Life-cycle cost analysis of possible solutions for converting existing single-family house into nZEB

The obligation of the nZEB building standard has become a certainty of almost two years for all new buildings in Romania. This is even more relevant in the current context of the energy price crisis, as more and more building owners become aware of the importance of energy efficiency and the use of renewable energy systems. Thus, in this paper possible solutions for converting an existing single-family building into a nearly zero-energy building are analyzed and presented. The building has been designed and executed in such a way as to have an energy performance above the minimum required according to the technical regulations in force at the time of design. The current energy performance of the building has been evaluated both theoretically using a dedicated calculation program and based on energy bills for one year period. Based on the current energy performance, a series of solutions have been proposed to increase the energy performance up to the nZEB level. Analyses in terms of energy consumption and life-cycle cost were performed to identify the cost optimal solution that leads to the nZEB upgrade.