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Insulating Glass Units (IGU’s)

Insulating Glass Units (IGU’s)

Insulating Glass Units (IGU’s) are leak proof combinations of two or more glass panes separated by a dry air space. The panes are separated by means of spacers, which are usually made of aluminium, and then hermetically sealed to the perimeter. The spacers contain desiccant (moister absorbing substance) to avoid vapor build up in between the panes. This feature is the difference between the IGU’s and double pane windows, as the latter are not hermetically sealed.

This technology is widely spread, as it allows saving energy and money, reduce pollution and improve the comfort inside a building. Usually, UGUs are used for windows, doors and skylights for commercial buildings and residential construction as well as in refrigeration units, control towers, rail transportation, cars and busses, marine applications, where energy efficiency is crucial.

In colder climates, window surfaces are usually colder than other surfaces in the home or building are more likely to have condensation built up on them. Water from condensation build-up and resultant water run-off can damage window frames and cause mould growing on them.

An IGU reduces the chances of condensation build up creating a thermal barrier between the inside and the outside.


The inner space in the IGU’s are usually filled with inert gases, such as argon or krypton, or gases (argon, krypton and oxygen) mixture, in some occasions – xenon and nitrogen. Inert gases are the choice because they do not react with other substances and their molecules move more slowly than molecules of other gases, therefore heat is not conducted in inert gases as quickly as in the air. This means that the heat cannot easily penetrate the IGU, so stops the room from overheating on hot weather. On the other hand, when it is cold outside, IGU’s do not let the air in the room cool down too quickly, due to the same inert gas properties. Thus, inert gas filling is insulating glass units reduce the necessity of air conditioning and heating devices, hence this technology allows lowering electricity expenses.


The most popular gas for this purpose is argon, as it is easy to produce (Earth atmosphere is 1% argon), and, consequently, pretty affordable. Krypton is a little more expensive, but its insulation properties are much better than those of argon; usually, argon filling is used for double pane IGU’s and krypton – for triple and quadruple IGU’s (used in especially cold regions, such as Alaska). The filling gases are absolutely not hazardous for humans and animals, also, their concentration and amount in the IGU´s are not that high to bring any harm. Despite the panes being hermetically sealed, approximately 1% of the filling gas per year leaks through the sealing points. As mentioned above, the gas is not poisonous, moreover, even with 80% of the gas IGU’s retain their properties, in their words, an estimated life of an insulating glass unit is about twenty years. Condensation or fog inside the unit may imply that it is losing the gas too quickly, in this case the manufacturer or installer’s consultation is required, as it is reported that in very rare occasions a possible sudden implosion of the window can happen as the result of argon leakage. The reason for this is that the molecular properties of argon and those of the basic components of the air – oxygen and nitrogen are different and pressurized argon leaking out at the sealing point, will move faster than the other gases can enter to replace it. This causes the pane bend inwards, as the pressure inside the window unit is lower than outside, so, under certain conditions, the window may shatter with a loud sound. Normally, the pieces of glass remain inside the window unit, but very occasionally the explosion can be strong enough for the pieces to fly out. The most probable reason for this is the difference of altitude between the installation place and the place where the IGU unit was initially pressurized, for this reason pressure equalizer valves are required for IGU’s at altitudes of more than 1200 meters above sea level.