The building was designed to be highly energy efficient and obtained the level A in the Italian energy certification [30]. Four buildings compose the entire project. In this study, only one building was evaluated. The building has nine stories in contact with the ground. The basement was not evaluated. On each floor there are four apartments of different sizes. The internal and external walls are made of X-Lam structure. The rock wool insulate was used in the envelope of the building. The aluminium windows with triple glass and argon gas, with a thermal transmittance of 1,1 W/m2K, were used. Shading devices in aluminium were used to reduce the solar irradiation on the building. Fig. 3 shows the thermal characteristics of the envelope of the building.    

The first parameter evaluate is the indoor comfort hours in the building. Through the adaptive comfort method [39] it was possible to determine the number of hours in which there is internal thermal comfort in the building throughout the year with and with no design solutions. The EnergyPlus computer programme, version 8.4, was used. This analysis consists in verifying if the use of design strategies allows for an improvement in the internal thermal comfort. Eq. (1) shows how to estimate the upper limit.

(1)                                                            Ulim= 0,31 x tpma + 21.3

where Ulim is the upper limit of the comfort zone (°C), tpma is the mean outdoor air temperature (°C).

Eq. (2) shows how to estimate the lower limit.

(2)                                                            Llim= 0,31 x tpma + 14.3

where Llim is the lower limit of the comfort zone (°C), tpma is the mean outdoor air temperature (°C).

Through the limits of the comfort zone is possible to define if the design strategies improved the thermal comfort conditions of the building. Eq. (3) demonstrates how to obtain the number of hours in which there is internal thermal comfort through the use of the design strategy.

(3)                                                                   Hcomfort = Ha  - Hb     

where Hcomfort is the increment in the number of hours in which there is internal thermal comfort over one year when a design strategy is used (h), Ha is the number of hours in which there is internal thermal comfort over one year with the use of a design strategy (h), Hb is the number of hours in which there is internal thermal comfort over one year without the use of a design strategy (h).

The primary energy demand was analysed through the LCA. Thanks to this analysis, it was possible to identify the energy balance, i.e., the energy saved over the building life cycle through the use of the design strategies (Eq. (4)).   

(4)                                                       LCEb= OEs - (EE+ME+DE) + ELR

where LCEb is the life cycle energy balance (kWh); OEs is the operational energy saved due to the use of the design strategy (kWh); EE is the embodied energy in the design strategy (kWh); ME is the maintenance energy due to the design strategy (kWh); DE is the demolition energy in the design strategy (kWh); ELR is the energy life-cycle of the component in the base case that will be replaced by a design strategy.

The embodied energy of the design strategies was obtained from three different data-base: ICE database [40], Ecoinvent 3 and the EPD certification of building materials. The average value and the standard deviation were used to analyse the design strategies (Fig. 5).