# Sustainable Modularity Approach to Facilities Development Based on Geothermal Energy Potential
## 3 Results and Discussion
### Energy Demands
The power demands \(P\) for heating were calculated for two different outside temperature settings:  
* \(Pa\)--for average outside temperature (per the procedure for establishing EPC class), and
* \(Pd\)--for design temperature (per the procedure for sizing the overall capacity of a heating system). The power demands \(Pd\) for the heating with regard to the outside design temperature were calculated based on \(Pa\), using the following formula  
\[Pd=\frac{Pa\times(t_{i}-t_{d})}{(t_{i}-t_{a})} \tag{2}\]  
where \(t_{i}\) is the designed interior temperature, \(t_{d}\) is designed exterior temperature and \(t_{a}\) is the average exterior temperature. The resulting power demands for the study cases are shown in Figure 14.  
During initial research, after developing the modularity-based approach, the modules were formed as single-purpose entities (one module for one type of balneological treatment--Figures 7, 11 and 12). This approach was rather successful in many cases, where it provided more options for interaction with the natural environment and versatility of outdoor balneological treatments on semi-private or private patios. However, extending such a concept to more units would be rather demanding because land occupancy, daily operation, supervision and other issues would have to be considered on case-by-case basis. The model used for the calculations is somewhat more compact with paired wellness modules (Figure 8). The initial module would obviously show higher energy demands for heating, but it is expected to be used in facilities that operate only during the summer. In both cases, special attention is dedicated to passive measures for thermal comfort during the summer, thereby minimizing mechanical ventilation and air conditioning while addressing the well-being of users, in addition to enhancing hygiene standards, new occupancy protocols and energy efficiency issues. Figure 14: Power needed for heating. Exploring energy performance of three development stages in two types of materialization provided six scenarios where some additional observations can be made regarding thermal envelope components:  
1. The share of the components' surface area in the overall thermal envelope area remained mostly constant throughout the development stages (Figure 15a). The ratio between the opaque and glazed elements was approximately 3:2 in all three stages, and the only component that showed a significant increase was the interior wall-to-unheated space as unheated technical modules are added. 2. The glazed surfaces accounted for more than half of heat transmission losses even in enhanced cases (Figure 15b). This component is key not only for energy efficiency but also for thermal comfort throughout the year, so the exact sun exposure and anticipated occupancy regime of particular facility should be specified on a case-by-case basis. 3. The materialization of opaque components reflects on the overall energy performance but further studies should be performed regarding the feasibility of using the enhanced option; the production of panels with more than 30 cm of thermal insulation (Table 3) requires technology and resources that might be more challenging for local companies. The composition of interior walls to unheated spaces may remain as proposed for the base case in all scenarios since their share in heat transmission losses is almost irrelevant (0.5-1.5%)
4. Since flat roofs cover a significant area, mounting PV units as additional renewable energy resources might cover the energy needs of electrical equipment. Regardless of the capacity of the location and the materialization variant, all development models consumed significantly less energy for heating than the geothermal potential provides. At Ljuba, the site with the lower capacity, development model 3 (maximum size) in the basic code-compliant state of materialization, and taking into account extreme external temperatures, yielded 35% of geothermal capacity; at Banatsko Veliko Selo 2, it was only 11%.