The targets for the building sector have been clearly defined starting with the Directive 2010/31/UE and ending with the long term strategy that implies the decarbonisation of the entire building sector. The aim consists in designing nearly Zero Energy Buildings (nZEB) starting from 2019 for public buildings and 2021 for all new buildings. For the energy retrofit of existing buildings, the last Directive 2018/844/UE on the energy performance of buildings sets a clear target for reaching nZEB also in the retrofit activity. Although that clear targets exists on a European level, some buildings are still poorly designed from the thermal point of view and are not able to meet these criteria. Thus, in many cases the thermal performance obtained in the design activity is not the one obtain in the operation phase of a building. That is why, not even buildings built after 2010, do not comply with the minimum recommended national thermal design criteria, and therefore need to be thermally retrofitted. Thus, the paper presents a thermography study done at a residential buildings, respectively the examination of the thermal performance of part of a façade. The focus is placed on a window-wall area that is examined by Infrared Thermography. The resulted thermograms are reconstructed by means of artificial intelligence in order to establish the thermal performance of the examined façade and building envelope components.