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.

Unitized curtain walls are widely adopted in contemporary architecture for their lightweight construction, aesthetic qualities, ease of installation and high operational performance. They are particularly used in high-rise buildings, where glazed facades are designed to meet a broad range of performance criteria. Well-designed systems tend to perform satisfactorily in normal service conditions, but are more problematic in extreme events. In fact, post-earthquake surveys in seismic-prone regions reveal functionality losses and moderate-to-severe damage to glazed facades, with significant financial, social and environmental consequences. Despite studies on the seismic behaviour of unitized curtain walls, research in this field remains limited. In particular, experimental studies to date rarely assess both serviceability and ultimate limit states, fail to fully characterize the sequence of damage states until collapse and overlook the influence of design choices on the façade performance. To address these gaps, an extensive experimental campaign on full-scale unitized curtain walls was conducted to investigate the seismic behaviour of façade units, including variations in geometry, joint aspect ratios and type (dry-glazed or wet-glazed), frame detailing. The experiments involved quasi-static and dynamic loading, considering in-plane, out-of-plane and vertical movements. Air infiltration, water leakage and wind resistance tests were conducted before and after low-intensity shaking to assess the post-earthquake façade serviceability. Analysis of experimental data highlighted the significant influence of silicone joints on glass rotations and the structural strength hierarchy. Fragility curves were derived from damage observations, which revealed weather-tightness loss at a 0.71% drift ratio and silicone failure in specimens with low-displacement capacity frames.

Composite glass sandwich panels, consisting of glass face sheets bonded to linear stiffeners (spines) in the core region, can provide significant benefits in material efficiency, reduced thickness, and greater overall transparency. However, current analytical models of their mechanical performance fail to account for the non-uniform longitudinal stress distribution caused by shear-lag effects in wide structural panels. This study redresses this by means of experimental research on composite glazing panels with different loading and geometrical configurations. Six 4-point bending experiments were performed on 34 mm thick, 1000 mm long, and 700 mm wide composite glazing panels, made from soda-lime silica glass face sheets bonded to glass fibre-reinforced polymer core spines. Two types of adhesives were tested: a relatively low stiffness silicone-based adhesive, and a relatively high stiffness epoxy-based adhesive. The shear-lag effects are quantified in terms of effective width ratios (EWR). The study showed that the epoxy-bonded panels provided a significant degree of composite action (DCA = 0.85) whereas the composite action in the silicone-bonded panels was negligible. Furthermore, it was found that applying the EWR values from this study in a recently published analytical model yields predictions of maximum strains at mid-span that deviate by no more than 16 % from the experimental results.

The growing demand for sustainable building materials is stimulating considerable research on bio-composites intended for the construction sector. Despite the technical challenges associated with their durability and fire resistance, bio-composites can provide environmentally friendly, load bearing components with useful mechanical properties. This paper provides an overview of the current research activities at TU Delft Department of Architectural Engineering and Technology in exploring five plant fibre reinforced polymer (PFRP) composites for various load-bearing applications. In addition to mechanical performance and durability, each bio-composite achieved one or more characteristic that improves the environmental sustainability of the bio-composite, namely: 100% bio-based; fabricated with simple low-tech equipment; sourced from bio-genic waste streams; assembled into a functional meta composite; formable into complex 3D shapes; and reformable at end of life. The findings presented in this paper provide useful insights of the material selection and manufacturing methods for each of the PFRPs and corresponding data from the performance testing. Moreover, the paper provides overarching observations across the five bio-composites and key recommendations for the future development of environmentally sustainable PFRP load-bearing components.

The increasing frequency and intensity of heatwaves raises questions about the thermal vulnerability of buildings and, in particular, on how to assess their resilience to extreme heat. In this context, thermal fragility curves, which describe the probability of achieving or exceeding specific temperature thresholds for a building, serve as an effective measure to define the thermal vulnerability of existing buildings and identify tailored retrofit strategies. This study focuses on deriving thermal fragility curves for a case study: a 6-storey residential building constructed in the 1980s with a reinforced concrete structure and masonry infill walls. Dynamic thermal modeling and simulation were conducted over a one-year period using synthetic weather files generated to account for future heatwaves. The simulation results provide useful relationships in particular between: outdoor temperature and indoor Standard Effective Temperature (SET); and between outdoor daily maximum temperature and indoor SET. These relationships were finally analyzed to create and compare fragility curves using maximum likelihood fitting and the so-called Cloud methodology.

Glass is highly sensitive to damage accumulation during its service life, leading to a significant reduction in strength. Annealed glass used in glazing units of low-rise buildings can experience a 71–85% strength reduction after 20–30 years of natural weathering, which can be detrimental in structural applications. Despite these considerable reductions in strength, there are currently no well-established methods for repairing glass components, with hypothetical repair methods primarily limited to resin injection and little evidence on their durability or their efficiency in preventing water diffusion and subcritical crack growth. As glass panels increase in size, complexity and cost, the standard approach of replacing damaged components with new glass becomes unsustainable. This paper develops effective and durable thermal healing methods for damaged glass components. A systematic experimental investigation is undertaken involving controlled artificial aging of annealed glass, followed by thermal healing, microscopy and destructive flexural tests to assess the effectiveness of the repairs. Different thermal and hydrothermal profiles are explored showing that thermal treatment has potential for strength recovery. In fact, thermal healing for the flaws in this study, at high temperatures in the order of 300–500 °C, can fully restore and even increase the design strength of glass beyond new as-received strength. This suggests that thermal healing can support and promote repair and reuse of end-of-life glass, enhancing circularity in the architectural glass industry.

The use of glass in buildings poses several challenges to the structural engineer. The aim of this chapter is to provide a unified method for the structural design of glass elements in buildings based on the limit state design philosophy. The chapter identifies the structural performance requirements as functions of the intended application and provides advice on the calculations and prototype testing required for assessing the performance of the candidate design. The chapter also provides advice on material selection and connection design. Further useful sources of information for detailed design and specification are listed.

The control of glare in office environments is often retrospectively improvised using shading devices, typically internal blinds. Despite the leap towards energy efficiency goals, visual comfort is still being compromised in climates with high solar insolation resulting in intolerable glare. This paper discusses the visual performance of a novel glazing assembly comprising of two, independently switchable (solar Polymer Dispersed Liquid Crystal and Suspended Particle Device) interlayers intended to control the visible light transmittance into an indoor space. Readings of DGP in a full-scale test cell are presented together with an analysis of the visual appearance of the glass.

Direct reuse and recycling of materials can significantly reduce the net environmental impact of the global construction sector. The feasibility of reuse and recyclability of building systems is affected by the materials used and the interfaces between constituent components. Yet there is a lack of quantitative methods for assessing the environmental benefits of alternative recovery strategies for multi-component and multi-material systems over the building lifetime. In this work, a novel assessment method was developed to enable a systematic and quantitative evaluation of the transient environmental reclamation potential (RP). The reclamation potential is a measure of the ability to disassemble and reuse recovered building systems at their end-of-life and is influenced by the constituent components and the interfaces between components. The proposed method accounts for the technical service lifetimes of components, including performance degradation over time, and can thus inform decisions on the most suitable recovery route for new and existing designs. The graphical outputs from the RP assessment are a network diagram which highlights the system components and connections between components, and an RP-graph which illustrates the embodied environmental impact and reclamation potential over time of alternative reuse/recycling strategies. The methodology is demonstrated on a glazed double-skin façade where the influence of component service lifetimes and replacements over time is quantified in terms of embodied energy and embodied carbon. The outcomes of the assessment can guide decision-making in design for disassembly (DfD) strategies and/or aid in the identification of high-value material recovery strategies at the end-of-life stage.

Façade engineering is facing an era of extraordinary challenge to meet the surge in demand for buildings that are environmentally sustainable and enhance occupant wellbeing. Facades, also known as building envelopes, play a major role in the resource-efficiency of buildings and the quality of its indoor environment. Consequently, the development of effective design approaches is crucial for generating appropriate façade solutions. Façade design is complex and multi-disciplinary involving several and oftentimes conflicting performance criteria. Systematic and holistic design procedures are, therefore, required to achieve optimal trade-offs. Over the last decades, researchers in this field have used computational tools and power to address this challenging problem within the context of multi-criteria design approaches. This paper reviews the existing research in this field, and presents the state-of-the-art review from simple to advanced decision-making procedures currently used at the early design stages, where decisions have a disproportionally large impact on the façade performance. The paper provides a complete description of the design variables and objectives typically involved. Alternative multi-criteria design methodologies regarding discrete decisions and automated optimization are reviewed, each with salient pros/cons, and overall conclusions are drawn. Finally, the paper discusses ongoing trends and research needs, namely, the development of uncertainty-based procedures to enable more informed decision-making; the inclusion of structural/seismic safety considerations in the design process to achieve higher socio-economic benefits; the integration of smart building information modeling and processing technologies to facilitate smarter design decisions; and the adoption of integrated design approaches to promote climate-adaptive solutions that enhance resilience.

Creating safer and more resilient building facades has become a primary concern in contemporary design, particularly in earthquake-prone regions, where there is a potentially high impact on financial, social and environmental losses. Glazed curtain wall systems are widely used in modern architecture. Yet, despite decades of research efforts aimed at enhancing the understanding of their seismic behaviour, it is not clear how design choices affect the response of glazed facades. This is crucial given the wide range of glass, framing and joint variations that are at our disposal. With a focus on unitized curtain walls, this paper provides insights into the influence of design variables on façade seismic response by means of an extensive experimental campaign and an associated parametric study to test alternative designs under both quasi-static and dynamic loading conditions. The variables considered included variations in unit dimensions, glass and joint aspect ratios, joint and framing detailing, and support conditions. This research delves into a statistical analysis of the experimental results, in order to define parameters such as glass and façade unit rotations, frame elongations and distortions, utilization factors at different intensity levels. The results provide insights that guide façade design decisions for achieving desired seismic performance levels.

The performance of the building envelope is crucial for minimizing operational carbon emissions of buildings and maintaining indoor comfort. Contemporary building envelopes, such as engineered glazed façades, achieve high performance levels but often add a significant amount of embodied carbon. There is therefore an incentive to reduce the thickness of the glass panels, but the minimum thickness possible is often not governed by strength or manufacturing limits but rather by the deflection (serviceability) limits. Despite objective criteria guiding serviceability limits, user acceptance of deformation remains unexplored, leading to conservative designs. This paper introduces a novel method for measuring user satisfaction with glass deformations, aiming to establish acceptance thresholds comparable to objective criteria. The study involves a novel experimental campaign to assess volunteers' levels of perception and acceptance of various glass deformations. The glass was deformed using a bespoke electro-pneumatic system at levels corresponding to below, above, and at the current serviceability limit. The results demonstrate the feasibility of measuring human responses to deformations in the glazing and provide essential data for setting serviceability limits. The experiments and corresponding user satisfaction feedback indicate that the current serviceability limit of L/50, may be relaxed, thereby presenting opportunities for material efficiency, such as the adoption of thinner glass in facades. The methodology effectively captures human responses, revealing that changes in reflection were the primary reason for the perception of movement; leading to a higher perception of glazing movement and a lower acceptance at night. Overall, participants felt safe regardless of their prior knowledge on glass properties, and providing this information to participants did not improve acceptance, which was already sufficiently high. The findings from this research fill an important knowledge gap in understanding user acceptance of glass deformations, crucial for comprehensive user satisfaction assessments and evidence-based reductions in glazing thickness.

Recent technological developments make perovskite solar cells (PSCs) particularly suitable for building integrated photovoltaic (BIPV) applications on vertical building envelopes, but the relatively short lifespan of PSCs requires frequent replacement, thereby generating substantial waste. Careful consideration of circularity credentials of this novel technology is therefore essential prior to the extensive implementation of vertical PSCs in building envelopes. This paper provides a circular economy approach for the implementation of PSCs in vertical envelopes and assesses its economic feasibility by life cycle cost analysis in Europe. The process of recycling PSC is developed. The economic performance of PSC envelopes is provided and compared to that of the conventional rigid BIPV system. Uncertainty analysis and sensitivity analysis of economic indicators are then performed to identify the influential parameters. The findings indicate that the PSC envelope has a significant potential for circular BIPV components and that PSCs applied on vertical envelope are economically viable.

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.

Lack of knowledge about the properties of weathered (used) glass is currently a major barrier to glass reuse. This results in probably unnecessary recycling or down-cycling of architectural glass at the end of life. Avoiding this creates a significant opportunity to reduce resource depletion and decarbonize the built environment. This can be done by developing an optical non-destructive test method that estimates the strength of naturally weathered glass by characterizing surface flaws. This allows excessively damaged glass panels to be removed for surface repair or recycling. Specimens were made from 50+-year-old monolithic flat glass taken from a façade in the Hague, Netherlands, where it was exposed to salt in the air, water, cleaning, and abrasion from wind-driven dust and sand particles. The specimens were examined using a microscope and a handheld optical profilometer to determine surface flaw characteristics. The glass specimens were then tested using a ring-on-ring (coaxial double ring) setup. Similar tests were also conducted on new as-received float glass to provide a benchmark. Both the indoor-facing and outdoor-facing sides of the weathered glass and the air and tin side of the new glass were tested. A statistical analysis of the test results was made using conventional Weibull statistics. The results show that after 50+ years of natural aging the strength of the glass is significantly reduced and that the non-destructive scanning method trialed in this study can locate and determine in many cases the size of critical surface defects thereby allowing for direct safe re-use of 70+% of the glass. The handheld optical profilometer can identify severe damage on the glass, but further research and software development is needed to improve the accuracy and consistency of the scanning method and to automate this technique for routine/large-scale applications including as a prerequisite for surface repair.

The applications of architectural and automotive laminated glass continue to grow. This is largely due to the enhanced safety in extreme events, such as blast. However, the complex interaction between the glass fragments and the polymer interlayer after glass fracture is still only partially understood, with existing analysis methods adopting a semi-empirical approach for the post-fracture response. These include a plastic yield-line analysis based on a failure pattern repeatedly observed during blast tests. In recent research it was demonstrated that yield lines can develop in fractured laminated glass through the composite bending action of the glass fragments, working in compression, together with the interlayer working in tension. This paper investigates the influence of the inertia loading associated with blast response, which has not been explicitly studied previously, with the aim of understanding the pattern of yield lines observed in blast tests. Impact tests are performed on laminated glass specimens using foam projectiles launched from a gas gun, which simulate the loading from a blast pulse. These tests demonstrate that the yield line pattern formed under short-duration dynamic loading depends on the loading intensity, thereby providing further evidence of a dynamic, plastic collapse mechanism in which inertia plays a significant role.

High-performance glazing technologies are essential for achieving the occupant comfort and building energy efficiency required in contemporary and future buildings. In real-world applications, glazing façades are selected from a steadily increasing number of glazing technologies. However, the authors could not identify a systematic and comprehensive review and classification of glazing technologies in the literature. This creates a barrier when comparing typologically different glazing technologies and combining multiple technologies in a glazing unit. This paper provides a systematic review and classification of established and emerging glazing technologies based on publications from 2001–2022 which were interpreted following the PRISMA methodology. This study reveals that the majority of high-performance glazing systems used in practice are in multi-layer glazing configurations and that the glazing system performance can focus on including additional and multiple functionalities, which aim at improving overall building performance. It was also found that there is a large potential for improvement of multilayer, evacuated, aerogels, electrochromic, and solar cell glazing by incorporating other technologies or innovative materials in multi-layer glazing units for either improving existing technologies or for the development of new ones. However, their longevity, robustness, and cost affordability should be ensured.

Since the beginning of 2021, CEN/TS 19100 Design of Glass Structures has been available in its first three parts. The fourth part is expected soon. This Technical Specification of the European standards organisation CEN is as a pre-standard of a corresponding future Eurocode. These documents constitute the first ever comprehensive design code for the entire structural glass engineering field on the European market for the first time. In addition to a clear outline, the Technical Specification has been drafted to be compatible with EN 1990 “Basis of Design” and to address glass-specific design matters, particularly related to robustness and redundancy. Although the standard still has the status of a CEN/TS, thereby allowing the European nations the option of whether to introduce it, either in full or in parts, it already contains national openings through which the European countries can adapt the design results to their own safety level by National Determined Parameters (NDPs). Such an approach already anticipates the future Eurocode, which is expected to be published as EN 19100—Design of Glass Structures. This article provides some context on the history and concept behind the new documents and gives an overview of the design rules and the corresponding technical background of the different parts of CEN/TS 19100.