## 1 Introduction
For instance, using 8 cm of thermal insulation made of polystyrene foam with added graphite (Expanded Sintered Polystyrene, EPS) in an external wall based on reinforced concrete and bricks (0.981 W/m\({}^{2}\)K) can reduce wall transmittance to 0.21 W/m\({}^{2}\)K, achieving a 51.8% reduction in primary energy demand [10]. In ref. [16], four scenarios are proposed with different energy efficiency measures and HVAC systems for block apartment buildings in Prishina, Kosovo, showing a reduction in heating energy demand by 116.7 MWh/year, natural gas demand (gas boilers partially replaced by heat pumps) by 243.49 kWh/year, and 86% mitigation of carbon dioxide emissions after implementing the measures. [PERSON] et al. [17] presented some simulations of two envelope scenarios in Milan (internal and external insulation) using Integrated Environmental Solutions: Virtual Environment (IESVE) software, indicating that the external insulation scenario provided a slightly lower peak thermal flow rate. [PERSON] et al. [18] performed energy audits of 11 comparable multifamily buildings in Poland, revealing that rebalancing heating systems and using thermal insulation materials could effectively reduce energy consumption. To enhance the thermo-physical properties of building facades, polyvinyl chloride-coated polyester fabric material can reduce space heating energy demand by about 9.8% [19]. An innovative insulating plaster material made from corn production waste and natural hydraulic lime of Wasselonne can decrease thermal energy losses by 20-40% in historic buildings [20]. Retrofit actions on the envelope of residential buildings across various locations were evaluated by [PERSON] et al. [21]. Results proved that the insulation material on internal walls can improve building energy performance. Dynamic simulation models are widely adopted to assess building energy performance and related efficiency actions. These models optimize overall system performance and evaluate real-time system operation [22]. Among the tools available, the TRaNsient SYstem Simulation (TRNSYS) software is commonly used by researchers. TRNSYS, based on a library of validated components, produces highly reliable results [23]. Dynamic models not only simulate the real properties of the building envelope but also model HVAC systems, providing robust and accurate evaluations of building energy consumption and proposed energy actions. Many studies in the literature on residential building renovation highlight the importance of accurately detecting reductions in energy consumption and actual economic savings for users. In this context, this paper aims to demonstrate the real advantages of using a dynamic simulation approach when a large number of buildings implement energy refurbishment actions, also considering possible economic incentives. To this end, detailed models are presented to evaluate the economic and energy savings from the adoption of particular energy measures related to building envelopes and the replacement of traditional boilers. These models are developed for various building geometries and shapes using the TRNSYS environment, a well-known tool in the research community. The ultimate goal is to estimate the energy, environmental, and economic savings associated with the application of such measures for two penetration scenarios. The results of this work can be valuable for system designers and end users, providing an accurate assessment of the energy and economic performance of different thermal insulation materials for external walls and novel heating systems. This study does not investigate the performance in the summer period due to the reduction in cooling energy demand after the energy retrofit of the condominium buildings. In the reference scenario, the condominium buildings under consideration are not equipped with cooling systems, and the primary focus of this study is on reducing energy consumption during the heating season.