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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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Evaluating a New Suite of Luminance-Based Design Metrics for Predicting Human Visual Comfort in Offices with Daylight

Van Den Wymelenberg, Kevin; Inanici, Mehlika. (2016). Evaluating a New Suite of Luminance-Based Design Metrics for Predicting Human Visual Comfort in Offices with Daylight. Leukos, 12(3), 113 – 138.

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Abstract

A new suite of visual comfort metrics is proposed and evaluated for their ability to explain the variability in subjective human responses in a mock private office environment with daylight. Participants (n = 48) rated visual comfort and preference factors, including 1488 discreet appraisals, and these subjective results were correlated against more than 2000 unique luminance-based metrics that were captured using high dynamic range photography techniques. Importantly, luminance-based metrics were more capable than illuminance-based metrics for fitting the range of human subjective responses to data from visual preference questionnaire items. No metrics based upon the entire scene ranked in the top 20 squared correlation coefficients, nor did any based upon illuminance or irradiance data, nor did any of the studied glare indices, luminance ratios, or contrast ratios. The standard deviation of window luminance was the metric that best fit human subjective responses to visual preference on seven of 12 questionnaire items (with r(2) = 0.43). Luminance metrics calculated using the horizontal 40. band (a scene-independent mask) and the window area (a scene-dependent mask) represented the majority of the top 20 squared correlation coefficients for almost all subjective visual preference questionnaire items. The strongest multiple regression model was for the semantic differential rating (too dim-too bright) of the window wall (R-adj(2) = 0.49) and was built upon three variables; standard deviation of window luminance, the 50th percentile luminance value from the lower view window, and mean luminance of the 40. horizontal band.

Keywords

Discomfort Glare; Controls; Daylighting; Visual Perception

An Investigation of the Daylighting Simulation Techniques and Sky Modeling Practices for Occupant Centric Evaluations

Inanici, Mehlika; Hashemloo, Alireza. (2017). An Investigation of the Daylighting Simulation Techniques and Sky Modeling Practices for Occupant Centric Evaluations. Building And Environment, 113, 220 – 231.

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Abstract

Occupant centric performance approaches in daylighting studies promote design decisions that support human visual comfort, productivity, and visual preferences, along with more conventional energy efficiency criteria. Simulating per-pixel luminance values and luminance distribution patterns for the entire scene allows us to analyze the occupant centric metrics and performance criteria. However, there are a number of different sky models, complex fenestration models, and simulation techniques that produce either conventional point in time images or annual luminance maps. This paper discusses the similarities and differences between different techniques; and a comparison analyses provides insight about their impact on occupant centric lighting measures. The comparisons for sky modeling include the conventional CIE skies (Clear, Intermediate, and Overcast), measurement based CIE models, Perez all-weather skies, and high dynamic range image based skies. The comparison of simulation techniques include point in time simulations, image based lighting simulations, and annual luminance simulations (threephase and five-phase methods). Results demonstrate that measurement based sky models match real world conditions with reasonable proximity, and generic CIE skies consistently underestimate the indoor lighting conditions. Annual simulation methods provide a large database of temporal luminance variations, where individual instances are comparable to point in time simulations. Long term luminance simulations provide opportunities to evaluate the percentage of the year that a given luminance based criteria is met or violated. (C)2016 Elsevier Ltd. All rights reserved.

Keywords

Complex Fenestration Systems; Scattering Distribution-functions; Discomfort Glare; Visual Comfort; Daylit Spaces; Validation; Radiance; Performance; Offices; Design; Sky Models; Daylight Simulations; Point In Time Simulations; Image Based Lighting; Annual Lighting Simulations; Annual Luminance Maps