Insulating Glass Units Research Articles

Using COSMOSWORKS abilities in construction glass strength research

Considered the issues of definition maximum acceptable load on supporting construction, made of glass. Object of research is a complex construction – insulated glass unit. Glass unit has two loaded layers of three in triplex and central layer – air chamber. Air chamber is formed by rubber layer, connecting external layers of triplex by perimeter. Glass unit loading is single-sided, only on top layer. Glass unit fastening was made only in four corner points. Researches were made in program complex COSMOSWORKS. Maximum acceptable load is searched by iterative calculation with step-by-step increase of calculation load on model. Established, that covering deformation and the stress distribution in them changes linearly. The value of maximum acceptable load for glass unit with special geometrical and physical characteristics was calculated. In this article the optical, thermal and other glass unit properties were not considered. The article presents the results of glass unit analysis when only mechanical action is applied to them. Temperature effect on glass units was not considered in this article.

Criteria for climatic applicability of modern window types

Currently, the assignment of the required values of the technical and operational windows characteristics (such as resistance to heat transfer, air permeability, sound insulation, etc.) is carried out based on the technological capabilities of the window industry, and not on the basis of scientifically substantiated requirements for ensuring the microclimate and energy buildings efficiency in the design practice of most countries (as it happens in the case of external walls which are in almost identical operating conditions with windows, for example). One of the most common types of windows in modern construction practice are single windows with insulated glass units and profiles made of PVC and aluminum alloys. They were originally developed for operation in Western Europe where they have proven themselves well over many years of operation. However, their widespread use in the climatic conditions of the Russian Federation and the countries of Eastern Europe showed a number of problems during operation which is expressed in a decrease in the technical and operational characteristics of windows due to temperature deformations of their profile elements. This circumstance testifies to the limited area of application of these structures in terms of climatic conditions. The authors of the work introduce the concept of “climatic applicability of windows” in order to determine the rational application areas of types of windows which would ensure the fulfillment of the specified requirements for the comfort of the microclimate of the premises in any operation period of the building. Based on the results of the analysis of the work of third-party researchers and the authors own works the authors have determined a set of criteria for the climatic applicability of modern types of windows based on winter operating conditions. Promising areas for further research were considered.

Issue of heat mirror films overheating

The study focuses on the issue of coated thin plastic films overheating due to the absorption of solar radiation. These films are suspended within the sealed space of dual-pane insulating glass units (IGU). Films are deformed due to thermal stress and the glazing ceases to carry out its function. The surface temperature of the glazing system was evaluated from energy balance during a sunny day. It was supposed the intensity of solar radiation 1000 W/m2. Solar radiation incidents perpendicular to the surface of the glazing. Spectroscopic measurement was performed and optical properties of glasses and films were evaluated. Finally, suitable glazing was designed, which partially prevents transmission of the solar radiation into the inner space of glazing and the thin plastic films are not significantly overheated.

Using Transparent Conducting Coatings for Warming Transparent Roofs

The possibility of using multilayer structures based on transparent polymeric films with conducting coatings as heaters for removing snow cover is discussed. It is established that the heaters with cellular polycarbonate slabs 4 mm in thickness are more efficient. The specific capacity spent by these heaters on warming by 20°C is 300 W/m2; for comparison, the capacity of the heaters pasted to the insulating glass unit surface is 420 W/m2.

Comparative study on the overall energy performance between photovoltaic and Low-E insulated glass units

A novel semi-transparent building integrated photovoltaic (BIPV) laminate was developed and introduced in this paper. It was produced by cutting standard mono-crystalline silicon solar cells into small strips and then making electrical connections between each strip before laminating the cells between two layers of glass. The overall energy performance and energy saving potential of the BIPV insulated glass unit (IGU) under real world conditions were identified through a side by side comparative study. Compared to the reference IGU, the BIPV IGU had lower solar heat gain coefficient (SHGC) but much higher U-factor. The average HVAC electricity saving of the BIPV IGU was about 10% relative to the reference IGU. Daylighting measurement and analysis were carried out to evaluate the trade-offs associated with the BIPV IGU between daylight, glare, and lighting energy use. The results indicated that the BIPV IGU is better than the reference IGU in reducing discomfort glare. However, if the most conservative viewpoint near the window is used for the assessment, a lower transmittance BIPV IGU is required to bring the overall discomfort levels below the perceptible level. Lastly, the net energy saving potential associated with the novel BIPV IGU was identified based on the power, thermal and daylighting performance. On average, the BIPV IGU saved 16.8% of the total electricity use of the room. Further studies and improvement on the energy conversion efficiency of solar cells, the optimal transmittance as well as the thermal properties would make this technology more energy-efficient and affordable.

Managing Glass Waste in Energy Efficient Building Retrofitting: Barriers and Opportunities for a Circular Economy

Making cities resilient and sustainable is only possible if the energy consumption of buildings is reduced. Retrofitting is one of the main tools of the environmental policies developed in cold and temperate climates, leading to the replacement of products considered inefficient. This is particularly the case for glazing, which is a key element in the energy system of a building. However, most of the glass waste generated by renovation is landfilled while the development of a circular economy in the glass industry seems today highly challenging. This paper studies barriers and opportunities to increase the recycling and repair of insulating glass units. To do so, we follow three approaches: a literature review, a series of interviews and a case study of a glazed office district in Brussels. This article provides a comprehensive overview of the main issues relating to the management of glass waste in the building sector and underlines the importance of economic instruments to support the spread of sorting and recycling practices. The need to rethink the systems for assembling insulating glass units with a view to facilitating the sorting of their components also appears as a necessary and stimulating path.

Stress-strain state of Insulated Glass Unit in structural glazing systems

Stress-strain state of Insulated Glass Unit in structural glazing systems

Repositioning Messeturm–Maximum Transparency

The Messeturm (“Trade Fair Tower”) in Frankfurt is currently adjusted to the requirements of a modern office building. The lobby area has been enlarged by a highly transparent facade consisting of oversized insulating glass (IG) units. The IG units are curved and have a size of up to 17 m $$\times $$ 2.8 m. To obtain a perfectly curved facade, the IG units were fabricated with laminated cold-bended glass panes. Horizontally the IG units are supported by tapered stainless steel fins. Inclined steel beams connect the top of the facade fins with the tower structure creating a rounded roof. The vertical facade with its glass roof allows maximum transparency for people inside the lobby as well as for people passing by outside to the nearby trade fair grounds. The glass was fabricated by sedak. The facade was installed by seele on behalf of the owner OFFICEFIRST, the asset-management of Blackstone.

Insulating Glass Unit Quick Selection Guide

Abstract The structural design of sealed insulating glass units for wind loads involves complex structural mechanics procedures that address load sharing between two glass lites that vary in thickn...

Slumped IGU’s with large airspaces: engineering challenges and solutions

Aside from external cladding pressure loads that are always considered in IGU design, a variety of unique factors must also be addressed when analyzing the structural performance of a slumped IGU with a large air cavity. These factors include the volume of air within the cavity, the stiffness and strength of the outer and inner lites of glass, elevation changes between the glass fabrication facility and the building site, temperature changes over time, fluctuations in barometric pressure, and increased stress on the secondary structural perimeter seal. Appropriate deflection limits for mullions or other elements supporting the IGU must also be established due to the increased stiffness of the IGU resulting from the slumped glass geometry. Engineering challenges related to the design of slumped IGU’s will be highlighted and explained using Nike’s new retail flagship store in New York City, Nike House of Innovation 000, as a case study for a dynamic facade featuring custom carved and slumped insulating glass units. Principal analysis methods, testing procedures, and a summary of the various software tools used to evaluate the slumped IGU’s will be provided. The solutions shown will illustrate how the fundamental design and engineering approach taken for Nike can be successfully applied to other projects that incorporate slumped IGU’s into their facades.

Experimental investigation into fire behaviour of glazed façades with pendant type sprinklers

Façade systems play an important role in fire compartmentation of a building and reducing the likelihood of fire spreading through and outside of the building walls. The use of sprinklers in building regulations often allows for smaller building separation. However, no additional benefits are usually given to additional internal sprinkler protection of the external glass façade using standard pendant sprinklers. Four compartment fire experiments were performed with non-fire-rated aluminium façades with two- and three-layered Insulating Glass Units (IGU), protected by pendant-type sprinklers (DN15, K-factor = 80, T = 68 °C). Sprinklers were in row 14–55 cm from the glazing, with 1.514–1.83 m separation distance. In all experiments, façades achieved satisfactory performance in terms of glazing integrity, insulation and reducing the thermal radiation. Under a non-uniform water distribution, parts of the glass were dry (1.7%–15.7% of IGU area), where we have observed soot deposition and local damage to fire exposed glass layer, but no loss of the structural integrity. The temperatures on the unexposed side did not exceed 86 °C, the peak measured temperature of the internal glass surface was 173 °C. The performed experiments confirmed the capability of standard pendant-type sprinklers to enhance the fire protection features of a building façade.

Mechanical analysis and characterization of IGUs with different silicone sealed spacer connections - Part 1: experiments

Due to several advantages, insulated glass units (IGUs) are largely used in buildings to realize curtain walls, vertical partitions but also roofs or pedestrian systems. The typical IGU consists of two glass layers, either monolithic and/or laminated sections, that can mechanically interact via an hermetically-sealed air (or gas) cavity between them. As known, load sharing phenomena have a crucial effect on the actual mechanical response of a given IGU. Accordingly, simplified analytical methods are available in the literature to account for these load sharing effects. The existing approaches, however, assume that the spacers providing the mechanical connection along the edges of glass panels are infinitely rigid. In this paper, original experimental tests are proposed for IGU specimens characterized by the presence of different types of spacer connections, as obtained from on a selection of configurations of technical interest. The actual mechanical contribution of spacer components is then investigated, giving evidence of major findings from small-scale shear and IGU four-point bending tests. Based on comparative test observations, the edge connection efficiency is then assessed for the investigated configurations.

Energy Savings in an Office Building with High WWR Using Glazing Systems Combining Thermochromic and Electrochromic Layers

This paper assesses energy savings in terms of heating, cooling, and artificial lighting achieved in an office building with a high Window to Wall Ratio (WWR), located in Athens and Stockholm. Six different configurations of triple pane windows combining thermochromic, electrochromic, and low-e coatings in Insulated Glass Units (IGUs) are examined to quantify the potential of increasing energy savings in office buildings. The combination of electrochromic and thermochromic layers on the outer pane of the triple IGU, achieved an 18.5% and 8.1% reduction in annual primary energy use for Athens and Stockholm, respectively. The used switching strategy ensured the visual comfort of the employees and provided adequate daylight in both cases. It was found that in Stockholm the cooling system can be downsized considerably, achieving important cost reduction in the HVAC system. The analysis also takes into account the reduction of thermal storage in the building envelope due to the switchable windows. This reduction is beneficial in the case of Athens, but it can reduce energy savings in Stockholm. Therefore, for colder climates, it is important to increase window heat gains through the development of layers with higher g-value in the clear state and through the application of appropriate switching strategies.

Experimental and numerical investigation of thermal improvement of window frames

This article presents experimental and numerical determinations of thermal transmittance performed on three different types of window frames (vinyl, aluminium, and wooden) within the same insulated glass unit. Good agreement between experimental and numerical results was attained. Using the numerical models, thermal improvement techniques of the frames and their influence on thermal transmittance of frames were studied. The first thermal improvement technique was using the insulation materials inserted inside large air cavities. By filling the cavity of vinyl frame with the polyurethane foam, thermal transmittance of vinyl frame was lowered by 10%. The second technique was based on repeating the procedure with materials installed inside frames with the materials that have lower thermal conductivity. This technique can be applied on thermal breaks and on steel profiles inside cavities. The result of this thermal improvement (attained by replacing thermal break material with material that has lower thermal conductivity) was certain reduction of the thermal transmittance of frames, by 9%. Using stainless steel instead of the oxidized steel was reduction of the thermal transmittance of vinyl frame by 3%. For the case of wooden frames the influence of shifting glazing unit deeper into profile upon the thermal transmittance of the frame was analyzed. Installing the glass unit by 5 mm deeper into the wooden frame reduced glass thermal transmittance by 5%.

Primary Seal Deformation in Multipane Glazing Units

Quadruple glazing has become a high-end standard in the field of sealed insulating glass units. With more than three glass panes a set of internal heat-related technical problems emerges. Durability, being the most pressing problem, requires careful management of the primary sealant deformation, especially under summer environmental conditions. Namely, the role of the primary seal in insulating glass units is to protect their humidity-sensitive, low-emissivity coatings from moisture and the quality of such protection is a key factor in durability. In this paper, a new methodology is proposed for a feasibility assessment of a new multipane insulating glass unit design, where proper design enables avoidance of excessive strain on the primary seal. It focuses on the calculation of the primary sealant strains, which are nonhomogeneous and multiaxial according to different loading conditions. This approach leads to analytical expressions that enable convenient identification of the critical location on the primary sealant. Finally, feasibility is assessed with the proposed methodology for the newly developed highly insulative six-pane facade unit by means of a comparison of the calculated strain state with the anticipated allowable strains, based on technical practice.

Assessment of the Wind and Temperature Loads Influence on the PVC Windows Deformation

The PVC windows application experience in various climatic conditions shows that at their operation the windows profile deformations can be observed. One of the reasons for these deformations is the climatic loads influence on the windows – wind pressure, solar radiation, negative outside temperatures. The profile elements deformations affect the window tightness and the normal window hardware operation. The calculated loads combinations on windows in winter and summer were analyzed. For window as external element of building is more critical winter loads combination – the combined effect of wind pressure and negative temperature. The work was done the analysis of the effect of negative temperatures and wind pressure on the PVC window deformation. The studies were performed in laboratory conditions on the basis of two testing centers. Three PVC Windows with different profile thickness were tested. The temperature deformation of the casements and mullions profiles of this windows were analyzed. These deformations have to take into account in the static calculations. But the engineering methods creation for calculating windows for the wind and temperature loads effect requires additional research. They are associated with the study of the joint work of the windows constituent elements (profiles, insulating glass units, hardware).

Heat Transfer Through Insulating Glass Units Subjected to Climatic Loads.

One of the structural elements used in the construction of insulating glass units (IGUs) are tight gaps filled with gas, the purpose of which is to improve the thermal properties of glazing in buildings. Natural changes in weather parameters: atmospheric pressure, temperature, and wind influence the gas pressure changes in the gaps and, consequently, the resultant loads and deflections of the component glass panes of a unit. In low temperature conditions and when the atmospheric pressure increases, the component glass panes may have a concave form of deflection, so that the thickness of the gaps in such loaded glazing may be less than its nominal thickness. The paper analyses the effect of reducing this thickness in winter conditions on the design heat loss through insulating glass units. For this purpose, deflections of glass in sample units were determined and on this basis the thickness of the gaps under operating conditions was estimated. Next, the thermal transmittance and density of heat-flow rate determined for gaps of nominal thickness and of thickness reduced under load were compared. It was shown that taking into account the influence of climatic loads may, under certain conditions, result in an increase in the calculated heat loss through IGUs. This happens when the gaps do not transfer heat by convection, i.e., in a linear range of changes in thermal transmittance. For example, for currently manufactured triple-glazed IGUs in conditions of “mild winter”, the calculated heat losses can increase to 5%, and for double-glazed IGUs with 10–14 mm gaps this ratio is about 4.6%. In other cases—e.g., large thickness of the gaps in a unit, large reduction in outside temperature—convention appears in the gaps. Then reducing the thickness of the gaps does not worsen the thermal insulation of the glazing. This effect should be taken into account when designing IGUs. It was also found that the wind load does not significantly affect the thickness of the gaps.

Heat Losses through Insulated Glazing Placed Horizontally or Diagonally

Heat transfer through insulating glass units is a complex phenomenon. Heat exchange occurs here through conduction, convention and radiation. In practical calculations of heat losses in buildings, the declared value of the thermal transmittance (U) is most often taken into account, which is valid for vertical panes. Currently, more and more horizontal and diagonal glass partitions are made. The aim of the article is to analyze, on the basis of the adopted calculation model, the influence of the angle of glazing slope on the thermal transmittance in different weather conditions. The different wind speed and the possibility of radiative cooling were taken into account. Radiative cooling is a phenomenon manifested by a drop in temperature on the surface of horizontal and diagonal building partitions below the external air temperature. It occurs at night under a cloudless sky. It was found that in the case of horizontal or diagonal glazing heat losses increase significantly, which affects the energy balance of the building. Radiative cooling, especially in windless weather, is an additional unfavorable factor.

Effective R-value of enclosed reflective space for different building applications

Many parts of the building envelopes contain enclosed airspaces. Also, the insulating glass units in fenestration systems, such as curtain walls, windows, and skylight devices, contain enclosed spaces that are normally filled with air or heavy gas such as argon, xenon, or krypton. The thermal resistance (R-value) of an enclosed space depends mainly on the type of the filling gas, emissivity of all surfaces that bound the space, the size and orientation of the space, the direction of heat flow through the space, and the respective temperatures of all surfaces that define the space. Assessing the energy performance of building envelopes and fenestration systems, subjected to different climatic conditions, requires accurate determination of the R-values of the enclosed spaces. In this study, a comprehensive review is conducted on the thermal performance of enclosed airspaces for different building applications. This review includes the computational and experimental methods for determining the effective R-value of enclosed reflective airspaces. Also, the different parameters that affect the thermal performance of enclosed airspaces are discussed. These parameters include the following: (a) dimensions, (b) inclination angles, (c) directions of heat flow, (d) emissivity of all surfaces that bound the space, and (e) operating conditions. Moreover, numerical simulations are conducted using a previously developed and validated model to investigate the effect of the inclination angle, direction of heat transfer, and the coating emissivity on the R-values of enclosed spaces when they are filled with different types of gases.

Study of Deflection in Insulating Glass Units Under Climatic Loads Simulation

Insulating glass unit (IGU) is a commonly used filling element in transparent building partitions. The component glass panes in the unit are connected to each other on the edges by a spacer in such a way, that the space between them forms a tight gap filled with gas. The state of the gas in the gap can be described, with sufficient accuracy, by the law of ideal gases. Periodic changes in external climatic factors, above all atmospheric pressure and temperature, result in deflection of the component glass panes, which generates secondary loads associated with the change of gas pressure in the gap. The static quantities in the glass panes (deflection, stress) are therefore the result of the state of temporary equilibrium between the gas pressure in the gap and the external pressure. Measuring the deflection of component glass panes in operating conditions is time-consuming, because it requires waiting for changes in weather factors – these changes are often unpredictable. The aim of this article is to develop the concept of a test stand allowing the measurement of the deflection of the IGU models under the conditions of climatic loads changes simulation, where these changes can be controlled over time and generated in an orderly manner. The presented project meets these requirements. The stand is built from a massive main frame, which is the basis for the placement of deflection sensors, which is accompanied by a supporting frame, that allows placing glass panes with different thicknesses. The tested model of IGU is equipped with threaded elements, thanks to which it is possible to regulate the gas pressure inside the gap and monitor its temperature. An additional function of the stand is the ability to assess the tightness of the connection of component glass panes with the spacer, which may be an alternative to the standard way of testing this parameter.