Glazing Systems Research Articles

Numerical evaluation of an optically switchable photovoltaic glazing system for passive daylighting control and energy-efficient building design

Adaptive control of solar heat gain and visible light transmission through windows is perceived to be a potential measure for enhancing energy conservation and visual comfort in buildings. In this study, a novel versatile window, named Building Integrated Photovoltaic (BIPV) smart window, was proposed to offer simultaneous improvement of daylighting control, on-site electricity generation and building energy efficiency, compared to traditional BIPV windows with static optical properties. The key components of the proposed system include an optically switchable thermotropic layer made of Hydroxypropyl Cellulose (HPC) hydrogel, crystalline-silicon photovoltaic cells, clear glass and low-emissivity (low-e) glass covers. The thermotropic layer can respond to heat by autonomously changing its visible and near-infrared optical properties, with which the amount of solar radiation into building spaces can be manipulated and thus the risks of excessive solar heating and illumination can be prevented. Apart from excellent solar modulation, the BIPV smart window can collect a proportion of the light scattered from the thermotropic layer and concentrate it onto the integrated PV cells for extra electricity generation. An innovative methodology has been proposed to predict the optical, thermal and electrical properties of the BIPV smart window under varying ambient conditions. Numerical simulations have been carried out in EnergyPlus to predict the window's performance when it is applied to an office-type environment in the climate of Nottingham, the UK. The influence of different window design scenarios, in terms of Window-to-Wall Ratio (WWR), orientation and transition temperature, has been investigated. It was found that using the BIPV smart window can achieve an annual energy saving of 36.6% but also a more comfortable indoor luminous environment, compared to the counterpart BIPV window (with no thermotropic layer integrated), when installed in the south-oriented office with a WWR of 25%.

Photothermal and energy performance of an innovative roof based on silica aerogel-PCM glazing systems

The glazing systems are considered as the critical components in terms of the building energy consumption owing to the undesired insulation performance and poor thermal inertial mass. To overcome those challenges, the glazing systems integrated with silica aerogel and PCM (SA-PCM) are confirmed as a promising technology to improve photothermal performance. However, the inevitable conflict remains between the energy saving and daylighting performance when the PCM and silica aerogel are filled into two different layers. Therefore, an innovative roof based on SA-PCM glazing systems is proposed, in which the original PCM layer is divided into five cavities for filling PCM and air. A numerical model to investigate the thermal performance and energy efficiency of the innovative roof is developed. The evaluation of the thermal performance of the innovative roof is conducted by the indicators of temperature decrement factor and temperature time lag, while the energy efficiency is evaluated by the total heat loss through the inner surface of the innovative roof. To evaluate the optical performance of the innovative roof, the dynamic optical properties (transmittance, absorptance, and reflectance) are obtained in conditions of different PCM fill ratios. The photothermal and energy performance of the innovative roof are investigated over a 24-hour period in the severe cold region of the city Daqing (China). The results show that the thermal performance of the innovative roof is improved with the addition of PCM amount embodied in the decrease in magnitude and the increase in phase shift of temperature waves on the inner surface. Besides, both the transmittance and absorptance of the innovative roof change significantly along with the PCM fill ratio over the course of the day, while the change in reflectance is slight. Additionally, the optimal energy performance of the innovative roof occurs at 80% fill ratio of PCM, in which the total heat loss and the energy saving rate account for 2595 kJ/m2·d-1 and 11.37%, respectively. Based on the principle of prioritizing the energy efficiency while considering the demand for light transmission properties of the innovative roof, the fill ratio of PCM is recommended as 60%.

Modelling and simulation of building integrated Concentrating Photovoltaic/Thermal Glazing (CoPVTG) systems: Comprehensive energy and economic analysis

In this paper a novel Concentrating Photovoltaic/Thermal Glazing system (CoPVTG), developed at the Centre for Sustainable Technologies of the University of Ulster (Belfast, UK), and exploiting concentration technology, is presented and investigated. The innovative device consists in two glazed panels of which the external one is moulded to form several lenses that concentrate the solar radiation onto photovoltaic cells lines. Thanks to the specific behaviour of these lenses, the solar radiation is capable to reach the indoor environment during the winter months (when it's more useful), while it ends onto the photovoltaic cells during the summer months (reducing the solar gains while also providing electricity to the building). To increase the electricity production, a forced air flux can be created inside the glazed cavity to reduce the PhotoVoltaic cells temperature, and the obtained hot air can be exploited for diverse purposes. Finally, such device is conceived to be integrated into existing windows framing to boost its adoption in new or refurbishment construction. With the intention of studying the device under a wide range of boundary and working conditions, a dynamic simulation tool was developed in MATLAB environment and validated trough experimentally gathered data. With this tool it is possible to investigate the performance of the novel device integrated into several buildings. Specifically, a case study analysis was performed by considering an office building located in five different localities. From the conducted analyses, interesting results and design criteria are obtained. Specifically, the CoPVTG adoption returns higher electricity yield vs. standard semi-transparent window, ranging between 54 and 84% in case of cold and hot weather zones, respectively. In term of overall economic performance, the adoption co CoPVTG allow for a HVAC system running cost reduction, for the investigated case study, ranging from 20 to almost 100% depending on the considered weather zone.

Thermal Parameters Calibration and Energy-Saving Evaluation of Spectral Selective Absorption Film Coated Glazing System Based on Heat Transfer Simulation

Spectral selective absorption film (SSAF), a solar control film, has a special energy-saving mechanism. In the previous studies of SSAF coated glazing systems, thermal parameters (global thermal transmittance (U) and solar heat gain coefficient (SHGC)) calculated by traditional algorithms were not verified. In order to evaluate the energy-saving effect of SSAF coated glazing systems accurately, U and the SHGC were calibrated and then used for energy consumption simulation. Firstly, the simulation models of the heat transfer process of SSAF coated glazing systems were established by COMSOL Multiphysics, considering simplified linear attenuation of radiative transfer. After being validated, the simulation models were used for the calibration of U and SHGC by the Multiple Linear Regression (MLR) model. As a result, the calibration coefficients of U and SHGC are 1.126 and 1.689, respectively. Secondly, the thermal parameters of SSAF coated glazing systems calibrated by the calibration coefficients were used for a building energy consumption simulation case. The result showed that the inner surface is the best coating position for single glazing systems (SG), while the outer surface is the best coating position for double glazing systems (DG) in hot summer and cold winter zone, hot summer and warm winter zone and the moderate zone of China.

Polymer dispersed liquid crystal retrofitted smart switchable glazing: Energy saving, diurnal illumination, and CO2 mitigation prospective

Smart switchable glazing provides better thermal control and daylighting performance in building compared to conventional glazing. The polymer dispersed liquid crystals (PDLC) glazing can switch translucent to transparent when an active electric field is applied. Solar and visible light properties were measured experimentally for four different colored PDLC film glazing (pink, yellow, blue, and white) in transparent (on) and translucent states (off). The PDLC glazing unsteady-state thermal transmittance (U-value) and solar heat gain coefficient (g-value) were computed to analyze heat gain/loss through glazing. The measured solar optical properties were used to compute the solar heat gains and cost savings when existing glazing in a library building was replaced with different PDLC glazing systems. The PDLC glazing has shown substantial reductions in building cooling loads which correspond to cooling cost savings. Different colored PDLC glazing systems (on/off-states) were studied for cooling cost savings to replace tinted bronze glazing (TBG) in an existing building in a cooling-dominant climate. In on-state, white PDLC glazing (PDLCW-on) had concluded the highest mean air-conditioning cost savings (5.76 $/m2) and total air-conditioning cost savings of 8286.6 $ with the lowest payback time of 8.92 years (on-state) compared to other studied PDLC glazing in on-state mode. PDLC glazing systems have also shown substantial mitigations in CO2 emissions. The white PDLCs in on-state (PDLCW-on) had reported the highest CO2 savings of 101.5 tCO2/year among all PDLC glazing studied in on-state mode. Daylighting analysis was performed to know the daylight accession and distribution inside the building interiors with Design-Builder (V 6.1.8.021). The average daylight factor (DF) metric of PDLC glazing was well above the minimum recommended level for library interiors as per Indian codes. The color rendering properties of PDLC glazing systems were also investigated for interior visual acceptability.

ДЕФЕКТЫ И ПОВРЕЖДЕНИЯ КОНСТРУКЦИЙ КРОВЛИ ПРОИЗВОДСТВЕННЫХ ЗДАНИЙ

The article continues the authors' series of articles on defects and damages of industrial buildings. Here are descriptions of typical damage to roofing: rolled waterproofing carpet, metal coverings, parapets and aprons, light-aerating lanterns, glazing and storm sewer system. As in previous articles, a description of the damage, causes of occurrence, possible consequences during development, a recommended assessment of the technical condition of the structure and recommendations for elimination are given. The article also provides a generalized analysis of the causes of defects and the most likely areas of damage formation.

Impact of the Geometric Form of the Building Envelopes on The efficiency of Natural Lighting in the Office Space.

Envelopes play an important role in Office Buildings.They affect visual comfort for the user Driven by architectural trends and the need to maximize natural light In order to realize required visual comfort conditions. advanced glazing systems, Geometric formation of the outer building envelope proper self- shading properties and control and lighting controls should be studied comprehensively Optimized fenestration system design may improve exploitation of daylight. and it can be controlled to harvest maximum daylight thus reaching the maximum depth naturally illuminated. The paper explains the design relationship between both configuration of office space and between the system of the glazing and the transmission of natural light inside the space, in terms of the design characteristics of the office space (proportions, dimensions), in order to achieve visual comfort to improve the efficiency of the environmental performance of Office Buildings. This paper discusses the study of the environmental effects of the glazing façades of office buildings and their impact on the efficiency of natural lighting and visual comfort. The paper relies on simulation using, the Grasshopper program, in analyzing of the building’s Envelopes and its external elements and the architectural space, in order to find the proper form for improving visual performance.

Investigation of the effect of Inter-Building Effect on the performance of semi-transparent PV glazing system

Semi-transparent photovoltaic glazing (STPVG) systems integrated into buildings have been widely used in engineering projects. It not only has the lighting function of a translucent envelope but also can be used for solar power generation. However, current researches rarely consider the Inter-Building Effect (IBE) on the performance of the STPVG system. In this paper, a real-time shadow model of the building complex and an STPVG system power generation model with the shadows of the surrounding buildings are developed and validated. Then the models are used to simulate and analyze the influence of building shadow on the performance of the STPVG system. The results show that the power performance of the STPVG system decreases significantly under the shadows of the surrounding buildings. And the percentage decrease in power generation and power conversion efficiency is greater than the percentage decrease in solar radiation received by the STPVG system. The lower the building floor and the larger the building spacing, the greater the influence of the surrounding building shadow on the power performance of the STPVG system. This study helps evaluate the feasibility and energy payback period of STPVG systems and provides theoretical guidance for the application of translucent STPVG systems in buildings.

Passive Design Strategies for Energy Efficient Buildings in the Arabian Desert

This study aims to assess passive design features through the extensive modifications of building envelopes to affect the energy efficiency of residential buildings in hot arid climates. In support of the aim of this research, the annual electric energy bill of a typical residential building in Sharurah was collected and analyzed. Then, the DesignBuilder simulation program was used to investigate how different modifications of building envelopes could affect the energy consumption of the residential buildings under common scenarios. Varied thermal insulation, different types of glass, shading devices, and green roof were investigated with this perspective. The simulation results show that thermal insulation can significantly reduce annual energy consumption by as high as 23.6%, followed by green roofs. In contrast, shading devices and glazing system types were fewer superiors. The results also indicate that the effective combination of certain strategies can reduce total energy consumption by 35.4% relative to the base case (BC) of this research.

Building glass retrofitting strategies in hot and dry climates: Cost savings on cooling, diurnal lighting, color rendering, and payback timeframes

Building glazing is a weak thermal envelope that admits too much solar heat, resulting in increased air conditioning expenditures. An optimal glazing system must be chosen to promote the thermal and visual comfort of building interiors. The current study examines how different glass retrofits affect the air-conditioning cost savings of an office building in a hot and dry region of India. To assess the thermal performance of the building, the apertures of the office building were retrofitted with brick glass, stained, tinted, reflective, laminated, polymer dispersed liquid crystal film glazing, and double-glazed window systems. The spectral characteristics of the studied retrofit glazing systems were measured experimentally, and a mathematical model was developed to estimate the heat gain, cooling cost demand, and energy savings for air-conditioning. The polymer dispersed liquid crystal film glazing retrofit provided the highest average air-conditioning cost savings (5.11 $/m2), while the air-filled double-glazing configuration showed the lowest (0.30 $/m2), relative to the original glazing installation among the other retrofits tested. The examined retrofit glazing systems have a colour rendering index of more than 80, indicating appropriate lighting quality. The findings of this study are critical in determining the most energy-efficient retrofit glazing solutions for energy-conscious building design.

ENERGY EFFICIENT BUILDING DESIGN: TIMBER FRAME CONSTRUCTION BASED IN HEMP FIBER INSULATION

Energy efficient building concerns to the structure and using the process that is environmental liable and material efficient all around a building lifecycle. The basic principle of this building to minimize the energy consumption for heating and cooling system. The paper investigates the thermal behavior of hemp fiber insulation in timber framed wall panels for which timber framed structures will be experimented. Steps to enhance the energy performance were applied to building structure, window area, window glazing, lightning, heating ventilation and air conditioning (HVAC) system. We were measured the U-values of timber walls, hemp fiber insulation and window glazing. Results showed that energy efficient building enjoy the benefits of saving 40-50% energy by reducing greenhouse gases emissions into atmosphere. We have discussed about the rating system of energy efficient building or green building. In this paper, information pertaining to building life cycle and detailed explanation regarding fundamentals of building energy will be provided.

Human-plant centric shading control: Considering the impact of shading systems on both occupants’ and plants’ requirements

Traditionally, control strategies are applied to automate switchable electrochromic glazing systems (EC) to save energy and provide comfort for occupants indoors. In addition, the plants’ minimum requirements and the consequences of active shading on the supplemental artificial lighting for plants should be considered when designers want to embrace Biophilic design. This paper introduces a simulation workflow to evaluate the impact of shading activation on both human and plant requirements year-round using combined climate-based daylight (Radiance) and building energy simulation tool (TRNSYS). Finally, the simulated total electricity demand for supplemental lighting for plants in a prototypical office room in temperate climate condition are presented and discussed under different control strategies.

발열유리 창호시스템의 발열량에 따른 실내공간 열적 쾌적성능 분석

Purpose: In this study, an approach using the heated glazing window system as an auxiliary heating system is evaluated in terms of thermal comfort. Heat loss through window parts can occur relatively high because of low thermal resistance, which causes keeping lower surface temperature of the window, typically when outdoor air temperature is lower. With such issues, occupants may feel thermal discomfort near window parts mainly due to the radiant temperature asymmetry. In this study, an approach using the heated glazing window system as an auxiliary heating system is proposed to improve the performance of occupant‘s thermal comfort in a conditioned room. Method: For this analysis, a floor radiant heating system is considered as the main heat supply system in the conditioned zone. The internal thermal information of the room is calculated using a two-dimensional heat transfer analysis simulation (i.e., TRISCO). To quantitatively analyize the thermal comfort of the space adjacent to the window, the Predicted Mean Vote(PMV) at each point is derived by dividing the internal space into a two-dimensional grid. Result: As a result of the analysis, it was found that the heated glazing window system contributes to making the indoor thermal comfort uniform and can improve the thermal comfort of the window adjacent area. The maximum PPD deviation of the indoor space is about 6.3% when the heated glazing system is not operated, 1.8% under the heating of 20W/㎡, and 0.08% under the heating of 40W/㎡

A zirconium-free glaze system for sanitary ceramics with SiO2-CaCO3-TiO2 composite opacifier containing anatase: Effect of interface combination among SiO2, CaCO3 and TiO2

TiO2 is an ideal substitute to ZrSiO4 ceramic opacifier, yet it is limited to application because of the undesirable yellowing resulting from rutile formation. Herein, the SiO2-CaCO3-TiO2 composite opacifier (Si-Ca-Ti) was constructed. The glaze used Si-Ca-Ti presents a superior opacification performance than ZrSiO4 opacified glaze without causing yellowing, showing L*, a*, b* values of 94.81, -0.67 and 3.23. By comparison, the glaze using SiO2, CaCO3, and TiO2 mixture shows lower opacification and yellowish surface with L* and b* values of 92.99 and 5.36. It is revealed that there is a close interface bonding among SiO2, CaCO3 and TiO2 in Si-Ca-Ti, which promotes their combination reaction to generate opacification phase titanite and inhibit rutile formation when sintering, resulting in the white surface and opacification improvement of the glaze. This study proposes a green and efficient strategy to achieve white and highly opacified glaze for sanitary ceramics, exhibiting good application prospect.

Breathing Lessons: Development of a Custom Motorized Facade

For a new corporate headquarters in San Francisco's Mission Bay district, SHoP Architects designed a semi‐conditioned atrium space inside the external glazed envelope known as “the commons.” To ventilate this space, the facade contractor developed a transparent, steel‐framed glazing system featuring motorized bi‐fold units. These operable window units, 3.0 m wide by 4.4 m tall, are computer‐controlled in conjunction with operable skylights to maintain comfortable temperatures in the atrium and significantly reduce the need for mechanical ventilation. This paper describes the engineering and design development of this dynamic facade. A number of kinematic options were studied, resulting in the final configuration whereby window operation is guided in the visible upper and lower rails. In the upper rails, the self‐weight is resolved via newly developed double vertical hybrid rollers. The necessary lateral stability is provided by scissor arms mounted on both sides at the top and bottom, which prevent the window from moving sideways on one side over the entire opening stroke. The windows are operated via two of the currently largest chain drives on the market (lift/pull force 1500 N). In addition, a linear locking drive moves a push rod with three double claws, which additionally keep the window in the “closed” position. The chain drives are synchronized and internally controlled with the linear locking drive. All components are integrated and concealed in the central mullion. A complete opening takes approximately 155 seconds. Safety strips integrated circumferentially in the frame protect the device, while closing, from objects that are accidentally left in the window rebate and will switch off the device automatically. The units are constructed according to the European Machinery Directive 2006/42/EG, and a risk analysis was carried out in advance. The drive technology and all electrical components are UL‐certified.

Influence of metallo-dielectric optical properties on thermal resistance and solar heat gain coefficient of multi-pane glazing systems in hot and cold climates

ABSTRACT The design of efficient windows and building facades in relation to their energy-saving potentials can be developed through an advanced computational modeling analysis, and thus an effective basis of comparison of the thermal performance of glazing systems can be realized. This study simulates the behavior of window systems that integrate partitioning radiant shades, where the latter are situated between typical glass panes comprising an insulated glazing unit. The partitioning shades comprise of spectrally selective metallo-dielectric coatings that modulate optical transmittance in the visible, infrared and mid-infrared regions. Wide variety of window configurations are studied, and the results are analyzed based on the system performance criteria of thermal resistance (R-value and U-value) and solar heat gain coefficient. The comparative performance assessment of single, double, triple and quadruple ‘pane’ glazing systems in relation to internal and external environmental conditions is presented. The effects of different parameters such as fill gas, inter-pane distance, pane thickness and optical properties of coatings on thermal behavior of the fenestration system are presented. Optimal design parameters for cold and hot climates are proposed; and the results show that it is possible to reduce up to 90% heat loss in winter for the most effective configuration.

HVAC electricity and natural gas saving potential of a novel switchable window compared to conventional glazing systems: A Canadian house case study in city of Toronto

This paper investigates performance of a novel switchable window to reduce HVAC energy consumption of a typical Canadian house located in city of Toronto. Energy saving potential of the proposed glazing system is compared with highly efficient low emissivity coated double and triple pane static windows with low, medium, and high solar heat gain coefficients. Glazing systems material properties are chosen from LBNL experimentally validated international glazing system data base, (IGDB). EnergyPlus software is used to simulate and predict heating and cooling loads of the house with natural gas furnace and electric coils as the building HVAC system. Considering windows orientation, two operation strategies are developed to enhance performance of the switchable window inter-pane coatings and adjust desired solar heat gain and thermal resistance in winter and summer. Medium and high window to wall ratio effects on glazing systems performance are investigated and the result shows that proposed system significantly reduce building heating and cooling energy consumption. Considering window to wall ratio of 90%, compared to conventional clear single and double pane windows, energy analysis shows that switchable glazing system decreases HVAC annual energy bill by 47% and 33%, respectively.

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.

Numerical analysis on the thermal performance of PCM-integrated thermochromic glazing systems

Thermochromic glazing and phase-change materials are capable of adapting their optical and thermal properties in response to temperature variation, without consuming additional energy. They are therefore ideal construction materials for passive building envelopes. In this study, the energy-saving potential of combining the two materials into one adaptive glazing system is investigated numerically. Computational fluid dynamic models were constructed to simulate the thermal performance of different adaptive glazing systems consisting of the two materials. The models were tested against two existing experimental studies, and good agreements were found. Based on the models, the applicability of the novel glazing systems for a south office building façade was investigated for summer and winter in Shanghai, China. It was found that PCM-integrated thermochromic triple glazing units outperform normal double-glazing units by reducing total heat gain by up to 32% and 40% for a sunny and cloudy day in summer, respectively. In winter, however, they tend to block more desirable solar radiation and hence are not as effective as normal double-glazing units.

Performance of smart glazed overhang systems for US residential buildings

In this paper, the application of smart glazing systems as shading devices is evaluated for US residential buildings. Specifically, static and dynamic overhangs are considered using smart glazing that can change their tint state to reduce the heating and cooling thermal loads for prototypical housing units in high-rise apartment buildings. The tint settings as well as the overhang tilt angles are specified on hourly, daily, and monthly basis depending on the window orientation and the time of the year to minimize the annual energy demand for the housing units. The performance of smart glazed overhang systems is compared to both static and dynamic shading devices made-up of conventional opaque materials. In addition, the impacts of various design and climatic conditions are considered to assess the energy performance of the smart glazed overhangs. The results of the analysis indicate that the annual energy consumption for existing housing units with conventional windows located in Boulder, CO, can be reduced by over 7% for static smart glazed overhangs and by over 22% for dynamic smart glazed overhangs. These savings are even higher with larger windows and wider differentials between optical properties between clear and dark states. The smart glazed overhangs allow the use of low-cost smart glazing as a retrofit measure for existing buildings. Moreover, the smart glazed overhangs allow the specification of large windows for new constructions with limited energy penalties.