Scenario Approach

Monitoring indicators and model assumptions concerning data on the building envelope and thermal system characteristics were identified for the definition of both the Basic Case, which represents the current situation of the residential building stock of Piedmont region, and the scenario analyses. As regards the model assumptions, they were chosen as to represent the most probable conditions and by adopting a reasonable compromise between the advantages and disadvantages of their application within the Basic Case and the scenarios.

The calculations of the energy performance of the Basic Case and the scenarios were performed by using some representative buildings of the regional residential building stock derived from the “Building Type Matrix” of the TABULA project. The frequency of each building-type within the stock allowed to quantify the energy performance of the entire regional housing stock.

The Basic Case (Figure 2) is characterized by indicators of the building envelope and indicators of the thermal system. The former are separately related to the vertical opaque enclosures and to the windows, of which eight and four U-value ranges have been defined respectively. The latter are represented by nine different heat generators, each of which is characterized by a specific energy carrier. The current state of the regional housing stock is defined by means of combinations of walls and windows U-value ranges and heating system types for each construction period. Each combination represents a percentage of the total residential building stock (RBS) floor area.

The three developed scenarios, i.e. Trend Scenario, Cost-optimal Scenario and Target Scenario (Figure 3), concerning the energy refurbishment of the housing stock differ from each other for the following properties:

-       types of retrofit actions and requirements of the energy efficiency measures,

-       amount of refurbishment actions in the building stock,

-       energy and environmental performance resulting from the application of the actions.

Depending on the scenario, the second and the third listed properties represent alternatively the input and the output data (i.e. the result) of the analysis.

The calculation of the Basic Case and the scenarios energy performance was carried out according to the procedure of the technical specification UNI/TS 11300, which is the Italian calculation method for the building energy certification and the compliance verification of minimum energy performance requirements for new and existing buildings.

Results

The results are shown in terms of Summary Indicators (Figure 4), which consist in the following annual quantities:

-       CO₂ emissions (m_{CO2,heat supply});

-       total heat demand (q_total);

-       CO₂ emission factor heat supply (f_{CO2,heat supply}).

The Trend Scenario and the Cost-optimal Scenario do not reach the 2030 and 2050 targets far and they do not achieve the 2020 benchmark for a little amount. Both the Trend Scenario and the Cost-optimal Scenario follow the actual trend of energy refurbishment in Piedmont region and present similar results, even if different energy efficiency measures and requirements are applied. In fact, the Trend Scenario applies the most common measures whose requirements (e. g. U-values of the building envelope components) are fixed by a regional decree; while, the Cost-optimal Scenario considers the cost-optimal requirements for the energy efficiency measures got from the national application of the comparative methodology complying with Article 5 of Directive 2010/31/EU (EPBD recast).

The sole scenario that attains the national climate protection targets in the reference years is the Target Scenario, as it has been really created at this scope in order to discover the annual trend of energy refurbishment that should be followed to reach the targets. The effective trend would consist in a global energy refurbishment of 2 % of the regional residential building stock floor area every year, although considering the same technologies and the energy efficiency requirements of the Trend Scenario. The current trend of improvements is therefore inadequate, as it is based above all on partial building renovations, and the annual global actions involving both the building envelope and the thermal systems are just 0.1 % of the housing stock floor area.