Today, more than ever, when you build a house or renovate a house when you have the choice of the new fixtures is of utmost importance, not only from the aesthetic point of view. It is shown that one of the main routes of escape of heat from the inside to the outside of the dwelling is caused by the doors and above the windows. So, to save energy (and therefore money because of heating costs), it is essential to choose modern frames, which, in addition to the strength, durability and aesthetics to take into account in particular of the thermal insulation. Since the thermal insulation works in both directions, will be useful even in summer. In fact, the windows that limit the dispersion of heat during the cold season, act in the same way, even during the warm season, but in reverse, that is, tend to prevent the external heat from entering the house.


The parameter used to evaluate the performance of thermal insulation of windows is the thermal transmittance, which has as its unit W / (m ^ 2 * K). Represents the average heat flux per unit area that passes through a window placed between two environments with different temperature. The higher this number, the worse the insulating capacity of the frame. During the fixtures we can distinguish three elements that determine the ability to isolate the heat. The most important is the type of glass used. The second from the structure and the material from which the frame is formed and the third, which is partially responsible for the construction company that realizes the house, the greater or lesser precision, sealing and waterproofing of the interface between the window frame and the wall. This article addressed the choice of frames, we will consider only the first two aspects.

Let’s start with the choice of the type of glass that uses the frame. As is easily understood, this is the part that most of all influence the thermal transmittance because it is the one that offers the greatest area of connection between the outside and the inside from the house. Clearly they are to avoid fixtures that use only a glass, now rare. The choice lies between the double glazing and the latest triple glazing. The modern double glazing, to avoid that the entire space can be dirty or moisture can enter there, are made ​​watertight and inside they contain, normally, an inert gas such as argon or krypton. These types of glasses are also known as double glazing. The triple-glazed windows are similar to double glazing but have two airlocks. ‘S finest cases, they are used so-called low-emissivity glass, which, while facilitating the penetration of light, they prevent the heat radiation to the outside of the body warm places inside the house. This is achieved by coating the faces of some glasses with special metallic oxides. Compared with single glazing, double glazing transmittance U has a low emissivity by about half, while the triple-glazed windows transmit heat up to four times less than the single glass.