An insulated glass unit is a unit that is designed to keep your home cooler during the summer and warmer in winter. It is made up of two panes, although there are some with three or four panes. These panes are separated from each other by a spacer. The spacer is fixed onto the panes using a sealant. IGUs may be filled with gas so as to improve thermal ability. Such gases include Argon and Xenon.
Components of Insulated Glass Units
Insulated glass units are made up of different components which include;
- A spacer
The function of a spacer in an IGU is to create airspace in between the two panes of glass and hold the desiccant. Also, it helps maintain the structural integrity of the unit. It comes in a wide range of widths and lengths. Tiny perforated breather holes run through the center of the spacer, around its innermost surface.
These perforations allow for the passage of gas into the spacer, in order to reach the desiccant, which is housed there. You can also choose to use a foam spacer, which is already pre-desiccated. There are different types of spacers, including; warm edge, aluminum, and steel profiles in various colors.
- Corner keys
Spacers can be joined or bent at the corners, and corner keys are necessary in order to enable this purpose. Corner keys are also known as connectors, and they come in various colors and sizes that are compatible with specific spacers. Gas fittings are available too.
A desiccant comprises thousands of beads that are housed inside the spacer. The sole purpose of the desiccant is to absorb any moisture that is present in the air and therefore keep this moisture from condensing on the inner surfaces of the glass. Getting a good quality desiccant will ensure that only moisture vapor is absorbed, and none of the inert gases that are used in the making of the IGU.
Sealed units form cavities. These cavities are usually filled with inert gases, including Xenon, Argon, and Krypton. The gases filling the cavity are used in order to make the IGUs more efficient.
There are two types of sealants which are; the primary and secondary sealant. The primary sealant acts as assembly support, as the sealed unit is undergoing construction. This ensures that the unit has a low moisture and gas permeability rate, thus restricting the movement of inert gases and vapor in and out of the unit. It is available in various sizes and compatible with different systems as well.
A secondary sealant is present in a dual-sealant system. It bonds the spacer and glass, thus sealing the edges of this unit, which ensures that there is no moisture ingress. Additionally, it protects from gases that come in and out of the insulated glass unit.
Thermal stress is among the several factors which may cause the glass to break, despite the absence of a projectile. The breaking of glass is usually as a result of the temperature imbalance within the glass, rather than a reflection of the quality of the glass. Now that you know the structure of an insulated glass unit, it is also essential to know the factors which can affect their thermal stress break risk.
When you are working with your glass supplier and IGU fabricator, you must discuss thermal stress analysis with them. When you conduct the study before you begin working on the IGU, it will be possible for architects to specify the proper glass to be used.
Factors that Influence the Thermal Stress Break Risk
Here are the factors that influence the thermal stress break risk of your glass.
Clear or Colored Glass
Glass may be tinted, clear, or ultra-clear; and may come in different colors, which includes blue, gray, green, as well as bronze. The clear glass absorbs low solar radiation, while tinted glass absorbs more solar radiation than its clear counterparts. This has the ability to make the tinted glass take in heat, thus making it more susceptible to breakage as a result of thermal stress. Clear glass is less likely to break because of the low absorption rates.
The Coatings – On the Inner or Outer Surface
The two types of coatings, reflective and low-emissivity coatings, improve solar performance in the glass. They achieve this by reflecting solar radiation from the sun, and they can be put on any of the four surfaces present in a dual-pane insulated glass unit. Despite their being placed in the inner surface of the IGU, the orientation of the coating, as well as the risk that is associated with thermal stress, should be taken into account.
Sunny or Shady Structures
Shady structures in your outdoors are among the most dynamic factors that you can consider when doing an analysis of thermal stress. These structures include trees, overhangs, and adjacent buildings. When you minimize the locations on which there might be a non-uniform shading of your insulated glass unit, you help to prevent extreme temperatures.
Such shadings can increase the temperature of your glass by either reflecting the radiation via the glass or by causing a reduction in the conduction and convection of heat away from the unit. You should ventilate the air spaces around your window glass, in order to reduce thermal edge stress. You should also ensure that there is a reasonable gap between the glass and drapes, blinds, or shades (several inches will do).
Where to Place a Vent
If your registers, grilles, and heating system (like Wood Pellet Stove) vents directly face your glass units, the glass will heat up because of the resultant warm air. Under specific conditions, the glass may actually break. In order to avoid this, ensure that you place your vents in a strategic manner. This is to make sure that there is a reduced thermal stress risk to your IGU. A good tip is to avoid placing your vents between your glass and the shading devices.
How to Frame It
When you get a glass framing system with low heat capacity, you also minimize the chances of thermal stress breaks. Structural gaskets, as well as narrow metal framing, are appropriate, as they have little effect on the temperature of the glass around the edge. On the other hand, massive framing may have a more significant effect, thus causing a thermal imbalance, which means a higher risk of breakage.
How to Prevent Breakage Risk?
As much as there is a thermal stress breakage risk on your insulated glass unit, there are ways through which you can prevent it. They include;
Glass Type for Your IGU Project
The glass comes in a wide range of colors, and the type of glass used will influence its ability to absorb radiation from the sun. The glass types include clear glass, as well as tinted ones. Glass that is ultra-clear and clear has a low absorption rate; therefore, they do not heat up. This makes the glass less likely to break because of thermal breakage stress, unlike their tinted or spectrally-selective counterparts.
Coating Type and Location
Both the reflective and low-emissivity coatings absorb and reflect radiation. Therefore, you can place them on a surface location in your insulated glass unit, which will decrease the amount of radiation absorbed by the panes. Using these coatings on the outer rather than inner pane will result in less thermal breakage stress risks on your IGU.
Outdoor Shading Patterns
The shading pattern really is an important factor when it comes to ensuring that thermal stress is reduced. When you minimize the locations of your IGU project, it means that your glass panel has a lower coverage by shade. This will enable you to avoid extreme gradients of temperature due to seasonally-varying shading patterns, hence, reducing the breakage risk.
Indoor Shading Devices
These devices impact the thermal load on your glass as much as outdoor shading patterns do. Indoor shading devices such as drapes and blinds reflect solar radiation back into the IGU, therefore, increasing the temperature of your glass. Reducing the shading devices will result in increased conduction and convection of radiation away from your glass.
Heating Register Location and Orientation
In the building in which you are carrying out the IGU project, it is important to place the registers in such a way that warm air is deflected away from the glass. This, therefore, results in less heating and reduces the chances of your glass breaking.
Get a framing system with a low-heat capacity for your insulated glass unit. This way you will minimize the risk of your glass breaking.
Getting an IGU for your building may be a taxing undertaking. However, with this guide, you have all the information you require to make a well-informed decision. Because you know how each factor affects the thermal breakage stress risk on your glass, you can now better understand why you need to undertake preventive measures to safeguard the well-being of your system.
It is, therefore, easy for you to get a good IGU system for your building.
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