The various types of windows are divided into four classes based on air tightness. Class 4 is the most performing and guarantees the best anti draft behavior, class 1 is the lowest. A further class 0 indicates the windows that have not been tested for the evaluation of air permeability. If you are planning to change the windows and are considering the various types of windows this is an indication that may come in handy. And keep in mind that the same classification also applies to doors.
The classification based on the air tightness of the various types of windows and windows generally takes place according to the UNI EN 12207 standard. It defines the flow of air that passes through the test sample, suitably closed, subjected to test pressures. Class 4 windows and doors are the most anti-draft, and consequently also the most anti-noise, but be careful: the evaluation only concerns the window and is referred to the test in the laboratory, not in operation.
The latter is a critical aspect in the choice of various types of windows. And this is why, when evaluating its performance, we should always talk about the 'window system', including the frame, window frame and glazed part. For a window system to be efficient in terms of airtightness, professional assembly and periodic adjustment of the hardware are important so that the sash closes well on the fixed frame.
For the air tightness of the various types of windows window seals are important. They must always be applied continuously along the entire perimeter of the stop joints and must not change over time, but remain elastic and easily replaceable. A good advice when choosing a window is to prefer models with sturdy gaskets but also easy to change periodically.
Do you have the problem of drafts from the windows but it is not necessary to change the windows? You can remedy with a draft excluder sealing tape or, if you really do not see a technical alternative, with the classic 'sausage' draft excluder. You can also buy them online and follow the installation instructions in the article how to eliminate drafts from doors and windows