Measurements in Greece of installed windows and comparison between the given air permeability classification and the classification applied to the building envelope

According to the European regulation EN 12207:2017-03, the air permeability of windows and doors is categorized in four different classes and when they are installed on the building envelope, the declared air permeability class should remain unchanged.  
The approach is to perform on-site measurements and to confront 40 different cases of windows and doors installed on new and retrofit projects in Athens, Greece.  
The purpose is to discover and highlight the most common errors to the correct installation and suggest easy tactics to prevent them.  
At the same time, beside the correct installation testing, the measurements registered and confirmed separately on-site each frames air permeability class and compared to the declared one by the manufacturer. The results are that in some cases, the declared classification was different than the classification measured on-site, which means that the product was faulty without any visual confirmation.  
The conclusion is that at 95% of the cases, the installed classification was minor of he declared one. This conclusion confirms that the installation methods are not evolved technically as the frame industry has and the given quality of the window manufacturer is not applied on the building envelope. This situation leads to energy losses because of the bad technical instructions, even though the owner of the building has invested on a better-quality product.  
This reality urges the need to evolve the legislation and impose mandatory air-tightness checks during every application of window and doors on the building envelope.