P.P. de la Barra Luegmayer
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Interface design for lighting and shading controls
Device type, position, and system cues influencing user preference and acceptance
The integration of smart control systems in office buildings can be disruptive when individual preferences and expectations for control interfaces are overlooked. Understanding how human–building interaction influences environmental comfort and acceptance is essential for creating user-centered designs. This study aimed to evaluate the effectiveness of usability testing as an innovative method for assessing building system control interfaces and user interaction with automation. Specifically, we examined user preferences for shading and lighting controls in a controlled office laboratory, varying by “Type of Device” (analog vs. digital), “Position” (wall, desk, or split), and “System Cues” (information richness). In an experimental setting involving 20 participants, we investigated how these factors influence satisfaction and acceptance of automation. Using an adapted Post-Study System Usability Questionnaire (PSSUQ), we evaluated satisfaction with Ease of Use, Reachability, and Information. Findings show that while participants’ initial expectations favored simple analog controls, preferences shifted toward digital, information-rich systems after hands-on interaction. Ordered logistic regression confirmed that Reachability (β=2.317) and Ease of Use (β=1.831) were the strongest predictors of Overall Satisfaction (p<0.001), placing interface position as the primary design characteristic. However, preferences varied by office type: in shared offices, users preferred wall-mounted controls to facilitate shared access and visibility. These insights offer actionable guidance for designing smart control interfaces that enhance user satisfaction, support personal control, and promote greater acceptance of building automation.
Building automation and control systems (BACS) are central to energy performance and occupant comfort in non-residential buildings. Comfort is inherently multi-domain, including thermal, visual, acoustic, and air quality requirements. Multi-domain BACS involves frequent trade-offs across domains when conflicting control actions arise, such as providing glare control versus daylight availability. Yet existing occupant-centric control research treats building services in isolation, and prior multi-domain comfort reviews rarely examine how multi-domain demands are integrated into BACS decision logic across services. We conducted a systematic review of 43 studies to examine how multi-domain occupant demands are represented and operationalized in BACS. Across the evidence base, thermal comfort is universal, while visual and air quality are frequently included. Acoustics is rarely addressed due controllability constraints. Most studies remain unimodal in their demand representation, even when multiple domains are in scope. Integrated BACS implementations are therefore largely built on within-domain formulations. Multimodal demand models that encode cross-domain and combined effects are uncommon and are rarely implemented in integrated BACS. Rule-based strategies dominate multi-domain controllers. Optimization-based and learning-based controllers are also used, but they often rely on fixed weights or reward terms that make trade-offs difficult to interpret. In addition, actuator choice is rarely made explicit when multiple services can achieve the same target state. Future research should benchmark unimodal and multimodal demand formulations under comparable control contexts, extend bottom-up multimodal models beyond thermal and air quality into integrated BACS, especially for façade control, and develop transparent, preference-aware policy designs that make priorities and service actions understandable.
Daylighting and lighting controls build on a long history of personalized systems and methods, from prehistoric torches to adjustable desk lamps. They allow for individual control over (day)light spectrum and intensity, catering to personal needs and promoting circadian health and cellular processes (i.e., photobiomodulation). Additionally, they can reduce glare and improve visual comfort, leading to increased productivity and well-being. Despite this long history, studies formulating “personalized environmental control systems” (PECS) in the daylighting and lighting domain are rare. In this paper, we present preliminary results from a comprehensive review, where 31 papers were identified from an initial pool of 5,238. The findings highlighted two key benefits. First, semi-automated PECS offer the highest energy savings, highlighting the importance of understanding the relationship between users and automation. Secondly, PECS provides improved occupant experience since the ability to control their environment empowers occupants, leading to increased comfort and productivity. Overall, PECS have the potential to facilitate individual control over lighting and visual parameters, ultimately enhancing visual comfort and satisfaction as well as beyond-visual well-being. Our research builds upon the ongoing work of IEA EBC - Annex 87, which investigates the energy and environmental benefits of PECS. ...
Daylighting and lighting controls build on a long history of personalized systems and methods, from prehistoric torches to adjustable desk lamps. They allow for individual control over (day)light spectrum and intensity, catering to personal needs and promoting circadian health and cellular processes (i.e., photobiomodulation). Additionally, they can reduce glare and improve visual comfort, leading to increased productivity and well-being. Despite this long history, studies formulating “personalized environmental control systems” (PECS) in the daylighting and lighting domain are rare. In this paper, we present preliminary results from a comprehensive review, where 31 papers were identified from an initial pool of 5,238. The findings highlighted two key benefits. First, semi-automated PECS offer the highest energy savings, highlighting the importance of understanding the relationship between users and automation. Secondly, PECS provides improved occupant experience since the ability to control their environment empowers occupants, leading to increased comfort and productivity. Overall, PECS have the potential to facilitate individual control over lighting and visual parameters, ultimately enhancing visual comfort and satisfaction as well as beyond-visual well-being. Our research builds upon the ongoing work of IEA EBC - Annex 87, which investigates the energy and environmental benefits of PECS.
Towards Occupant-Centered Automated Façade
Interaction Requirements to Enhance Acceptance of Automated Control Strategies
Using a mixed-methods approach, the research combines systematic literature reviews, controlled laboratory experiments, and large-scale surveys. The findings show that while automated façades can substantially reduce lighting energy use, their overall performance depends strongly on occupant interaction. Five key factors influence acceptance: personal preferences, environmental conditions, context, façade technology, and control logic. In particular, interaction design, such as how quickly and in what way façade systems adjust, control usability, and information availability, plays a critical role in shaping satisfaction and behavior.
Experimental results demonstrate that disruptive automation increases override actions, whereas systems that are understandable, predictable, and easy to control foster trust and acceptance. Survey data further show that occupants prefer differentiated levels of automation depending on context, building service, and time of day, with a general tendency toward “mixed-control” strategies.
The dissertation frames an “interaction gap,” arguing that energy efficiency and occupant comfort depend on occupant-centered design. It concludes that effective façade strategies must integrate clear communication, low-effort override options, and context-sensitive control.
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Using a mixed-methods approach, the research combines systematic literature reviews, controlled laboratory experiments, and large-scale surveys. The findings show that while automated façades can substantially reduce lighting energy use, their overall performance depends strongly on occupant interaction. Five key factors influence acceptance: personal preferences, environmental conditions, context, façade technology, and control logic. In particular, interaction design, such as how quickly and in what way façade systems adjust, control usability, and information availability, plays a critical role in shaping satisfaction and behavior.
Experimental results demonstrate that disruptive automation increases override actions, whereas systems that are understandable, predictable, and easy to control foster trust and acceptance. Survey data further show that occupants prefer differentiated levels of automation depending on context, building service, and time of day, with a general tendency toward “mixed-control” strategies.
The dissertation frames an “interaction gap,” arguing that energy efficiency and occupant comfort depend on occupant-centered design. It concludes that effective façade strategies must integrate clear communication, low-effort override options, and context-sensitive control.
A Pre-Occupancy Evaluation (PrOE) was conducted in a German office before a design intervention. This study compares the data obtained from the German office in a one-time and a continuous questionnaire to evaluate their respective benefits and limitation in informing required design solutions for a pilot area. Both a one-time online questionnaire and a continuous feedback system (implemented using QR codes) were used to collect data on occupant (dis)satisfaction with the office design.
The results of this research show different perception on occupant’s satisfaction between the two surveys. Both surveys show congruency in the dissatisfaction with open offices without partitions than in shared enclosed offices. The one-time survey highlights a lowest satisfaction with the availability of personal control, while the continuous survey presents lowest satisfaction with the acoustic privacy. ...
A Pre-Occupancy Evaluation (PrOE) was conducted in a German office before a design intervention. This study compares the data obtained from the German office in a one-time and a continuous questionnaire to evaluate their respective benefits and limitation in informing required design solutions for a pilot area. Both a one-time online questionnaire and a continuous feedback system (implemented using QR codes) were used to collect data on occupant (dis)satisfaction with the office design.
The results of this research show different perception on occupant’s satisfaction between the two surveys. Both surveys show congruency in the dissatisfaction with open offices without partitions than in shared enclosed offices. The one-time survey highlights a lowest satisfaction with the availability of personal control, while the continuous survey presents lowest satisfaction with the acoustic privacy.
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, occupants 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.
User interaction with smart glazing
Effect of switching speed under overcast sky condition
Visual Connectivity Index (VCI)
Performance Metrics to Evaluate the Ability of Indoor Space and Facade Systems to Connect to Outdoors
This article introduces the Visual Connectivity Index (VCI)—a metric designed to evaluate indoor-outdoor visual connectivity. VCI measures the relationship between a façade system and the indoor space it encloses, assessing how uniformly and seamlessly the interior connects to the exterior through the façade system while considering multiple observer positions. VCI contributes to three key areas: (1) It enables the evaluation of a façade system’s impact on visual connectivity and its interaction with enclosed space; (2) It provides a performance-based measure of visual connectivity (3) It facilitates the comparison of alternative design solutions within the framework of architectural design.
By synthesizing the complex phenomenon of indoor-outdoor visual connectivity with the role of the façade in shaping this relationship, Visual Connectivity Index (VCI) presents a novel and valuable approach that has not been previously explored. To demonstrate its application, this study systematically compares the performance of 20 design alternatives across three different façade systems, resulting in a total of 60 iterations. The results indicate that VCI is sensitive to various design options, enabling a thorough evaluation of different architectural design choices. ...
This article introduces the Visual Connectivity Index (VCI)—a metric designed to evaluate indoor-outdoor visual connectivity. VCI measures the relationship between a façade system and the indoor space it encloses, assessing how uniformly and seamlessly the interior connects to the exterior through the façade system while considering multiple observer positions. VCI contributes to three key areas: (1) It enables the evaluation of a façade system’s impact on visual connectivity and its interaction with enclosed space; (2) It provides a performance-based measure of visual connectivity (3) It facilitates the comparison of alternative design solutions within the framework of architectural design.
By synthesizing the complex phenomenon of indoor-outdoor visual connectivity with the role of the façade in shaping this relationship, Visual Connectivity Index (VCI) presents a novel and valuable approach that has not been previously explored. To demonstrate its application, this study systematically compares the performance of 20 design alternatives across three different façade systems, resulting in a total of 60 iterations. The results indicate that VCI is sensitive to various design options, enabling a thorough evaluation of different architectural design choices.
Indoor Air and Thermal Quality in School Buildings
Demonstration of BIM-Integrated IoT Window Signaling System
The Smart Readiness Indicator (SRI), introduced by the European Union in 2018, assesses a building’s capacity to accommodate smart-ready services. This evaluation focuses on optimizing energy efficiency, aligning operations with occupant needs, and responding to signals from the grid. Previous studies have evaluated SRI feasibility in various locations and retrofit scenarios, estimating the costs associated with implementing smart technologies in existing European buildings. However, the specific impact of digitizing distinct building services on SRI scores remains unexplored. Particularly, adaptive façade technologies show potential in enhancing overall building performance, being worthy to understand how these services influence the smart readiness rating of buildings. This study investigates the impact of adaptive façade technologies on SRI scores and user satisfaction. A case study of an office building in Delft (The Netherlands) was selected to assess the impact of smart technologies on energy efficiency and comfort. This paper shows preliminary results from the pre-intervention phase, where the SRI was calculated for both the baseline condition and a scenario with the highest possible level of smart services for the building envelope. The results from the SRI methodology showed an increase of approximately 4% in energy efficiency and 15% in terms of energy flexibility. In addition, the SRI predicts similar improvements in user convenience, information, health & well-being, but only 4% in user comfort. This was confirmed by the assessments on user perception and preferences. Users reported to be “slightly satisfied” with several comfort domains. Additionally, several users considered better control of external shadings very important, which was currently reported as very disruptive by users. This preliminary finding shows potential for smart services applied at the façade level to improve user satisfaction if aspects of interaction and convenience are adequately addressed. Post-intervention phase data is now required to confirm these preliminary findings.
Glass serviceability limits
New evidence from human-centred studies
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. ...
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.
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.