Insulating Glass Units Research Articles

Lightweight insulating glass unit

Lightweight insulating glass unit

Thermal-deformation behaviors of the primary sealants in double, triple, and multi glazed insulating glass units

Polyisobutylene (PIB), commonly used as the primary sealant of double, triple, and multi glazed insulating glass units (IGUs), provides the key moisture barrier function and determines the expected lifespan of the IGUs and even the entire glass curtain wall systems (GCWSs). Slipping and debonding of the PIB, caused by temperature changes, have resulted in numerous instances of premature failure of building envelopes. However, available research is inadequate in accurately evaluating the service environment of IGUs and thermal-deformation behaviors of this energy-saving building material. This paper presented a simplified method for analyzing the thermal environment of IGUs, considering outdoor air temperature, solar radiation, wind speed, and angle to the horizontal. A numerical modeling method was proposed and validated with the heat transfer tests. Three finite element (FE) models were built and utilized for the precise analysis of temperature-induced deformations of double, tripled, and quadruple glazed IGUs. Simplified calculation formulas for the maximum thermal deformation of PIB in the X and Y directions under different temperature conditions were obtained, taking a new concept “cavity-to-pane ratio” into consideration. Finally, the relationship between the PIB’s temperature-induced deformation and its probability was proposed. The results show that the IGUs in Beijing suffer more than 22 % of their time in harsh service conditions where the difference between indoor and outdoor temperatures exceeds 20 °C. For DIGUs, the maximum temperature-induced deformations of the PIB in X (along the short side of the panel) and Y (along the long side of the panel) directions are 0.142 and 0.214 mm, respectively, corresponding to shear strains of 28.4 % and 42.8 % for the PIB with a thickness of only 0.5 mm. For TIGUs, the maximum deformations increase to 0.159 and 0.239 mm, corresponding to shear strains of 31.8 % and 47.8 %. For QIGUs and the other multi-glazed IGUs, these values can increase to 36.8 % and 55.4 % or more. The methodology proposed in this paper aims to lay the groundwork for further addressing premature failure issues and optimizing edge bond constructions of multi-glazed IGUs.

Towards maximum cost-effectiveness: multi-objective design optimisation of insulating glass flat-plate collectors

A significant challenge in the advancement of solar thermal heating systems lies in the unexplored techno-economic potential of insulating glass flat-plate collectors. These collectors are constructed in accordance with the specifications of standard insulating glass units and have emerged over the past decade as a promising design concept for enhancing the cost-effectiveness of solar thermal systems. However, substantial findings regarding the techno-economic viability of their production are still pending. The aim of this paper is to optimise insulating glass collector designs for solar district heating applications by identifying key design parameters that maximise cost-effectiveness. This study employed a five-stage methodology. It included thermo-hydraulic collector modelling using MATLAB/Simscape and the CARNOT Toolbox. The model was validated against experimental performance tests. A Latin hypercube computational design with 250,000 samples was set up to train supervised machine learning metamodels and perform a multi-objective optimisation using an elitist genetic algorithm. The study identified the argon concentration, collector length, and width as critical parameters influencing efficiency. Larger, thinner collectors demonstrated superior performance due to reduced convective losses and increased aperture-to-surface ratios. The optimisation revealed that the insulating glass collectors could achieve a 7.7 percentage point increase in efficiency, a 19.4 % reduction in material cost, and a 14.5 % decrease in weight compared to market-available flat-plate collectors. However, the direct economic comparison was not considered strong in evidence due to a lack of economic data from technology providers. The most cost-effective designs featured an argon concentration of 99 %, sealing thickness of 31.2 mm, and a glazing thickness of 4.1 mm, and 4.5 mm, while collector length and width varied more significantly. The research findings indicate the techno-economic potential of insulating glass collectors, demonstrating their ability to outperform conventional flat-plate collectors in terms of cost-effectiveness and efficiency. Future studies should focus on producing and testing larger modules and incorporating production costs to fully realise their potential for solar district heating applications. This study provides valuable guidelines for IGU designers and producers aiming to develop cost-effective and efficient solar thermal collectors for district heating systems.

Shock-tube tests on conventional windows: Exploring retrofit concepts for enhanced blast protection

Ensuring blast protection for existing buildings, especially addressing the vulnerability of conventional windows, is a significant challenge. Such unprotected windows can shatter even with moderate blast loads, posing a substantial risk of injury to occupants. This article discusses experimental research on enhancing the blast protection of single casement windows with insulating glass units and frames made of unplasticized polyvinyl chloride (uPVC). A retrofit concept using anti-shatter films, metallic sash reinforcements, adhesive bonding of the glazing to the sash frame, and a burglary resistance fitting-system was developed and tested in an explosion-driven shock-tube. Moreover, novel patches made of glass fiber-reinforced polymer applied to the corners of the window frames have been tested and proven effective in providing additional strength to the window. The study concludes that the tested combination of retrofit measures can significantly reduce hazards from window fragments without compromising functionality or aesthetics.

On the lightweight design of laminated insulating glass units in cruise ships

ABSTRACT Modern cruise ships employ many large windows to enable passengers to enjoy the marine environment. Most windows are insulating glass units (IGUs) consisting of laminated glass and a hermetically sealed cavity. These laminated IGUs exhibit three physical effects under bending: (1) geometric nonlinearity of the glass panes, (2) shear transfer in the laminated glass, and (3) load sharing due to the hermetically sealed cavity. The Authors have previously studied the (1) and (3) effects on the window mechanical behaviour and glass pane thickness determination. Hence, this paper investigates through optimisation how all these effects together lighten the IGUs, and how the shear transfer affects the IGU mechanical behaviour with the optimised thicknesses. All three combined effects have positive effects on the IGU weight. These results are more pronounced for large and thin IGUs subjected to high design loads. For example, the choice of interlayer material is less important (for optimum weight) for small windows subjected to a low design load. Since all the effects are important, using the finite element method is recommended to achieve a lightweight window design.

Reuse and remanufacturing of insulated glass units

AbstractMany office and residential buildings in Europe need to be renovated in the near future to meet current energy efficiency requirements. This often comes down to updating the insulation performance of the building envelope including the windows. Most “old” windows consist of a frame and a double insulated glass unit (IGU) or even monolithic glass panes – typically without any low-e coating. These non-coated double glazings have a Ug-value of 2.7 W/m2K (single glazing even 5.2 W/m2K). Modern coated triple glazed IGUs provide Ug-values of up to 0.5 W/m2K.This paper deals with the question of how old insulating glass units can be re manufactured to match the state of the art in terms of the energy efficiency. For this purpose, dismounted IGUs from the 1980s are used. After analyzing the remaining functionality, the double IGUs are disassembled. The single glass pane is cleaned, and the old edge sealing is removed. The old glass pane is combined with a new coated low-e glass and a spacer system to form a new upgraded IGU with warm edge technology. This study demonstrates that remanufactured IGUs can achieve the performance of IGUs made from new glass.

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.

Laminated insulated glass units under blast loads: Experimental and numerical study

Laminated insulating glass units (IGUs), commonly used in modern buildings, are prone to shattering from explosive loads, causing significant damage and loss. Existing research on IGUs is constrained by a lack of experimental validation and comprehensive numerical analyses, as large-scale explosion tests are rarely reported due to safety and cost concerns. Furthermore, previous modeling efforts often oversimplify critical factors such as the supporting structure, component interactions, strain rate effects, hourglass energy, and failure criteria, leading to an inadequate representation of glass behavior under explosive loads. This paper addresses these gaps by conducting large-scale explosive test on glass system and utilizing sophisticated nonlinear dynamic analysis with LS-DYNA for simulation. The research considers the influence of the support system and incorporates detailed considerations of component interactions, constitutive relationships, and strain rate effects in the numerical simulations. The results confirm that the proposed model successfully replicates the crack patterns and damage observed in experimental test. Also, it accurately predicts the trajectory, quantity, and size distribution of glass fragments. The proposed modeling approach offers a more informed assessment of damage and improves the evaluation of glass safety in practical applications.

Experimental validation of the Betti’s Analytical Method for Double Glass Units

The structural response of Insulating Glass Units (IGUs), formed of glass plates sealed by perimeter metal spacers entrapping a gas, is strongly influenced by the complex interaction between the glass plates and the gas, as well as by the structural coupling of the plates through the spacers. The former effect, called “load sharing”, depends on the flexural stiffness of the plates and the pressure variation of the compressible gas due to applied actions. The more accurate and direct model to evaluate the load sharing is the recently proposed Betti’s Analytical Method (BAM) (soon included in the new Eurocode on structural glass), which allows to evaluate the IGUs response under the most various support conditions and external loads. In this paper, the BAM model is revisited, and the result obtained by means of conjugate BAM-numerical analyses are carefully validated by means of comparison with the results of experimental tests. In particular, the results of an extensive experimental campaign, performed on Double GUs (DGUs) subjected to line-distributed and concentrated loads, both at the environmental and at high temperature, are presented. To properly account for the influence of geometric parameters on the DGU response, elements with various aspect ratio, glass thickness and cavity thickness have been considered.

Case Study on the Re-use Potential of Insulated Glass Units

Glass is an energy intensive material that is essential to buildings and their energy consumption. Its transparency allows for natural daylighting and the use of solar heat gains. In the context of the refurbishment politics of the EU as a result of the Paris Agreement on climate goals, significant amounts of glass waste in form of windows and façades are to be expected. In order to minimize the environmental impact of glass by preserving the embodied carbon and substitute newly produced glasses, the Re-use of glass is considered to be of highest potential. When reusing panes, energy and raw material can be saved that otherwise would be consumed for the production of new glass. This way, the common principles of sustainability - sufficiency, efficiency and consistency - can be realized for the life cycle of flat building glass. The following case study estimates the potential of different scenarios for circular waste treatment of glass panes by applying the 9R Framework to insulating glass units (IGUs). The scenarios are defined and presented. A life cycle assessment (LCA) using identical system boundaries for these scenarios was executed and the results are compared to producing IGUs entirely with new glass. Finally, the feasibility of the strategies is evaluated and recommendations for the processing of glass in stock are derived.

Re-Glass: Product Development Pathways for Post-Consumer Glass

Our research examines the viability of recycling soda lime glass from post-consumer Insulated Glass Units (IGU), mixing various types of architectural glass cullet and fusing them into flat plates by using electric kilns. Those kilns operate at lower temperatures than standard float glass production, which significantly reduces manufacturing emissions. The research outcomes suggest the potential for near-site operations, reducing transportation logistics, costs, and emissions. Strength and emissivity tests were performed on the recycled glass samples, to assess challenges arising from various production parameters including: glass types, processing methods, annealing temperatures and schedules, cullet sizes and distribution. These explorations offer high-level perspectives for developing post-consumer glass solutions driven by emissions and logistics primarily, and tectonics secondarily, exploring the cost-effective diversion of glass products from landfill to generate solutions staying within the built environment. The research examines performance aspects of recycled glass as emblematic of sustainability in design and underscores the role (and implications) of texture in architectural materiality. Performance and viability are weighted with considerations for the US market (hauling distances, energy grid emissivity across states, market culture, labor rates, incentives, or lack thereof). This exploration proposes innovative avenues for integrating distinctive, sustainable recycled glass as a hallmark into architectural frameworks.

Remanufacturing insulated glazing: five levers through value network mapping of two pioneering projects

Abstract In façade retrofit projects, several challenges are hindering the reuse of insulated glazing. As a result, 1.5 million tons of insulated glass units (IGUs) are being downcycled or landfilled in Europe each year. Yet, niche practices in which IGUs are remanufactured prove that recurring challenges can be tackled. Therefore, this research identifies levers to overcome challenges from two pioneering projects: the swimming pool in Stuttgart-Feuerbach (Germany) and elderly home Betsy Perk (The Netherlands). Through interviews, a detailed analysis of the IGU remanufacturing process is conducted, mapping material flows, steps of the remanufacturing process, the value network (showing roles involved and their main interactions in materials, money, and intangible flows), and specific answers to pre-specified recurring challenges. These potential levers include assigning a reuse coordinator, building a complementary network with early involvement, conducting a feasibility study, specifying reuse ambitions in the tendering documents and/or quotations, and organising the logistics pragmatically. Instead of being one-on-one solutions, the identified levers could tackle several challenges at once. Altogether the results of this study provide a better understanding of reuse practices of façade components. In further research, multiple projects will be compared allowing practitioners to overcome the recurring challenges and to increase reuse in the construction sector.

Effect of angle of incidence on the optical-electrical-thermal performance of photovoltaic insulated glass units

Photovoltaic insulated glass units (PV-IGUs) possess significant potential for achieving simultaneous power generation, thermal insulation, and natural lighting in buildings. However, the optical properties of PV-IGUs are influenced by real-time variations of the Angle of Incidence (AOI), thereby intricately impacting its optical-electrical-thermal performance. Therefore, an optical-electrical-thermal coupling model was developed to evaluate the impact of real-time AOI on the optical-electrical-thermal performance of cadmium telluride (CdTe) PV-IGUs. Through outdoor experiments, the model's accuracy was validated with acceptable errors between experimental and simulated data. After validation, the optical-electrical-thermal performance of PV-IGUs were analyzed under different operational conditions and AOIs. Results revealed that when AOI exceeds 45o, there is a reduction in absorptance up to 60.76% in terms of optical performance. Notable variations were observed across AOIs regarding thermal-electrical performance, with a maximum temperature difference of 16.08 °C for the PV cells and a maximum disparity in power generation of 140.51 Wh/m2 under solar radiation of 800W/m2. Additionally, an increase of AOI and decrease of photovoltaic coverage ratio (PVR) for PV-IGUs result in higher variation of the solar heat gain coefficient (SHGC), reaching up to 69.81% when PVR is 0.1. This study established a reliable foundation for accurately evaluating the performance of PV-IGUs.

Mitigating Blast Hazards: Experimental Evaluation of Anti-Shatter Films and Catcher-Cable Systems on Conventional Windows

In light of terrorist attacks and accidents, the need for structural protection against explosive events has increased significantly in recent decades. Conventional unprotected windows pose a particularly high risk of injury to building occupants due to glass fragments and window frames being propelled into the interior and exterior of a building. This article addresses new experimental research on the protection of conventional single casement windows with insulating glass units (double-paned) and window frames made of un-plasticized polyvinyl chloride (uPVC) against blast loads. Entire window systems were tested in ten shock-tube tests using different retrofit-configurations. The retrofitted protective measures include anti-shatter films and catcher-cable systems. Furthermore, the influence of steel profiles inserted in the window frames is investigated. The applied blast loads met the requirements for ER1-certification according to EN 13541:2012 (tested at a reflected peak overpressure of 66.7 kPa and a reflected maximum impulse of 417.7 kPa∙ms). In the test series, various measurement methods were used to capture the velocity of the window fragments, the dynamic cable forces, and the hazard. The data provide valuable information for the design and implementation of catcher-cable systems for existing buildings, which can improve the occupant safety in the event of an explosion.

Accurate determination of the static equilibrium in insulating glass units under climatic loading

In the area of glazing façades and windows, the increasing environmental demands have boosted the development of insulating-glass units (IGUs). There is already 4–6 pane glazing on the market, with heat transmittance Ucw < 0.40 W/m2K, which offers exceptional energy efficiency and living comfort. There is still a lack of standardized engineering methods for their design, however. The lateral load resistance of glass panes in insulating glass units is addressed in the standards EN 16612 and ASTM E1300-12a, but in both, the calculation methods employed are simplified by way of the linearization of the gas law and are applicable only to double and triple glass units. In this paper, we present a recursive method that accurately satisfies the conditions of static equilibrium and the gas law. The methodology preserves the rationale of EN 16612, in which the problem is split in two components: single glass pane bending and load sharing in IGUs, with the results of the former serving as input to the latter. The proposed methodology is based on the Taylor expansion of the gas law and equilibrium equations, which, in contrast to the standard method, completely eliminates the linearization error through a recursive process. Verification cases show that the error due to linearization can reach up to 30 %, a deficiency that the proposed method eliminates. Unlike the methods in the standards, ours provides a general solution for IGUs consisting of an arbitrary number of glass panes. Despite this general applicability, it preserves computational efficiency, simplicity, and suitability for basic engineering design. Beyond improving the existing calculations for double and triple glass units, the proposed method also represents a simple, stable and robust calculation approach for multi-pane IGUs, e.g. quadruple glass units, which are already on the market, as shown by real case studies. For practical purposes, a condensed presentation of the calculation process for these IGUs is given in the Appendix.

Optimizing the thermal performance of the window with horizontal transparent insulation slats: A comprehensive analysis and comparative evaluation

Using slats made of transparent insulation material placed within the insulated glass unit (IGU) cavity can effectively reduce convective heat exchange in the gas cavity and improve windows' thermal resistance. A denser slat arrangement in the cavity of the Window with horizontal Transparent Insulation Slats (WTIS) contributes to better convective suppression within the gas-filled cavity. Still, it also raises concerns regarding excessive heat conduction along the slats. Therefore, further investigation is necessary to explore the optimal structure. In this study, we evaluated the thermal performance of WTIS using a validated numerical model and WINDOW7.8, considering various slat spacing, slat thickness, slat width, and cavity thickness. The air-filling and argon-filling cases were discussed. Furthermore, we experimented with testing the thermal performance of WTIS under different temperature conditions and validated the software calculation results. The results demonstrate that reducing the slat thickness and increasing the slat width is beneficial to improve the thermal resistance. The results identified an optimal slat spacing value of WTIS, which depends on both the cavity thickness and slat thickness and increases with their increase. The thermal resistance of optimized argon-filled WTIS is 39.47%-74.07% higher than that of argon-filled IGU.

Towards a quality protocol for enabling the reuse of post-consumer flat glass

AbstractArchitectural flat glass typically follows a linear life cycle. Its recyclability potential is not yet fully exploited due to the challenges of collecting it as well as the issues in quality compatibility with a float furnace. While the challenges of recycling glass remain, there might be the opportunity to do even more than recycling: reuse. A robust reuse practice calls for a qualification of the properties and performances by means of a quality protocol as well as the identification of the new use. This study explored the prospect of reusing post-consumer architectural flat glass panes for remanufacturing in insulating glass units. A set of IGUs harvested from residential buildings in Belgium was disassembled manually in the laboratory and the collected glass panes were classified in different quality levels as a function of the size and density of surface defects. The influence of the lifespan of the insulating glass as well as the face of the insulating glass unit was also considered. Through this study, it was found that post-consumer glass with high surface quality can exhibit similar strength values of pre-consumer glass. This suggest that it would be possible to reuse post-consumer glass in a safe and valid manner.

Passively Maintained Closed Cavity Façade—Experimental Validation of the Mathematical Thermal Model

Although glass façades have been on the market for over a century, new improvements, following sustainable standards, are still being invented. An improvement of the actively maintained CCF has occurred in passive maintenance with natural ventilation of the cavity and insulation glass unit placed on the external side, which has served as a true motivation for further research. To develop the idea, a new type of CCF was invented, followed by the creation of the software, whose purpose is to determine optimal CCF façade components. During this research, an experimental and mathematical model was made regarding the thermal behavior, later validated by the measurements on-site in Rugvica, Croatia. Using simplified but unconventional methods, numerous formulae and variables, a simulation of climatic loads onto the CCF was conducted. Validations of the thermal model were made during winter and summer periods for southern and western façade orientation, explaining how heat transfers from the environment to close cavity façade elements. It was found from the analysis that air temperatures of the façade elements follow the outer air temperature, by constant air exchange with the outer space. The results showed great potential with up to 3 °C (5–10%) of difference in experimental and calculated results, thus creating a basis for further improvement of the software with the addition of structural and hygric behavior of the façade element, regarding climate conditions.

Experimental study on racking resistance of timber double-skin façade elements

The use of double-skin façade (DSF) is a quite new approach in building renovation process, complementing conventional renovation strategies. A double-skin facade is an envelope wall construction that consists of two transparent surfaces separated by a cavity and can essentially improve thermal and acoustic resistance of building envelope. Main double-skin wall components are usually composed of hardened external single glazing pane and internal three-layer insulation glass unit (IGU) which are rigidly bonded to the frame structure. Recently, many studies have analysed thermal and acoustic performance of DSF elements, but practically none in a sense of structural behaviour, especially in determination of racking resistance of such wall elements. Moreover, in terms of reduction of global warming potential, an eco-friendly timber frame instead of common used steel, aluminium or plastic frame is investigated in this analysis. The developed load-carrying real-size composite timber-glass DSF wall elements are subjected to experimental racking test using two different types of adhesives (polyurethane and epoxy) and consequent bonding type alternatives of connecting the internal three-layered thermal glazing to the timber frame. The obtained results for the maximal fracture force and racking stiffness are compared with previously tested prefabricated timber-glass wall elements using a single-skin three-layered thermal insulating glazing only. The results evidently demonstrate that this new approach of prefabricated load-bearing double-skin façade elements can essentially improve racking resistance and stiffness comparing with previously studied timber-glass wall elements and can thus be fully recommended especially in structural renovation process of old buildings. However, a lot of parameters still significantly effect racking resistance of such elements and thus have to be further numerically or parametrically investigated.

In situ detection of product age and argon concentration as measure of the re-use potential of insulating glass units in buildings

High level circular use of post-consumer insulating glass units will contribute to lower the environmental and social impact of insulation glass industry. The application of various circular strategies for insulating glass units (IGU’s) is rising. The product age will give an indication of the remaining life-time of an IGU, but a method which includes screening a technical quality is needed to check if an IGU is indeed suitable for re-use on a high level of circularity. In this study the argon concentration is suggested as discriminative quality. Energy efficient double glazing applied in windows of buildings situated in The Netherlands were studied. Product codes were noted and unraveled. Measurements were performed using the Sparklike Laser Portable, a non-invasive argon measuring device, which generates argon concentration, glass thickness and cavity width values. In addition, measurements were performed with a Glass Check thickness meter. The resulting data were analyzed. Measuring errors were explored and used to setup a testing procedure. Threshold values of the product age and argon concentration were selected for different circular strategies. In conclusion, a screening method using the product age and argon concentration to determine the circular use potential of insulating glass units is proposed.