Search Results (16)

Silicone structural glazing (SSG) sealants are crucial sealing materials in modern building curtain walls, whose performance degradation may lead to functional and safety issues, posing significant challenges to building safety maintenance. This study comprehensively investigated the effects of temperature, humidity, stress, and ultraviolet (UV) irradiance on the durability of SSG sealants through multi-gradient matrix aging tests, revealing the influence patterns of these four aging factors on tensile bond strength (TBS). Based on aging test data and degradation patterns, a novel degradation model for TBS aging was established by incorporating all four aging factors as variables, enabling the model to reflect their combined effects on TBS degradation. The unknown parameters in the model were calculated using the Markov chain Monte Carlo (MCMC) algorithm and validated against experimental data. A recursive algorithm was developed to predict TBS degradation under actual service conditions based on the degradation model and environmental records, with verification through outdoor aging tests. This study established a service life prediction methodology that combines the degradation model with environmental data through recursive computation and standard-specified strength limits. The results demonstrate that increasing temperature, humidity, stress, and UV irradiation accelerates TBS changes, with influence intensity ranking as UV irradiation > temperature > humidity > stress. Synergistic effects exist among all four factors, where UV irradiation shows the most significant coupling effect by amplifying other factors’ combined impacts, while UV’s primary influence manifests through such synergies rather than independent action. Among temperature, humidity, and stress combined effects, temperature contributes approximately 50%, temperature–humidity interaction about 35%, with temperature-related terms collectively accounting for 90%. The degradation model calculation results show excellent agreement with experimental data (R² > 0.9, MAE = 0.019 MPa, RMSE = 0.0245 MPa). The characteristic TBS minimum value considering material discreteness and strength assurance rate serves as a reliable criterion for service life evaluation. The proposed prediction method provides essential theoretical and methodological foundations for ensuring long-term safety and maintenance strategies for glass curtain walls. Full article

More and more modern buildings are using glass curtain walls as their building envelope. The large area of window leads to a significant increase in solar heat gain, resulting in an increase in the cooling load and energy consumption of the building envelope. In the calculation of building cooling load, the thermal performance parameter of windows, the solar heat gain coefficient, is used to calculate the solar radiation heat gain of the windows. The window-to-wall ratio of buildings with glazing facades is large, and the phenomenon of escape of incident solar radiation cannot be ignored. In order to calculate the solar radiation escape rate, a dynamic model of solar radiation escape rate incorporating the solar path tracking model is developed in this research, which can achieve big data simulation analysis based on actual meteorological conditions. The model is programmed and simulated using MATLAB R2024a software. Five representative cities from different climate regions in China are selected and the variation rule of solar radiation escape rate are analyzed on three different time scales: day, month, and year. The influence of building orientation was also calculated and analyzed. The numerical calculation results indicate that the escape solar radiation rate varies with the incident angle of solar radiation at different times. It was found that the smaller the solar azimuth angle and solar altitude angle, the smaller the escape rate of solar radiation. The latitude of a city has a significant impact on the solar radiation escape rate. The weighted average of the solar radiation escape rates for each city were calculated for both summer and winter. Regardless of the season, the city’s location, and the orientation of the room, the value of solar radiation escape rate varies from 8.64% to 10.33%, which indicates that the solar radiation escape phenomenon cannot be ignored in glass curtain wall buildings. The results can be used as a reference value of solar radiation escape rate for the correction of actual solar heat gain of buildings in different climate regions. Full article

Glass curtain walls (GCWs) have become prevalent in office buildings, owing to their lightweight and modular characteristics. However, their lower thermal resistance, compared to opaque walls, results in increased energy consumption. Incorporating phase-change materials (PCMs) provides a viable solution through which to address the susceptibility of GCWs to external conditions, thus enhancing thermal performance and mitigating energy concerns. This study delves into the influences of the glazing solar heat gain coefficient (SHGC), the glazing heat transfer coefficient (U-value), and PCM thickness on the energy performance of buildings. Using Design Builder (DB) software version 6.1.0.006, a multi-story office building was simulated in different climatic zones in China, covering the climatic characteristics of severe cold, cold, hot summer and warm winter, cold summer and winter, and mild regions. The simulation results quantitatively elucidated the effects of the glazing parameters and the number of PCMs on thermal regulation and energy consumption. A sensitivity analysis identified the glazing SHGC as the most influential factor in energy consumption. Additionally, by employing Response Surface Methodology (RSM), the researchers aimed to achieve a balance between minimal building energy consumption and economic cost, ultimately determining an optimal design solution. The results demonstrated significant energy savings, ranging from 20.16% to 81.18%, accompanied by economic savings, ranging from 15.78% to 79.54%, across distinct climate zones in China. Full article

China is committed to reaching peak carbon by 2030 and carbon neutrality by 2060. The goals of reducing energy consumption and building a “beautiful China” are being urgently pursued in China. The building studied in this paper is located in the city of Turpan, where the problem of excessive energy use among buildings is significant due to the region’s hot summers and cold winters. Additionally, the fact that the office building studied in this paper has an east–west orientation is significant: the building’s main façade is oriented to the west, comprising a large area of single-layer glass curtain wall. Based on this, this paper proposes optimization strategies from two perspectives of renovation and new construction. Four design options are proposed at the retrofit level: glazed circular curtain wall; glazed enclosed curtain wall; west-facing double-glazed curtain wall circulation combined with south-facing light from the east; recycling of windows on the inside of the exterior glass curtain wall. These suggestions focus on retrofitting the glass curtain wall on the west elevation of the building. Two design options are proposed at the new-build level: west-facing south-oriented light and west-facing north-oriented light. These suggestions were primarily built around the idea of changing the orientation of the windows on the west elevation. The results show that the optimal solution is to implement the west-facing double-glazed curtain wall circulation combined with south-facing light from the east. This program shows a 64.14% reduction in heating energy consumption, a 77.12% reduction in cooling energy consumption, and a 69.67% reduction in total energy consumption. The above research has improved the deficiencies in the performance-based energy efficiency retrofit of office buildings in the region and provided new ideas and suggestions for policymakers and designers to build energy-efficiency retrofits in the early stages. Full article

A refined design procedure for the seismic retrofit of warehouses or, more generally, single-storey RC frames bounded by “drift-sensitive” masonry infills and glazed curtain walls, is proposed in this paper by means of hysteretic braces. The calculation method is based on displacement-based design (DBD) procedures in which both the as-built frame and the dissipative braces are modelled through simple linear equivalent SDOF systems arranged in parallel. In this regard, with respect to the provisions of the Italian Building Code, two refinements are introduced: (1) the definition of two performance targets tailored to the protection of glazed curtain walls (among most expensive non-structural components) and to ensure an acceptable level of damage level for masonry infills; and (2) the adoption of a more accurate formulation for the estimation of the equivalent viscous damping developed both by the main frame and the dissipative braces. The refined design method is applied to a case-study building and the achievement of the performance targets is verified through NLTH analyses. Full article

Enclosed airspaces of various effective emittances exist in the building envelope in walls, roofs, and double/triple glazing windows, curtain walls and skylight devices. Assessing the energy performance of a building component with enclosed reflective airspaces requires evaluation of all modes of heat transport inside the airspace. The thermal resistance (R-value) of the enclosed airspaces depends on the dimensions and orientation of the airspace, and the emittance and temperature of all surfaces that bound the airspace. To the best of our knowledge, the existing methods used around the world to evaluate the airspace thermal performance (e.g., ISO 6946, AUS/NZ 4859, and methods based on the U.S. NBS data) are one-dimensional and assume isothermal conditions on the hot and cold surfaces. In actual applications, however, the temperatures of both the hot and cold surfaces vary (i.e., they are non-isothermal), and the heat transfer takes place via conduction, convection and surface-to-surface radiation. In some cases, convection is absent or negligible, as is the case for downward heat flow or situations with a small temperature difference between the hot and cold surfaces. Radiation transport is significantly reduced by the presence of a low-emittance surface in the heat flow path. One of the goals of this study is to answer the question “is it a good assumption to use the isothermal conditions on both the hot and cold surfaces for determining/reporting the R-value of enclosed airspaces for different building applications?” A complete evaluation of the thermal performance of enclosed airspaces that includes the impact of bounding materials can now be undertaken in multiple dimensions with convective transport described by computational fluid dynamics. In addition to providing a relatively complete evaluation of the thermal performance of the enclosed airspaces, the adequacy of popular simplifying assumptions can be evaluated. This paper describes the computational process used, along with examples of the variation in thermal resistance with the airspace aspect ratio, realistic thermal boundary conditions and radiative heat transport on all surfaces that bound the airspace. The analysis completed in this research shows that the assumption of isothermal hot and cold surfaces affects calculated R-values for enclosed reflected airspaces by less than 3%. This was demonstrated for the five conventionally considered heat-flow directions and effective emittances from 0 to 0.82. Full article

The building envelope provides thermal comfort, an excellent visual view, and sunlight for the occupants. It consists of two parts: (i) an opaque (non-transparent) part (e.g., walls and roofs) and (ii) a transparent part (e.g., windows, curtain walls, and skylight devices). Recently, the use of fully-glazed facades, especially in large cities, has increased due to their aesthetical and structural advantages. This has led this study to review the performance of the currently passive smart glazing technologies. Phase Change Materials (PCMs) as latent energy storage material is the focus of this review, as well as other individual and combined techniques, including shading systems, solar cells (photovoltaic), and chromogenic (thermotropic and thermochromic) materials. PCM-integrated glazing systems have been extensively studied and rapidly developed over the past several decades from the standpoint of unique system designs, such as passive, active, and passive/active mixed designs, intelligent management, and sophisticated controls. In the academic literature, numerous studies on PCM-integrated building envelopes have been conducted, but a comprehensive review of PCM-integrated GUs combined with other passive and active techniques using dialectical analysis and comparing the climatic conditions of each study using Köppen-Geiger climate classification climate classification has been performed only rarely. Consequently, the primary objective of this study is to reduce this discrepancy for all types of glazing, excluding glazed roofs. This review article also contains literature tables as well as highlights, limitations, and further research suggestions at the end of each subsection. Full article

Most perimeter zones are thermally susceptible to the variation of outdoor conditions, especially due to a large amount of heat gain through glazing. To reduce heat gain, spandrel panels are generally installed in curtain walls of commercial buildings. For the present study, thermal performance in an office located in the perimeter zone was investigated using Computational Fluid Dynamics (CFD) simulation. By varying the spandrel panel heights, thermal comfort was assessed quantitatively. The findings suggest that when the spandrel panel height was 0 m, the highest temperature was observed in all cases. As the height of the spandrel panel was increased, the temperature decreased. For thermal comfort evaluation, Predicted Mean Vote (PMV) values at 1.5 m from the floor in all cases were larger than zero. PMV values in all cases were within the range of slightly cool to warm. When the spandrel panel height was 0 m, the highest thermal sensation (warm) among the cases was observed, which may cause thermal dissatisfaction for occupants. In addition, thermal comfort was deemed satisfactory based on the criteria of ASHRAE standard 55, when the height of the spandrel panel was higher than 0.6 m. Full article

Vertical building enclosures known as Double-skin façades (DSFs) have become recognized as a promising façade type for buildings that place emphasis on sustainable, green, and energy-efficient design performance. DSFs are highly integrated across engineering and architecture; however, there remain limited centralized knowledge repositories that offer designers’ insight into these performance trends, multi-disciplinary collaboration, and tradeoff metrics, as well as how to go about modeling DSFs for performance under applicable loading systems when conducting design. As such, the main objective of this paper is to provide a better understanding of different types of DSF systems and their attributes from the perspective of multiple disciplines, as well as different modeling approaches. The methodology adopted is rooted in the principles of systematic literature review of design standards, research papers, and software manual literature, as well as a qualitative evaluation based on structural performance aspects. From the study, many different configurations of DSFs exist that impact each engineered system, where those system attributes impact multiple systems. This results in a need to parametrically iterate configurations within software to find a balance in DSF performance. Furthermore, there exists software easily capable of simulating these systems, yet the designer must carefully construct the models with different levels of sophistication towards DSFs and the software. This paper contains concise summaries of key attributes that designers need to consider when their project has a DSF system, along with different software modelers from which they can choose, correlating to the complexity of the design stage along with the appropriateness of the calculations. Full article

In the cyclic racking evaluation of curtain wall systems, physical testing with instrumentation is the standard method for collecting performance data by most design professionals. The resulting testing of full-scale mockups can provide many types of data, including load and displacement values at different stages of loading through failure. While this type of data is valuable for product/system development/fabrication and design, such data can also provide a means for simulation validation of the curtain wall cyclic performance under simulated earthquake loading. Once the simulation study is validated using the test results, then parametric studies by designers can be conducted with greater ease, ideally with commercial software packages, without the need for testing. For the results of this research study, a practical industry formulated finite element modeling (FEM) approach was used to predict the performance of the curtain wall mockups. Here, unitized four-sided structural sealant glazing (4SSG) curtain wall system mockups that incorporate a re-entrant corner were subjected to cyclic racking displacements per the American Architectural Manufacturers Association (AAMA) 501.6 Structural Sealant protocol. System performances, including displacements, were obtained from the FEM study and used to calculate the effective shear strain of the structural silicone and the drift capacity of the system. This paper describes the details of the techniques developed for FEM, the analysis results, and shows an example application of the numerical modeling approach for mockups with racking test results available. The goal of this modeling approach was to create and test methods that practicing consulting engineers can quickly conduct in their offices on common commercially available software often available to them. Full article

Curtain wall glazing systems are a major part of a building due to the multiple roles they have, including occupant protection against environmental effects and the transfer of loads to the structural system. From a structural perspective, limited analytical guidelines and methods exist to aid designers in their determination of the curtain wall performance without extensive simulation or laboratory testing. This study takes experimental data from full-scale, “unitized”, four-sided structural sealant glazing (4SSG) curtain wall system mockups featuring a re-entrant corner subjected to cyclic racking displacements in accordance with the American Architectural Manufacturers Association AAMA 501.6 protocol to derive and establish equations that predict the relative displacements of the glass relative to the glazing frame, based on the amount of inter-story drift. Through derivation and testing, sealant cohesive failure and glass cracking were identified as limit states and corresponding drift levels were determined to control many of the equations. Displacements from the newly derived equations were correlated to the effective shear strain value experienced by the structural silicone in the mockup concurrently with the curtain wall’s drift capacity. This paper provides detailed derivation of the kinematic equations for possible use by glazing design professionals. Such equations can help designers to more easily predict the drifts that cause damage to such systems by manual calculations without the need for expensive mockup testing or time-intensive computer models. Full article

This article describes the characteristics of one type of sealing system used in warm edge glazing units and analyses the possible causes of damage. Attention was focused on the performance of the dual seal, PIB/silicone system. This type of glazing is widely used for modern curtain walls and roofs of office buildings and shopping centres. Study was focused on PIB displacement defects, which affects both the appearance and thermal performance of the curtain wall system. Wide-ranging field surveys were conducted to examine the problems identified in some office buildings. The information gathered in this way was used to identify the critical areas and causes of seal displacement in the analysed insulating glass units (IGUs). Laboratory tests were conducted on PIB and silicone seals retrieved from the removed defective units. The properties of these materials were determined and used to evaluate the applied edge sealing system and build a representative numerical model. Due to the problems encountered in deriving accurate analytical formulas, finite element (FE) approximation was used as a problem solving tool. The generated FE model and strain analysis were the key parts to obtaining a true representation of the actual behaviour of IGUs subjected to various environmental loads, taking into account the influence of the air cavity. Results of computer simulations and laboratory tests were compared for model validation. The effect of changes in ambient pressure was examined, showing the development of tensile strains in the silicone and PIB, which can lead to debonding. The greatest principal strains occur at the silicone/butyl rubber interface and this location should be considered to be the most susceptible to failure. The observations are summarised in the final conclusions. Additionally, as field study showed, after ten years in service, the percentage of damaged units is considerable. More frequent IGUs inspection should cover both appearance and thermal imaging to detect unsealed panels. From the standpoint of both durability and appearance, dual silicone/PIB should be phased out in favour of modern seal systems. Full article

Modern heritage buildings designed in the 1950s and 1960s often feature poor seismic performance capacities and may require significant retrofit interventions. A representative case study in Florence, i.e., the edifice housing the Automobile Club Headquarters, is examined here. The building was designed in 1959 with an articulated reinforced concrete structure and presents some enterprising solutions for the time, including suspended floors accommodating large glazed curtain wall façades in the main halls. The original design documentation was collected with accurate record research and checked with detailed on-site surveys. Based on the information gained on the structural system by this preliminary investigation, a time-history assessment analysis was carried out. Remarkable strength deficiencies in most members and severe pounding conditions between the two constituting wings, which are separated by a narrow technical gap, were found. As a result, a base isolation retrofit hypothesis is proposed in order to improve the seismic response capacities of the building without altering its elegant architectural appearance, being characterized by large free internal spaces and well-balanced proportions of the main structural members. A substantial performance improvement is obtained thanks to this rehabilitation strategy, as assessed by the achievement of non-pounding response conditions and safe stress states for all members up to the maximum considered normative earthquake level. Furthermore, the very low peak inter-storey drifts evaluated in retrofitted conditions help in preventing damage to the glazed façades and the remaining drift-sensitive non-structural components. Full article

New light envelopes for buildings need a holistic vision based on the integration of architectural design, building simulation, energy management, and the curtain wall industry. Water flow glazing (WFG)-unitized facades work as transparent and translucent facades with new features, such as heat absorption and renewable energy production. The main objective of this paper was to assess the performance of a new WFG-unitized facade as a high-performance envelope with dynamic thermal properties. Outdoor temperature, variable mass flow rate, and solar radiation were considered as transient boundary conditions at the simulation stage. The thermal performance of different WFGs was carried out using simulation tools and real data. The test facility included temperature sensors and pyranometers to validate simulation results. The dynamic thermal transmittance ranged from 1 W/m²K when the mass flow rate is stopped to 0.06 W/m²K when the mass flow rate is above 2 L/min m². Selecting the right glazing in each orientation had an impact on energy savings, renewable energy production, and CO₂ emissions. Energy savings ranged from 5.43 to 6.46 KWh/m² day in non-renewable energy consumption, whereas the renewable primary energy production ranged from 3 to 3.42 KWh/m² day. The CO₂ emissions were reduced at a rate of 1 Kg/m² day. The disadvantages of WFG are the high up-front cost and more demanding assembly process. Full article

This study compares the impact of the recently developed electrochromic glazing technology on load reduction by comparing it with the double-glazing and shading devices that are sold commercially for high-rise residential buildings in Korea. These buildings are similar to large office buildings in terms of their high window-to-wall ratio. The energy consumption of such buildings was simulated using an analytical model of a high-rise residential building. The patterns between the heating and cooling loads were found to be similar to that of office buildings, in that the cooling load was considerably higher than the heating load. This study hypothesizes that the load reduction performance of electrochromic glazing with variable solar control and high solar radiation rejection is superior to that of existing double-glazing products and shading devices. This hypothesis was tested by analyzing the cooling and heating loads of buildings with different types of double glazings. Bleached electrochromic glazing exhibited lower transmittance than colored glass double glazing, low-e double glazing, and double glazing with a shading device, and is thus not effective in reducing heating load. Colored electrochromic glazing provided higher solar radiation rejection than colored glass double glazing and low-e double glazing, and thus is effective in reducing cooling load. Full article