This strategy implemented by the Energy Efficiency Communication, which proposes mid and long-term objectives for the EU’s energy efficiency policy. In particular, it proposes a new energy efficiency target of 30% for 2030. With current measures, the EU will achieve energy savings of 18-19% by 2020, and to reach this 20% goal, it would be enough if all the member states only apply the agreed legislations without any need of additional measures. Also, the recast of “European Energy Performance of Building Directive" (EPBD) defined ambitious levels in two fundamental areas in order to reach the mentioned targets. The first aim is to spread nearly zero energy buildings (n-ZEBs) that are characterized by a very high energy performance (requiring almost zero or very low amount of energy) which will be largely covered by energy produced from renewable sources. The second aim is to identify cost-optimal levels of energy performance requirements for buildings.

The Commission Cost-Optimality Delegated Regulation (EC, 2012a) introduced a comparative framework methodology to determine a cost-optimal level of minimum energy performance of buildings and buildings elements. It establishes the necessity to take into account the global lifetime costs of buildings, and determining their future energy performance requirements. Furthermore, investment, operational, maintenance, disposal and energy saving costs of buildings will be considered. In this way, it is possible to evaluate the energy performance of the building, along with the financial aspects.

In order to follow the above mentioned regulations, a real single family house is chosen, located in Piedmont Region, Italy, to study and introduce different energy scenarios.

The aim of this study is using the cost optimal methodology as an evaluation tool at the primary stage of the project in order to identify different energetic configurations. In fact, the goals expected to achieve by the end of this study are reducing the required budget in the energy packages, initial investment, and energy consumption costs coming afterwards. The goal is to explore a common method that can be used as a support in the various decision-making processes, those emerge during the architectural design, technology choices, and energy scenarios.

In detail, different solutions with different initial investment cost values for envelope configurations and plant systems were selected, while the architectural aspects of the building remained with no change.

The chosen methodology follows different steps; the starting point consists in the energy evaluation by adopting different envelope configurations, which effects the energy demand. The envelope components are chosen to fulfill the energy performance requirement levels based on the building regulation of the city of Turin. The component’s U-transmittances are almost the same, but different in terms of internal mass. So it was for this reason that internal thermal comfort was analyzed.

Furthermore, the energy calcu for heating, cooling, lighting, and HVAC sywas assessed by using the software “EnergyPluh allows performnamic energy simulation.

Second step is evaof the financial performance, which is calculated by the gst methodology as a decision-making tool betferent energy scenarios. Finally, by comparing theinds os in a graph, the cost optimal level can be and further it helps to make an adequate design choialyzing the relationship between energy performances and costs, those are applied during theife cycle of the .

In order to confrobustness of results obtained from the cost optimal methodology, different sensitivity analysis are carried out by varying some effective inputs.

So, at the end the most convenient energy package will be chosen based on the best architectural aspects, and optimized energy and economic packages.