The diversification of the defence industry at the backbone and city-forming enterprises of the complex will directly affect the diversification of single-industry towns, the production facilities transformation of the complex and real estate of single-industry towns. The prospects for the development of the city-forming enterprises of the defence industry and related single-industry towns in the context of a decrease in the state defence order seem unfavorable. The diversification of defence industry complex will affect the formation of a high-quality living environment in a single-industry town.The article considers three alternative solutions to the state and status of these objects – their reconstruction, transformation or possible liquidation. It is noted, that it is possible to solve the urgent task of improving the energy efficiency of buildings through the use of both technical and architectural means during the reconstruction of the industrial complex of the defense industry and real estate of a single-industry town.