View source for Gas filling for thermal conductivity

[[Category:Done 2021-01-31]]
[[File:640px-Contemporary_Paudash_Cottage.jpg|400px|framed|right|Figure 1. A home that uses gas-filled windows that visually are not any different than air filled windows, but provide a greater level of temperature regulation and greater energy efficiency.<ref>"Contemporary Paudash Cottage". Licensed under Public Domain via Wikimedia Commons - http://commons.wikimedia.org/wiki/File:Contemporary_Paudash_Cottage.JPG#/media/File:Contemporary_Paudash_Cottage.JPG</ref>]]

<onlyinclude>'''Gas filling''' is a method where a low-conductivity inert [[gas]], such as [[Argon]], is used instead of [[air]] in [[window]] cavities in order to reduce [[heat]] transmission through the window.</onlyinclude> Windows which use this method are known as ''Insulating gas units''.<ref name ="RE1">Green Globes. (March 28, 2015). ''Inert Gas Windows'' [Online]. Available: http://www.greenglobes.com/advancedbuildings/_frames/fr_t_building_inert_gas_window.htm</ref> Although air is most commonly used to fill cavities, the use of an inert gas such as argon and krypton can reduce window heat transfer, increasing the [[insulation|insulating]] abilities of the window. Although krypton and argon are both colourless, odourless, and non-toxic, argon is most commonly used as it insulates well without being extremely expensive.<ref name="RE1"/> For an argon gas filled window the cost is only $30-$40 more.<ref name="RE2">Juan Rodriguez. (March 28, 2015). ''Benefits of Argon Gas Filled Windows'' [Online]. Available: http://construction.about.com/od/Doors-And-Windows/a/Argon-Gas-Window-Benefits-Of-Argon-Filled-Windows.htm</ref> Krypton is more effective at reducing heat loss but is about 200x more expensive than argon. Gases such as sulphur hexafluoride or [[carbon dioxide]] can be used to reduce [[sound]] transmission but are not as effective as the inert gases in preventing heat transfer.<ref name="RE1"/>

==How They Work==
These insulating glass units are designed to regulate the [[temperature]] of homes better, keeping them warm in the cold months and cool in the hot months. Argon, Krypton, or other inert gases are pumped inside the cavities in a window, between the panes of a sealed glazing unit, resulting in a mixture of the fill gas and air. These gases are colorless, so they do not prevent visible light from entering the home, and odourless. Argon is [[density|denser]] than the [[atmosphere]], and this provides more [[thermal efficiency]] than having simply air between the panes.<ref name="RE3">Lowes. (March 28, 2015). ''The FAQs on Gas-Filled Windows'' [Online]. Available: http://www.lowesforpros.com/Construction-and-Contractors/The-FAQs-on-Gas-Filled-Windows#sthash.0Zrhw3fe.dpuf</ref> Krypton is again denser than argon and thus provides somewhat more thermal efficiency, although it is more expensive. It is these densities that slows the movement of heat through the window itself. Generally, a standard gas-filled window consists of two to three litres of gas sandwiched between panes of glass or other glazing material.<ref name="RE4">PPG Glass Education Center. (March 28, 2015). ''Pros and Cons of Gas Filled Windows'' [Online]. Available: http://educationcenter.ppg.com/glasstopics/gas_insulating_glass.aspx</ref> The more gas is used, the better the window will insulate. 
The gas within the window will gradually diffuse overtime at an estimated rate of 0.5-1.0% per year.<ref name="RE1"/> This leakage however does not noticably affect the performance of the window itself, with the window still being significantly more energy efficient even twenty years down the road, even while accounting for leakage.

The insulating performance of these windows can further be enhanced by adding an [[e-coating]]. When 90% argon is used to fill these windows in a window that also has a low-e coating the insulating value can be improved by 16%.<ref name="RE4"/>

==Benefits & Drawbacks==
Gas filling in windows can be beneficial in many different ways. In addition to improving the energy efficiency of windows they can:<ref name="RE1"/><ref name="RE2"/>
* Reduce heat loss during the cold months
* Reduce unwanted heat gain during the warm months
* Increase [[R-value]] of windows
* Increased levels of soundproofing
* Reduces possibility of condensation and frost
* Blocks ultraviolet rays which can cause fading of materials in home

However, these types of windows also have some drawbacks:<ref name="RE1"/><ref name="RE2"/>
* Can only be used in sealed window units
* Expanding and contracting gas can cause leaks if not sealed properly
* Gas dissipates slowly from the window, lowering the efficiency over time
* Metal [[spacers]] are no longer a good choice as they leak

==For Further Reading==
*[[Insulation]]
*[[Fenestration]]
*[[Home energy use]]
*[[Energy efficient building design]]
*[[U-value]]
*Or explore a [[Special:Random| random page]]

==References==
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