Inert gas filling lowers the U-value of insulating windows
Thermal insulation has a major impact on energy savings and, therefore, has great potential for improving climate protection. The biggest energy leaks in buildings are windows. The insulating effect of insulating windows can be significantly improved with inert gases such as krypton.
Temperature differences strive to equalize - that is a basic law of physics. We try to prevent this equalization in buildings and save heating energy with increasingly sophisticated means of thermal insulation, for example, with insulating windows. Although these have been around for decades, they are constantly being perfected.
Air conducts heat too well
The quality of the glass and the processing play a decisive role in the insulating properties of double or triple insulating windows. But what is between the panes also has a major influence on the thermal balance: the lower the thermal conductivity of the filling gas in the space between the panes, the better the insulation.
The simplest filling gas is air. Unfortunately, however, it has a comparatively high thermal conductivity. The noble gases argon and especially krypton, which is rare and, therefore, more expensive, achieve significantly lower values.
Better insulating effect, smaller pane distance
The superior insulating effect of this gas makes it possible to keep the distance between the individual panes smaller than with conventional insulating glass windows. The optimum distance between panes is 16 millimeters for argon and only 8 to 12 millimeters for krypton.
The U-value can be reduced by 0.3 to 0.5, depending on the filling gas and gas filling level. Double-pane insulating glass filled with krypton achieves insulation values comparable to much heavier triple-pane insulating glass filled with argon. There is also a desirable side effect: windows filled with the inert gas have improved sound insulation.
The U-value
The insulating effect is indicated by the U-value. It indicates how much heat a building material lets through. The lower the U-value, the better the insulation. A simple pane of glass, for example, has a U-value of 5.8, insulating glass with air filling is 3.0. With argon as a filling gas, U-values below 1.5 are achieved, with krypton even below 1.0.
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