The circular economy (CE), as an antidote to the ubiquitous and dominant global economic concept characterized by the uncontrolled exploitation of natural resources and the flow of materials from producers to users to landfills, has become inevitable. The application of circular business models is especially needed in the building sector, as one of the main consumers of natural resources and energy, considerable polluters, and substantial producers of waste. Since architects are important participants in the process of designing and building structures, it is clear that circular principles should be incorporated into architectural design (AD) as well. This paper deals with the analysis of the degree of application of circular principles in AD in Serbia and the challenges and difficulties that architects face in this endeavor. The methods used in the research included an unstructured interview on the basic principles of CE, a case study of selected housing renovation projects in Niš, Serbia (as an illustration of the principles that deal with extending the life of buildings in the domestic environment), and a survey on the degree and importance of the application of the CE principles in AD among architects in Serbia. The case study results and survey results led to the outline of guidelines for future AD in accordance with CE principles and recommendations for creating a working environment for the architects that is more circular oriented.

Relations among neighbors are a key indicator of the strength of a local social community, contribute to social cohesion and are an important factor in achieving a higher level of social sustainability. On the other hand, the environment in which people live plays an important role in encouraging social contacts and developing relationships between people. In order to establish social interactions between neighbors within a multifamily apartment building (MFAB), it is necessary to provide adequate spaces for communication between residents. This was especially emphasized during the mobility restrictions caused by COVID-19, although this necessity is permanent. This paper analyzes the influence of the physical characteristics of common spaces in MFABs on the quality and intensity of contacts among residents of MFABs in the City of Niš, Serbia. In order to determine the current quality of these spaces as a physical framework for interactions among residents and to identify the wishes of users regarding interactions with neighbors in these spaces before and during COVID-19 pandemic restrictions, a survey was conducted. The analysis of the survey results and numerous examples of housing design led to (1) the formation of guidelines for future designs of MFABs and (2) recommendations for redefining the standards regulating the field of housing construction in the region, both applicable during the period of the pandemic and after it.

In times of radical social transformations, the demand for flexibility of space can be identified as one of the strategic priorities of maintaining the urban environment. In the context of social, economic and environmental sustainability, housing must imply an integrated ability to respond to programme changes, which can be achieved through the concept of flexibility. By identifying and applying certain design principles, it is possible to prevent the problem of functional obsolescence and unsuitability of the living environment that modern cities are facing. The apartment as an immediate living environment is the most direct indicator of the degree of adaptability of the physical surrounding to modern human needs. The analysis of basic design principles, using an example of flexible apartment, examines the spatial correlations and laws of the relationship between elements of the plan, which provides the basis for the authors to draw the conclusions about the reality of applying this concept in practice.

This paper presents architectural project and simulation of energy consumption and production of a model of Energy Efficient House for Decentralized Energy (DE). The house model is designed for the area of Serbia, based on the needs of an average Serbian family. The model is designed to investigate opportunities for DE of typical house geometry with advantages of passive solar architecture combined with active solar systems and heat pump. Simulation of the model was performed for the climate conditions for the city of Nis. Thermal load for designed net-zero energy efficient home for a period of one year was simulated by means of trnsys software. With respect to renewable energy sources in Serbia, production of electrical, heating, and cooling energy by solar photovoltaic/thermal collectors, heat pump, and heat storage is considered. The balance of simulated annual electricity production and consumption show that the house model can produce 51% of its energy demands. Simulation results are used to determine pathways for model modification towards more effective solar harvesting for electricity production.