Argon-filled double glazing

Conventional Double Glazing involves the creation of a double skin of glass filled with dry air so designed as to increase the energy efficiency of any building in which it is used by reducing the heat losses through the windows. This form of double glazing is far more effective than a single paned window.

Further improvements in the effectiveness of the glazing can be achieved by the choice of glass used in the construction of the panels or by changing the air within the panels for a gas that has a greater degree of thermal performance and cost efficiency. The choice of gases available are Argon,Xenon or Krypton.

Argon, a colourless, odourless, non-flammable, non-reactive, inert gas is the favoured choice as it is far less expensive than the other two. The introduction of the gas into the cavity of a double glazed unit reduces the heat conductance between the panes, helping to keep more heat in during the winter and out in the summer. This phenomenon results from the fact that the density of the gas is greater than the density of the air. Where appropriate the thermal insulation can be further improved by using a Low e energy saving glass on one side of the sealed unit. This combination of Argon Gas and Low e energy saving glass can achieve an improvement in thermal performance in the region of 50% over and above that of a standard sealed unit. The addition of the gas lowers the u-value of the unit as the gas has a 34% lower thermal conductivity than air. Argon filled panes have u-values ranging from 1.8 to 1.9 while air filled windows have u-values of about 0.27. Although Argon-filled units cost around 5% more than air-filled units, they can improve a double glazing window’s U value by over 30%. In modern houses were the window areas can be large the saving to be gained from having Argon filled windows can be significant. Combined in a sealed unit with low emissivity glass, for example “K” Glass, the benefits are increased even more.

In addition to the energy saving benefits, because the gas is 6 times denser than air there will also be an improvement in the acoustic performance of the double glazing. This can again be further enhanced by the choice of glass used.

The raised internal temperature of the Argon filled window further minimises the risk of condensation settling on the internal surfaces of the glass.

The use of Argon as a filling is not without criticism in that over a period of time it is felt the gas loses its effectiveness. Properly constructed windows with Argon fillings should last the lifetime of a double glazed window. During manufacture it is generally accepted that the double glazed unit should achieve a 90% fill of gas. Over time this concentration will gradually evaporate, at an estimated rate of 0.5 to 1% per year. Double glazed units filled with Argon do not degrade significantly until they reach 75% concentration, giving up to 20 years of high performance.

There appears to be divided opinion as to whether the increased cost of using Argon filling gives value for money. While windows filled with the gas will provide some increased energy efficiency, the cost is increased as well. With the push towards increased energy efficiency, most new or replacement windows offered by quality manufacturers today all use argon filled glass and many do not provide other options, so the point is somewhat moot. Where you need to make a decision about the comparison of increased cost set against the increased efficiency is in existing double glazed windows that you are considering having filled with argon gas. In most cases, it would not be cost effective to spend the money to simply fill your existing windows with argon gas because the energy savings you will enjoy will not cover the initial cost for quite a long time.

If considering new Argon filled window, if these are not offered as standard,the purchaser must consider whether the energy savings and other benefits truly outweigh the increased initial outlay involved.