The JBPS archives offer a telling list of papers on the development of daylight simulation. From the founding stones of annual daylight simulations, better known as Climate-Based Daylight Modelling (CBDM; Laouadi, Reinhart, and Bourgeois Citation2008; Mardaljevic Citation2008), to refined methods for simulating complex optical properties using Radiance-based ray-tracing (McNeil and Lee Citation2013) or photon-mapping (Schregle, Grobe, and Wittkopf Citation2016) techniques. Balancing computation time and accuracy – especially for assessing visual comfort – is at the core of several studies. Papers explored the generation of optical functions to describe complex shading devices using photon-mapping (Grobe Citation2019) and GPU-based processes for faster ray-tracing and real-time response (Jones and Reinhart Citation2019). Other papers investigated in depth the accuracy of input geometry (e.g. the modelling of trees (Al-Sallal and Al-Rais Citation2013) and varying levels of detail in façades (Agarwal, Pastore, and Andersen Citation2024)) and optical properties (e.g. material reflectance (Brembilla, Hopfe, and Mardaljevic Citation2018)). Using data from real spaces to train machine learning models is an alternative to detailed simulations (Liu, Colburn, and Inanici Citation2020) that has gathered momentum in recent years, especially for the design of daylight-linked control strategies (Jo, Choi, and Park Citation2023; Katsanou, Alexiadis, and Labridis Citation2019). At the same time, research and discussions on CBDM metrics flourished, with the ambition of finding quantities and thresholds that well correlate to human’s visual experience (Nezamdoost and Van Den Wymelenberg Citation2017). The latest developments in daylight simulation follow discoveries on the physiological and psychological (i.e. non-visual) effects of light on human’s health and wellbeing. Papers investigated tools that can simulate the spectral nature of visible light and new metrics related to circadian effects (Pierson, Aarts, and Andersen Citation2023), as well as the combined effect of daylight and access to views on façade form finding (Pouyanmehr et al. Citation2022). Emerging concepts on reuse and circularity of facades are also being combined with daylight and solar performance (Dervishaj and Gudmundsson Citation2025). The challenge that lies ahead for daylight simulation is the seamless integration of these new variables and indicators within fast, dynamic annual assessments that can achieve the desired temporal and spatial resolution.

In recent years, several studies have assessed the influence of automated façades on energy savings, IEQ, and occupant satisfaction. However, discrepancies exist between the expected advantages of automated façades predicted in research and the actual benefits observed in real-world tests. To assess how automated façade operation enhances building performance, in particular within office building contexts, this study reviews and analyzes current evidence on the influence of automated façades. In this review, 91 studies were identified presenting evidence of their performance. A total of 34 studies investigated performance in laboratory settings, 23 in real office buildings, and 34 in simulations. Only 13 laboratory studies and 17 real office building studies included human participants. Visual and thermal quality were the main indoor environmental domains investigated, with limited exploration of others. Existing studies show large variability in contextual factors (e.g., type of shading and control) or experimental designs (e.g., different benchmark scenarios), hindering the comparison of results. Consistent evidence shows the potential of automated façades for energy savings, particularly in lighting and cooling demands, which outperform manual control systems. Automated controls are more effective in reducing excessive daylight and glare, while evidence of the impact on thermal and air quality remains limited. Regarding occupant satisfaction, evidence is unclear since, in some cases, users prefer manually controlled façades and, in others, automated ones. Further research is suggested on human-centered studies in real office buildings to capture occupant behavior and preferences while exploring solutions that dynamically identify and integrate factors affecting occupant interaction with buildings.

Rising temperatures are leading to an increase in the cooling demand of buildings. Electrochromic (EC) glazing can be a promising solution for controlling solar heat gains while maintaining outdoor views. This paper presents the results of the monitoring of prototype panels of a novel type of inkjet-printed EC glass under real use and weather conditions in a small office building in the Netherlands. This building contained two identical west-facing meeting rooms of which one was equipped with EC triple glass IGUs and the other with normal triple glass IGUs. Each room was equipped with local heating/cooling units of which the energy use was monitored, and with an extensive environmental sensor network. Sensor and calendar data was fed into an energy balance model for each of the rooms for the entire measurement period, allowing to correct for differences between the two rooms with respect to heat losses and gains and use conditions. The results of the monitoring showed that in the meeting room with EC glass IGUs, the heating demand increased by 34% in Jan.-Mar. 2024 while in Sept. 2023 the cooling demand decreased by 3%. The main reason for the increase in heating demand was found to be the lower g-value of the EC glass IGUs in clear state as compared to the normal IGUs. The almost similar cooling demand was a result of a trade-off between the lower direct solar transmittance of the EC glass IGUs and the heating up of the absorptive layer inside the IGUs. Furthermore, an experiment with participants showed that in general in dark state, satisfaction with view clarity, daylight colour and daylight availability was higher for the EC glass IGUs. In transparent state, no significant difference was perceived between the EC glass IGUs and standard IGUs, except for view clarity.

Rising temperatures are leading to an increase in cooling energy demand and thermal discomfort due to overheating. Despite dynamic switchable glazing being a promising solution for controlling solar radiation while preserving user access to outdoor views, their cost is currently a barrier to their widespread adoption. The recent development of low-cost inkjet-printed switchable glazing offers a cost-effective alternative; however, its performance remains uncertain concerning its contributions to energy efficiency and user satisfaction in terms of thermal comfort and visual experience. This study presents a multi-domain evaluation of the performance of a novel low-cost inkjet-printed glazing with users in terms of their satisfaction with the environment, personal control and interaction. In comparison to a conventional façade with static glazing and external roller blinds, the EC glazing performed better than the conventional façade if the shading is fully down. In this case, higher satisfaction was measured in terms of view clarity, daylight access and colour in the room with the EC glazing. When comparing the performance of the EC glazing at the clearest state with conventional glazing with blinds raised, users’ satisfaction was not significantly different, except for the satisfaction with view clarity. Despite the long transition time of the EC glazing, users were not significantly dissatisfied with the speed of transition. Overall, these preliminary results show that this novel EC glazing is well-accepted by users especially as an alternative to traditional dark roller blinds, but further research is required to investigate its performance during summer.

The standardised weather files commonly used for building simulation are compiled from many years of data. Particular to a specific location, these standardised weather files are generally known as Typical Meteorological Years (TMYs). In contrast, Actual Meteorological Years (AMYs) comprise data for a specific site over a defined period of an actual calendar year. The Copernicus Atmosphere Monitoring Service (CAMS) provides freely available satellite-derived radiation data covering Europe, Africa, the Middle East and parts of South America. CAMS data were used as the basis for solar radiation AMYs. For three locations in Europe, multi-year AMYs are used to test the suitability of TMY files as a reliable representation of prevailing sun and sky conditions. Examples are given for London (Gatwick), Rome (Fiumicino) and Stockholm (Arlanda), where, for all three locations, a full decade of AMY data at both 15 min and 1 h time-steps are evaluated alongside four contending standardised TMY files. For all three locations, the decade of AMY data proved to be surprisingly homogeneous, whereas the four TMYs were at variance with each other, and markedly dissimilar to the AMYs. Consequently, the authors propose a reconsideration of the use of TMYs for compliance purposes in particular, and building simulation in general. Given the unexpected findings, and their potentially far-reaching implications, the weather file evaluation is preceded by a detailed validation of CAMS-derived illuminance data against ground measurements taken in the UK. The results of the validation revealed remarkably good agreement between the CAMS-derived and ground measured illuminance data.

Practical applications: This paper provides compelling evidence that the methods currently used to select solar radiation data for TMYs result in standardised weather files that do not faithfully represent actually occurring conditions over a recent decade. A more reliable method for the evaluation of ‘typical’ annual profiles of solar radiation is described. The findings have relevance for the selection and curation of solar radiation data for all building simulation applications. In addition to supporting the basis of the TMY evaluation, the validation of CAMS-derived illuminance data revealed that CAMS more generally can serve as a valuable – and freely-available – daylight resource for a variety of practical applications. These include the in-situ validation of CBDM metrics and the generation of boundary daylight conditions for light-dosimetry field studies. Or indeed any application where reliable recent data on daylight/solar parameters for specific locations and at high temporal resolution are needed.

The high density of the urban fabric poses a real challenge for adequate daylight design in residential buildings. European and national building standards do not provide sufficient guidelines on if and how to consider the urban context at design stage. This study assessed the impact of simulating different urban densities on the indoor daylight performance of typical Dutch apartments. Results showed that not including the surrounding environment when designing a new building leads up to an 85% overestimation of daylight performance, causing an insufficient daylight provision for most apartments built at the lower floors. Furthermore, settling for daylight target values any lower than the minimum standards specified by EN17037 (median illuminance of 300 lx) will lead to insufficient melanopic light levels. In this regard, two new metrics are introduced to compare the non-visual performance between apartments: Melanopic Autonomy and Melanopic Isotropy. These metrics enable the characterisation of non-visual performance of an entire space, rather than of a single occupant position. Last, the analysis explored the relationship between indoor daylight performance and urban density indicators; while the results are limited to the sample considered in this study, a promising relation was noticed for the floor-space index and for the open-space ratio.

Smart dynamic building technologies can help to significantly reduce operational energy and carbon emissions. However, human acceptance remains a significant barrier, particularly for switchable glazing used in smart windows. This study examines how users are affected by the speed and direction of transitions in the transparency of fast switchable glazing, specifically dynamic liquid crystal technology under overcast sky. Perceptual and behavioural data including facial action units, were collected through an experimental campaign in a semi-controlled environment where the glazing transparency was transitioned at two rates (1 and 10 s). It was found that user perception remained consistent regardless of transition speed or direction, but override behaviour was influenced by both factors. In the absence of glare, user overrides were primarily driven by the transition direction, with more users reacting to transitions from dark to clear. Faster transition rates led to an increase in user overrides for both transition directions. Unlike those who did not override, users who overrode the automated glazing control strategy had a negative perception of the visual environment and the window control system. Users directed their gaze more towards the glazing when this was transitioning, suggesting possible distractions. Users were clustered based on their background knowledge and reported preferences. These clusters showed a good correlation with the override delay times. However, the agreement with actual behaviour was low, indicating that a larger number of variables and clusters should be tested to predict user behaviour. Nevertheless, clustering users highlighted the importance of considering individual differences for interaction strategies.

The adaptive control of sunlight through photochromic smart windows could have a huge impact on the energy efficiency and daylight comfort in buildings. However, the fabrication of inorganic nanoparticle and polymer composite photochromic films with a high contrast ratio and high transparency/low haze remains a challenge. Here, a solution method is presented for the in situ growth of copper-doped tungsten trioxide nanoparticles in polymethyl methacrylate, which allows a low-cost preparation of photochromic films with a high luminous transparency (luminous transmittance T_lum = 91%) and scalability (30 × 350 cm²). High modulation of visible light (ΔT_lum = 73%) and solar heat (modulation of solar transmittance ΔT_sol = 73%, modulation of solar heat gain coefficient ΔSHGC = 0.5) of the film improves the indoor daylight comfort and energy efficiency. Simulation results show that low-e windows with the photochromic film applied can greatly enhance the energy efficiency and daylight comfort. This photochromic film presents an attractive strategy for achieving more energy-efficient buildings and carbon neutrality to combat global climate change.

Smart buildings are equipped with automated control systems that provide a comfortable indoor environment, aiming simultaneously at energy savings. Control systems for shading devices applied in practice are mostly driven by a rule-based approach, that is usually tested under simplified conditions and hence its effectiveness in complex real-life cases is questionable. The present study develops an optimized glare-based control strategy for Venetian blinds in a real-life open-space building with totally transparent facades. The research is based on the case study of the Co-Creation Center at the TU Delft campus, which can host three different types of events: presentations, meetings and workshops. The control strategy is developed within Grasshopper, a tool for parametric and optimization problems. Radial Basis Function Optimization (RBFOpt) is utilized for the computation of the optimal blinds’ states. Within the developed control strategy, cylindrical illuminance (Ecyl) is used as a glare index, giving the opportunity to evaluate its performance. Results show that the optimized algorithm can improve the existing visual conditions in the building by an average of 80% for all activity types, although it leads to an average increase of 7% of the time when electric lighting is needed, in comparison to the current rule-based control. Finally, Ecyl displayed an overall agreement of 92.5% with DGP-based glare assessments, proving that in spaces with multiple windows and uncertain occupants’ view direction, a view-independent index can predict glare risks as well as a state-of-the-art view-dependent metric.

Visual defects, in particular haze, in glass and façade technologies can significantly impact the aesthetic quality and human experience of daylight and views in buildings. The glass and façade industry increasingly requires methods that can objectively predict and measure the subjective user experience of haze. This is required to appropriately inform the manufacturing process, ensuring optimal functionality and performance, and avoiding material waste and economic losses due to the replacement of defective glazing. Existing methods for measuring haze are not appropriate for assessing large samples, either at manufacturing sites or in-situ. However, haze defects are often only exhibited and visible when glazing is produced in large samples or installed under real luminous conditions. This paper introduces a novel luminance-based method that measures haze by evaluating the halo around a light source that is observed through the glazing. This method is initially tested in a controlled laboratory setting on small glazing samples with varying level of haze. The halo serves as a proxy for haze severity and it is quantified by using luminance-based measurements. In this work, the newly-proposed method is verified by comparing the ranking in haze severity of different samples as performed by means of a standard haze meter and the newly proposed method. Additionally, the paper examines the dependence of this ranking on factors such as camera setup distance and light intensity. It was found that the proposed method was able to effectively ranks samples differing in haze intensity by more than 0.1 orders of magnitude. Positioning the camera closer to the glazing and using higher light intensity yielded more accurate results. However, for haze levels below 1% and differences smaller than 0.1 orders of magnitude, the accuracy is insufficient. To define the expected level of accuracy of methods for haze characterisation in-situ, the sensitivity of the human eye to haze under varying luminous environments and view content needs to be quantified.

3D modeling of indoor spaces is a prerequisite for daylight simulation, and the accuracy of the 3D models has a significant impact on the simulation. The goal of this study was to quantify the errors caused by modeling indoor spaces at different accuracy levels to find the optimal balance between the reliability of the results and labor investment. For this purpose, we introduce a level of detail (LOD) concept for indoor spaces based on the size of non-permanent indoor objects by inclusion and exclusion from the simulation scene. The errors corresponding to models with low accuracies are measured by climate-based simulation using an improved two-phase method. Our results show that inaccurate modeling of indoor spaces causes between 10-70% error in TAI with 25% median across all spaces.

Optimizing the layout of residential buildings based on daylight performance and view quality is crucial to visual comfort and well-being of building occupants. Machine Learning (ML) methods offer valuable support for performance-based decision-making process at the early-stage building design. In this study, a novel workflow is introduced to integrate ML models into the architectural design process. With the designer’s input floor layout designs, the presented multimodal ML model predicts daylight provision and view quality, which are then translated into practical visual representations by a post-processing step. This approach allows input designs to be evaluated by the ML model, leading to enhanced design decisions while preserving the designer’s autonomy. Results for the best-performing model, implementing ResNet50 and a fully connected network, led to a Mean Square Error (MSE) of 0.0440 and 0.0478, and an R2 score of 0.7411 and 0.7815 for the daylight and view metrics, respectively. The results of the daylight and view predictive models are further interpreted according to different apartment categories and at various resolutions. These results indicate that the method could be viable for predicting daylight provision and view quality in early design tools, providing designers with faster feedback that supports informed decision-making during design iterations. Ultimately, the challenges of the study and further improvements are discussed.

Façade properties influence human responses in a multidomain manner and these interactions needs to be accounted for effective façades design, particularly to increase resilience to extreme heat. From existing research, it remains unclear whether the glazing colour properties can influence occupant thermal sensation, preferences, and acceptance, or whether higher temperatures affect glare sensation or view perception. This study investigates the combined influence of tinted glazing in façades through a preliminary experimental campaign with human participants exposed to varying glazing hues (neutral and blue) and indoor air temperatures. While previous research has examined the impact of coloured daylight on thermal and glare sensation under thermal conditions close to neutrality, this paper compares occupant responses at neutral and warm thermal conditions by performing repeated measurements.

An experiment was conducted to measure potential differences in human thermal sensation, acceptance, preference, and glare sensation under two thermal conditions (operative temperatures of 25°C and 30°C) and two daylight colours (neutral and blue). Thirty-nine participants were exposed to different combinations of temperature and glazing colour in a randomized order. Data were collected using questionnaires and thermal physiological sensors to capture human responses to these varying conditions. In terms of visual perception, the results demonstrate a distinction between the two visual scenarios, particularly regarding obstruction and glare at a neutral temperature. At the level of thermal sensation, the impact of blue-tinted glazing is not statistically significant with this number of participants. However, a slight difference is observed between the two scenarios at both temperature levels.

Optimizing the built environment via simulations of building models hinges on standardizing data acquisition. In this research, we put forward distinct levels of detail for geometry and material inputs, specifically tailored for indoor daylight applications. We primarily focus on understanding the uncertainties arising from imprecise estimations of material optical properties and incomplete geometrical inputs in climate-based indoor daylight simulations. Employing a Monte Carlo approach, we analyzed six office and teaching spaces, creating 20 variations for each by altering geometrical completeness and material accuracy. The technique of excluding non-permanent objects below certain sizes in four graduated steps was used to derive and test the impact of various geometrical levels of detail. Our findings reveal that different levels of geometrical completeness lead to errors ranging from 1.08% to 18.05%. Additionally, a twofold increase in simulation time was noted when geometrical detail was enhanced relative to the most basic model. Errors stemming from imprecise definitions of material optical properties showed a normal distribution. The uncertainty in simulation outcomes showed a linear rise with increasing input material uncertainty, lying between 10% to 30%, depending on space configurations. We observed heightened uncertainty near openings, attributed to window transmittance effects. The research underscores that daylight predictions are markedly more sensitive to transmittance uncertainties than to those in reflectance, regardless of the window-to-floor ratio. These insights may help to guide a more efficient data acquisition process of indoor spaces for daylight simulations.

The presence of sensor networks to monitor environmental conditions and the automation of blinds and lighting systems controls is now commonplace in buildings, especially public ones with a high number of occupants. However, implementing control algorithms that are sufficiently reactive to variable sky conditions and that actually meet occupants’ needs is still a challenge. In the present study, we investigate and compare advanced and simple control algorithms developed for a variable occupancy, open space, small sized conference venue. Operation and performance resulting from an optimized approach are assumed to be the benchmark strategy, and two other control algorithms of varying complexity are compared with it. Results show that the optimized control strategy performs best overall, but only marginally compared to the other two strategies. It performed especially well in meeting glare protection requirements, as a glare-related parameter was embedded into its objective function, but it also led to erratic movements of the blind slats’ tilt and it required significantly higher computation times than rule-based control strategies. These two factors make it impossible to implement such strategy as it is in the real building, and indicate that a practical control implementation can be more effective than an optimal one.

Myopia is on the rise worldwide and its onset can be triggered by environmental factors, including light exposure. Guaranteeing an adequate exposure to daylight is particularly important for young children, whose eyes need the best conditions for a healthy development. Monitoring and assessing light levels in school buildings is therefore paramount for studies on myopia but it can prove challenging. This paper paves the way for the use of climate-based daylight simulation as a tool to complement field studies on myopia. Existing simulation tools were found to characterise vertical spot illuminance with an acceptable error range (rMBE=8,7%; rMAE=35,4%), as well as cumulative daily illuminance (rMBE=-10%; rMAE=12,6%). Spectral simulation resulted instead in larger errors, mostly for wavelengths at the edges of the visible range, previously found to be important factors in the onset of myopia. Despite current limitations, simulation tools could become an essential support for future research on myopia.

Recent earthquakes have confirmed the vulnerability of our built environment, resulting in significant socio-economic losses, market disruptions, and environmental damage. Additionally, climate change is causing more frequent and severe weather-related events such as heat waves, which are impacting the construction sector and the health and well-being of building occupants. This emphasizes the pressing need to increase society's overall resilience by focusing on the various hazards that buildings may encounter throughout their lifespan. Although the need for a multi-risk analysis has been recognized in current performance-based design approaches, existing studies mostly focus on single hazards thereby neglecting the impact assessment of multiple hazards on the building performance.

This paper explores the economic and social losses of buildings due to earthquakes and heat waves. The study focuses on a high-rise building consisting of a reinforced concrete structure and masonry/cladding facades, and designed for two different locations in Europe. By means of a numerical model, time-history non-linear analyses are carried out to estimate the probable maximum losses in terms of repair costs and injuries/fatalities. In addition to earthquake scenarios, the study conducts dynamic energy simulations and comfort analyses that consider local climate scenarios and extreme heat events. The energy analysis calculates the economic losses caused by weather-related power consumption while the impact on occupants is assessed in terms of discomfort hours. Results from the seismic and energy simulations are finally compared to quantify and discuss the impact of the two different extreme hazards on the building performance and their potential consequences.

Wat te doen als je prachtige gekromde glazen gevel onverwacht als vergrootglas blijkt te werken? Het fenomeen, dat al enigszins bekend was van de beruchte “Walkie Talkie” in Londen, is al eens eerder beschreven in Bouwfysica in 2018 [1]. Helaas kon dat artikel niet voorkomen dat ook in Nederland dit probleem vorig najaar plotseling optrad bij een nieuw gebouw dat op het punt stond opgeleverd te worden. Smeltende auto-onderdelen op het ondergelegen parkeerterrein, mogelijk gevaar voor bezoekers en een ongeruste opdrachtgever waren het resultaat. Parametrische tools en software voor simulatie van bezonning hielpen het ontwerpteam en de opdrachtgever om samen te zoeken naar de meest geschikte oplossing.

User experience and satisfaction with the facade play a significant role in user comfort and energy efficiency of buildings. This paper explores the concept of User-Facade archetypes to inform the user-centred design of shading devices based on the perceived level of importance of different environmental domains at the workplace. A questionnaire was developed to collect data on users’ perceived level of importance of different environmental domains, user characteristics and other preferences. Based on the associated level of importance of the domains affected by shading devices (thermal conditions, access to daylight, access to outdoor view, privacy and glare mitigation), users were then clustered into eight different archetypes, which associated different "weights" to each comfort domain. The study also found a significant correlation between the associated level of importance and the reported frequency of interaction with shadings because of thermal comfort, glare mitigation or privacy. Overall, users that associated high levels of importance to several environmental domains also reported high perceived levels of importance for personal control at the workplace. Only one archetype reported low importance for personal control at the workplace. Further work is required to validate these archetypes by capturing actual user behaviour and preferences in real workplaces. However, these findings provide preliminary and valuable insights into the possibility of clustering users on their preferences and using this for informing a more user-centred design or operation of shading devices.

Indoor environmental quality (IEQ) has become a prominent topic in the building sector. This has led to a broadening of the scope of design guidance – which until recently had primarily focused on energy demand reduction – towards the inclusion of human-centred parameters such as comfort, health and wellbeing. The National Engineering Policy Centre’s 2022 report Infection resilient environments: Time for a major upgrade shows how important a topic this has now become. Major building rating schemes now include IEQ in their assessments, either as standalone certifications or within broader remits. However, as the focus shifts from the building fabric to human inhabitants, it becomes ever more important not to rely solely on models and simulations. To deliver effective results, assessments of IEQ need to be performed during the operational stage and for a prolonged period of time – ideally over weeks or months – or, even better, they should become an integrated and permanent feature of a building system. Thinking about IEQ monitoring as an integrated part of buildings’ systems means that there need to be expert figures who design, commission and maintain such monitoring systems, and who can interpret and communicate relevant IEQ data to building owners and occupants. We believe that this role largely falls within the responsibility of a professional member of CIBSE, who acts in collaboration with facility managers, digital security experts and Internet of Things technicians. This Technical Memorandum aims to provide a starting point for all building professionals, to help them get acquainted with the units and instruments used in monitoring thermal comfort, indoor air quality, luminous quality and acoustic quality, and with the infrastructure needed to properly manage the data flows deriving from them. Relevant case studies are provided for each of these areas of IEQ, including approaches that are still very much in development, to provide lessons on how to build upon and ultimately improve the quality of the buildings we all live in. The main purpose of this guidance document is to give an overview of how data collected in real buildings can convey meaningful information about indoor environmental quality (IEQ). This guidance is primarily aimed at professionals within the building and construction sector who are approaching the world of sensors and environmental data for the first time, as well as at conscientious landlords who are assessing the value of monitoring their properties. The design and management of a system for continuous measurement of IEQ directly concerns building services engineers and allied professions. The management of the indoor environment falls within the domain of building services engineers and their involvement in tasks such as measurement and data analysis is likely to grow with improvements to technology and changing expectations and regulations. This document is written for all building services specialisms, and specifiers are encouraged to seek out experts for complex or advanced implementations. The individual chapters of this document are meant to serve as primers on current technologies and recommendations.