circadian rhythm. This discovery has led to a new subject area in the field of lighting design focused on controlling the spectrum of light that these photoreceptors are sensitive to. Currently, work in the field of circadian lighting design is concentrated on the use of artificial light sources for circadian stimulus. This is largely due to the advent of the widespread use of LED technology, which has proven that it can be a significant source of light that can delay or advance the circadian clock. The use of daylight to provide circadian stimulus has been a given in this field of design, however, there has not been very much research into how the built environment affects our ability to effectively receive this stimulus from daylight. In this research, the groundwork is established to start to create a set of guidelines to help architects and designers maximize the potential for daylight to provide circadian stimulus at the earliest stages of a project. This is accomplished through a series of lighting simulations that explore and test various architectural parameters that affect daylight-driven circadian lighting, with simultaneous consideration given to photopic lighting availability and visual comfort. The architectural parameters tested in this study included window head height, building orientation, shading devices, visual obstructions to the sky, and room depth. The results show that informed design decisions could maximize circadian potential in a given space, while achieving visually satisfactory luminous environments.

Keywords

Action Spectrum; Melanopsin; Environments; Sensitivity; Framework; Stimulus; Rod; Circadian Lighting; Daylight; Lighting Simulation; Alfa