*3.2. Building Envelope Retrofitting Measures*

In all the retrofitting cases a reduction in heating and cooling consumption occurs. Its magnitude is linked to the relevance of the retrofitted building component on the energy consumption of the examined house, depending on the single case's geometric and thermo-physical parameters. Figure 6 shows the primary energy savings and the reduction of local emissions compared to the current situation. Evaluating the single interventions, the largest primary energy savings are linked to the interventions of isolation on the vertical opaque walls, on average equal to 16.3%, while, the smallest savings derive from the window ones, about 6.8%. This is due to the fact that, in many dwellings, the windows have been recently replaced. The intervention of insulation on ceilings and floors allows on average savings of 14.0% and 8.5%, respectively. However, the retrofitting of the whole building envelope can lead to a primary energy saving of about 30.8%. The trend of savings in local emissions is qualitatively similar to the primary energy one, although amplified: for vertical opaque walls a saving of 26.3% is achievable; for ceilings, 18.9%; for floors, 11.8%, and for fixtures, 11.5%. It leads to on average 47.6% in the case of the whole retrofitted building envelope. The reason for this amplification lies in the fact that, as seen, most of the heating systems are gas-fired and require local combustion to generate heat.

**Figure 6.** Resulted savings of (**a**) primary energy consumption; (**b**) local emissions.

Figure 7 shows the variations in the use of renewable energy and the number of flexible loads at each retrofitted building component.

**Figure 7.** Resulted changes in (**a**) renewable energy use; (**b**) flexible loads.

The considered insulation interventions lead to a reduction in heating and cooling consumption, i.e., storable loads.

Moreover, the small variations are connected to the reduction of the electric consumption of the components of the heating system such as circulation pumps and fans, and to the reduction of cooling consumption, in the houses, if present.

Considering the whole building insulation intervention, the reduction of renewable energy use is less than 2% and the reduction of flexible loads is less than 5%.

Indeed, in the current plant configuration of Italian houses, a redevelopment intervention of the building envelope weakly affects the flexibility potential of the house. Yet, it entails valuable energy savings and reductions in local polluting emissions. In absolute terms, in the case of the whole building envelope retrofitting, flexible loads vary from 1043 to 1002 kWh/y.

#### *3.3. Heating, Cooling, and DHW Systems Upgrading*

In all the upgrading cases, a reduction in heating and cooling consumption occurs. Its magnitude is related to the relevance of the redeveloped element on the energy consumption of the analyzed dwelling, depending on the single case geometric and thermo-physical parameters.

Figure 8 shows the primary energy savings and the reduction of local emissions compared to the current situation. The largest savings in primary energy are observed for interventions on the heating system's heat generator, due to the high incidence of heating consumption on overall consumption [54]. For the upgrade option #6 the savings are on average equal to 6.5%, while for upgrade option #7 they are on average equal to 8.6%. Almost negligible savings, i.e., <1.5%, in all the other upgrading options occur.

Referring to the local emissions, the achievable reduction due to the installation of a heat pump as a heat generator and as the DHW production system are huge since they are 66.9% and 17.8%, respectively.

**Figure 8.** Resulted savings of (**a**) primary energy consumption; (**b**) local emissions.

Figure 9 shows the variations in the renewable energy use and the number of flexible loads at each system upgrade. Similar to the previous KPIs, the changes in those two thanks to the installation of heat pump are very significant (#7, #9). For the system upgrading #7, the increase in renewable energy use is on average 360% while, for the system upgrading #9, the variation is 45.4%. It is remarkable that for the other system upgrading the changes are very small: −1.2%, −2.1%, and −1.7% for #6, #8, and #10, respectively. The same behavior can be found for the changes in flexible loads. Indeed, system upgrading #7 and #9 imply their significant increases, about 147.0% and 80.1%, respectively. Then, small decreases occur for system upgrading #6, #8, and #10, i.e., −3.8%, −5.7%, and −4.8%. In absolute terms, the flexible loads in the system upgrading #7 reach 2111 kWh/y, whereas in #9, they reach 1443 kWh/y.

**Figure 9.** Resulted changes in (**a**) renewable energy use; (**b**) flexible loads.

The results of the simulations carried out confirm the usefulness of the heat pumps to increase the flexibility of the loads [62,63], as a basic element of a system that must necessarily include storage systems [64–66]. Anyway, the location of the storage system inside the dwellings remains to be explored. As a matter of fact, the DHW storage system is generally small [23] and easy to install inside the dwelling. Nevertheless, the storage system required for space heating is much larger, depending on the climate zone, the characteristics of the house, and the behavior of the occupants [67] together with needed preservation of architectural appearance when the building is considered historic or even listed [68].

## *3.4. Combined Building Envelope Retrofitting and System Upgrading*

Finally, given the small changes observed in the previous section, the intervention to upgrade the cooling system was excluded.

Figure 10 shows the primary energy savings and the reduction of local emissions compared to the current situation. In terms of primary energy savings, the five combined scenarios are substantially equivalent, with savings ranging between 32.6%, in the case of #11, and 35.7%, in the case of #14.

**Figure 10.** Resulted savings of (**a**) primary energy consumption; (**b**) local emissions.

Referring to local emissions, the achievable reductions are larger than 50% for all the combined scenarios, being able to reach 84.9% in the case of scenario #15, i.e., with complete electrification of space heating and DHW production.

Figure 11 shows the variations in the renewable energy use and the number of flexible loads at each combined retrofitting and system upgrading. As the outcome of system upgrading scenarios, the introduction of the heat pump as a heat generator significantly increase the renewable energy use, reaching on average values greater than 150% as in the case #15. Even in terms of flexible electric loads, a strong increase in the flexibility potential occurs, reaching 116.4% in the case of #15.

**Figure 11.** Resulted changes in (**a**) renewable energy use; (**b**) flexible loads.

In absolute terms, the value of flexible loads in scenarios #12, #13, and #15 reaches 1.329, 1.399, and 1.725 kWh/y, respectively.

These results are numerically lower than those found for scenario #7 where there was the installation of the single heat pump for space heating purposes. However, in this case, the lower increase in flexibility potential matches with positive values of all the other KPIs, i.e., primary energy savings, local emission reduction, and renewable energy use. Furthermore, the reduction of the heating demand has as a further positive aspect, an easier insertion of the storage system within the dwelling due to its new smaller required size [67].

## *3.5. E*ff*ects of the Proposed Measures*

The changes deriving from the implementation of renovation measures are summarized in Table 6 reporting the values computed of the four KPIs.

