The aim of the research is to assess the change in the cost over time of building modernization projects in Ukraine. According to experts, approximately 75% of Ukraine's housing stock consists of Soviet-era buildings characterized by uninsulated building envelope and inefficient worn-out heating, ventilation, and air conditioning (HVAC) systems. Over the course of two years of military conflict in Ukraine, around 140,000 residential and over 500 administrative buildings have been destroyed. Considering the necessity of analyzing the possibilities for energy-efficient construction and/or restoration, the study presents ways to enhance the energy efficiency of buildings using a specific administrative facility in Kyiv as an example. Specifically, the authors conduct an analysis of various combinations of additional thermal insulation layers and changes in the heat supply source on the building's energy consumption and, consequently, the level of carbon dioxide emissions reduction. A comparative economic assessment of the proposed technical solutions is conducted using a life cycle cost approach and considering the risks of possible changes in energy tariffs and/or fixing them at a certain level. Additionally, the authors draw attention to the fact that despite significant changes in Ukrainian legislation and substantial progress towards improving energy efficiency in the construction sector, the provision of highly energy-efficient buildings and decarbonization is occurring at a slow pace due to the demotivating energy tariff policy for energy efficiency