Considering the military impacts in Ukraine and the global push toward decarbonization, we evaluate opportunities for achieving a low‐carbon transformation in the construction sector. In particular, we analyze the effects of enhancing the building's thermal insulation and supplying heat via renewable energy sources during the modernization of an existing administrative building in Ukraine to meet European Union requirements. This analysis considered economic, technical, and environmental factors. Thus, we present the results of dynamic modeling of the building's energy consumption at different levels of building insulation using the DesignBuilder software and provide an integrated forecast of the payback period for investments in improving the building's thermal insulation and using heat supply options such as heat pumps and pellet boilers). To assess emissions reduction of the proposed building modernization options, an analysis of the existing national methods of calculating carbon dioxide emissions was carried out. The use of photovoltaic panels for electricity supply was considered in the PV∗SOL software as an option to reduce carbon dioxide emissions, which can be taken into account through the Net Billing mechanism, including when using a heat pump for heating.