Glazed Curtain Wall Research Articles

Investigating perforated egg crates as dynamic shading systems for open-plan offices in tropical climates

This study explores the use of perforated egg crates as a dynamic shading system to improve daylight quality by achieving better uniformity in open-plan offices. Glazed curtain walls, although a popular choice in modern open-plan offices, can cause problems especially in tropical climates, such as glare and heat particularly near the windows. As egg crates (EC) generally perform better as shading devices than plain horizontal or vertical systems, this study simulated three different combinations of perforated, solid, overlapping and non-overlapping egg crate models for an existing open-plan office building in Indonesia. Daylight measurements of the existing horizontal shading device without any egg crate (NO-EC) were first recorded. Subsequent simulations of non-overlapping perforated (EC-NP) egg crate models with different blade widths and blade rotation angles in accordance with the sun elevation angles on specified working hours were performed. Similar simulations were then performed for two combinations: other combinations of overlapping solid (EC-OS) and overlapping perforated (EC-OP) egg crate models. Finally, a full-scale site mock-up of the EC-NP and NO-EC were tested under real-life climatic conditions. Results show that EC-NP provides better uniformity than the other two combinations, which is within the range of 0.59–0.99. This is due to the deeper penetration of daylight achieved by the overlapping placement of the horizontal blades in front of vertical blades, while keeping the building envelope shaded.

Optimizing the indoor thermal environment and daylight performance of buildings with PCM glazing

With the development of energy efficient technologies for glass envelopes, using thermal storage techniques to improve their thermal inertia has become a trend in research. In the present study, the heat transfer and day-lighting models of a building with PCM glazing curtain wall (PGC) were developed. Multiple parameters such as glazing internal surface temperature, PCM liquid phase rate, indoor temperature, natural illumination, and daylighting coefficient were quantitatively analyzed to evaluate their indoor thermal environment and daylighting performance. The results show that the application of PGC can significantly improve indoor temperature uniformity and indoor thermal comfort compared to silica aerogel glass curtain wall (SGC) and hollow glass curtain wall (HGC). By filling 10 mm thick PCM, the temperature fluctuation of the inner surface of the glass and the midpoint temperature of the room can be reduced by 35 %, the peak temperature of the inner surface of the glass can be delayed by 0.89 h, and the average indoor natural light value and indoor daylight factor are satisfactory at 453.26 lx and 9.63 %, respectively. However, as the thickness of the PCM increases to 15 and 20 mm, the liquid fraction of the PCM and the energy storage performance of the PGC are greatly reduced, and natural daylighting does not meet the GB/t-50033-2013 limit.

A case study on flanking noise transmission through curtain wall in an office building

Curtain walls are a popular architectural element for the design of modern commercial building façade. With the advanced technologies and recent developments in building materials, curtain walls are developed with different lightweight materials, providing a spectacular visual identity of buildings and a number of functional design advantages to building interiors, including acoustic comfort, weather resistance, and thermal comfort. With the availability of high-performing glazed curtain walls these days, external noise in a commercial building adjacent to busy roads and railway lines is easily controlled, and acoustic comfort at internal space be achieved to suit the design intent. However, the lack of building design integration between building envelop, structural, and interior systems would often lead to airborne flanking noise transmission between different occupancies resulting in poor acoustic privacy. Such a post-design issue is often undesirable to the occupants and is an expensive exercise to retrofit. In this paper, a case study is conducted in a building where office workers in a three-story office building raised concerns about noise annoyance and acoustic privacy between two different tenancies on levels one above the other. This paper discusses the acoustic issues causing the compromised acoustic privacy, the method of acoustic investigations, the recommended noise control mechanisms, and finally the outcome of mitigation measures.

Seismic Retrofit of Warehouses with Masonry Infills and Glazed Curtain Walls through Hysteretic Braces: Refinement of the Italian Building Code Provisions

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.

Recommendations for Improvement of the Thermal Performance of an Office Building Based on Retrofitting the Glazed Curtain Wall

Glazed curtain wall systems have become indispensable particularly in office buildings due to their light weight, aesthetic appearance, easy installation, and resistance to climate conditions. Curtain walls, however, also have problems in terms of thermal efficiency because of their wide, glazed windows and metal frames that have high thermal conductivity. The aim of this study is to offer proposals for improving the thermal performance of an office building with a glass curtain wall system built in a hot-humid climate zone. An office building constructed in Antalya, Turkey was modelled with the help of DesignBuilder energy simulation software, and various modifications were made to the model in order to improve the thermal performance of the building. With the improvements proposed in the study, it is possible to decrease the annual thermal loads of the whole building by 6.6%, and the annual thermal loads of the space with the curtain wall by 33.2%. The study revealed that applying an additional skin is more effective than lowering the U-value of the glass of the curtain wall in terms of thermal performance improvement.

Blast enhanced façade design by means of an optimal balance between security and sustainability

The major objective of this paper is to show that glazed curtain wall has a surprising potential for blast enhancement. However, often this potential is partially lost because of inaccurate and only presumed safe side approach. Indeed, in curtain wall it is much important to assess properly the beneficial effect of the deformable supports, framing and possibly brackets, on the glazing response under blast wave effects. Only in this way a true balanced design approach can be carried out and the protective requirement can be integrated into the façade design by preserving the architectural requirements, comfort, classical energy efficiency requirements and novel demand for sustainability. On the other side the large variability of materials and component behaviour under nonlinear range and the uncertainties related to the blast threat recommend a flexible calculation tool, which must be coupled with a sensitivity analysis on the most relevant inputs. For this reason, a Multi Degree of Freedom approach shows several advantages with respect to the Explicit Dynamic Finite Element Analysis, considering also the large number of geometry, component design and blast load variations are existing in a typical application of the protection on a high rise building. The impact of the calculation method is demonstrated by means of a comparative exercise and by means of real case applications.

Study on Human Thermal Comfort in Asymmetric Radiant Heat Environment in Large Space

In order to study indoor temperature distribution in a large space and thermal comfort of human, an environmental test and questionnaires were carried out at an airport in Xi’an in summer. The results show that the temperature distribution in the space is asymmetric. The room temperature increases from cooling floor to 0.1m high, but then it has little change within 1.5m high. However, the temperature fluctuation in horizontal is significantly influenced by internal equipment, lighting, elevator and etc. According to the environmental parameters and subjective voting, 55% of the PMV values are greater than 0.5, and more than half of the thermal feelings near the heat source and glazing curtain wall are “warmer”. Properly increasing the wind speed of air vent could effectively improve the environmental comfort.

Developing FEM Procedures for Four-Sided Structural Sealant Glazing Curtain Wall Systems with Reentrant Corners

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.

Derivation of Kinematic Equations Based on Full-Scale Racking Tests for Seismic Performance Evaluation of Unitized Four-Sided Structural Sealant Glazing Curtain Wall Systems

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.

Hybrid system strategy on double skin façade to optimize thermal performance on research building

One of the most efficient methods to optimize thermal performance in a building is the practical design of the façade. The double skin façade‘(DSF) is a crucial decision for handling the interaction between outdoor and indoor spaces. It also offers some spatial diversity in the design process. Recently, a lot of focus has been paid to it instead of the more traditionally glazed curtain wall. This is because of its potential to reduce energy effectively, achieve thermal comfort in the building, and save costs. The indoor spaces near to the glazed facades will become warm due to high incidence solar radiation on the East-West facades in Malaysia’s tropical environment. In the tropics, one of the solar heat gain reduction approaches is the use of double skin-facade (DSF). One of the fundamental components of the double-skin facade is the blinds. Blinds located in the cavity of the double-skinned facade and buffer the building from solar heat gain or perform the role of a pre-heater for ventilation air. In general, the temperature of the blinds is high, which is helpful in the cold period but problematic in the hot period. To minimize the cooling loads of the building, technological innovations for the shading system are considered. Plants can dissipate absorbed solar radiation into resistant and latent heat. Plants turn radiation into the latent heat. This paper aims to study the effectiveness of a double skin façade and explore improved innovative design for a double-skin façade design integrated with vertical green on research building to optimize thermal performance. This paper will collect data of the thermal performance of double skin façade, precedent study and run simulation analysis to achieve the aim of the paper.

Enhanced Seismic Retrofit of a Reinforced Concrete Building of Architectural Interest

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.

DSF studies towards energy efficiency for a tall building design in the Mediterranean climate

Tall buildings around the world are increasing at an accelerating pace. However, this fast-pace development is not in tandem with today’s environmental considerations towards reducing high carbon emissions, mainly relating to the building sector (close to 50% of carbon dioxide (CO2) emissions). The vast scale and energy demands of tall buildings call for an in-depth study of this building typology towards improving energy efficiency. An important consideration for lowering energy demands is the configuration of the building envelope that acts as the mediator between indoor and outdoor conditions, according to the climate and microclimate of the building’s location. Current architectural practices of fully glazed curtain wall envelopes make this relationship problematic, by resulting in high-energy loads for achieving thermal comfort. Over the last few years, a step forward towards energy efficiency is the use of a double-skin façade (DSF). Its application, however, is lacking consideration of the specific climatic conditions that will essentially result in an energy efficient design. Previous research revealed that the most energy efficient DSF in the Mediterranean climate is with LowE glazing as the outside DSF layer. Further studies on DSF cavity width for a hot climate, were in favour of wider cavities, as these reduce the high cooling loads that are associated with this climate. Additionally, simulations of an office building in the Mediterranean climate, confirmed that cooling energy is also present during winter (airtight DSF), suggesting for a more active DSF envelope design throughout the year. A further study is then conducted through simulations, where the DSF design alternates between an open / closed DSF, and comparisons are made in relation to DSF width, building height above ground, outdoor environmental conditions and interior thermal comfort, for further improving the energy efficiency of tall building design.

Numerical research on thermal performance of water-flow window as hospital curtain-wall

Water-flow window can reduce indoor cooling load from direct solar radiation and preheat domestic hot water at the same time. It is quite suitable for hospital with patient wards and large demand of hot water, especially buildings with large area of glazing curtain-wall. Field measurement was carried out during July 2018 at a major comprehensive hospital in Shenzhen, and the inner surface of the four-storey west-facing glazing curtain-wall reached over 45.6oC in the daytime. The year-round energy-saving potential is investigated by applying water-flow window to the curtain-wall through programme simulation, with a pre-validated FORTRAN programme. The results show that the year-round solar energy utilization rate can reach as high as 9.4%, and the indoor thermal environment is better, compared with conventional window design. The preheated water can be used in wards for showering and help building energy conservation. Water-flow window has great potential for large-scale application within similar buildings.

Video Capture Technique Analysis of Four-Sided Structural Sealant Glazing Curtain Wall Systems for Racking Performance

Video Capture Technique Analysis of Four-Sided Structural Sealant Glazing Curtain Wall Systems for Racking Performance

Integrated shape memory alloy devices toward a high-performance glazed curtain wall seismic retrofit

Recent dynamic events, such as Alaska and San Fernando earthquakes, have shown shortcomings in contemporary façade design processes, exacerbated by the occurrence of non-structural component damage and failure when subjected to extreme wind loads or seismic events. Accordingly, in the present work the feasibility of an original and advanced dissipation technology is pursued investigating on the façade performance by testing and modeling strategies.Initially, based on the experimental activities performed at the Construction Technologies Institute (ITC) laboratories of the Italian National Research Council (CNR), numerical simulations are run to interpret and reproduce the experimentally tested response of two full-scale façade units. Thereafter, sophisticated 3D finite element models are calibrated acquiring information on the fundamental mechanisms accountable for the dynamics in façades.Subsequently, by virtue of the peculiar properties of Shape Memory Alloys (SMA), such as superelasticity and shape memory effect, innovative curtain wall joints are designed, focusing on the improvement of the façade energy dissipation performance and on the enhancement of the overall structural behavior.Finally, the improvements are demonstrated both globally and locally: on one hand, traditional and novel curtain wall force-drift capacity curves are compared; on the other hand, the effectiveness of the suggested device is shown, when built on a reference structure.

Numerical investigation on the seismic dissipation of glazed curtain wall equipped on high-rise buildings

The dynamic interaction between glazed curtain wall stick systems and modern high-rise mega-frame buildings is investigated. In the present paper, four moment resisting frames (MRFs), consisting of thirty- and sixty-storey steel-based prototypes, are designed according to European standards: internal concentrically braced frame (CBF) core, outriggers and belt trusses are adopted to limit inter-storey drift and second order effects. Force-displacement relationships are derived from available full-scale test data performed on non-structural aluminium façade units. Therefore, 3D finite element (FE) models are developed to interpret the physical phenomena involved in façade dynamics: as a result, equivalent 1D nonlinear links are calibrated to simulate these phenomena independently. Nonlinear time history analyses (NLTHAs) are executed to investigate the potential combination of stiffness and strength of such hybrid systems, i.e. achieved through the integration of glazed curtain walls on the MRF lateral force resisting system (LFRs). Local and global performance will be shown in terms of inter-storey drifts and displacement peak profiles, forces and percentage peak variations, highlighting static-to-seismic load ratios in critical members and the sensitivity to the structural height. Conclusions point out that, even if accurately designed according to current standards, the façade omission from the seismic analyses of high-rise structures may lead to a crucial underestimation in the dissipation capacity of the building.

Climate Change and its Influence on Glazed Curtain Wall Design

ABSTRACTThe climate change is a fact and has huge influences on the design of modern building envelopes. The climate change and its effects were analyzed and a management plan for a holistic curtain wall design was developed that helps to reduce the material loss and human suffering and that improves the reconstruction process. A first step of this is an energy efficient curtain wall design that results in a CO2 reduction and influences the frequency and intensity of the climate change as a whole. Secondly, special designed digital simulation processes offer possibilities to check and fine‐tune product characteristics that minimizes the vulnerability in case of extreme weather events. Acute event management can be done by combining disaster prediction tools with early alert systems that can be used to release a home protection service which, for example, shuts down self‐controlled shutters in case of a hurricane. The last step of the management plan deals with a fast recovering of the environment after a natural disaster. Building components are classified into two groups depending on their significance for the curtain wall. Class A components should not be affected in case of an event as they are responsible for the structural stability of the curtain wall or are very expensive. Class B components are cheaper design features or protection devices that are allowed to get damaged and must be designed for easy access and replacement. A final evaluation of the management plan gives information where current glazed curtain wall design provides already good solutions and where additional action and innovation is needed.

Numerical analysis of convective heat transfer coefficient for building facades

The latest architectural trends demand an extensive use of glazed curtain walls running from building floor to ceiling. While glazing poorly controls the heat flow, it is important for viewing, daylighting, and solar design features. In order to evaluate building energy consumption accurately, knowledge of convective heat transfer coefficient (CHTC) distribution over the façade of the building is important. In this article, high-resolution numerical simulations that use three-dimensional steady Reynolds-averaged Navier–Stokes and energy equations are performed. Convective heat transfer coefficient values at the windward facade of five buildings, with rectangular floor plans, and heights of 3, 10, 15, 20–30 stories, have been produced. The influence of building height on CHTC distribution is investigated at Reynolds numbers ranging from 0.7 × 106 to 33 × 106, and a correlation equation as a function of building height and a reference wind velocity is developed. For example, as the height increases from 10.1 to 101 m in the study cases, the surface-averaged convective heat transfer coefficient on the windward façade increases by 55%. The high-resolution spatial distribution of convective heat transfer coefficient over façade of the tallest building indicates that the top-corner zone convective heat transfer coefficient values are higher by 24% and the base-center zone values are lower by 27% compared to the average CHTC value, implying the necessity for zonal treatment.

Revealing the thermal environmental quality of the high-density residential tall building from the Brazilian bioclimatic modernism: The case-study of Copan building

Looking back to the glorious years of Brazilian modernism between 1930 and 1964, the country´s architectural heritage reveals an environmental design approach still relevant to buildings of today. In this context, the COPAN building (1966), located in São Paulo (latitude 23°S), is one of the most iconic buildings of its time with 1.160 residential units encompassing various types of studio flats (called in Portuguese “kitnets”) as well as one, two and three bedroom apartments distributed across six blocks of independent vertical circulation accesses. This naturally ventilated tall building is recognized by its massive concrete curvilinear structure of 140 m high, shaded towards the north and northwest orientations by horizontal concrete brise-soleis and opened with a single glazed curtain wall on the south and southeast orientations. The thermal performance of the Copan building was investigated by means of fieldwork and analytical procedures. The fieldwork included measurements in loco of environmental variables in four residential units, during warm and cooler periods of the year (2016) and interviews with a sample of 100 occupants, this was followed by thermal dynamic computer simulations performed with the Thermal Analysis Simulation Software (TAS). The adaptive comfort model defined in ASHRAE 55-2013 was adopted as the performance criteria for analytical studies. One of the main conclusions of these technical studies was about the combined effect of thermal inertia, external shading and controlled natural ventilation resulting in steady thermal conditions, with air temperatures oscillating between 24 °C and 26 °C when external temperatures reach as high as 32 °C in a typical warm afternoon.

Glass facades under seismic events and explosions: a novel distributed-TMD design concept for building protection

Glazing facades generally represent one of the most critical building components, from a structural point of view, since providing a physical separation and barrier for the building occupants. In this regard, especially under the action of extreme loads, they require specific design concepts voted to protect the building occupants. In this paper, the feasibility and potential of special mechanical connectors interposed at the interface between a given multi-storey primary building structure and the glazing facade are investigated via accurate finite-element models, under the action seismic and explosive loads. Given the case study of a 4-storey steel framed structure enclosed by a glazing curtain wall, both the global and local effects and potential benefits due to additional vibration control systems (VCSs) are preliminary assessed via numerical simulations, giving evidence of the activation—once properly designed—of a distributed-tuned-mass damper (TMD) concept involving the glass facade as a structural component of the 3D building. Differing from traditional TMD applications in civil engineering systems—namely consisting of lumped mass, damping and stiffness terms—these beneficial contributions are derived from the enclosing glass panels. Taking advantage of earlier research studies, in particular, where major efforts have been spent for the potential of visco-elastic VCSs, careful consideration is paid in this paper for the feasibility of elasto-plastic (PL) connectors, giving evidence of their response and effects under both seismic events and explosions. As shown from FE results partly discussed in the paper, the full 3D assembly can take benefit from the proposed design concept, hence suggesting the further development of the explored passive mitigation tool for the protection of the primary building structure.