**3.1 Energy analysis**

Numerical simulations have been performed in order to calculate the energy need in configurations C1, C2, and C3. Results have been obtained in both quasistatic and dynamic condition. Two different locations have been considered: (i) Milan, located in the Italian climate zone E (heating degree days in the range 2101–3000, heating period from the 15th of October to the 15th of April and collects about 4000 cities), and (ii) Palermo, located in the Italian climate zone B (heating degree days in the range 601–900, heating period from the 1st of December to the 31st of March and collects about 150 cities).
