## 2 Materials and Methods  
### The Building  
A residential single-family house built in Padova (north of Italy) in 2018 has been considered in this paper as the application case study. The building is a detached triple-story house and consists of two heated floors and a nonheated title. In Figure 1, the building 3D model developed in Google SketchUp is shown. The ground floor includes a kitchen, living room, stairwell and bathroom, while on the first floor, three bedrooms, two bathrooms and a stairwell are present. Additionally, a technical room and an unconditioned garage are located on the ground floor. All rooms have a net height of 2.7 m except for the technical room and garage, which are characterized by a lower height (2.4 m). The total net floor area of the building is about 162 m\({}^{2}\), while the gross conditioning volume is equal to 705 m\({}^{3}\).  
The considered residential building is characterized by a high-insulated envelope. Indeed, although it was designed in 2017 and built in 2018, the current demanding limits on transmittance are respected [26]. In particular, the external walls, the slab-on-grade and the roof transmittance values are, respectively, equal to 0.24, 0.14 and 0.24 W m\({}^{-2}\) K\({}^{-1}\), while for buildings submitted for energy refurbishment, the standard requires 0.28, 0.29 and 0.24 W m\({}^{-2}\) K\({}^{-1}\), respectively. Eleven external windows having a total surface of 33 m\({}^{2}\) are present in the building. Each window is characterized by low-emissivity double glass (4/12/4) filled with argon. The window frame, made of pliable wood, has a U-value of 1.3 W m\({}^{-2}\) K\({}^{-1}\). Consequently, the overall window transmittance is equal to 1.67 W m\({}^{-2}\) K\({}^{-1}\). The window solar factor is 0.67, and additionally, internal light-color mobile shields are present.  
The tridimensional model of the building has been implemented with Google SketchUp and successively imported within the TRNSYS environment [27]. All features of the building have been defined in the plug-in TRNBuild (Type 56) of TRNSYS, and the numerical model of the HVAC system, reported in Figure 2, has been developed in Simulation Studio. As pointed out in Figure 2, several types from both standard and TESS libraries are included in the model. In particular, Type 534 is used for the thermal energy storage, Type 114 simulates the behavior of single-speed pumps, and Types 647 and 649 are employed for diverters and mixers, respectively. Additionally, the room thermostats are implemented through Type 2d (on-off controller) and are included within macros RT_C (see Figure 2). Specific numerical models introduced by [PERSON] and [PERSON] in [28] are used to evaluate the performance of the ASHPs and GCHPs considered in this paper.  
In order to define all the elements that influence the energy balance of the building, internal heat gains due to people, equipment and artificial lights have been considered. According to the results of a survey carried out with the building owner, the hourly occupancy profile of the four tenants has been implemented in TRNSYS. The thermal sensible and latent heat emitted per person is equal to 75.5 W and 29 W, respectively, corresponding to a condition of sedentary activity [29]. Regarding the artificial lighting, LED lights are installed in the building's rooms for a total electric power of 724 W. When the lights are switched on, the heat gain is 10% of the total electric power. In this regard, an on-off logic connected to the solar radiation impacting the building's external surfaces has been defined in the numerical model.  
Figure 1: Building 3D model: southwest (**a**) and northeast (**b**) view.