Fenestration System Research Articles

CFD Simulation of Heat Transfer Through a Window Frame

The use of various coatings with a low level of radiation on the glass elements of window structures, filling the interglacial space in double-glazed windows with inert gases instead of air, increasing the number of cameras in double-glazed windows, other constructive measures aimed at improving the thermal insulation properties of double-glazed windows, led to a significant increase in the thermal resistance of the fenestration system. However, little has changed in the design and construction of window frames and edge areas adjacent to building facades, leaving these elements responsible for heat transfer through modern windows. In this article, with the help of three-dimensional CFD modeling, the thermal insulation properties of window frames are investigated in the most complete setting, taking into account the effect on heat transfer through the profile of the window frame of the adjacent walls of the building facade on one side and the double-glazed unit on the other. Finding out the thermal insulation parameters of the window frame will help to make appropriate changes in its design.

Optimum fenestration characteristics in mediterranean Tunisian context: An energetic, economic and environmental (EEE) study

This paper aims to investigate the energy performance of several techniques integrated into the fenestration system of an office building. The first step was to compare the simulated and real energy consumption of a case study of an office building located in Tunis City. In a second step, the study explores the impact of a glazing retrofit solutions on annual energy saving. To determine the possible energy savings for the existing office building in various climatic zones, we performed several simulations, using the Design Builder software.For these zones, the optimum window-to-wall-ratio (WWR), ensuring a compromise between daylighting and energy consumption, is found to be 40%. Then, for the chosen WWR, we evaluated a retrofit process involving existing commercial technologies such as double-glazed insulated windows, as well as innovative technologies consisting of intelligent coating, in addition to passive techniques including several shading concepts.It is found that, the double-glazed window with outside reveal depth of 20 cm equipped with both low-emissivity (LoE) and electrochromic (EC) coatings ensures the lowest annual energy consumption. Besides, energy savings depends on the climate zone; it reaches 23% in hot climates (ZT3) and almost 20% in cold (ZT1) and temperate climates (ZT2). The possibility of using electrochromic coating was excluded following the economic study because of its exorbitant cost. In fact, this type of renovation can lead to payback periods of up to 74 years for the cases treated.The optimized window designs consist in using a double-glazing window with a LoE coating, an outside reveal depth of 20 cm, and as a shading system (Overhang). These designs save 8 to 20% of energy and reduce CO2 emissions by 6 to 10 kg CO2/m2 per year, with a payback period of less than 6 years depending on the climatic zone.

Experimental and numerical study of an energy-efficient building fenestration system with seasonal adaptability

Previous building-integrated solar thermal fenestrations were limited to the single function, either air heating or water heating. Thus, they failed to meet the seasonal thermal needs of buildings. To address this limitation, this paper proposed a novel building fenestration-integrated solar collector. This system is designed to harness solar irradiation on the fenestrations for air heating in winter and recover irradiation for water heating in summer, effectively addressing seasonal thermal demands and improving annual solar utilization efficiency. Firstly, the prototype of the proposed system was fabricated, and its thermal performance was tested. The experimental results indicated the thermal efficiency of 40∼50% for air heating and 39% for water heating. Subsequently, a mathematical model of the proposed system was developed and experimentally validated. Based on the validated model, a comparative performance analysis was conducted between the proposed system and double clear glazing. Additionally, the energy-saving potential and economic viability of the proposed system were predicted. Compared to double clear glazing, the proposed system exhibited a higher solar heat gain coefficient (SHGC) in air heating mode, lower SHGC in water heating mode, and lower U value at night. The prediction outcomes underscored the substantial energy-saving advantages conferred by the proposed system across diverse building types. The projected payback periods in subtropical and tropical regions were estimated to be around 2–4 years.

RESEARCH ON WINDOW TREATMENTS THAT MAKE PRIVACY AND VIEW COMPATIBLE

In this study, we investigated a fenestration system that divides the roller blinds into multiple layers, closes partially to ensure privacy, and opens the other areas to achieve both view, daylighting and solar heat gain. In the experiment in the controlled space, subjects evaluated “visibility from inside”, “estimated visibility from outside” and “openness”, and in addition to that, subjects also evaluated “view”, “brightness” and “total satisfaction” in the experiment in the actual environment. As a result, we confirmed the visual satisfaction improved by this system.

Solar Angle Model for Daylight Redirection in Prismatic Panel

An advanced complex fenestration system can utilize uniform daylight. Nonetheless, an inefficient design would increase solar heat gain and indoor temperatures, besides uneven light distribution that would cause the "cave effect." Prismatic panels are widely used as complex fenestration systems, providing uniform daylight. This paper proposes a computational model that integrates optical principles like Snell's law with environmental variables and visualizes the performance of prismatic panels in terms of redirection angle while encountering the prism refractive index and geometry at the specified geographic location. The proposed model entails a prismatic panel as a daylight system for redirecting daylight. In contrast to detailed modeling needed for simulation in software programs like Radiance, this computational tool provides a more straightforward and efficient solution for the initial design of light redirection panels that rely on the principle of refraction and evaluate their annual performance based on the angle of deviation. The model's applicability has been demonstrated by utilizing various triangular prism design examples with diverse materials in Frankfurt and Helsinki.

Analysis of dynamic louver control with prism redirecting fenestrations for office daylighting optimization

Daylighting with redirecting complex fenestration system (CFS) may improve the indoor luminous environment. This study is to explore the strategies for controlling louver tilts of dynamic micro-prism film louvers corresponding to different solar incident angles, to optimize the work-plane illuminance (WPI) at the middle/back zone of the analyzed large-depth office, based on the simulation results of daylight filtering. To reduce the rotation frequency of the slats, several slat tilt angles were tested to adapt to the changes of different sun incident angles. The study compared the annual daylight performance and glare levels of the three CFSs with dynamic metal louvers, dynamic micro-prism film louvers, and micro-prism film, using the Five-phase method (5-PM). The results showed that the dynamic micro-prism film louvers combined with the proposed control strategy provided a better daylighting luminous environment, regarding the improved useful daylight illuminance (UDI) at inner space, and yielded less glare occurrence rates at space close to windows, compared with dynamic metal louvers and double glazing. Furthermore, the study proposed the combined dynamic louvers that consisted of micro-prism film slats and metal slats to reduce the possible glare on the premise and improve the indoor illuminance at the inner space. The simulation results showed that the combined dynamic louvers could reduce the discomfort glare occurrence rate by 68.9%, compared to the discomfort rate with double glazing at the front zone; UDI300-2000 lx of the combined louvers could be improved by 23%, compared with that of double glazing at the front zone. Compared with the metal louvers with similar low glare occurrence rate, the combined louvers could improve UDI100-300 lx at front/middle/back zones by 7.9%, 29.1%, and 2.9%, respectively, and UDI300-2000 lx by 40.0%, 11.7%, and 5.7% at these zones, respectively.

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

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

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

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

A study of Indoor Environment of Large Glazed Office Building in Semi Arid Climate

In recent years the rate of buildings with large glazed facades is rapidly increasing, particularly in office buildings. Where, the creation of a suitable thermal and visual comfort is a significant factor affecting productivity. The use of large glazed facades without adapted shading measure generates thermal and visual discomfort, wich ranges from uncomfortable environment conditions to serious health effects. Specialized work and literature about performance evaluation of large glazed office buildings in relation to their environment are lacking in semi arid climates, characterized by significant intensity of solar radiations in the summer period of the year. This study investigates the impact of large glazing areas on thermal and visual comfort in a sample of naturally ventilated office building located in the semi arid climate of Algeria (36°, 17 N and 7°, 23’ E). A Post Occupancy Evaluation technique (POE), being a mainstream activity in the process of building operation phase is used for this purpose. The main objective is to stress practitioners, specifically architects, to take conscious decisions in an early phase of design process. The study clearly highlighted discomfort in the studied office building. It included unacceptable temperature arising from glazed facade; overheating due to excessive solar gains; insufficient ventilation and poor daylighting. The results indicate that such large fenestration system is not recommended in summer time. However, a judicious choice of the glazing size and type by simulation tools must balance lighting and thermal needs.

A critical review of fenestration/window system design methods for high performance buildings

Fenestrations allow for natural daylight and outdoor views, but also represent the least thermally efficient portion of the building envelope, and thus can be a source of unwanted direct sunlight and associated discomfort glare. A well-designed fenestration system operated with proper control strategies is capable of reducing building energy usage significantly while maintaining a both thermally and visually comfortable environment for occupants. This paper reviews and analyzes window design studies for high-performance buildings, which could be interpreted as decision-making processes to achieve the window performance goals by controlling a series of design variables (e.g., location and dimensions of windows, glazing type, etc.). An overview of available design options for window systems to date is introduced first, and then the decision-making methodologies of window systems are categorized and analyzed to present a comprehensive review, where we present a detailed analysis of sequential knowledge-based design methods and simulation-based optimization methods. Last, potential challenges and future research trends are identified and analyzed to help promote all automatic simulation-based optimization design methods for high performance fenestration systems.

Transition Planes for Visual Comfort: Out View with Complex Fenestration System Design at Restaurants in Spain

This work deals with daylighting for quality indoor atmospheres, considering building skins. In recent years, almost all retrofit facades of restaurants are highly glazed façades, boosting glare, sun ray absorption and overheating inside. Most of the time, they are not integrated with daylight control; therefore, lighting and out view requirements are not so balanced. Taking into account this daylighting complexity, an alternative façade system is proposed to simulate by Radiance. Previously, perception simulations are compared with measured data, in order to discretize the simulations. In addition, for one point three different view are assessed as: work plane, relation plane and the out plane. Subsequently, two virtual façade models, windows combined by complex fenestration system (CFS) as prismatic film (PF) and highly glazed façade, are tested according to daylighting. For that, three indexes have been used: daylight glare probability (DGP), daylight glare index (DGI) and daylight autonomy (DA). The results show that the proposed complex façade has a good light contribution with less absorption, while maintaining the outside view. In addition, the DGI is needed to test the out plane, because DGP is more suitable for lower luminance; therefore, each visual plane should be assessed regarding different visual comfort conditions, or parameters and methods. Accordingly, the mean DGI result of window combined by CFS is approximately lower in 5% than highly glazed façade. However, the DA of highly glazed is higher in 5%, but the DA of window combined by CFS is enough, above 80%. Definitely, the complex scene at restaurant with the proposed integrated façade system improves light performance and indoor atmosphere.

Evaluation for the safety and effectiveness of the in situ fenestration system in TEVAR for aortic arch pathologies: protocol for a prospective, multicentre and single-arm study

IntroductionThoracic endovascular aortic repair (TEVAR) has gradually become the mainstream therapy for aortic arch pathologies (AAP). Our centre developed the in situ fenestration (ISF) system according to years of clinical...

Experimental demonstration and performance evaluation of a complex fenestration system for daylighting and thermal harvesting

Two significant design strategies for mitigating building energy consumption are daylight redirection and solar energy harvesting. Effective daylighting implementation enhances the amount of useful natural light within a space and offsets the need for electric lighting. Solar energy harvesting systems can mitigate energy costs from mechanical systems by managing incoming thermal loads or capturing solar energy that can be used to supplement thermal systems in the building. While there are many available façade-based technologies that can perform daylighting or solar thermal energy harvesting, there remains a limitation in available systems that can perform both of them simultaneously. This paper, describes the design and experimental demonstration of a Liquid Filled Prismatic Louver (LFPL) system, which combines both energy-saving strategies. The LFPL system was installed in a south-facing room in New York City and evaluated for indoor daylight penetration and potential for thermal energy harvesting. Daylight redirection is achieved through the prismatic louver geometry and proper orientation, whereas thermal energy harvesting is achieved through IR absorption from the liquid (e.g., water) within the prisms. Daylighting performance was evaluated by illuminance measurements at key locations within the space, whereas thermal harvesting performance was evaluated through temperature measurements and thermal imaging analysis. We show that the LFPL system, with all prismatic elements oriented at the same angle, achieve a 2-fold and 8-fold enhancement in daylight redirection to the ceiling, for prism orientations of 10° and 20°, respectively. We also demonstrate the system’s capability to adjust to specific lighting needs, within the space, through the dynamic individual orientation of prismatic elements; thus, achieving a concentrated ceiling illuminance enhancement of ~100 times and ~200 times at 2.5 and 4.3 m away from the window sill, providing workplane illuminance enhancement of 6 and 2 times more than in the case of the control room with regular windows. Furthermore, we show a reduction of potential heating loads at locations close to the window from the combination of infrared absorption in the water volume and the redirection of the incoming solar radiation, leading to a reduction of the workplane temperature by an average of 7–10 °C.

Photon mapping in image-based visual comfort assessments with BSDF models of high resolution

Data-driven models replicate the irregular Bidirectional Scattering Distribution Functions (BSDFs) of optically Complex Fenestration Systems in daylight simulation. RADIANCE employs the tensor tree to store the BSDF at high directional resolution. Its application in backward ray-tracing is however challenging, since the density of stochastic samples must match the model resolution. BSDF proxy and peak extraction address this problem, but are limited to cases when either the fenestration geometry, or the shape and direction of the transmission peak are known. Photon Mapping is proposed to efficiently sample arbitrary BSDFs from the known sun direction. The existing implementation in RADIANCE is extended to account for light sources and their reflections in the field of view, that are of particular importance for visual comfort assessments. The method achieves a high degree of accordance with ray-tracing, and reduces simulation times by ≈95% with data-driven models of high resolution.Abbreviations: BRT: Backward Ray-Tracing; BSDF: Bidirectional Scattering Distribution Function; CBDM: Climate-Based Daylight Modelling; CFS: Complex Fenestration System; DGI: Daylight Glare Index; DGP: Daylight Glare Probability; FPM: Five Phase Method; GPGPU: General Purpose Graphics Processing Unit; LCP: Laser Cut Panel; OoC: Out-of-Core; PM: Photon Mapping; RMSE: Root Mean Squared Error

Performance assessment of the BTDF data compression based on wavelet transforms in daylighting simulation

The bidirectional transmittance distribution function (BTDF), which is used to characterize the light transmission of a complex fenestration system (CFS), commonly involves bulky volume of data that can be a challenge to data storage and transmission in lighting simulation tools and on compact platforms. This paper introduces a compression scheme that is based on planar wavelet transforms with three levels of decomposition to efficiently compress the BTDF data of CFSs and maintain fidelity in daylighting simulation. The root-mean-square error (RMSE) and transmittance error (TE) of compressed medium-resolution BTDF data using three different wavelet bases were evaluated for five different CFS samples at various compression ratio. Based on the results, the generic error from compression did not exceed 20% with CDF9.7 basis for compression ratio up to 200. In the case of rendering an image of a scene in which a CFS was installed at the upper daylighting section of an unilateral façade, errors began to be noticeable at a compression ratio above 70. The uniformity factor g1 was discovered to be relatively sensitive to compression (below 15% error), while the average horizontal illuminance and daylight glare probability (below 10% error) were immune to compression ratio below 100. Compression was also evaluated for a high-resolution BTDF data of external Venetian blinds in the simulation of work-plane illuminance (WPI). With a HDR imaging technique based sky luminance map, the WPI simulation had unnoticeable errors for compressed BTDF data within a compression ratio of 100.

A method to evaluate glare risk from operable fenestration systems throughout a year

Nowadays buildings are being designed with large glazed areas mainly due to aesthetics considerations but also to achieve daylit spaces. However, large glazed facades are prone to cause glare problems for building users. To mitigate this risk, it is important to predict existing glare metrics dynamically and reliably in the early stages of the design of a facade. Current evaluation methods for dynamic glare are either computationally too expensive or not suitable for operable façade systems. In this study, a new method is proposed to calculate the Daylight Glare Probability (DGP) index in a computationally efficient fashion, while allowing the fenestration system to switch states during the annual simulation. The method is based on a matrix formalism to calculate the vertical illuminance at a view position, and also on the calculation of a luminance map of the field of view solely from the direct component of the light sources. A first validation of the proposed method is presented. An office setup in Freiburg is monitored with a luminance camera for different weather conditions and different façade systems. Additionally, the calculation of the DGP index by the proposed method is compared with the calculation of the DGP by backward raytracing with high rendering parameters. The proposed method has been implemented in a building simulation program, called Fener. A case study is presented to illustrate the new possibilities offered by the Fener tool. The glare risk of three different textile roller blinds, with similar visible transmittance but different openness coefficient, is assessed.

Fenestration refurbishment of an educational building: Experimental and numerical evaluation of daylight, thermal and building energy performance

Although strict building energy codes are implemented periodically in many countries, buildings continually consume a momentous quota of total primary energy. Potentially, new buildings can satisfy current building energy codes, while existing buildings require refurbishment. Recently, the fenestration system of a 4-story educational building located in Cheonan, Republic of Korea (36.815oN, 127.114oE) has been refurbished from single glazed double-sliding window system with aluminum (Al) frame to double low-e glazed double-sliding window system with polyvinyl chloride (PVC) frame. The main objective of this study was to investigate the performance of the window system prior to and after refurbishment, using experimental and numerical tools. In particular, daylight environment of a demarcated space within the reference building was examined. Thermal behavior of glazing systems and window frames was scrutinized using infra-red (IR) thermography. The dynamic behavior of window system in relation to building energy performance was evaluated through EnergyPlus. Reference data of the building and nominal operational schedules were used as inputs for the building model, while inputs for the window system were based on optical and structural parameters of its data sets. Owing to thermal inertia, temperature of the single glazing was on average 0.7–1.9 °C higher than the double glazing. Considering linear radiant heat loss through Al and PVC frames, the former showed an avearge temperature of 5 °C higher than the latter. Although electrical lighting energy consumption increased, the overall annual building energy consumption of the renovated building reduced by 51.1 GJ (i.e. 4.3%).

A workflow for retrofitting façade systems for daylight, comfortable and energy efficient buildings

The building façade not only provides the aesthetic signature of a building, but also important functions, such as daylight provision, glare protection, solar gain management and visual contact with the outside, which make the building usable and energy efficient. These functions often oppose each other, so the selection and design of façade systems and their control for a certain building application should depend on those functions that the designer wants to promote to the detriment of the other functions. In the context of the H2020 RenoZEB project, this paper presents a workflow for the conceptual planning of façade systems as applied to building retrofitting. The proposed workflow consists of analysing the space from the point of view of the functions of its façade. In a first step, the analysis of the case study leads to the definition of the design requirements, i.e. the relevance of the different façade functions and their priorities. The second step involves the selection of a suitable fenestration system and control strategy for the retrofit solution. In this step, an optimization process for the control strategy is proposed based on state-of-the-art thermal and daylighting simulations. In a third step, the annual performance of the retrofit solution is evaluated in order to check if the requirements are fulfilled. The proposed workflow is illustrated with a case study, in which the automation strategy of a retrofitted façade system is optimized for two different applications: a residential and an office building in Bilbao (Spain).

An approach to calculate the equivalent solar heat gain coefficient of glass windows with fixed and dynamic shading in tropical climates

In tropical climates, glass windows are important for a building's energy efficiency. By providing shading on a glass window, direct solar incident radiation can be restricted. This lowers the cooling energy consumption in buildings. The most commonly used method to provide shading is by using fixed shades such as overhangs and fins. Another method is to provide dynamic shades that can be controlled based on incident solar radiation on the façade. Shading is a method to control the solar heat gain coefficient (SHGC) and visible light transmission (VLT) of a vertical fenestration. This study is performed to obtain the equivalent SHGC of vertical fenestration with fixed and dynamic shading. Prescriptive requirements of energy codes, such as ASHRAE 90.1 and ECBC-India, limit the maximum SHGC value of fenestration. The effective SHGC with fixed shading is defined as the equivalent SHGC. The energy codes define tabular methods for the calculation of the equivalent SHGC that is generally given as a function of overhangs/fins depth, glass orientation, and latitude of the building. This tabular method generally does not cover all orientations, shading depths, and locations. Further, the equivalent SHGC for dynamic shade is either not defined in most of the codes or regarded as the minimum SHGC of the fenestration system. Herein, a simulation-based approach is proposed to calculate the equivalent SHGC for fixed and dynamic shades. A tool has been developed that uses EnergyPlus, the weather file of the building location, window and shading dimensions, and set point for dynamic shades, to perform parametric energy simulations to calculate the equivalent SHGC.

Convection at the indoor side of complex fenestration systems: the ASHWAT model revisited

This paper examines the three-temperature problem of convection at the indoor side of a complex fenestration system (CFS) based on recent theoretical developments, namely the extended Newton formulation and the dQdT technique. CFD solutions were obtained for natural convection at the indoor side of various CFS configurations. The dQdT technique was then implemented numerically to obtain the paired heat transfer coefficients of each configuration. The results were used to assess the approximate relations used in the ASHRAE Window ATachment (ASHWAT) tool. The comparison shows that while there is remarkable agreement between the ASHWAT estimates and dQdT results for roller blinds, discrepancies exist between results for venetian blinds. Furthermore, although use of a delta resistor network to model convection at the indoor side is valid and relatively accurate for roller blinds, the application of this model to CFSs with venetian blinds requires additional levels of approximation. Nevertheless, the heat transfer rates calculated based on the approximate resistor-network model are in close agreement with the CFD results.