Clear Glass Window Research Articles

Laboratory and field validation of the performance benefits and costs of thin triple-pane windows in residential buildings

The adoption of high-performance triple-pane windows that significantly reduce heat transfer has been slow, in part because they are thicker, heavier, and more costly than double-pane windows. One path to increase adoption of triple-pane windows is to replace the conventional double-glazing insulated glass unit (IGU) with a modified triple-glazing design that uses a very thin central pane of glass. This thinner triple-pane IGU can then be “dropped in” to the double-pane IGU pocket without requiring major modifications to frame design. The Department of Energy sponsored laboratory and field testing of thin triple-pane windows by Pacific Northwest National Laboratory. This article presents findings from both the Lab Homes study and subsequent field demonstrations carried out over a 3-year period (2020–2023). The laboratory and field studies demonstrated the manufacturing and distribution feasibility of thin triple-pane windows, successfully installed at multiple sites, using double-pane frames from four different manufacturers and thin triple-pane IGUs from two different manufacturers. Compared to a home with double-pane, clear-glass windows, testing demonstrated average whole-home heating energy savings of 12% and cooling energy savings of 27% for thin triple-pane windows. Improvements in comfort, sound insulation, and condensation potential were noted in both laboratory and field studies.

A sustainable utilization approach of waste biomass resources to smart materials for buildings

Resource utilization of solid waste promotes resource conservation, energy transformation and sustainable development. In this study, we developed a synthetic strategy for converting biomass waste, such as waste bamboo powder, into a smart material with thermochromic properties - hydroxypropyl cellulose (HPC). The synthesis process includes extraction of cellulose and modification with hydroxypropyl groups. The maximum extraction efficiency of cellulose from raw bamboo powder was up to 48 % by carefully adjusting the reaction conditions including NaOH concentration, reaction time, and treatment temperature. The maximum yield of modification process was achieved to 1.32 g/g by optimizing alkalization temperature, alkalization time, NaOH concentration, propylene oxide concentration, etherification temperature and etherification time. The samples were characterized by a variety of techniques such as FTIR, 1H NMR, XRD, SEM to validate the micro-structure of the extracted cellulose the HPC materials. Moreover, this study explored the potential application of HPC hydrogel in smart window application, and evaluated its building energy saving efficiency under different climate conditions through computational simulation. The corresponding results showed that the HPC hydrogel smart window could have significant energy saving potential compared to ordinary clear glass window. This novel approach of converting waste resources into high valued thermochromic materials for smart windows, not only reduces waste disposal demand for excessive land-use and energy consumption but also shows a positively contributes to sustainable development, environmental protection, as well as energy conservation.

Passive Window Energy Performance in Buildings: Modeling of Apartment Buildings in Indonesia

Along with urban growth in urban areas and energy consumption, which continues to increase every year, the selection of windows in the initial design is essential to obtain buildings that are not energy intensive. Selecting the correct window in the blueprint design reduces building energy consumption. Smart windows, especially thermochromic windows, are one of the most promising window technologies because they are the most economical and have passive control with zero energy input, which holds good promise for energy-saving applications. Apart from that, double-glazing windows are also frequently used in energy-saving applications. Therefore, a study compared the energy-saving potential of thermochromic and double-glazing windows to clear glass windows, using computer modeling through EnergyPlus, in high-rise apartment buildings in cities throughout Indonesia's diverse climates. From the modeling results, total energy consumption can be reduced by around 8.91% to 10.96% of total building energy consumption by replacing the conventional clear glass with double-glazing windows or more able to reduce about 20.22% to 24.19% by replacing the conventional clear glass with thermochromic windows. Furthermore, this potential varies depending on geometric shapes, materials, building facades, local climate, and building orientation. Nevertheless, considering the potential benefits, these windows are highly suitable for application in buildings seeking to reduce their energy consumption and improve energy efficiency.

The space of the glazed window in nineteenth-century London

ABSTRACT During the nineteenth century, the widespread adoption of clear-glass windows facilitated the development of a new space of urban experience. The area immediately adjacent to the inside or outside of the glass window became an important venue in which the daily life of the city unfolded. Before the advent of industrially produced glass, urban shops and dwellings were either open or closed to the outside. The integration of glazed windows into the structures of nineteenth-century cities, however, created a new hybrid space of urban experience, allowing persons to be part of the outside life of the city, whilst simultaneously remaining physically separated from it.

Modeling, Simulation, and Performance Analysis of a Liquid-Infill Tunable Window

Solar shading is important in buildings for better indoor thermal/light environment and energy conservation, especially in the tropical region. Compared with conventional windows with additional fixed shading devices, windows with adaptive self-shading functions take up less space and require less management labor. The present investigation focuses on a compact liquid-infill tunable window, which can provide adaptive shading with colored liquid-infill according to the surrounding environment. The numerical model of the liquid-infill tunable window was established on the basis of the law of energy and mass conservation, which enabled prediction of the adaptive response of the window under different boundary conditions. Then the thermal performance of this innovative window was analyzed in comparison with triple-layered clear glass windows. Influences of solar radiation level, incident angle, and ambient temperature were taken into consideration. The window was proven to be efficient in reducing indoor heat gain in the cooling season under strong solar radiation. With an 60° incident angle, the total indoor heat gain through window can be reduced by 1.60–8.33%. In the future, the established numerical model may be inserted into existing building simulation software as an energy-efficient window module to evaluate its energy and economic performance. The present study may inspire architectures and engineers in the design of near-zero energy and/or carbon neutral buildings.

Study on indoor adaptive thermal comfort evaluation method for buildings integrated with semi-transparent photovoltaic window

Semi-Transparent Photovoltaic (STPV) windows have the potential of active energy-saving and have attracted more attention in recent years. Due to the selective absorption effect of solar cells on solar radiation, the indoor thermal environment and human thermal comfort of buildings integrated with STPV windows are considerably different from that with clear glass windows, and there are few studies on this. In this paper, the indoor human thermal comfort of buildings integrated with STPV window was investigated. Firstly, experiments and subjective questionnaires for the indoor environment were conducted in STPV and clear glass window buildings respectively. Secondly, the influence of illuminance on thermal sensation was statistically analyzed, with the consideration of visual effect, non-visual effect, as well as visual and non-visual coupling effect respectively. On this basis, an innovative thermal comfort evaluation method was provided. The thermo-physiological effect, light-physiological effect and light-psychological effect were comprehensively considered in this method. Finally, the reliability was verified by comparing with TSV. According to tests and questionnaires, it was found that the indoor thermal environment of the STPV window was an uneven thermal environment, and the subjective thermal sensation was more inclined to be slightly warm. When investigating the effect of illuminance on thermal sensation considering visual and non-visual coupling effect, it was found that illuminance had a significant influence on thermal sensation in different illuminance ranges. Meanwhile, it indicated the coupled effect of thermal environment and daylight environment on the thermal comfort of human.

Say Cheese! Snapshots of the Living Mouse Brain

The human brain is a highly complex system comprised of billions of cells, called neurons, that are all interconnected. Normal brain function depends on effective communication between neurons, which requires signals to travel down a nerve cell and then over to the next cell it is connected to. Several diseases result from impairments in the communication between neurons, which is why it is important to study these signals in the living brain. Since the living human brain is difficult to study, scientists use simpler organisms like mice. To see mouse neurons, a piece of skull is replaced with a clear glass window. Powerful microscopes can then be used to capture snapshots of neurons deep inside live brains! Clever use of lasers to excite chemical “tags” inside the neurons makes them glow with fluorescent light. Join us as we explore the inner workings of neuron communication in the living brain.

High-transparency Clear Glass Windows with Large PV Energy Outputs

Multiple modern glass and window products based on novel glazing designs, metal-dielectric coatings, and proprietary interlayer types have been developed recently. Advanced windows of today can control properties such as thermal emissivity, heat gain, colour, and transparency. In more recent and more novel glass products, solar energy harvesting through PV integration is also featured. Typically, semitransparent and also highly-transparent PV windows are purpose-designed, to include luminescent materials, special microstructures, and customized electric circuitry. Recently, significant progress has been demonstrated in building integrated highly-transparent solar windows (VLT up to 70%, with Pmax ~ 30-33 Wp/m2, eg Clearvue PV Solar Windows); these are expected to add momentum towards the development of smart cities. These Clearvue window systems are, at present in 2021, the only type of high-transparency and clear construction materials capable of providing significant energy savings in buildings, simultaneously with renewable energy generation. The technology has already been deployed and tested in both commercial property applications and in R&D greenhousing. Of special interest is the combination of properties provided by Clearvue solar window products, which includes significant power conversion efficiency (~3.3%), which is achieved in windows of colour rendering index of 99%, simultaneously featuring high PV Yield in multi-oriented building-integrated PV (BIPV) installations.

Impact of BIPV windows on building energy consumption in street canyons: Model development and validation

Photovoltaic components have been increasingly integrated into the façades of buildings as a means to enhance their energy efficiency in recent years, yet the impact of using building-integrated photovoltaic (BIPV) windows in street canyons has been rarely studied due to the lack of modelling tools. In this study, we developed a new parametrization scheme for BIPV windows, and incorporated it into building energy simulations coupled with a single-layer urban canopy model. Evaluation against in-situ measurements and EnergyPlus simulation suggests that the coupled model is able to reasonably capture the diurnal profiles of BIPV window temperature, building cooling load, and outdoor microclimate. A set of simulations were conducted to examine the impact of BIPV windows on summertime building energy consumption and outdoor air temperature in different street canyons. Compared to clear glass windows, BIPV windows can reduce canyon air temperature and building cooling load. Temperature reduction is found to increase with window coverage but does not change significantly with canyon geometry. Savings on cooling energy consumption vary between 9.16% and 63.71% for the studied neighbourhood in Phoenix, US, but tend to be higher for open street canyons with north–south orientation and large window-to-wall ratios. The coupled model takes into account the dynamic interactions between building energy consumption and the outdoor microclimate, thus providing insight into the benefit of using BIPV windows at the neighbourhood scale.

Improvement on Window Glassing for an Enhanced Indoor Thermal Environment of Tropical Office Buildings

The intense solar radiation absorbed through the window glassing and transmitted into the indoor environment constitute thermal discomfort and increased cooling energy demand for buildings in the tropical climatic zone. This is because tropical climates are generally characterised by hot thermal distress almost all the year round. The need for improvement on window glassing of office buildings arise as a result of the global consensus on reducing energy demand of building sector. In office buildings, higher level of thermal and visual comfort is required for productive work performance within the indoor environment. This place office buildings in a position to enhance the realisation of a sustainable environment in the tropical climatic zone. This paper focus on effect of two types of window glassing on indoor air temperature and achieving improvement on single pane ordinary clear glassing window through the use of low-solar gain low-emissivity windows of two existing office buildings in the warm-humid zone of the tropical climate of Nigeria. An experimental investigation was scheduled during rainy and dry seasons of the year to collect outdoor and indoor microclimatic data of air temperatures in the west-facing natural ventilated office spaces within the existing office buildings through the use of Tiny Tag Ultra 2 Dual Channel Temperature/Relative Humidity (TGU-4500) Data loggers. Data collected were sorted and analysed through descriptive statistics. Improvement on single glassing window of existing office building was obtained through calculation of heat gain characteristics and comparison with that of low-solar gain low-emissivity glass window heat gain characteristics. Results showed that single pane ordinary clear glassing window exhibits higher indoor temperatures in the monitored office space. 89.54% improvement was recorded by using low-solar gain low-emissivity glass window over single pane clear glass window in the investigated office buildings. The study therefore recommends the use of low-solar gain glass low-emissivity window in office buildings within the warm-humid zone of tropical climate of Nigeria.

Solar-assisted desiccant dehumidification system to improve performance of evaporatively cooled window in hot and -humid climates

This study examines the performance of an integrated evaporatively-cooled window (ECW) with a desiccant dehumidification system (DDS) combined with a photovoltaic/thermal (PV/t) system. The hybrid system (ECW-DDS) is applied on a glazed building surface to reduce its temperature and the associated space-cooling load. The system performance is studied during the summer months with hot and humid conditions in which the benefits of passive cooling systems are generally restricted. Mathematical models for each system component/process were integrated to predict the system effectiveness for a case study of a typical office space located in Jeddah, Kingdom of Saudi Arabia. The integrated system effectiveness was compared to two cases where the system was not installed for a clear double glass window and where only the ECW system is employed without the dehumidification of ambient air. The hybrid system (ECW-DDS) proved to reduce the inner window temperature by 5 °C, 7 °C, 4 °C, and 5 °C for June, July, August, and September, respectively resulting in an 11% decrease of the total cooling load over the summer months. In addition, the ECW-DDS system performed much better than the ECW system when humid conditions prevailed in September. For instance, the air leaving the evaporative cooler on a typical day of September recorded a temperature reduction of 14% in the case of the ECW-DDS system compared to 1% only in the case of the ECW system.

Study on the overall energy performance of a novel c-Si based semitransparent solar photovoltaic window

This paper introduces a novel c-Si based building integrated photovoltaic (BIPV) laminate. It was produced by cutting standard crystalline silicon solar cells into narrow strips and then automatically welding and connecting the strips into continuous strings for laminating between two layers of glass. The overall energy performance of the BIPV insulated glass unit (IGU) including power, thermal and daylighting performance was investigated experimentally. The daily energy conversion efficiency of the active solar cell area was about 15% on sunny days, but it was less than 12% on cloudy days and overcast days. Due to the combined effect of both the semi-transparent PV laminate and the insulated glass unit, the solar heat gain coefficient (SHGC) of the BIPV IGU was as low as 0.25, which was much lower than commonly used glazing windows. Daylight analysis by means of high dynamic range (HDR) cameras and daylight glare probability (DGP) indicated that the BIPV IGU could reduce discomfort glare to some extent compared to clear glass windows. The net energy production of the BIPV IGU was estimated without considering the differences in HVAC energy use in this study. The artificial lighting energy consumption was about 431 W h/day while the average BIPV electricity production for the same period was 1940 W h/day. The net power generation was therefore 1509 W h/day for this BIPV IGU in Berkeley, California. Shading tests for the BIPV IGU were also conducted and the results revealed that the vertical configuration of solar cell wiring in the BIPV laminates was much more sensitive to horizontal shading patterns than vertical shading models. Thus, if shading was unavoidable in some cases, a reasonable arrangement of PV strings should be considered to bring down the energy loss as much as possible. Also, the impacts of environmental factors on the energy conversion efficiency of BIPV IGU were analyzed. Specifically, the power output declined by 0.42% of the peak power for each Celsius degree temperature rise. Thus, if more attention was paid to the heat dissipation issue of BIPV IGU, the overall energy conversion efficiency would be improved.

Thermal and daylighting performance of glass window using a newly developed transparent heat insulated coating

Abstract In subtropical Hong Kong, solar heat gain through glass windows contributes to a significant proportion of building cooling load. Therefore, in cooling dominated areas, the principal of window design includes both utilizing natural daylight and eliminating solar heat gain. In this study, a new heat insulated coating combined antimony-doped tin oxide (ATO) and cesium tungsten bronze (Cs0.33WO3) was developed. Based on measured properties of different glass samples, thermal and daylighting performance of different glass windows, including a clear glass window, a double-layer glass window, a low-e glass window and a coated glass window, were evaluated based on numerical simulation. Results indicate that the developed heat insulated coating can effectively reduce the solar heat gain while maintain the indoor daylighting illuminance at a high level. Up to 9.5% of building energy use can be saved if the coating is applied to south facing clear glass windows.

Study of Various Glass Window and Building Wall Materials in Different Climatic Zones of India for Energy Efficient Building Construction

The commercial and residential buildings consume about 33% of energy for cooling and day lighting in India. This paper aims to present thermal performance of buildings constructed with various building and window glass materials in five different climatic zones of India. The climates considered include: hot and dry (Ahmedabad), moderate (Bangalore), cold (Guwahati), warm and humid (Madras), and composite (New Delhi). In this study, four building materials such as laterite stone, dense concrete, burnt brick, and mud brick were selected and four glasses such as clear, bronze, green, and bronze-reflective glasses were used for windows. Spectral characteristics of four glasses were measured experimentally by using Perkin-Elmer lambda 950spectrophotometer in the wavelength range of 300 -2500 nm as per ASTM standards. A mat lab code was developed to compute the solar optical properties such as transmittance and reflectance of glasses as per European standards in entire solar spectrum region. The building models were designed in Design builder 4.3.0.039 and thermal analysis was carried out in Energy plus 8.1.0.009. The solar heat gain in buildings was investigated. The results revealed that the mud brick wall building with south bronze-reflective glass window as energy saving from the least heat gain point of view among eighty building models studied. The results also showed that the mud brick wall building with bronze, green and bronze reflective window glasses reduces heat gain through wall by 2.52%, 3.83%, and 6.46% as compared to the mud brick wall building with clear glass window. The results helps in selecting energy saving combination of wall envelope and window glass materials for reducing air-conditioning loads in residential and commercial buildings of five different climatic zones of India.

Natural Ventilation Using Glazed Solar Chimney and Hot Water Collector Production

This paper presents a report on the development and experiment thermal performance of a multi-purpose glazed solar chimney and hot water collector production (GSC-HWC) under the tropical climate conditions in Thailand. The GSC-HWC configuration consists of double pane layers 0.60 m height and 0.50 m width. The external layer is a glazed solar hot water collector, with non-reflective painted black pipes 0.01 m diameter to produce approximately 10 liters of hot water. The internal layer was a clear glass pane with a thickness of 6 mm. The GSC-HWC has 0.08 m air gap with two openings 0.24 m x 0.12 m located at the bottom of interior glass pane and at the top of exterior glass pane. The openings exhaust hot air to the ambience and covered with anti-insect screens. The panes can be removed for easy maintenance. Comparing the experimental results between GSC-HWC and a single clear glass window (SG) of the same size (0.60m high, 0.50m width and 0.006m thick,) revealed that indoor temperature of the GSC-HWC room was significantly less than the SG room,. Furthermore, the finding indicated that the GSC-HWC can induce ventilation and reduce heat from sunlight whereas the daylight gain was nearly the same as single glass window room. The water temperature of GSC-HWC was relatively high and sufficient for domestic use. As a result, the GSC-HWC is expected to promote the growth of solar energy usage; save energy in heating, cooling and ultimately help the environment.

Improving energy and visual performance in offices using building integrated perovskite-based solar cells: A case study in Southern Italy

Building integration of innovative photovoltaic technologies, defined by high efficiency and optical properties allowing their use as a replacement of solar control films, offers new opportunities for energy saving. In order to estimate this potential under real world conditions, we have carried out simulations for this scenario based on an existing office building located in Bari (Italy). The building has a significant amount of transparent surfaces combined with transparent shades, while office layout corresponds to a typical Mediterranean configuration with several single/double offices (2.9m by 6.6m). We investigate the effect of the replacement of standard clear glass windows with new windows integrating perovskite-based semi-transparent photovoltaic modules, and the replacement of the original transparent shading system with high performance opaque perovskite-perovskite tandem cells. In particular, the attributes that were directly influenced by the proposed modifications were investigated in detail, including overall energy consumption for heating, air conditioning, and artificial lighting, evaluated against the overall energy yield given by building-integrated photovoltaic modules. Results showed that under ideal conditions (no obstructing buildings) yearly savings up to 18% could be obtained. In presence of nearby buildings savings dropped to 14%. Considering that fabrication costs for this technology are promisingly low and that this is currently the only neutral colored semi-transparent photovoltaic, the above results are promising, particularly for buildings with large window-to-wall ratios.

Experimental and Theoretical Studies of Window Glazing Materials of Green Energy Building in Indian Climatic Zones

Abstract Buildings consume plenty of power for providing thermal and visual comfort inside the buildings. This paper aims at presenting the experimental results of spectral optical properties of the most widely used window glazing materials. The window glazing materials studied include clear glazing, bronze glazing, green glazing and grey coloured glazing materials. A Matlab code employing the British standard method was developed to compute transmittance and reflectance of window glasses at normal incidence angle. This code uses experimentally obtained spectral optical property data from Perkin Elmer lambda 950 spectrophotometer for the computation of transmission and reflection of window glasses. A computer program was developed for computing the total solar radiation passing through glass materials. The heat gain through different glass windows of eight coordinal orientations such as east, west, north, south, northeast, northwest, southeast and southwest in four climatic zones of India was investigated. The solar radiation through south oriented glass was found to be the least among all other orientations studied in four Indian climatic zones. The cooling load through south oriented bronze, glass, green glass and grey glass window were reduced by 23%, 31% and 37%, respectively, as compared to the south oriented clear glass window in four climatic zones of India. The grey glass window is observed to be the most energy efficient as it reduces maximum cooling loads within the building as compared to the other considered glazing materials. The results of this paper are helpful in designing energy efficient commercial buildings for reduced cooling loads.

Assessment of energy performance of semi-transparent PV insulating glass units using a validated simulation model

This study evaluated the energy performance of an a-Si semi-transparent PV insulating glass unit (IGU) via numerical simulation and experimental tests. Combined with the measured optical and electrical characteristics of the PV laminate, an integrated model was developed to simulate the overall energy performance of the PV IGU in EnergyPlus. Outdoor experiments were conducted to validate the accuracy of the simulation model. The proper consistency between the simulation results and the experimental data indicated that the simulation model was reliable for predicting the overall energy performance of PV IGU. With the validated model, a sensitivity analysis was conducted to investigate the influences of air gap depth and rear side glass, and an optimal design scheme was proposed to maximize the energy efficiency of PV IGU in Hong Kong. Finally, the energy saving potential of the optimized PV IGU compared to the other commonly used window systems was evaluated. It was found that the energy saving potential of the optimized PV IGU was 25.3% and 10.7%, respectively, compared to the single clear glass window and the Low-E glass window. The methodology developed in this study is expected to provide a useful reference for simulating the energy performance of PV IGU.

Simulation of Various Wall and Window Glass Material for Energy Efficient Building Design

Buildings consume huge amount of energy for forced ventilation and artificial day lighting. Use of appropriate material combinations for walls and window glass can help in reducing energy consumption for cooling and lighting. This paper presents the thermal properties of four building materials such as, laterite stone, dense concrete, burnt brick and mud brick. It also presents the experimentally measured optical properties of glass materials such as, clear glass, bronze glass, green glass and reflective. In this study building of size 5m X 5m X 3.2m with four wall materials and four glass materials were designed using design builder software. The thickness of the wall was considered as external wall with thickness 0.22m. All the walls covered with cement plaster on either side. Roof of the building is made of reinforced cement concrete and floor is dense concrete. Thermal analysis was carried out using by Energy plus software. Single sized glass windows were placed in south direction (Due to less heat gain in south direction) for Mangalore city (12.870N, 74.880E), Karnataka, India. Different window to wall ratios (20%, 40%, 60%, 80% and 100%) were maintained for buildings. Total eighty building models were investigated for heat gain into buildings. From the results, it is observed that irrespective of the window to wall ratio, mud brick walls with reflective window glass were observed to be energy efficient from the lower heat gain point of view, and laterite stone wall building with clear glass windows were observed to be the worst due to their higher heat gain values. At 60% window to wall ratio mud brick walls with reflective window glass have 24.93kWh heat gain and dense concrete walls with clear glass have 32.9 kWh heat gain. The results of the study help in establishing the best combination of wall and glass materials for minimum heat gain into buildings.

Investigating Influence of Different Materials on Window Thermal Performance

This study is an experimental research study in order to find the effectiveness of the heat transfer and to compare the temperature behaviors of the windows with different layers made of various materials. The windows were divided into four types: 1) clear glass window with aluminum frames, 2) clear glass window with wooden frames, 3) wooden window, and 4) double layered window with a clear glass and aluminum sliding window (the inner layer) and a wooden louvered window (the outer layer). In this study, the heat transfer values of the materials were analyzed. The temperatures of the air and material surfaces were checked. The size of the created prototype was 1.00 x 0.50 meters installed in the test box that had foam insulation on its five sides. Data were recorded for 24 hours. The results show that the heat resistance of the wooden materials was approximately 1.4 times higher than the glass materials. The air temperatures inside all test boxes were higher than that of the surrounding air. The highest air temperatures inside the test boxes were 36.5 - 56.7 °C during 01.00 p.m. – 02.40 p.m. The lowest air temperature was 25 °C at 06.00 a.m. The clear glass window with aluminum frames had the highest temperature in the test box and the highest difference between the temperatures at day and night. The double layered window had the lowest difference. Finally, it can be concluded that the double layered window could effectively protect heat transferring into the buildings, reduce the cooling load, and facilitate energy conservation