Many, perhaps most, consider that a double-glazed window contributes to the thermal insulation of their home and reduces air conditioning and heating costs in summer and winter respectively.

And they would have been right to think so in the event that the double glazing had been constructed in a way that would have justified the description “energy efficient”.

Unfortunately, however, most often the double-glazed window in their house is nothing more than a common glass pane, which has better thermal insulation “behavior” compared to the classic single-glazed window, but it is not a factor of substantial energy savings.

The four-season energy glazing of Vlavianos is manufactured using special coatings (Low – e) that impede the transfer of heat from the surrounding area to the interior of the house and vice versa, thus ensuring savings that are estimated to be as high as 50% in terms of the cost of cooling or heating a household.

In fact, it is estimated that a four-season energy glass saves about 300 kilowatt hours per square metre of surface area per year.

It should be noted that the largest percentage (about 35%) of the thermal transmission and losses of a property is carried out by windows and balcony doors, while the corresponding percentages of “responsibility” of the masonry (25%), the floor (20%) and the roof (20%) are smaller.

According to relevant statistics, the thermal insulation of a house that has real energy glazing in windows and balcony doors is improved by 220% compared to common double glazing and by 400% compared to windows that have single glazing.

It is clear, then, that double-glazed frames do not necessarily ensure a satisfactory level of thermal insulation and therefore do not automatically lead to energy savings.

And this is because there are many categories and qualities of glass on the market, which makes it difficult to identify them and to choose those that have the appropriate special coatings and thermal permeability properties (degree of obstruction of heat transfer between the interior and exterior of the property). for high performance.

The performance difference in terms of thermal insulation between the common double glazing of a window or a balcony door and a truly energy-efficient four-season glazing is quite large.

Factors determining performance

However, apart from the separation of ordinary glass from energy glass, there are significant differences between them and these energy type glass panes. Thus there are two-season energy glazing and four-season energy glazing.

The differences have to do mainly with the coating that each one has, the gap between the two panes of glass, but also the permeability in terms of solar radiation.

The coating consists of metallic elements and is applied to the inner side of the glass pane during its construction phase.

Thus, the external aspects of the energy double glazing can be handled exactly like a common glass (e.g. when we clean it), since its energy efficiency is not affected since this is determined by the coating that the glass pane has on its internals sides.

Also, we should know that the energy efficiency of the glass pane is not affected by its thickness (whether it is 4 mm, 6 mm, or 8 mm), but only by the coating.

This coating, from the moment the energy glass pane is manufactured and then sealed, remains unchanged over time.

In ensuring high thermal insulation, an important factor is also the gap between the two glasses that make up the double glazing.

The maximum benefit occurs when the gap between the two panes of glass is about 16 millimeters, as well as when some noble gas (Argon, Krypton, Xenon, etc.) diffuses between them.

It should be noted that the Vlavianos company, usually adds some of the specific gases to the air chambers in order to further improve the thermal insulation of the glass pane.

These noble gases have the property of increasing the thermal insulation of the glass pane by about 20% more, however over time – and depending on the type of glue used for sealing – they gradually diffuse into the atmosphere.

It is estimated that every 10 years, about 50% of the amount of gas present in the double glazing is “lost”.

In any case, the cost of the gas is small and it is estimated that its amortization takes place already within the first or even the second year after the installation of the glass panel.

The third element that separates energy glazing from one another has to do with the level of solar radiation transmittance.

Depending on the needs of the household and the climatic conditions of the area where the property is located, there are glasses with a lower or higher solar coefficient, which determines the amount of sun penetration in the space without at the same time preventing the provision of natural light inside the residence.

Thermal insulation and sound insulation only with proper installation by Vlavianos

Of course, in addition to buying the right quality glass panel for each case, it is important to pay special attention to its installation.

The correct placement is the element that essentially ensures both the improvement of the thermal insulation of the property and the strengthening of its sound insulation.

In order to achieve this purpose, the panes should not be in contact with the frames but rubber should be inserted between them and the frames on both sides (internal and external).


Here it should be noted that the replacement of the glass panes does not imply the replacement of the frames.

The frame of an opening (window or balcony door) is “responsible” for only a small part of the total losses, which directly depends on the dimensions of the opening, the cross-section and shape of the profile, the material and the quality of its construction.

In addition, the frame makes up on average 20% of each opening and therefore cannot play a more important role in saving energy than the glazing that covers 80% of the surface of an opening.

Thus, each interested party should weigh the benefit and cost of replacing the windows of their property, especially since in most cases the new glazing can be applied without any problem to the existing frames.

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