Glass or a combination of several glasses is the main part of the window structure, which occupies the largest part of the opening in terms of area. Therefore, energy efficiency indicators depend to the greatest extent on the correct choice of glass.
However, it is impossible to visually determine the quality indicators of window glass. Only a specialist with a trained eye without a specification can assume (only assume!) how a double-glazed window will cope with energy saving. If you want to figure out which double–glazed window is installed, we give you some tips on where to start.
"If you want to figure out how it works, read the instructions." The advice is also relevant for window designs. When drawing up a contract for the manufacture of a window, it must necessarily include not only the dimensions, but also the formula of the double-glazed window. It is also often printed on stickers that mark the glass in the manufacture of double-glazed windows. Over time, the stickers are removed, but the contract remains with you.
The fastest way to decipher the formula is a specialist of a window company or an installation master, but if there are no such nearby, we will describe the main points.
Usually the double-glazed window formula has the form A1-B-A2, but it can be more complicated: A1-B1Ag-A2-B2 Ar- A3i.
Let's figure it out. The double-glazed window formula describes its design, starting with the outer glass. Each element of the formula is the thickness specified in millimeters. Thus, in our first formula A1-B-A2:
In practice, the formula of the simplest single-chamber double-glazed window looks like this: 4-16-4. After the explanations, it becomes clear that in this double-glazed unit, two glasses with a thickness of 4 mm are located at a distance of 16 mm from each other.
In modern double-glazed windows, additional glass functionality is often used, which will also be encrypted in the formula in the form of indexes. We have already used two of them in the second, more complex formula – Ar and i. What do they mean and what other indexes are there?
All letter designations are placed after the numbers to which they relate. Let's now decipher our second formula - A1-B1Ag-A2-B2Ar- A3i:
As you can see, it becomes clear that this is a two—chamber double-glazed window, the chambers of which are filled with argon, and the inner glass is energy-saving. This design will definitely keep a lot more warmth and comfort in the room compared to the first, single-chamber.

If the window has been installed for a long time, all the stickers have been removed, and the documents are lost, it will be difficult to figure it out. Here are some tips on what you can pay attention to:
"Folk" methods for determining energy-saving spraying (using the color of the flame in the reflection) are extremely unreliable. Only representatives of window companies can accurately determine whether there is spraying with the help of special equipment. It is not worth buying such a detector — its price is high, but it will be useful to you well, if once or twice in your life.
As you can see, even from a visual study of a double-glazed window, you can collect a lot of information. But it is better to leave all the documents after the installation of structures. In this case, after some time you will be able to return to this information, evaluate the energy efficiency indicators of the structure and, if necessary, improve them by installing a new double-glazed window with improved characteristics.
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