Nowadays, there is a global urge to reduce the energy consumption, in order to slow down the environmental pollution. Since the building sector is one of the main energy consumers in Portugal, there is a great pressure for enhancing the energy efficiency in this sector. Currently the measure with more potential to effectively reduce the buildings energy consumption is the new Portuguese thermal regulation. However, to guarantee a good performance in reducing the energy consumption, the thermal regulation must present a good precision in the heating and cooling needs estimation. Therefore, the calculation model of this regulation was evaluated in relation to a dynamic simulation tool - VisualDOE. This evaluation was carried out applying both estimation methods to the Test Cells built in the School of Engineering of the University of Minho and the results obtained demonstrated a good performance of the thermal regulation.