A double glazed window is primarily a thermal or heat insulating window. Due to its particular construction it is superior to most windows fitted with a single pane. The most important advantage is the effect that a double glazed window has. It functions 24 hours a day and 7 days a week – without being activated or controlled – as a passive system. Double glazed windows prevent the waste of valuable and expensive energy.
The advantage of this system are plain to see: the less heat is lost, the less heating must be supplied. Decisive here is the so-called U-value of the window. This defines the heat transmission value, i.e. how much heat is given out by the construction element to the outside world, and can be much improved by incorporating two or three panes of glass.
Investigations by an independent expert, the TÜV Rhineland, has shown that even a lowering of the U-value by 0.1 per square meter window surface area helps to save one liter of heating oil per year. A standard house with one family (construction >2000, 160m2) will typically have an oil consumption of 13.6 liter per square meter, which gives an average consumption of 2176 liter heating oil (the amount will be higher when the household water is also heated with oil).
Assuming 25 square meters of window surface we can already calculate a saving of 70 liters a year, when single glazing is replaced double glazed insulating glass.
Depending on the current price of oil then a higher standard of window glazing could save a typical household up to 240 and 260 Euro per year on heating costs.
Apart from this purely financial gain double glazed windows with insulation offer the advantage that the house fulfills the latest standards laid down for Energy Saving. The question of whether replacement is worthwhile can best be answered by an independent energy auditor on site.
|Glazing||Heat throughput (U-value)|
|Double glazed insulating glass||2.8|
|Double glazed thermal insulating glass||1.0-1.2|
|Triple glazing thermal insulating glass||0.5-0.7|
Naturally a good window should not only help to keep heating costs down. Further features of a reliable window are as follows:
Double glazed windows have a particularly stable and strong frame due directly to the double glazing. The options include wood, uPVC or aluminium as well as a composite wooden-aluminium combination, all of which can be made stronger using the right fittings. Thus, double glazed windows belong to that category of window that is difficult to break open under force, even with tools, due to its characteristics and its construction. But security means much more as simply the perfect protection against burglars.
The window must also be safe for the residents within. The glass must neither break during regular cleaning or when placed under a light amount of pressure, nor must that window prove to be a difficult barrier to overcome for the fire fighters in the event of fire. Similarly the double glazed window should be easy to open and close for any adult but equally it must limit the journeys of discovery of a toddler or small child.
In the area of sound insulation, double glazed windows (with resonator) are among the best available models of window. A fixed frame of wood (optionally with aluminium cladding) together with the double pans provides a pleasant feeling of peace and quiet indoors.
Thanks to the fact that noise is reduced to a minimum, double glazed windows are especially suitable for houses on streets subject to heavy traffic.
Freqently one finds windows in older buildings which are a simple wooden window with single glazing. A double glazed window on the other hand consists of two panes of glass between which there is either air or a noble gas. The airtight frame connects these two panes and completely encloses the space in between. For this reason the frame must be more stable and more heavily built to hold both panes in place.
The advantage hereby is that as long as the frame remains airtight no dust can get into the separating spaces and the window only needs cleaning, like a conventional wooden window, from outside.
Cleaning double glazed windows is therefore no different to cleaning conventional windows.