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To understand how daylight gives shape and life to architectural spaces, whether existing or imagined, requires quantifying its dynamism and energy. Maintaining these details presents a challenge to simulation and analysis methods that flatten data into discrete images or virtual sensor points from a point and time. To address this challenge, this thesis presents a new method for sampling and evaluating simulated daylight. It is intended as a bridge between image-based and sensor-based methods; one that can produce image-level high accuracy directional distribution data with much shorter simulation times that are closer to sensor-based methods. Instead of producing a fixed grid of points, pixels, and sun directions, an iteratively guided sampling approach structured by the discrete wavelet transformation captures the distribution of light incident on a viewpoint with a variable density. By storing the direction vector and effective solid-angle of each sampled ray, the data can be directly evaluated for any luminance-based quantity and view direction. Coupled with daylight coefficients, where the contributions from regions of the sky-dome are recorded rather than associating a value to every possible sky distribution, these methods reduce simulation time at three stages by reducing the number of samples. With fewer samples, it takes less time to render, less time to combine with sky values, and less time to evaluate potential glare sources. Through a series of simulated reference validations, this thesis shows that the proposed method can reproduce the value predicted by a high quality reference simulation in a small fraction of the time. The method achieves higher accuracy results compared to those of existing simulation methods that rely on simplifications. The method is robust across a wide range of daylight conditions and can be tuned to the desired scope of the output. The method can be applied to render a single image in high detail or used to calculate glare metrics in order to evaluate a whole building zone. This method enables a more complete characterization of daylight and visual comfort across an occupied zone; one that is less biased by proxy measurements, representative point selection, or assumptions about glare-causing pathways. Using these methods, we can more reliably understand how daylight will respond to proposed interventions, which should be useful for guiding design, regulatory standards, and improving performance.

Avoiding discomfort glare is one of the critical aspects of maintaining visual comfort, which significantly influences occupants' overall satisfaction with their indoor environment. Discomfort glare prediction models have been developed for various lighting conditions, and their equations commonly use either contrast and/or saturation terms to account for glare caused by excessive luminance contrast or excessive overall brightness, respectively. Daylight Glare Probability (DGP), which includes both terms (hybrid model) and thus accounts for both effects, is one of the more robust ones. However, the predictive performance of discomfort glare models is limited to the luminous conditions and light source types found in the dataset from which they were developed. As daylight glare models like DGP are typically derived from glare evaluations in brightly lit environments, their performance in dimmer conditions, such as those found in deep open-plan workspaces away from the window, could be limited. This thesis, therefore, aims to extend the prediction range of existing discomfort glare models to reliably cover low-light ranges as well. To determine which conditions are most critical to focus on, the luminous ranges covered in previous laboratory studies were compared to those that can be expected in open-plan offices where low-light conditions may occur. The identified range of missing lighting conditions was then used to design and conduct two new user studies in semi-controlled dim daylit conditions to supplement prior discomfort glare datasets. In the first study, participants evaluated four scenes in which the size and luminance of the glare source were varied, and in the second, participants evaluated four scenes in which it was the size and position of the glare source were varied. In parallel, the models that currently perform best in dimmer conditions were identified using an existing dataset of glare evaluations in daylit conditions: contrast-driven models were shown to outperform saturation-driven models in dim conditions, while the more versatile hybrid metrics tended to perform well overall. Hence, the hybrid format was found to be better suited for extending glare models. To create a comprehensive training dataset for this model extension, the data obtained from the two user studies were combined with experimental data from other recent studies containing high-contrast scenarios, namely with the sun disc visible through fabric shadings and low-transmittance glazing. A new best-fit discomfort glare prediction model was then proposed for the broader targeted range of luminous conditions. Based on preliminary performance checks, the new hybrid model appears to fit the participants' glare responses better in low-light conditions than the reference model, DGP, while maintaining a fit equivalent to DGP in brightly lit conditions. The new user studies also revealed an unexpected finding: the summation of multiple glare sources in glare model equations can sometimes result in an over-prediction of discomfort glare. More research will be needed to validate the newly proposed model using a larger test dataset that does not include data points used for any model development. This thesis' findings may help to advance daylight glare prediction in indoor spaces by broadening the range of validity of prediction models to dimmer conditions, thus improving the overall reliability of visual comfort appraisal in the built environment.

Over the past years, increasing efforts have been devoted to understand how people perceive the indoor environment with the goal to improve building design and operation. Studies have separately addressed the effects of the four main aspects that influence the perception of the indoor environment, i.e., visual appearance, thermal condition, acoustic ambiance, and air quality. However, building occupants are simultaneously exposed to multiple indoor stimuli and their perception of the indoor environment depends on the mutual combination and interaction of such stimuli. Despite the increasing interest in the topic, few studies on the interactions between indoor factors are available. Most of them have focused on interactions between thermal and visual factors due to their large implications for energy consumption and building design. In this context, electric lighting has been primarily used as visual stimulus, leaving a knowledge gap on interaction effects in daylit environments. To address this challenge, this doctoral thesis focuses on the effects of visual and thermal interactions on human responses, with the use of daylight as the sole source of light. Two types of visual-thermal combinations are investigated: temperature and "daylight color" (i.e., daylight transmitted through colored glazing) and temperature and daylight quantity (i.e., illuminance levels). The aim of this work is threefold: (i) understand the effect of daylight color and quantity on thermal perceptual and physiological responses; (ii) investigate the influence of indoor temperature on visual perception of daylight; and (iii) explore the effect of daylight and temperature combination on the overall comfort perception. To address the previous aspects, four experiments were conducted. Two of them were carried out in an office-like test room to investigate both visual-thermal combinations. One field study was performed to further explore temperature and daylight quantity interactions. One experiment was conducted in a test room with the use of virtual reality to further investigate temperature and "daylight color" interactions. The results of this thesis show that daylight and temperature do interact, influencing human responses in a perceptual rather than in a physiological way. The interaction effects are bi-directional, as temperature influences visual perception, and daylight color and quantity affects thermal perception. Daylight conditions and indoor temperatures simultaneously and equally contribute to the overall comfort perception, but only after a relatively long exposure to the visual stimulus. The findings of this research suggest that indoor factors should not be considered separately but in combination. The integration in both research and practice of interaction effects between indoor factors will ultimately contribute to the improvement of comfort conditions inside buildings. Potentially, this integration will also allow to reduce the energy consumed in buildings to guarantee occupants' comfort due to the extension of the comfort ranges that currently neglect interaction effects between indoor environmental factors. Disentangling for the first time the complex relationship between daylight and indoor temperature, this research constitutes an additional step towards understanding interactions of indoor factors and contributes to the establishment of a comfortable and energy-efficient built environment.

The profound impact of daylight on occupants is broadly recognized in the fields of architecture and lighting. In particular, the façade and its interplay with light is a central design element, while the diversity of daylight in space is widely acknowledged as a source of interest and stimulation that enriches our spatial experience. However, little is known about how the façade geometry and the resulting daylight patterns affect occupants. Moreover, we have limited knowledge on the impact of space function and of regional differences on human perception. This thesis investigates the effect of façade and daylight patterns on human responses, while simultaneously examining the impact of space function and regional differences on these responses. The literature suggests two important challenges in current experimental methods in lighting research that might be contributing to the aforementioned knowledge gaps: the changing daylight conditions, which create an unstable variable, and the use of rating scales as the sole method of data collection. To address these challenges, this work introduces two main methodological contributions: the use of immersive virtual reality (VR) as an experimental tool, and the collection of physiological data as a complementary measure to rating scales. Specifically, a novel experimental method that combines VR with physically-based scenes was developed and tested against real environments in experiments that examined its adequacy regarding the perception, presence, and physical symptoms of participants. Following the positive findings for the adequacy of this method, VR was employed in a series of experimental studies that investigated human responses to façade and daylight patterns, and laid the foundation for a wider study that was replicated in Switzerland and Greece. In all studies, each participant was immersed in a daylit interior space with varying façade configurations of a constant aperture ratio, and the impact of façade geometry, sky type, and spatial context on participant responses was examined in different experimental designs. The outcomes of this work revealed that the façade and daylight patterns impacted both the subjective and physiological responses of participants. In particular, façade and daylight patterns consistently influenced the spatial experience, such as how pleasant, interesting, exciting, calming, and complex the space was perceived. The façade geometry also impacted spatial attributes that are traditionally considered objective, such as the perceived brightness, spaciousness, and satisfaction with the amount of view in the space. Moreover, the presented façade and daylight patterns significantly affected the participants¿ heart rate, demonstrating in a VR setting that façade elements and their interaction with light can have quantifiable effects on occupants. The perceptual effects of façade geometry were shown to be robust to changes in the sky type, as well as the function, type, and window size of the space. In addition, no differences were found between the responses of participants in Switzerland and Greece, revealing the generalizability of these design-driven perceptual effects across latitudes in Europe. The findings of this thesis demonstrate the importance of façade design as a powerful driver of the spatial experience, outlining new directions in the design of buildings that are not only comfortable and energy efficient, but also delightful for their occupants.

This dissertation proposes a novel gaze-driven approach for dynamic discomfort glare assessments as a first step towards understanding human responsive comfort with respect to daylight. The objective was to observe the natural gaze behaviour in relation to glare for office spaces with the conditions implicitly constrained by real world luminous conditions. In the existing visual comfort models human behaviour is not sufficiently considered. These models employ only subjective assessments, which lack an objective understanding of the factors affecting the perceptual mechanism of light-induced visual discomfort. They so far have not integrated the inter-dependencies of visual discomfort perception and human gaze responses and have been limited to a fixed-gaze assumption directed towards the office task area. In this dissertation, a gaze-driven approach is developed and adopted in the discomfort glare assessments. The assessments were done in a series of experiments in simulated office setting under different lighting conditions where participants’ gaze responses with means of mobile eye-tracking as well as their subjective assessments were recorded while monitoring photometric quantities relevant to visual comfort using high dynamic range luminance imaging. Integration of the luminance images coupled with eye tracking enabled us to obtain the gaze-centred luminance fields, which gives a better estimate of actual luminance values perceived by the eye, used as a basis to investigate the gaze direction dependencies of visual comfort. This PhD dissertation describes different stages of conception of this novel dynamic discomfort glare assessment method. In the experimental phase, two pilot studies were made for proper integration of the adopted methods and techniques into discomfort glare assessments. Development of several routines, algorithms and tools to identify and translate the gaze directions in order to derive the actual luminance field perceived by the participants were needed to achieve this goal. A final comprehensive experimental phase was realised to investigate gaze behaviour in response to light. As a first validation step, the gaze-driven approach was compared to the fixed-gaze approach. Then the effects of different luminance levels as well as different view outside the window on the dynamic shifts of the gaze were investigated.The developed approach demonstrates the need to integrate gaze direction patterns into visual comfort assessments, which move us beyond the existing assumption of a fixed-gaze direction towards a gaze responsive comfort.