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The role of window glazing on daylighting and energy saving in buildings
Abstract
Energy conservation in building arena is essential issue for achieving sustainable environment. However, buildings experienced significant amount of heat gain or loss through window and this will affect the thermal comfort of buildings׳ occupants. Building without window is able to save energy, but it is not recommended due to the benefits of natural light on visual comfort and the biological effect of natural light on humans. Hence, window design plays important role in building architect. One of the essential parts of window is the glazing. Selecting a window glazing is complicated when energy saving and daylighting aspects of a building are considered concurrently. Optimization techniques offer a balance solution for the contradictions in selecting a window glazing of energy-efficient building. This paper intended to reveal the impacts of window glazing on the energy and daylighting performances of building through the previous researches. Then, the optimization techniques used by various researchers in choosing a glazing are highlighted. The emerging glazing technologies were discussed as well.
... The results of this study are consistent with findings in the literature. For exam the energy savings associated with improved insulation and glazing align with con sions of [28], which reported an 11-14% reduction in EUI from similar upgrades. A tionally, the flood resilience measures corroborate the recommendations of [29], w emphasized the dual benefits of energy efficiency and hazard mitigation [30]. ...
... The results of this study are consistent with findings in the literature. For example, the energy savings associated with improved insulation and glazing align with conclusions of [28], which reported an 11-14% reduction in EUI from similar upgrades. Additionally, the flood resilience measures corroborate the recommendations of [29], which emphasized the dual benefits of energy efficiency and hazard mitigation [30]. ...
This study explores the integration of Building Information Modeling (BIM) and Geographic Information Systems (GISs) to enhance sustainable energy efficiency and flood resilience in residential buildings, with a case study from Quetta, Pakistan. The research leverages BIM to optimize energy performance through scenario-based energy consumption assessments, thermal efficiency, material properties, and groundwater considerations, ensuring structural integrity against water infiltration. Enhanced insulation and double-glazed windows reduced energy use by 11.78% and 5.8%, respectively, with monthly energy cost savings of up to 48.2%. GIS tools were employed for high-resolution flood risk analysis, utilizing Digital Elevation Models (DEMs) and hydrological data to simulate flood scenarios with depths of up to 2 m, identifying vulnerabilities and estimating non-structural damage costs at PKR 250,000 (~10% of total building costs). Groundwater data were also incorporated to evaluate their impact on foundation stability, ensuring the building’s resilience to surface and subsurface water challenges. A novel BIM-GIS integration framework provided precise 2D and 3D visualizations of flood impacts, facilitating accurate damage assessments and cost-effective resilience planning. The findings demonstrated that incorporating flood-resistant materials and design modifications could reduce repair costs by 30–50%, highlighting the cost-efficiency of sustainable resilience strategies. This research advances sustainable and resilient construction practices by showcasing the dual potential of BIM-GIS integration to address energy efficiency and groundwater-related structural vulnerabilities alongside hazard mitigation challenges. Future applications include automating workflows, integrating renewable energy systems, and validating models across diverse climatic regions to promote the global adoption of innovative urban planning solutions.
... Previous studies on the thermal performance of photovoltaic (PV) windows have demonstrated that these windows offer significant advantages in cooling-dominated regions [9]. In the heating season, the heating load may increase because incoming solar heat gain is low with PV glazing. ...
... It was suggested that the PVCVG could enhance the thermal performance and overcome the deficiency of the PV glazing. Previous studies on the thermal performance of photovoltaic (PV) windows have demonstrated that these windows offer significant advantages in cooling-dominated regions [9]. In the heating season, the heating load may increase because incoming solar heat gain is low with PV glazing. ...
The synergistic active-passive utilization of solar energy in buildings plays an important role in achieving nearly zero-energy buildings. Building-integrated photovoltaic (BIPV) is a crucial initiative to reduce heating energy consumption, especially in cold climate zones with abundant solar radiation. However, few studies have examined the impact of design parameters of photovoltaic combined vacuum glazing (PVCVG) on building energy efficiency in Lhasa. This study assessed the energy performance of several typical windows and PVCVG with various Window-to-Wall Ratio (WWR) design conditions and investigated how the WWR and orientation of PVCVG influence energy consumption using DesignBuilder7.0 software. The findings indicate that PVCVG exhibits great energy-saving potential in Lhasa, with both orientation and WWR of PVCVG substantially affecting energy consumption. Specifically, when the south-facing WWR exceeds 40%, the energy generated by the three kinds of PV windows can meet the building’s requirements. The optimal orientation for PVCVG is southward, followed by east and west orientations. PVCVG reaches optimal energy satisfaction when the south WWR is 85%. This study is expected to provide useful information for improving energy use efficiency in cold climate zones with abundant solar radiation and promoting sustainable building development.
... Building envelopes include both walls and windows, with the windows playing a crucial role in shaping the indoor environment [32] by influencing daylighting [33] and contributing to occupants' psychological well-being through views [34]. Additionally, the insulation performance of the building envelope is affected by the window-to-wall ratio (WWR) [35][36][37], which also determines the potential area for PV module installation. ...
... Additionally, as shown in Figure 2b, the distance between buildings is greater than the height of the front building, further minimizing shading effects. Building envelopes include both walls and windows, with the windows playing a crucial role in shaping the indoor environment [32] by influencing daylighting [33] and contributing to occupants' psychological well-being through views [34]. Additionally, the insulation performance of the building envelope is affected by the window-to-wall ratio (WWR) [35][36][37], which also determines the potential area for PV module installation. ...
The performance of facade-applied photovoltaic (FPV) systems in high-rise apartment complexes varies based on the height and layout of the buildings, influencing the overall energy efficiency of the complex. This study assesses the potential of FPV systems to achieve electricity self-sufficiency in apartment complexes. Focusing on a single apartment complex in Seoul, South Korea, the geometry and layout of each building are used to estimate electricity consumption and assess the impact of FPV systems. The electricity consumption of the apartment complex was estimated based on the electricity energy use intensity derived from the analysis of public data and the gross floor area of the apartment complex, yielding an annual electricity consumption of 1803.7 MWh. Two types of photovoltaic (PV) systems were considered: rooftop-mounted photovoltaic (RFPV) systems and FPV systems installed on the south-facing facades of buildings. Three FPV design scenarios were examined (Scenario A: full facade coverage; Scenario B: horizontal-only installation; Scenario C: vertical-only installation), with no design variations for the RFPV system. The RFPV system was estimated to contribute 30.7% (553.8 MWh/yr) of the complex’s electricity consumption. The remaining electricity consumption, 1249.9 MWh/yr, is met by the FPV systems, with self-sufficiency rates under the three FPV design scenarios found to be 83.3% for Scenario A, 33.6% for Scenario B, and 64.6% for Scenario C. These findings highlight the need for additional PV installations or the incorporation of other renewable energy technologies to achieve full electricity self-sufficiency. This study provides a foundational model for applying PV systems to high-rise apartment complexes, offering insights for further research and real-world implementation.
... In addition, the size and style of windows have a big impact on a building's thermal comfort. Furthermore, the type of window has a significant impact on its thermal performance [106]. New generation windows, such as those equipped with vacuum glazing and improved U-values, are potentially capable of reducing the energy consumption of buildings. ...
... New generation windows, such as those equipped with vacuum glazing and improved U-values, are potentially capable of reducing the energy consumption of buildings. Hee et al. [106] observed a remarkable 63% improvement in the U-value by incorporating aerogel-filled windows. Feng et al. [107] reported that use of gasochromic smart windows can lower the HVAC loads by up to 30%. ...
The indoor comfort of occupied buildings has become essential, as it significantly affects the productivity and health of occupants. This review provides a comprehensive overview of air and thermal comfort studies in residential buildings using alternative materials. This study aims to provide the trends and the state of the research in this field, to summarize the optimization methods, and to offer a perspective on future studies. The results demonstrate that in comparison to traditional air conditioning systems, natural ventilation systems, and air purifying plants have the potential to reduce energy consumption and carbon emissions in buildings by up to 60%. Also, cross-laminated timber (CLT) buildings can achieve energy savings of up to 30% compared to conventional buildings due to their superior insulation properties and reduced thermal bridging. This review has provided highlights to help the building owners to promote a healthier environment, reduce energy consumption and achieve more comfortable indoor air quality. The study promotes incorporating innovative materials and use of natural ventilation systems, smart air conditioning systems and air purifying plants.
... Pencere boyutu, en-boy oranı ve konumunun ısı kaybı üzerindeki etkisi de incelenmiş ve soğuk iklimlerde pencere eğiminin ve boyutunun etkileri araştırılmıştır [16]. Bir çalışmada cam filmleriyle birlikte çift camlı pencerelerin enerji kullanımını artırdığı bildirilirken [17], simülasyonların kullanıldığı bir başka çalışmada sıcak ve diğer iklimlerde soğutma yükünde %17 ila %47 oranında bir azalma olduğunu gösterilmiştir [18]. İnsan alışkanlıkları binaların ısı kaybını önemli ölçüde etkilemektedir ve bu durum otomatik iklimlendirme sistemlerinin insan davranışlarının enerji tasarrufu üzerindeki olumsuz etkisini azaltabileceğini düşündürmektedir [7]. ...
Küresel ısınma ile bağlantılı olarak dünya çapında birçok felaket meydana gelmektedir. Sera gazlarının emisyon seviyelerini azaltmanın yollarını bulmak için birçok çalışma yürütülmektedir. Fosil yakıt tüketiminin azaltılması emisyonları azaltmak için kullanılan en yaygın yöntemdir. Bu çalışmada belirli cam filmi özelliklerine sahip bir model binada sağlanacak ısı kazancının kestirimi gerçekleştirilmiştir. Sonuçlar, saydam ve renkli cam üzerine kaplanmış üç film tipi için karşılaştırmalı olarak verilmiştir. Isı kazancı kestirimi, şehir, cam, bina ve nem özellikleri dikkate alınarak yaz günleri için uyarlamalı olarak yapılmıştır. Filmsiz saydam cam için elde edilen son oda sıcaklığı referans olarak alınmış ve diğer yedi tipte cam için kestirim bu referansa göre yapılmıştır. Örnek binanın konumu, sıcaklığı ve cephesi gibi özellikler dikkate alınarak elektrik tüketimi, karbon emisyonu ve fiyat açısından maliyet analizi yapılmıştır.
... Alghoul et al. examined the impact of window-to-wall rate and orientation on yearly heating and cooling energy consumption in an office room with simple double-glazed windows in the city of Tripoli [37]. Hee et al. reviewed case studies to provide insights on selecting the appropriate window glazing for optimum daylighting and energy savings in buildings [38]. Ozel studied the impact of the glazing area on the optimum thickness of insulation for varying orientations [39]. ...
... Energy consumption from buildings, including indoor cooling and heating, is rapidly increasing and now accounts for 40% of total energy use in developed countries [1][2][3]. Windows amplify the energy demands for cooling and heating interiors, and as the least energy-efficient component of a building, can account for as much as 60% of the building's energy consumption [4][5][6]. Therefore, the development of smart window technology is a paramount importance for enhancing the energy efficiency of buildings. ...
As living standards improve, the energy consumption for regulating indoor temperature keeps increasing. Windows, in particular, enhance indoor brightness but also lead to increased energy loss, especially in sunny weather. Developing a product that can maintain indoor brightness while reducing energy consumption is a challenge. We developed a facile, spectrally selective transparent ultrahigh-molecular-weight polyethylene composite film to address this trade-off. It is based on a blend of antimony-doped tin oxide and then spin-coated hydrophobic fumed silica, achieving a high visible light transmittance (> 70%) and high shielding rates for ultraviolet (> 90%) and near-infrared (> 70%). When applied to the acrylic window of containers and placed outside, this film can cause a 10 °C temperature drop compared to a pure polymer film. Moreover, in building energy simulations, the annual energy savings could be between 14.1% ~ 31.9% per year. The development of energy-efficient and eco-friendly transparent films is crucial for reducing energy consumption and promoting sustainability in the window environment.
... In light of the above, there are well-established protocols aimed towards a more sustainable building environment worldwide, with several opinions proposed for the redevelopment of the building stock, particularly in the context of energy [12]. More specifically, design standards and guides have been formulated to explore better approaches to building design [13] relating to the optimization of fenestration design [14,15] and zeroenergy, high-performing building envelope design [16,17]. Certain general and holistic concepts in both practice and research define the design objectives in terms of environmental impact and sustainability. ...
The effects of buildings on the environment can be reduced with research-based alternative building designs. This study focuses on reducing the building space to lower the overall size of a building as a strategy to reduce the building’s embodied energy. The aim of this study was to investigate the initial embodied energy (IEE) of a residential building that was systematically reduced in size. Using input–output-based hybrid analysis, the IEE for three architecturally distinct four-bedroom residential prototypes (P1, P2, and P3) was calculated. The IEE for P1 (525 m²), P2 (266 m²), and P3 (109 m²) were 3555, 2008, and 1000 GJ, respectively. This indicates a 72% reduction in embodied energy consumption when the largest prototype (P1) was transitioned to the smallest (P3). When analyzing IEE/m² and IEE/m²/occupant, it becomes apparent that larger spaces tend to have a lower IEE/m². However, when the occupancy increases, the IEE/m²/occupant decreases by 25–33%. Therefore, considering occupant-centered design for residential buildings, the benefits of a large house are not justifiable. These findings can help inform decisions regarding the optimization of residential spaces to minimize environmental impacts.
... Numerous studies have explored window optimization parameters such as orientation [5], window-to-wall ratio [6], and glazing properties [7]during the early design stages. The impact of window glazing on visual comfort and energy consumption has been extensively examined [8,9]. External shading devices, such as louvers, overhangs, and fins, have been investigated for their potential to control daylight quality, solar heat gain, and overall building function. ...
A great share of buildings' energy consumption in Iran is consumed in school buildings where the students' efficiency is highly dependent on thermal and visual comfort conditions. By considering the local microclimate and its influence on building performance, this study proposes an innovative methodology utilizing external redirecting transparent louvers applied to the external part of windows, to enhance the indoor visual and thermal comfort of school buildings in different climatic regions of Iran. Daylight Autonomy and Radiation are optimized as key factors for visual and thermal comfort, respectively, while simultaneously reducing energy consumption. The study focuses on simulated case studies of south-facing and north-facing classrooms located in four distinct climatic regions in Iran. The installation of louvers involves a constant parameter (number of louvers) and variable parameters (angle and width). The findings demonstrate the effectiveness of this approach across all four climatic conditions in Iran, emphasizing its potential to significantly enhance thermal and visual comfort. Specifically, the results indicate a substantial increase in visual comfort (up to 45%) in Sari, along with a notable improvement in thermal demand (40%) in Yazd.
... One of the key observations here is that although room depth (RD), glazing ratio (GR) and glazing transmittance (GT) were ranked higher in the overall ranking, the glazing transmittance was ranked lower for thermal energy metrics which signifies lesser importance. It is most likely attributed to the behaviour of GT that directly dictates how much visible light passes through the window and enters the space [44]. While GT may influence the solar heat gain of the space, other factors such as the U-value and solar heat gain coefficient (SHGC) of the glazing might play a more significant role in heat transfer into the space [45]. ...
Climate change may lead to more intense sunlight in tropical regions, potentially increasing the daylight available for buildings. While this can enhance natural lighting inside buildings, it may also exacerbate issues such as glare and overheating if not properly managed through shading devices and glazing treatments. Nevertheless, common strategies to mitigate heat gain and glare such as shades and blinds often obstruct natural light, necessitating increased reliance on artificial lighting. The conflicting interplay between daylighting and thermal performance can undermine building performance if not carefully considered. Existing research on the influence of key design parameters in tropical climates tends to focus predominantly on heat gain mitigation, neglecting other aspects. This study addresses these gaps by examining the holistic daylighting and thermal energy performance of buildings to develop optimised façade and resilient designs against climate change. The investigation encompasses an analysis of 11 design parameters of light shelves and building characteristics that are critical during the initial design stage. Global sensitivity analysis (GSA) is employed to identify the most influential design parameters affecting useful daylight illuminance, uniformity ratio, cooling energy, and solar gain energy. A case study involving double-story terrace houses in Malaysia is employed, with analyses conducted for the present and future climates of three Malaysian cities (Kuala Lumpur, Bayan Lepas, and Kota Bahru). The findings reveal that, across all three cities, glazing transmittance is the most influential parameter for daylighting performance, while room depth assumes primary significance for thermal performance. Although the relative ranking of parameters remains consistent between present and future climates, their magnitudes differ. In summary, this paper gives designers insights into the critical design parameters essential for achieving a balanced and resilient daylight-thermal design in tropical climates at the initial stages of the design process.
... The solar radiation transmission entering the interior through these transparent envelopes, along with heat exchange due to low thermal resistance, has the effect of significantly increasing the energy consumption of stations' environmental control systems for HVAC [6]. Consequently, transparent envelopes are often considered to be some of the least energy-efficient components of building envelopes [7,8]. The application of building shading technology is a powerful means to reduce indoor solar radiation and alleviate the upward trend in air-conditioning energy consumption in buildings with high WWRs and SRRs (as shown in Figure 1). ...
Railway stations are normally designed with glazing façades and skylights to achieve aesthetic requirements and facilitate visual permeability, but this design can lead to significant energy consumption. The implementation of dynamic external shading systems together with appropriate control strategies can significantly reduce the energy consumption of HVAC systems. This study numerically investigated the lighting and cooling energy consumption of railway stations equipped with external shading systems under various climatic zones, window-to-wall ratios (WWRs), skylight-to-roof ratios (SRRs) and roller-shade performance. The study shows that lighting energy consumption varies most significantly when the shading activation threshold is set between 50 and 200 W/m². The dynamic shading thresholds are influenced by natural lighting and solar heat gain, with the strategy changing from using natural light to reducing solar gain as the SRR increases. This study also provides the optimal activation thresholds and energy-saving rates for railway station buildings in different climatic zones using external roller shades for different external window scenarios. In Guangzhou, using roller shade A in a railway station under the maximum external window scenario achieves energy savings of 36.41%, while in Shanghai and Beijing, the energy savings are 18.12% and 23.13%, respectively. These results provide guidance for the use of dynamic external shading in railway stations in China and for the achievement of energy-reduction targets in the transport and building industries.
... Glazing systems of façades significantly influence the thermal and luminous performance of buildings, consequently affecting their energy performance [1,2]. Conventional glazing systems, which are usually passive, are limited by atmospheric conditions, often requiring artificial lighting and/or climatization equipment to ensure adequate visual and/or thermal indoor comfort conditions. ...
... Reducing the cooling and heating demands of buildings is crucial to pivot towards greener initiatives 4 . This reduction can be achieved by bolstering energy efficiency, which involves reducing incoming solar radiation and heat transfer from the interior to the exterior 5 . Introducing sustainable materials like low-emissivity coated glass and aerogel glazing offers a solution 6 . ...
To address the pressing need for reducing building energy consumption and combating climate change, thermoelectric glazing (TEGZ) presents a promising solution. This technology harnesses waste heat from buildings and converts it into electricity, while maintaining comfortable indoor temperatures. Here, we developed a TEGZ using cost-effective materials, specifically aluminium-doped zinc oxide (AZO) and copper iodide (CuI). Both AZO and CuI exhibit a high figure of merit (ZT), a key indicator of thermoelectric efficiency, with values of 1.37 and 0.72, respectively, at 340 K, demonstrating their strong potential for efficient heat-to-electricity conversion. Additionally, we fabricated an AZO-CuI based TEGZ prototype (5 × 5 cm²), incorporating eight nanogenerators, each producing 32 nW at 340 K. Early testing of the prototype showed a notable temperature differential of 22.5°C between the outer and inner surfaces of the window glazing. These results suggest TEGZ could advance building energy efficiency, offering a futuristic approach to sustainable build environment. In modern architectural designs, buildings account for~40% of global energy consumption, with windows responsible for 20-40% of the energy wasted within these structures. This issue is expected to worsen as global development continues, leading to more buildings being constructed and an increasing number of structures featuring extensive glass facades 1. Integrating sustainable materials into buildings can decrease energy losses and simultaneously generate energy. There are many attempts to implement solar photovoltaics in windows to produce electricity 2,3. However, they are expensive, require sunlight, and their performance could be affected by dust, heat, etc. Reducing the cooling and heating demands of buildings is crucial to pivot towards greener initiatives 4. This reduction can be achieved by bolstering energy efficiency, which involves reducing incoming solar radiation and heat transfer from the interior to the exterior 5. Introducing sustainable materials like low-emissivity coated glass and aerogel glazing offers a solution 6. Moreover, the development of architectural windows capable of intelligently controlling indoor solar radiation through changes in their optical transmittance holds great promise for reducing energy consumption in buildings 7. Recently, energy-efficient smart window technology has garnered noteworthy scientific attention, leading to the exploration of innovative materials and their integration with practical techniques to achieve desired multifunctional properties 8,9. Such as energy-saving glazing systems predominantly employ multilayer, vacuum, polymer-dispersed, thermochromic/electrochromic, low-emission, or phase change materials 10. However, while these materials enhance insulation, they neither generate nor conserve energy. Enter thermoelectric (TE) materials-renewable energy sources capable of directly converting heat to electricity. Various economic factors, such as the long-term uncertainty in the price of fossil fuels, are also stifling the development of TE devices on a commercial scale. Yet, integrating a thermoelectric generator (TEG) in glazing systems offers a dual advantage: minimising energy wastage and simultaneously harnessing this waste energy to produce electricity. TE materials stand out as a sustainable energy conversion approach. They can directly transform heat into electricity, leveraging the Seebeck effect. Moreover, TE devices offer the benefits of compactness, noise-free operation, ease of use, and low maintenance due to their lack of moving parts 11. Implementing TE materials in windows offers the opportunity to generate electricity through harvesting the inherent temperature gradient between the interior and exterior of a building 12 .
... Reducing the cooling and heating demands of buildings is crucial to pivot towards greener initiatives 4 . This reduction can be achieved by bolstering energy efficiency, which involves reducing incoming solar radiation and heat transfer from the interior to the exterior 5 . Introducing sustainable materials like low-emissivity coated glass and aerogel glazing offers a solution 6 . ...
To address the pressing need for reducing building energy consumption and combating climate change, thermoelectric glazing (TEGZ) presents a promising solution. This technology harnesses waste heat from buildings and converts it into electricity, while maintaining comfortable indoor temperatures. Here, we developed a TEGZ using cost-effective materials, specifically aluminium-doped zinc oxide (AZO) and copper iodide (CuI). Both AZO and CuI exhibit a high figure of merit (ZT), a key indicator of thermoelectric efficiency, with values of 1.37 and 0.72, respectively, at 340 K, demonstrating their strong potential for efficient heat-to-electricity conversion. Additionally, we fabricated an AZO-CuI based TEGZ prototype (5 × 5 cm²), incorporating eight nanogenerators, each producing 32 nW at 340 K. Early testing of the prototype showed a notable temperature differential of 22.5 °C between the outer and inner surfaces of the window glazing. These results suggest TEGZ could advance building energy efficiency, offering a futuristic approach to sustainable build environment.
... With recent advances in building materials, new window materials have also come up. Such innovative materials in the transparent elements of the envelope can help find solutions to improving building insulation, improving daylighting, and optimizing building energy use [9], [10]. ...
Windows are an important part of a building's envelope. Recent advances in materials technologies and the drive towards energy sustainable buildings has led to development of a class of window materials which have been broadly referred to as smart windows. These windows provide improved functionality in terms of daylighting, warmth, and view. They can also be part of building integrated photovoltaics, allowing buildings to be prosumers of energy. Smart windows in building designs have focused on improving building energy use efficiency, such windows can also play a role in improving the indoor environment. In this work, we present a scoping review of smart windows used in school classrooms and their impact on classroom indoor climate, that is the thermal environment and indoor air quality (IAQ). Through this review, we aimed to analyse the current research related to use of smart windows in classrooms and the research questions associated with smart windows and future climate resilience of classrooms. In the review process we divided smart windows into two main categories: smartness related to glazing material and smartness related to operational schedule. We provide an overall summary of the use cases for smart windows and their impact on classroom indoor climate of classrooms.
... High-performance windows allow sunlight to pass through in winter and reflect in summer, providing better thermal comfort inside the building [54]. There are several techniques to achieve improved window glass specifications, which include multilayer glazing, low-emittance coatings, vacuum glazing, photovoltaic glazing, self-cleaning glazing, PCM glazing, smart glazing, suspended films, gas-filled glazing, aerogel glazing [40,[55][56][57]. Not only that, but there are creative solutions, including reversible windows, transparent insulation materials-filled windows, solar-absorbing windows, ventilated double-glazed windows, and switchable electrochromic windows [58,59]. ...
... The effect of window size, aspect ratio and position on heat loss was also studied and the effects of window slope and size in cold climates were investigated [5]. While one study reported that doubleglazed windows with window films increase energy use [6], another study using simulations showed a 17% to 47% reduction in cooling load in hot and other climates [7]. Human habits significantly affect the heat loss of buildings, suggesting that automatic air conditioning systems can reduce the negative impact of human behavior on energy savings. ...
Many disasters are occurring around the world in connection with global warming. Many studies are being carried out to find ways to reduce emission levels of greenhouse gases. Reducing fossil fuel consumption is the most common method used to reduce emissions. In this study, the heat gain of a model building with specific window film properties is estimated. The results are presented comparatively for three film types coated on clear and tinted glass. The heat gain estimation is performed adaptively for summer days considering geographical location, glazing, building and humidity characteristics. Estimations are made for seven types of window films. A cost analysis is carried out considering the location, temperature and façade of the sample building.
... Glass plays a great role in the energy consumption of buildings: glazed areas are responsible for a major share of energy loss from the building envelope, culminating to 47% total heat loss in a typical residential building [6] and for 20-40% wasted energy in buildings in general [7]. This impact is further increased by the nature of the manufacturing process of glass, which is holistically energy intensive: the glass industry worldwide is reported to be responsible for 86 Mt. of CO 2 e emissions, and produces 150 Mt. of glass a year -42% of this is float glass used in construction industry (36.12 Mt) [8]. ...
This study aimed to contribute to the limited literature on energy efficiency (EE) retrofitting of old buildings, focusing on urban and low-income districts. The case study considered a small zone consisting of approximately 80 old family dwellings in Amman city. The conducted field survey was designed to collect basic data about occupants’ demographics, building conditions, energy consumption, awareness, and willingness to invest in EE measures. A large fraction of residents confirmed that no- or low-cost measures, such as switching off lights and bulb replacement, are already implemented. However, most of them had not even considered investing in EE measures to improve the thermal performance of dwelling envelopes. Equally important, none of the interviewed residents indicated that they would consider replacing old inefficient household appliances in the near future or acquiring new highly efficient machines unless there is direct financial aid or a grant program supported by the government or local authorities to enhance EE. The small fraction of people who showed some understanding of EE remain reluctant to invest in costly items, such as thermal insulation of external walls or replacing windows, most likely due to their very limited financial capability. It is recommended to introduce a tailored scheme to cause a positive shift in current energy consumption behaviors toward more efficient practices, leading to greenhouse gas (GHG) reductions in old residential buildings. This could only be achieved by creating and allocating a special fund to assist poor families in improving EE in their dwellings. Further investigations are highly needed to explore various subjects, including occupant psychological behaviors and responses related to energy use and EE in the residential sector.
This study proposes a new optimisation method for envelope thermal design based on genetic algorithm and building simulation combined with envelope thermal performance. The new method aims to obtain combinations of envelope thermal parameters that can further reduce building energy consumption and can be used to analyse the direction of optimisation of the envelope thermal design. Firstly, based on the genetic algorithm and the envelope thermal resilience performance index, the envelope thermal performance optimisation method is established for design and analysis. Then, a residential building in Shanghai is selected as an example, and the boundary conditions of the envelope thermal parameters are obtained. The proposed method is applied to optimise the envelope design. Finally, the optimisation process of the envelope for different types of rooms with different orientations is analysed using numerical simulation. The results show that the proposed optimisation design method can effectively reduce the heating and air-conditioning loads of the building (up to 25%–65% for the selected buildings). In addition, it is recommended that residential buildings in the Shanghai area use heavy mass walls with high thermal insulation capability as the building interior walls and windows with a small window-to-wall ratio and high thermal conductivity. The proposed optimisation method and its results can provide a reference for building design and help to promote the development of design methods for building envelope.
The increasing energy consumption and detrimental CO 2 emissions contributing to global warming underscore the urgent necessity for energy conservation, especially within buildings. Among different building components, fenestration plays a pivotal role as it accounts for the majority of heat transfer across the building envelope. This emphasises the significance of window-glazing technologies in enhancing their thermal performance. Furthermore, window-glazing systems can lead to overheating issues, particularly in summer, and glare issues, especially in winter. These challenges have spurred the development of various advanced glazing systems. This paper provides a comprehensive review of these advanced glazing technologies based on their functionalities and working principles, with a focus on parameters such as U-value, solar heat gain coefficient and visible transmittance. Among these technologies, vacuum and aerogel glazing systems exhibit superior thermal insulation properties, with U-values below 1 W/m ² K, making them suitable for heating-dominated climates. Smart window systems, such as electrochromic windows, are ideal for cooling-dominated climates due to their low solar heat gain coefficient (0.09–0.47) and visible transmittance (0.02–0.62). Photovoltaic window systems not only provide effective thermal insulation and solar shading but also produce additional power for on-site use. Some of these glazing systems feature complex structures, which present challenges when integrating them into existing building simulation software to assess their impact on building performance. Therefore, this paper also examines techniques for conducting energy and daylight performance simulations for buildings that make use of complex window systems. Ultimately, the authors propose an approach to characterise the thermal, optical and electrical properties of a complex photovoltaic window system within existing building simulation software, such as EnergyPlus. This approach facilitates a thorough investigation into the effects of complex window systems on building energy efficiency and indoor comfort.
As a passive cooling technology with no energy consumption and no pollution, radiative cooling has shown huge energy saving potential. However, its application in building glass still faces great challenges...
Windows constitute a significant portion of the facade in buildings and modern ground transportation vehicles, such as commercial skyscrapers, high‐speed trains, and subway systems. Traditional glass windows lack adequate thermal insulation and heat retention capabilities; Low‐Emissivity (Low‐E) glass can block external infrared radiation, it also impedes mobile communication signals, particularly those in the 5G Sub6G frequency band. This paper introduces an innovative metasurface glass designed to enhance 5G mobile communication signals within the interior of glass windows. Through simulation and experimental validation, this design has demonstrated a signal enhancement of over 10 dB within a 150 mm range before and after the focal point, and 100 mm in the vertical direction, compared to ordinary glass; at the focal point, the signal enhancement exceeds 15 dB. Furthermore, tests conducted across various real‐world scenarios have confirmed that within areas covered by 5G signals, the RSRP of the signal at the focal point has increased by approximately 6–9 dB. In addition, the outer surface of this metasurface glass possesses low‐emissivity characteristics, effectively blocking external infrared thermal radiation and reducing heat exchange with the interior of the glass window, thereby showing a significant advantage in maintaining a stable indoor temperature.
In this work, twisted helical cellulose nanocrystals films with preprogrammed circular polarization and near-infrared reflectance are fabricated via a blade-based 3D printing method. The films are composed of stacked nanoscale slabs with high birefringence from unidirectionally organized cellulose nanocrystals. By changing the printing director, we achieved two types of films: twisted helical stacks and anisotropic Bragg stacks. These films are highly transparent and clear, and the achiral anisotropic Bragg stack shows near-infrared spectral region reflectance (1.3–1.4 μm). In contrast, the twisted helical films show concurrent left- and right-handed circularly polarized properties, as opposed to left-handed natural cellulose nanocrystals films. We observe dual chiroptical properties with circular dichroism peaks due to circular Bragg reflectance in the visible region and suggest that the circularly polarized properties are extended to the near-infrared region. These observations prompted us to explore the transition between anisotropic Bragg stacks and continuous helical films via simulations. We show that the printed twisted films can act as optical metamaterials with dual helicity and fill the gap between known photonic structures—the conventional continuous chiral nematic material with a chiroptical appearance and the achiral Bragg stack with a controlled photonic bandgap. These printed twisted stacked films hold the potential of larger-scale printed ordering of unique anisotropic nanostructures for circularly polarized-sensitive photonic, thermal, and energy management applications.
Creating high performance buildings is crucial not only for energy conservation but also for enhancing indoor comfort and well-being of occupants. Complex Fenestration Systems (CFS) can modulate daylight and/or solar radiation, thereby improving the quality of indoor light and thermal environments. This paper provided a comprehensive review of the application of micro-prismatic materials (MiPMs) in CFS, analyzing and summarizing the design, manufacturing, evaluation methods, case studies, and implementation framework of MiPMs. The effectiveness of MiPMs in enhancing indoor light and thermal performance was analyzed and the limitations and future research directions of these materials were discussed. The review suggested that using mathematical models and algorithms to design the prismatic structure parameters could be an efficient approach. Integrating other materials or technologies and incorporating dynamic control could significantly further enhance the optimized performance of MiPMs. Ultra-precision machining is the core manufacturing technology for MiPMs, and the use of recycled materials may offer a more sustainable approach for material production. Through characterization via bidirectional scattering distribution functions (BSDF) and the ability to generate the data using goniophotometers or simulation tools, computer simulation can act as a time-efficient, and accurate method for performance evaluation of MiPMs. A summarized roadmap may help building owners and architects more effectively apply MiPMs in their projects. Future work might focus on enhancing product quality and weather resistance, standardizing test and simulation work, developing accurate and integrated analysis methods, and exploring integration of MiPMs with building integrated photovoltaic (BIPV) systems.
The domestic sector made up 16% of UK’s total greenhouse gas emissions in 2021. The build-to-rent market is experiencing a rapid expansion, but the energy performance and distinctiveness of this building sector are still generally undiscovered. Therefore, 423 build-to-rent flats from three build-to-rent developments in England were evaluated with top-down approach. Energy use intensities of flats were compared against domestic energy benchmarks and design targets. Possible determinants of energy consumption in build-to-rent flats, including EPC rating, number of bedrooms, air permeability, glazing area and glazing orientation were investigated through correlation analyses. Research discovers discrepancy between actual energy performance of the studied flats and design targets supporting UK’s 2050 net zero target. In this case study, number of bedrooms is identified as the most noticeable factor influencing energy consumption. Results of this study provide an introductory insight of the build-to-rent sector and serve as a starting point to encourage further exploration.
Practical application
This paper specifically focuses on build-to-rent buildings within the domestic sector. Energy use situations of build-to-rent flats in the UK were investigated with actual measured data provided by a build-to-rent developer. Results demonstrate the discrepancy between energy use in the build-to-rent flats being studied and existing domestic benchmarks. This paper provides insights to researchers, building developers and policymakers regarding the energy performance of this upsurging build-to-rent building sector and its associated influencing factors. It also contributes ideas on the importance of data sharing and development of energy benchmarking of the build-to-rent sector.
In buildings with double skin façades (DSF), the amount of light entering the internal spaces depends on the properties of the outer surface, the build-up of the layers of the façade, as well as their architectural features and shading devices (if any). However, studies focusing on the incidence of daylighting in buildings with DSF are still few and far between. In this context, this study aims at reviewing the previous academic research on the effects of DSF on daylighting in buildings, analysing the impacts of architectural design and detailing parameters (e.g. shading device, cavity depth, structure, skin fabric materials, and build-up, and the building and façade orientations) on the natural lighting of buildings with DSF. This study uses a scoping methodology to filter through the state-of-the-art in the literature on DSF. In this study, the literature search has been conducted using Scopus, Web of Science, and ScienceDirect leading into 148 major publications. The final number was narrowed down to 33 due to several reasons. Overall, results indicate that, compared to conventional façades, DSF decreases daylight levels, prevents glare, and enhances a more uniform distribution of light in internal spaces of buildings. Concluding remarks identify the gaps in the knowledge and pinpoint potential areas for future research.
This study explores modern residential buildings in rural areas of Wuhan and Guangzhou to assess the feasibility of achieving net zero energy buildings (NZEBs) through the transformation of existing buildings in southern China’s hot-summer–cold-winter and hot-summer–warm-winter regions. Energy simulations under various climatic scenarios identify effective energy-saving measures, such as the use of photovoltaic power generation. The results highlight substantial renovation potential, with energy reductions of approximately 85 kWh/m² (RCP2.6), 90 kWh/m² (RCP4.5), and 115 kWh/m² (RCP8.5). Living patterns significantly influence energy use, especially in buildings with more rooms, where the gaps in the energy demand with net zero standards can reach 560.56 kWh. At the monthly scale, different climate scenarios impact the feasibility of achieving NZEBs, particularly under RCP8.5, where eight rural housing types fail to meet the requirements, with six exceeding 200 kWh energy deficits and the largest energy deficit occurs in June 2090 in Guangzhou, reaching 592.53 kWh, while under RCP2.6, only two buildings with more rooms fail to meet NZE. In summary, in the hot-summer cold-winter region, the energy demand is higher but so is the solar yield. Therefore, under the most adverse RCP8.5 scenario, NZEBs are achievable for 9 months of the year, which is 2 months more compared to Guangzhou under similar conditions. Even after net zero transformation, new rural housing will face greater energy-saving challenges in future climatic conditions, especially under higher concentration pathways.
This chapter aims to provide a thorough description of the responsive envelope topic from a theoretical point of view to allow a clear understanding of the concepts proposed in the following sections. Firstly, this chapter begins with a detailed overview of the main available classification systems and nomenclatures adopted in this research field. Subsequently, this chapter explores the different functioning criteria of the main responsive technologies currently available. Each functioning criterion is described in a dedicated subchapter where the most promising and representative responsive technologies are described—in a specific section—from a technological point of view.
The purpose of this study is to highlight how panoramic windows can significantly enhance energy efficiency in interior spaces. The aim is to identify and discuss the main benefits and disadvantages of these windows, as well as their classification according to the destination of the respective space. Methodology: the study was based on extensive bibliographic research, analyzing various sources such as books, articles and specialized publications in the field of architecture and energy efficiency. The author evaluated and interpreted the data and results obtained, organizing them logically to provide a coherent presentation of the topic. Results. The effective utilization of panoramic windows offers numerous benefits for enhancing energy efficiency indoors, including improved thermal insulation, optimized utilization of natural light, efficient control of solar radiation, and promotion of natural ventilation. Despite associated drawbacks such as thermal losses and maintenance costs, proper classification and climate adaptation can maximize energy efficiency and indoor comfort in buildings. Scientific novelty. The study explores the energy efficiency of buildings through the optimization of panoramic windows across various climatic and cultural contexts, employing advanced technologies in thermal insulation and solar control. Results, derived from exhaustive research and empirical data, underscore the advantages of these windows in enhancing the energy efficiency of buildings. Practical significance. The study highlights the multiple practical advantages of panoramic windows, such as improving thermal insulation and solar control, leading to energy savings and increased indoor comfort. The efficient use of energy through these windows not only reduces CO2 emissions but also protects the environment, promoting responsible resource consumption and contributing to societal progress through ecological innovations.
A good daylighting strategy is necessary in order to decrease energy consumption for artificial lighting. To provide effective internal illumination, the placing of the right openings in the right positions with suitable type of window and glazing is important. This study focused on the various types and materials of the glass and window, in order to identify the quantity and quality of daylight that penetrates into the residential buildings. Based on a series of measurement, it was identified that type of glazing and window gives major significance on the performance of daylight and thermal performance in residential buildings. Keywords windows; illumination level; residential building; occupant’s perception. eISSN ISSN 2514-751X © 2018. The Authors. Published for AMER ABRA cE-Bs by e-International Publishing House, Ltd., UK. This is an open-access article under the CC BY-NC-ND license (http://creativecommons.org/licenses/by-nc-nd/4.0/). Peer–review under responsibility of AMER (Association of Malaysian Environment-Behaviour Researchers), ABRA (Association of Behavioural Researchers on Asians) and cE-Bs (Centre for Environment-Behaviour Studies), Faculty of Architecture, Planning & Surveying, Universiti Teknologi MARA, Malaysia.
A 20-month field study was conducted to measure the energy performance of south-facing large-area tungsten-oxide absorptive electrochromic (EC) windows with a broad switching range in a private office setting. The EC windows were controlled by a variety of means to bring in daylight while minimizing window glare. For some cases, a venetian blind was coupled with the EC window to block direct sun. Some tests also involved dividing the EC window wall into zones where the upper EC zone was controlled to admit daylight while the lower zone was controlled to prevent glare yet permit view. If visual comfort requirements are addressed by EC control and venetian blinds, a two-zone EC window configuration provided average daily lighting energy savings of 10% ±15% compared to the reference case with fully lowered venetian blinds. Cooling load reductions were 0% ± 3%. If the reference case assumes no daylighting controls, lighting energy savings would be 44% ± 11%. Peak demand reductions due to window cooling load, given a critical demand-response mode, were 19%-26% maximum on clear sunny days. Peak demand reductions in lighting energy use were 0% or 72%-100% compared to reference cases with and without daylighting controls, respectively. Lighting energy use was found to be very sensitive to how glare and sun are controlled. Additional research should be conducted to fine-tune EC control for visual comfort based on solar conditions so as to increase lighting energy savings.
In this paper, three kinds of PV glazing system applied to office building of Shanghai which located in hot summer and cold winter zone of China were studied. Building simulation software Energy Plus was used to simulate thermal load, lighting electricity consumption, and PV electricity generation. According to the simulation results of annual electricity consumption, taking SC as the comparison basis, the saving rate of single PV glazing system (SPV) was 3.6%, double PV glazing system (DPV) was 4.8%, and natural-ventilated PV glazing system (NVPV) was 6.7%.
Cutting edge, world leading, research is carried out in a wide range of subjects including medicine,nano technology, synchrotron radiation, geo sciences and environmental sciences.
The next generation of advanced fenestration products includes dynamic electrochromic (EC) windows which can modulate the solar energy entering a building by application of an applied voltage. The windows can be switched from 62% visible transmittance (Tvis), 0.47 solar heat gain coefficient (SHGC) to a fully tinted state with ⩽2% Tvis, 0.09 SHGC. EC windows save energy in buildings – the total energy use for an eight story ASHRAE 90.1 2007 commercial office building with EC windows was modeled using the eQuest building simulation program and compared with the energy use of the same building with a variety of static glazings. The simulations were carried out in three US climate zones, encompassing a broad range of environmental exposure conditions from hot and dry (Arizona) to very cold (Minnesota). For all climate zones, building energy savings with EC glass were ⩾45% when compared to single pane static glazings common in existing building stock. When EC glass was compared to ASHRAE 90.1 2007 code compliant glazings, energy savings greater than 20% were calculated for the same building configuration. Optimum EC window control and performance strategies were derived from the modeling results. The EC glass and dimmable electric lights were synergistically controlled to maximize the use of natural daylighting and minimize electricity for lighting. Since EC glass can tint to ⩽2%, shades and/or blinds are not required for glare reduction, and building occupants always have a comfortable working environment and an unobstructed view and connection to the outdoors. All static glazing systems were assumed to have manual shading devices that are pulled by building occupants when glare becomes uncomfortable. For integrated building control systems, the peak load is significantly reduced when dynamic glazings are part of the building envelope. Consequently, chiller costs are lower, and the upfront capital costs for new building construction are reduced. Another key benefit of EC glass, elucidated by the simulations is reduction of CO2 emissions. EC glass reduces peak load carbon emissions by as much as 35% in new construction and 50% in renovation projects.
The adoption of Phase Change Materials (PCMs) in glazing systems was proposed to increase the heat capacity of the fenestration, being some PCMs partially transparent to visible radiation.The aim of the PCM glazing concept was to let (part) of the visible spectrum of the solar radiation enter the indoor environment, providing daylighting, while absorbing (the largest part of) the infrared radiation.In this paper, the influence of the PCM glazing configuration is investigated by means of numerical simulations carried out with a validated numerical model. Various triple glazing configurations, where one of the two cavities is filled with a PCM, are simulated, and PCM melting temperatures are investigated. The investigation is carried out in a humid subtropical climate (Cfa according to Köppen climate classifi-cation), and “typical days” for each season are used.The results show that the position of the PCM layer (inside the outer or the inner cavity) has a relevant influence on the thermo-physical behaviour of the PCM glazing system. PCM glazing systems (especially those with the PCM layer inside the outermost cavity) can be beneficial in terms of thermal comfort. The assessment of the energy performance and efficiency is instead more complex and sometimes controversial. All the configurations are able to reduce the solar gain during the daytime, but sometimes the behaviour of the PCM glazing is less efficient than the reference one.
The indoor thermal quality is one of the main study topics in the sustainable building field. The HCRI-BIPV smart window was developed to be used in the indoor environmental control on building living quality. This paper describes the 0.75 kWp capacity of grid-connected system by photovoltaic energy, which was controlled by indoor thermal environment. The monitoring research scale is the office time, whose data is recorded between 08:00 am to 17:00 pm. When the indoor temperature was arrived 26 °C or higher, the windows would be opened to cool down by the fresh air, which made the indoor temperature less than 10 °C and more. The accumulative power performance of the smart window system has 130.01 wKh of the in six months research. For consideration of each evaluated factors, the HCRI-BIPV smart window not only offer the passive energy situation for its power loading but also improve the indoor thermal environment by natural ventilation. The research presented an intensely interesting data for Taiwan BIPV smart window development between the BIPV application and building energy design.
Fenestration is the most significant envelope design determinant of energy use in nonresidential buildings. This paper presents our assessment of energy use effects of low-emissivity (low-E) versus conventional glazings for a range of window-to-wall ratios in a daylighted office building, in representative hot and cold climates. Low-E glazings transmit ''cooler'' daylight than their conventional counterparts because, for a given visible transmittance, they reflect a much larger fraction of incident solar infrared radiation. We thus use the ratio of visible transmittance to shading coefficient, which we define as K/sub e/, to compare the effect of representative glazing characteristics on component and total-building energy use, peak electrical demand, and required cooling equipment sizes. It is concluded that insulated glazings with low-E coatings can provide lighting and cooling energy savings in both hot and cold climates. The most dramatic lighting, cooling, and total electricity energy savings are achieved for increases of K/sub e/ within the range of 0.5 to 1.0; higher K/sub e/s provide diminishing savings. The increased R-value of low-E insulated glass units provides significant benefits in cold climates and is not a liability in hot climates. Low-E glazings also help increase the mean radiant temperature of interior environments in winter and reduce it in summer, and provide greater architectural design freedom without adverse energy consequences. Further, the higher first costs of these glazings may be more than offset by savings from smaller cooling equipment, energy and peak-demand cost savings, long-term financial gains from better rentals, and increased productivity due to improved occupant comfort.
Window design, especially glazing choices, is a critical factor for determining the effectiveness of passive solar design. Windows are like a knife has two side; one is useful and the other is harmful. In this paper the effects of windows’U-value, window orientation and windows size on annual heating and cooling energy demand is studied considering the both energy and investment costs. The study has been performed for three different climate zones; Amman, Aqaba and Berlin. Four types of windows have been studied; single glazed, double glazed L, double glazed H and triple glazed.The results show that heating load is highly sensitive to windows size and type as compared with cooling load. Also, it is shown that with a well-optimized glazed window energy saving can be reached up to 21%, 20% and 24% for Amman, Aqaba and Berlin, respectively.
Adoption of daylight as an energy efficiency strategy is especially relevant for a climate like Malaysia, as the country experiences long sunshine hours throughout the year. An important aspect of effective daylight strategy is the performance of the window in permitting daylight entry. This paper presents a study conducted to account daylight availability in an office interior under various fenestration options; namely window-wall-ratio (WWR), glass types and application of external shading devices of varying depth. The study used IES RADIANCE software and the Daylight Factor method to analyse its outcome. Daylight Factor (DF) was used as the basis to estimate the percentage of daylit floor area of a generic 4.5m deep office cell. The optimum WWR to achieve the maximum percentage of daylit floor area for a 4.5m deep room are 40%, 55% and 65% for clear, tinted and reflective glass, respectively. The results from the daylight availability study also shows that application of simple horizontal shades does not significantly affect the amount of daylight indoor. In fact, application of external shades improves the daylight distribution whereby the illuminance intensity in areas closer to the windows were reduced, providing a gentle daylit indoor.
Energy efficiency has become increasingly important to the community, regulatory bodies and industry in
recent years. Dominant per capita energy consumption is associated with home used energy resources
which also contribute to greenhouse gases. The main objective of this work is to evaluate the direct
impacts of variations of multi-glazed windows on the sustainability through BIM software and
determining the rate of energy consumption and carbon foot print in accordance with the implemented
changes in a building. The altered parameters in this study are number of glazed layers, filled gases, sizes
and orientations of the windows. The case study is a 56.25 m2 hut which is built in one level and located
in Kuala Lumpur. The simulation is carried out by using ArchiCad 14 software which is one of the
pioneers in BIM and its new sustainability plug-in integrated into this software known as Grafosoft
EcoDesigner. It is concluded that the type of gas used in double and triple glazed windows and increasing
the size of windows to 41% of an area of the window to floor surface ratio do not differ significantly from
34% of area of window to floor surface ratio with regard to the energy consumption and carbon footprint
in tropical areas.
Using a three-dimensional finite volume model, the thermal performance of an electrochromic vacuum glazing was sim-ulated for insolation intensities between 0 and 1200 W m À2 . The electrochromic evacuated glazing simulated consisted of three glass panes 0.5 m by 0.5 m with a 0.12 mm wide evacuated space between two 4 mm thick panes supported by 0.32 mm diameter pillars spaced on a 25 mm square grid contiguously sealed by a 6 mm wide metal edge seal. The third glass pane on which the electrochromic layer was deposited was assumed to be sealed to the evacuated glass unit. The simulations indicate that when facing the indoor environment, the temperature of the glass pane with the electrochromic layer can reach 129.5 °C for an incident insolation of 600 W m À2 . At such temperatures unacceptable occupant comfort would ensue and the durability of the electrochromic glazing would be compromised. The glass pane with the electrochromic layer must therefore face the outdoor environment.
A number of significant changes have occurred in Advances in Solar Energy since Volume 1 appeared in 1982. The delays in publication of the second volume are the result of reorganization of the American Solar Energy Society, and the negotiation of a new publishing arrangement. Beginning with this volume, Advances is now published jointly by the Society and Plenum Press. The Editorial Board has been enlarged to be more representative of the different fields of solar energy conversion. Production of Advances is being expedited through the use of modern word processing equipment and the 'lEX typesetting-editing program. We have gone to a single-column format to ease the problems of presenting long equations, and we expect that the user of the volume will find it easy to read. The use of 'lEX will make last minute updates possible. The external appearance of the volume matches that of Volume 1. We expect that future volumes of this annual will be proceeding on schedule. We invite comments from users and correspondence from prospective authors of critical reviews. Karl W. Boer John A. Duffie CONTENTS CHAPTER 1 The Measurement of Solar Radiation Ronald Stewart, Daniel W. Spencer and Richard Perez 1.1 Abstract 1 1.2 Characteristics of Pyranometers ....................................... . 2 1.3 General Features of a Pyranometer ................................... . 3 1.3.1 Instrument Sensitivity 4 1.3.2 Response with Time 4 1.3.3 Sensitivity 4 1.3.4 Responsivity ................................................. .
The purpose of this paper was to report the effects of window views and indoor plants on human psychophysiological response in workplace environments. The effects of window views and indoor plants were recorded by measuring participant's electromyography (EMG), electroencephalography (EEG), blood volume pulse (BVP), and state-anxiety. Photo Impact 5.0 was used to simulate the environment in an office, where six conditions were examined: 1) window with a view of a city, 2) window with a view of a city and indoor plants, 3) window with a view of nature, 4) window with a view of nature and indoor plants, 5) office without a window view, and 6) office without a window view and indoor plants. Participants were less nervous or anxious when watching a view of nature and/or when indoor plants were present. When neither the window view nor the indoor plants were shown, participants suffered the highest degree of tension and anxiety.
This research aims to develop a methodology for the evaluation of the potential energy saving and energy generation of semi-transparent PV windows in Brazilian office buildings. The evaluation is based on computer simulations: a daylighting simulation for the investigation of the available annual daylight with different window systems using Daysim/Radiance program and the simulation of the energetic performance using the program EnergyPlus. The simulations were accomplished for two cities in two different climatic zones of Brazil and compared to a German city. The results show that it is possible to reduce the energy consumption for artificial lighting and air-conditioning using appropriate control systems and furthermore to generate energy using semi-transparent photovoltaic panels in windows. Though only one building geometry was analyzed the results suggest that the potential of this technology is high in Brazil.
This paper develops an overall methodology for investigating the thermal and power behaviors of semi-transparent single-glazed photovoltaic window for office buildings in Hong Kong. In order to estimate its overall energy performance, this study is conducted in terms of total heat gain, output power and daylight illuminance. Three simulation models are established, including one-dimensional transient heat transfer model, power generation model and indoor daylight illuminance model. A typical office room reference is chosen as case study, and the weather data from 2003 to 2007 from the Hong Kong Observatory are used as the simulation inputs. By incorporating the simulation results, the overall energy performance can be evaluated in terms of electricity benefits corresponding to five orientations of the studied typical office. The priority of office orientation considering overall energy performance is: south-east, south, east, south-west and west. The findings show that thermal performance is the primary consideration of energy saving in the entire system whereas electricity consumption of artificial lighting is the secondary one. The overall annual electricity benefits are about 900 kWh and 1300 kWh for water-cooled and air-cooled air-conditioning systems respectively. The application of semi-transparent PV glazed window can not only produce clean energy, but also reduce building energy use by reducing the cooling load and electrical lighting requirements, which definitely benefits our environmental and economic aspects.
The design and fabrication of a highly insulating window glazing is being studied at SERI. Computer aided design analyses indicate that an all glass, edge sealed vacuum window with spherical glass interpane spacers and a low emittance, coating,on one internal surface could exhibit a thermal conductance of less than 0.6 W/m2K (thermal resistance, R > 10°F ft h/Btu). Cost effective means of mass-producing such a glazing have been explored. A CO2 laser has been used to produce a continuous, leak tight welded glass perimeter at 580°C, and this process appears to be a promising approach. However, at this temperature in vacuum, few low-emissivity coatings retain their desirable properties. Systemmatic measurements were made on tin oxide (fluorine doped) and indium-tin oxide low-e coatings. The indium-tin oxide was shown to be improved by vacuum heating. The ratio of solar weighted transmittance to emittance (313 K black-body weighted), a measure of performance in this application, is shown to have a sharply defined maximum at a coating sheet resistance of approximately 5 ohms per square in both of these oxide semiconductor coatings.
Daylighting controls have the potential to reduce the substantial amount of electricity consumed for lighting in commercial buildings. Material science research is now pursuing the development of a dynamic prismatic optical element (dPOE) window coating that can continuously readjust incoming light to maximize the performance and energy savings available from daylighting controls. This study estimates the technical potential for energy savings available from vertical daylighting strategies and explores additional savings that may be available if current dPOE research culminates in a successful market-ready product. Radiance daylight simulations are conducted with a multi-shape prismatic window coating. Simulated lighting energy savings are then applied to perimeter floorspace estimates generated from U.S. commercial building stock data. Results indicate that fully functional dPOE coatings, when paired with conventional vertical daylight strategies, have the potential to reduce energy use associated with U.S. commercial electric lighting demand by as much as 930TBtu. This reduction in electric lighting demand represents an approximately 85% increase in the energy savings estimated from implementing conventional vertical daylight strategies alone. Results presented in this study provide insight into energy and cost performance targets for dPOE coatings, which can help accelerate the development process and establish a successful new daylighting technology. Published by Elsevier B.V.
In this paper, building simulation software Energy Plus was used to simulate thermal performance, and PV electricity generation of five kinds of glazing system install on the office building in four cities of China, Harbin, Beijing, Shanghai, and Shenzhen, which represent severe cold zone, cold zone, hot summer and cold winter zone, hot summer and warm winter zone respectively. According to the simulation results, the best glazing system for the severe cold zone Harbin and the cold zone Beijing is double PV system, while natural ventilated PV system for the hot summer and cold winter zone Shanghai, the hot summer and warm winter zone Shenzhen. The energy saving rates of the optimal PV glazing system compared to the local SC at Harbin, Beijing, Shanghai, and Shenzhen are 12.3%, 4.9%, 4.8%, 10% respectively.
Fenestration of today is continuously being developed into the fenestration of tomorrow, hence offering a steadily increase of daylight and solar energy utilization and control, and at the same time providing a necessary climate screen with a satisfactory thermal comfort. Within this work a state-of-the-art market review of the best performing fenestration products has been carried out, along with an overview of possible future research opportunities for the fenestration industry. The focus of the market review was low thermal transmittance (U-value). The lowest centre-of-glass Ug-values found was 0.28 and 0.30 W/m2 K, which was from a suspended coating glazing product and an aerogel glazing product, respectively. However, the majority of high performance products found were triple glazed. The lowest frame U-value was 0.61 W/m2 K. Vacuum glazing, smart windows, solar cell glazing, window frames, self-cleaning glazing, low-emissivity coatings and spacers were also reviewed, thus also representing possibilities for controlling and harvesting the solar radiation energy. Currently, vacuum glazing, new spacer materials and solutions, electrochromic windows and aerogel glazing seem to have the largest potential for improving the thermal performance and daylight and solar properties in fenestration products. Aerogel glazing has the lowest potential U-values, ∼0.1 W/m2 K, but requires further work to improve the visible transmittance. Electrochromic vaccum glazing and evacuated aerogel glazing are two vacuum-related solutions, which have a large potential. There may also be opportunities for completely new material innovations, which could revolutionize the fenestration industry.
A simulation study was conducted to evaluate lighting energy savings of split-pane electrochromic (EC) windows controlled to satisfy key visual comfort parameters. Using the Radiance lighting simulation software, interior illuminance and luminance levels were computed for a south-facing private office illuminated by a window split into two independently-controlled EC panes. The transmittance of these was optimized hourly for a work plane illuminance target while meeting visual comfort constraints, using a least-squares algorithm with linear inequality constraints. Blinds were successively deployed until visual comfort criteria were satisfied. The energy performance of electrochromics proved to be highly dependent on how blinds were controlled. With hourly blind position adjustments, electrochromics showed significantly higher (62% and 53%, respectively without and with overhang) lighting energy consumption than clear glass. With a control algorithm designed to better approximate realistic manual control by an occupant, electrochromics achieved significant savings (48% and 37%, respectively without and with overhang). In all cases, energy consumption decreased when the workplace illuminance target was increased. In addition, the fraction of time during which the occupant had an unobstructed view of the outside was significantly greater with electrochromics: 10 months out of the year vs. a handful of days for the reference case.
The adoption of phase change materials (PCMs) in glazing can represent a way of improving the low thermal inertia of transparent envelope components. PCM allows the internal surface temperatures of the glazing to be controlled, and this could improve the energy efficiency and thermal comfort performance of a façade.In the present work, a prototype of a simple PCM glazing system is proposed and its behaviour is compared with that of a conventional reference double glazed unit. The surface temperatures and the transmitted irradiances of the PCM glazing prototype and of a reference fenestration, measured over a six-month experimental campaign, have been used to numerically evaluate the indoor thermal conditions inside a typical office room. Different boundary conditions, ranging from summer to winter season, including the mid-season, have been analysed.The results concerning thermal comfort are illustrated and discussed in this work and the glazing prototype, the experimental set-up and the measurement methods are presented. The obtained results demonstrate the promising performance of the PCM glaizing system, which is able to contribute to the attainment of a better indoor thermal environment.
The adoption of Phase Change Materials (PCMs) in building components is an up-to-date topic and a relevant number of research activities on this issue is currently on the way. A particular application of PCMs in the building envelope focuses on the integration of such a kind of material into transparent envelope components. A numerical model that describes the thermo-physical behaviour of a PCM layer in combination with other transparent materials (i.e. glass panes) is developed to perform numerical analyses on various PCM glazing systems configurations. The paper illustrates the structure of the model, the main equations implemented and the hypotheses adopted for the model development. The comparison between numerical simulations and experimental data of a simple PCM glazing configuration is also presented to show the potentials and the limitations of the numerical model. While a good agreement between simulations and experimental data can be shown for the surface temperature of the glazing, the comparison between simulated and measured transmitted irradiances and heat fluxes does not always reach the desired accuracy. However, the numerical tool seems to predict well the thermo-physical behaviour of the system and may therefore represent a good starting point for simulations on different configurations of PCM glazing systems.
With building heating and cooling accounting for nearly 14% of the national energy consumption, emerging technologies that improve building envelope performance have significant potential to reduce building energy consumption. Actual savings from these technologies will depend heavily upon their performance in diverse climate and operational conditions. In many cases, early-stage research can benefit from detailed investigation in order to develop performance thresholds and identify target markets. One example, a dynamic, highly transparent, near-infrared switching electrochromic (NEC) window glazing, is the focus of this investigation. Like conventional electrochromics, the NEC glazing can dynamically tune its optical properties with a small applied voltage. Consequently, the glazing can block or transmit solar heat to reduce cooling or heating loads, respectively. Unlike conventional electrochromics, NEC glazings remain transparent to visible light, causing no adverse effect to daylighting or building aesthetics. This study utilizes the software COMFEN to simulate a broad range of NEC performance levels, for commercial and residential buildings in 16 climate-representative reference cities. These simulations are the basis for identifying performance levels necessary to compete with existing static technologies. These results indicate that energy savings are strongly influenced by blocking-state performance. Additionally, residential applications have lower performance requirements due to their characteristic internal heat gains. Finally, the most dynamic NEC performance level is simulated in competition with high performing static alternatives. Here heating and cooling energy savings range from 5 to 11 kWh/m2 yr for commercial and 8–15 kWh/m2 yr for residential, in many regions on the order of 10%.
This paper presents the results of a study investigating the energy performance of evacuated glazings or glazings which maintain a vacuum between two panes of glass. Their performance is determined by comparing results to prototype highly insulated superwindows as well as a more conventional insulating glass unit with a low-E coating and argon gas fill. The authors used the DOE-2.1E energy analysis simulation program to analyze the annual and hourly heating energy use due to the windows of a prototypical single-story house located in Madison, Wisconsin. Cooling energy performance was also investigated. The results show that for highly insulating windows, the solar heat gain coefficient is as important as the window`s U-factor in determining heating performance for window orientations facing west-south-east. For other orientations in which there is not much direct solar radiation, the window`s U-factor primarily governs performance. The vacuum glazings had lower heating requirements than the superwindows for most window orientations. The conventional low-E window outperformed the superwindows for southwest-south-southeast orientations. These performance differences are directly related to the solar heat gain coefficients of the various windows analyzed. The cooling performance of the windows was inversely related to the heating performance. The lower solar heat gain coefficients of the superwindows resulted in the best cooling performance. However, the authors were able to mitigate the cooling differences of the windows by using an interior shading device that reduced the amount of solar gain at appropriate times.
Improving the energy performance of building envelope is a key to promote building energy efficiency. As a part of building envelope, Windows are recognized as the weakness of building envelope in reducing building energy consumption and thus should be as more energy efficient as possible. Currently available window products, such as double-glazed windows and tinted double-glazed windows, have their limits in balancing the performance of indoor thermal environment, energy and daylight. However, thermotropic materials, which change their light transmission behavior reversibly, have a great potential in achieving an excellent comprehensive performance. Therefore, this paper carried out energy, daylight and indoor thermal environment simulations to investigate the performance of a developed novel kind of thermotropic material for energy-efficient windows using the building simulation software DeST. Results show that thermotropic double-glazed windows can reduce 70% and 53% of highly uncomfortable indoor thermal environmental conditions in west-facing room, respectively, compared with double-glazed windows and tinted double-glazed windows. Moreover, they can reduce 19% of cooling electricity requirements in west-facing rooms compared with double-glazed windows, and provide an appropriate indoor illumination condition.
This paper reports on experimental investigation of performance of a new type of PV-slat window (PV-SW). The main functions of this PV-SW are as follows: to admit sufficient daylight, to act as a shading device for decreasing direct heat gain through window glazing and to ensure indoor air movement, which improves resident's thermal comfort. To assess the performance of this PV-SW, two test rooms of 1×1×1.5m3 (H:W:L) volume were built using plywood and gypsum boards. At the first, the PV-SW of 0.5×0.6m2 surface area was located at the south-facing wall whereas the other room was equipped with a commercial transparent slat window of the same size.The PV-SW consists of six PV slats. The photovoltaic cells were connected in series giving a maximum electrical power output of 36W (12V×3A). The circuit was connected to a direct current axial fan, located inside the room, that requires a maximum power of 43W. The analysis of performance of this PV-SW was investigated based on power output, daylight factor and temperature difference between indoor and ambient.The experimental results showed that this multi-purpose PV-SW is extremely interesting as it can produce power up to 15W, decrease indoor temperature and provide sufficient light for housing. The maximum indoor illumination was about 750lx with slats angle of 68°. The room temperature was about 2–3oC lower than that of room equipped with transparent slats.
An electrochromic (EC) vacuum glazing (VG) is formed when a vacuum glazing is combined with an electrochromic glazing. Three glass panes are required, two of which may have a low-emittance coating separated by a pillar array, the space formed being evacuated and sealed contiguously by a metal edge seal, the third glass pane with an EC layer is sealed to the evacuated glass unit. With the EC glazing installed with the electrochromic component facing the outdoor environment, for an incident solar radiation of 300 W m−2, when the EC layer is opaque for winter conditions, the inside glass pane of the unit due to solar radiation absorbed by the low-emittance coatings within the vacuum gap and electrochromic layer is a heat source with heat transferred from the glazing to the interior environment.
This paper describes the results of experimental tests and computer simulation modelling aimed at evaluating the performance of an electrochromic (EC) window with respect to solar control in buildings. The research is carried out by a test-cell equipped with a small area EC double glazing unit (EC-DGU) where one pane consists of an EC device and the other of a clear glass. The performance of the device on global light transmittance control, internal temperature control and solar heat gain control, is investigated in summer-time under real sky conditions as a function of time, test-cell orientation and switching strategies (static and dynamic). Both experiments and numerical analysis show that the decrease of the heat load affecting the test-cell, normalized respect to a clear float glass, is maximum when the EC-DGU is set to its lowest transmitting state and amounts to about 50% for west orientation and about 60% for south orientation. In this latter, thermal load reduction registered when the EC DGU is driven in the dynamic mode (31%) is similar to that of a reflective low-e glazing.
The effectiveness of an autonomous responsive dimming (thermotropic) glass panel fabricated with a transparent heating layer and an electrochromic layer to provide additional active dimming control is examined through preliminary experiments and simulations. Thermotropic glass consists of two panes of glass sandwiching a polymer gel that undergoes a transition from clear to cloudy at a threshold temperature. Winter temperatures can thus prevent the glass from dimming when required for solar shading. With appropriate control of the heating layer, however, the performance of the panel with respect to office solar-shading requirements is demonstrated to be superior to that without the heating layer, despite the simplicity of the system. The configuration requires relatively low electric power, utilizing solar radiation energy to maintain the cloudy state as required. In a different approach, application of electrochromic layer for active dimming control is proposed and verified in various aspects with wavelength characteristics considering simulation.
The influence of windows on the energy balance of apartment buildings in Amman is investigated by using self developed simulation software (SDS) based on the ASHRAE tables for solar heat gain calculation and coaling load factor for latitude 32°, where Amman city is located. The calculations of energy saving are made to find out the influence of windows on the energy balance of apartment buildings in Amman. Also, the present investigation aimed to study the energy performance of windows of an apartment building in Amman in order to select the most energy efficient windows that can save more energy and reduce heating load in winter, the percentage of saving energy and saving fuel and money through time.Variations of type of glazing using eight types of glazing (clear glass, types A, B, C, D, E, F, and G) are made to find out the most appropriate type of glazing in each direction. Also the orientation of window is changeable in the main four directions (N, S, E and W). The area of glazing varies also in different orientation to find the influence of window area on the thermal balance of the building. The results show that if energy efficient windows are used, the flexibility of choosing the glazed area and orientation increases.It has been found that choosing a larger area facing south, east and west can save more energy and decrease heating costs in winter using certain types of glazing such as glass type A and clear glass, while decreasing the glazing area facing north can save money and energy. However, it has been found that the energy can be saved in the north direction if glass type B has been used. In the apartment building, it is found that certain combination of glazing is energy efficient than others. This combination consists of using large area of glass type A in the east, west and south direction, and glass type B in the north direction or reducing glazing area as possible in the north direction.
Given the importance of buildings on the energy balance in Greece, an attempt has been made to study their energy behaviour and thermal comfort. Our primary purpose is to provide an estimation of the building’s energy consumption and examine how this affects the comfort conditions. This includes the definition of thermal conditions acceptable for various activities at different times of day during each month of the year. We cannot underestimate the value of real measurements and observations of the building’s energy systems, but such data are not always available. The best opportunities for improving energy performance occur early in the design process. Our simulation results can give an indication on which end uses are the most energy consuming, the “weaknesses” of a building and thus urge the owner or engineer to take effective conservation energy measures.
This paper presents a different approach for thermal effective windows, i.e. windows that reduce the energy transmitted into or out of a room. The idea is to use a double sealed glass filled with a phase change medium (PCM) whose fusion temperature is determined by solar–thermal calculations. The PCM used is polypropylene glycol. The investigation includes modelling of the heat and radiation transfer through a composite window and optical investigation of conventional and PCM filled windows, testing of the window and comparison with numerical simulations. A one-dimensional model for the composite glass window is developed to predict the thermal performance as a function of the geometrical parameters of the panel and the PCM used. Optical measurements were realized using photo-spectrometry to determine the transmittance, reflectance and absorptance. The specimens used include single glass of different thicknesses, double glass of different gap spacing and thicknesses filled with air or PCM, and finally coloured PCM. The results indicate big reductions in the energy transmitted, specially in the infra-red and ultraviolet regions, while maintaining a good visibility. © 1997 by John Wiley & Sons, Ltd.
Until the 1970s, the thermal performance of windows and other fenestration technologies was rarely of interest to manufacturers, designers, and scientists. Since then, however, a significant research and industry effort has focused on better understanding window thermal and optical behavior, how windows influence building energy patterns, and on the development of advanced products. This chapter explains how fenestration technologies can make a positive impact on building energy flows, what physical phenomena govern window heat and light transfer, what new products have been developed, and what new products are currently the subject of international research efforts. 44 refs., 30 figs., 3 tabs.
A building-integrated multifunctional PV/T solar window has been developed and evaluated. It is constructed of PV cells laminated on solar absorbers placed in a window behind the glazing. To reduce the cost of the solar electricity, tiltable reflectors have been introduced in the construction to focus radiation onto the solar cells. The reflectors render the possibility of controlling the amount of radiation transmitted into the building. The insulated reflectors also reduce the thermal losses through the window. A model for simulation of the electric and hot water production was developed. The model can perform yearly energy simulations where different features such as shading of the cells or effects of the glazing can be included or excluded. The simulation can be run with the reflectors in an active, up right, position or in a passive, horizontal, position. The simulation program was calibrated against measurements on a prototype solar window placed in Lund in the south of Sweden and against a solar window built into a single family house, Solgaarden, in Aelvkarleoe in the central part of Sweden. The results from the simulation shows that the solar window annually produces about 35% more electric energy per unit cell area compared to a vertical flat PV module. (author)
This paper reports on the thermal and optical characterisation of PCM (phase change material) RT27 using the T-history method and spectrophotometry principles, respectively, and the experimental and numerical performance evaluation of a PCM-glazed unit. Various relationships describing the variations in the extinction, scattering and absorption coefficients within the phase change region were developed, and were validated in a numerical CFD model. The results show that: (i) during rapid phase changes, the transmittance spectra from the PCM are unstable, while under stable conditions visible transmittance values of 90% and 40% are obtained for the liquid and phases, respectively; (ii) the radiation scattering effects are dominant in the solid phase of the PCM, while radiation absorption dominates in the liquid phase; (iii) the optical/radiation performance of PCM can be successfully modelled using the liquid fraction term as the main variable; (iv) the addition of PCM improves the thermal mass of the unit during phase change, but risks of overheating may be a significant factor after the PCM has melted; (v) although the day-lighting aspects of PCM-glazed units are favourable, the change in appearance as the PCM changes phase may be a limiting factor in PCM-glazed units.
Innovative glazing systems with silica aerogel in interspace were investigated for energy saving in buildings.
Aerogel is a promising transparent insulating material, due to its low thermal conductivity (down to
0.010Wm�1 K�1), high solar factor, high daylight transmittance and remarkable lightweight. Four samples
were constructed with float and low-e glasses and granular or monolithic aerogel in interspace
(14 mm thickness). The main optical characteristics of the samples were measured, in order to estimate
the light transmittance sv, the solar factor g and the colour rendering index Ra, in compliance with EN
410/2011. Finally, the thermal transmittance was calculated. The monolithic aerogel glazings showed
the best performance with respect to granular systems, both for light transmittance (0.62 between
two 4 mm float glasses) and thermal insulation (0.6Wm�2 K�1). The solar factor was 0.74. Results
showed a very promising behaviour of aerogel windows when compared to the windows normally used
in Italy and in EU countries: monolithic aerogel between two 4 mm float glasses gave a 62% reduction in
heat losses, with a 17% reduction in light transmittance when compared to a double glazing with a low-e
layer; a high solar factor and colour rendering were also assured.
Windows have been found to be a particularly salient feature of the workplace, not only as a matter of preference but also for health and well-being. Depending on what is in the view, looking out of the window may provide numerous opportunities for restoration. This study investigated the effect of window views on job satisfaction and stress. The impact of two specific influencing mechanisms was examined: existence of forest views through windows in workplaces, and absence of forest views through windows in workplaces. The sample consisted of 931 office workers in Seoul, South Korea, 481 who could see forest views from their workplaces and 450 who could not see forest views. A set of self-administered questionnaires including job satisfaction and job stress measures was distributed to the sample from April to September 2004. The results showed a significant direct effect of forest views from windows on job satisfaction and stress. Respondents' personal information such as gender, age and job category did not influence on the window view effects. As expected, employees' job satisfaction and job stress were highly and negatively correlated.
A method is described for measuring the radiative and gas conductance of vacuum glazing while at room or elevated temperatures. Such measurements are used to determine the residual gas pressure, permitting studies to be made of the accelerated degradation of vacuum glazing. The heat flows associated with this method have been analysed using a detailed finite element model and the technique has been calibrated against both high accuracy measurements on a guarded hot plate apparatus, and calculations of the thermal conductance due to radiative heat transfer. The technique is reasonably accurate—total uncertainties are less than about ± 5 % and measurements are reproducible to about ± 2%, for temperatures over the range 20–200°C.
From the thermal point of view, windows represent the weak link between the internal and external ambients of a room. In cold climates, they are responsible for 10–25% of the heat lost from the heated ambient to the external atmosphere. In hot climates, the excessive solar radiation entering the internal ambient through the windows leads to increasing the cooling load of the refrigeration system. The use of absorbing gases filling the gap between glass sheets appears to be an alternative solution for thermally insulated glass windows. The other options one may incorporate filling materials such as silica aerogel or a PCM. In this work, a comparison between the thermal efficiency of two glass windows one filled with an absorbing gas and the other with a PCM and exposed to solar radiation in a hot climate is done. To model double glass window filled with infrared absorbing gases, a CW real gas model is used. A radiative convective conductive model and a radiative conductive model were investigated. Three mixtures of gases were used; a strongly absorbing gas mixture, an intermediate absorbing gas mixture and a transparent to infrared radiation mixture. To model the double glass window filled with a PCM, a relatively simple and effective radiation conduction one dimensional formulation is used. Heat transfer through the window is calculated and the total heat gain coefficients are compared and discussed.
The glazing unit for solar control, daylighting and energy conservation is a system consisting of two prismatic panes. The prismatic ribs of the panes are inclined by a certain angle to the horizontal within the window plane, exhibit identical cross-sections in the shape of a rightangle-triangle with a certain basic prism angle, are facing each other and are positioned such that just a small gap remains between the two panes. The lower rib faces of the outer prismatic pane are coated with a specularly reflecting layer and the upper rib faces of the inner prismatic pane are coated with a diffusely reflecting layer. The prismatic glazing unit can be used for common window tilt angles and for window directions with significant solar irradiation at sites with a temperate climate. It does not reduce the view to the outside appreciably and achieves — in comparison to other window panes — relatively uniform illumination of a room with daylight. During the summer and the transitional seasons it provides improved protection against solar irradiation and distinctly reduced irradiated heat fluxes. The reflecting surfaces of the prismatic ribs do not create glare.
The purpose of this study is to outline the theme of saving energy resources and its relationship with the preservation of the environment, as well as the importance of green marketing in achieving sustainability. The model of data collection was a survey conducted by self-administered questionnaire. After collection, the data were statistically analysed and interpreted. Most individuals claim to be concerned about environmental problems, with 68% of these belonging to the 'Savers' group. However, even though they may be concerned with environmental problems, the vast majority of individuals do not have any system of renewable energy in their homes, despite claiming that renewable energies are a viable option for protecting the environment. Women display behaviour that is more favourable to the saving of energy resources than do men. Educational levels are not significant for distinguishing the more pro-environmental individuals from the others.
A survey on prototype and currently commercial dynamic tintable smart windows has been carried out. The technologies of electrochromic, gasochromic, liquid crystal and electrophoretic or suspended-particle devices were examined and compared for dynamic daylight and solar energy control in buildings. Presently, state-of-the art commercial electrochromic windows seem most promising to reduce cooling loads, heating loads and lighting energy in buildings, where they have been found most reliable and able to modulate the transmittance up to 68% of the total solar spectrum. Their efficiency has already been proven in hot Californian climates, but more research is necessary to validate the products for colder climates, and to improve furthermore the commercial products in order to control the indoor climate in a more energy efficient way by reducing both heating and cooling loads.
The rapidly growing world energy use has already raised concerns over supply difficulties, exhaustion of energy resources and heavy environmental impacts (ozone layer depletion, global warming, climate change, etc.). The global contribution from buildings towards energy consumption, both residential and commercial, has steadily increased reaching figures between 20% and 40% in developed countries, and has exceeded the other major sectors: industrial and transportation. Growth in population, increasing demand for building services and comfort levels, together with the rise in time spent inside buildings, assure the upward trend in energy demand will continue in the future. For this reason, energy efficiency in buildings is today a prime objective for energy policy at regional, national and international levels. Among building services, the growth in HVAC systems energy use is particularly significant (50% of building consumption and 20% of total consumption in the USA). This paper analyses available information concerning energy consumption in buildings, and particularly related to HVAC systems. Many questions arise: Is the necessary information available? Which are the main building types? What end uses should be considered in the breakdown? Comparisons between different countries are presented specially for commercial buildings. The case of offices is analysed in deeper detail.
PV ventilated glazing technology for application in warm climate provides energy saving opportunities through the reduction in air-conditioning load, the daylight utilization, and the green electric power generation. In a working environment, the use of semi-transparent a-Si glazing is deemed better than the one with non-transparent c-Si solar cells. This paper reports an evaluation of its integrated performance using a small office room in Hong Kong as an example. An energy model of a PV ventilated window system is first introduced. Based on this together with the TMY weather data of Hong Kong and the daylight simulation capability of the EnergyPlus program, the overall performance analysis have been executed for different window orientations. It was found that a solar cell transmittance in the range of 0.45–0.55 could achieve the best electricity saving.