The IEE Passive-On project has drafted a proposal to adapt that Standard to the conditions that characterize Southern Europe, which is described in this paper together with its rationale. Compared with the original definition, one of the main changes is the introduction of explicit requirements on internal comfort during summer, in parallel to a limit to energy needs for cooling. The dynamic simulations conducted to test the new definition of the Standard in the context of Southern Italy (e.g. Palermo) show that the requirements identified by the Passivhaus Standard can be met by simplifying the envelope technologies (e.g. relaxing air-tightness design value) used in the context of Central Europe and adopting passive cooling strategies appropriately adjusted. Some simplifications of the ventilation system can be compensated by an increased role of thermal insulation of the building envelope and some of the choices can make energy needs tend to zero. In accordance with EN15251, thermal comfort is characterized according to Fanger’s PMV in cases where mechanical cooling is still required for peak situations, and according to the adaptive model where no mechanical cooling is required.