*3.2. First Step: Green Audit*

According to the previous above of the integrated energy and environmental audits of historic buildings, in this case study, different surveys were developed, including a thermography analysis, data were collected about the schedule and system plan, and a dynamic energy model was created to evaluate the building energy performance. Using this method, some energy efficiency measures were identified.

The entire building envelope does not have thermal characteristics similar to the energy behavior required by actual normative; the historical protection status and heritage value do not allow energy efficient interventions such as thermal insulation of external/internal walls or window substitution, so the best energy improvements cannot be adopted.

The energy performance of the building envelope is low, especially in some zones (such as the attic) or in some local points (for example, near the external systems placement or where, in previous years, a replacement and refurbishment has been completed with the use of different materials causing thermal bridges), so interventions should completed to maintain the integrity of the building structure.

The thermal energy lost through the windows is high, thermal loss and need improvement, especially into the curved partition. The intervention involves redoing the sealing between the frame and glass to maintain the historical elements and reduce the thermal bridge problem.

An electrical system intervention should be considered as the most important measure due to the high consumption and costs; the energy and economic savings should be achieved without altering the historical elements of the buildings that are listed and protected by the Historical Superintendent.

Intervention on the reduction of domestic hot water (DHW) should not be considered relevant due to its low use and cost.

Another useful tool in the audit step is dynamic simulations. A numerical model of Ca' Rezzonico was set up by Design Builder®(powered by EnergyPlus®) to validate simulated values with real consumption. As shown in Table 5, the deviation was 1% on average for natural gas and electricity use.

**Table 5.** Comparison of energy consumption between real data from bills and output simulation by the Design Builder model.

