We substantiated design and construction-technological solutions for increasing the energy efficiency of thermomodernizable buildings and structures based on the conducted calculation-and-experimental and numerical studies. We investigated effective structural parameters and material of examined elements of a thermomodernization system of residential buildings and structures, which started their operation before the 90-ies of the last century. We proposed a number of innovative design and construction-technological solutions for the thermomodernization of residential buildings and structures that provide simultaneous modernization of a system of central water heating and facade insulation. Distribution of the temperature field inside a building structure, temperature on the surface of a facade thermal insulation at variation of its thickness by different forms of making of new indents, where new pipelines of a two-pipe system of a central water heating are located, were investigated. In particular, we established that such placement of pipelines makes it possible to reduce heat losses from these pipelines significantly (by up to 74 %) comparing with the placement in a layer of facade insulation at the side of a wall. We investigated the dependence of the cooling time of a heat-transfer agent temperature to 0 oC at the complete cessation of its flow through pipelines on the thickness of a thermal insulation. We determined experimentally the minimum thickness of a facade insulation layer, which is 50 mm, for the studied temperature mode and operating conditions, as well as for characteristics of the materials used, the geometry of pipelines and the facade insulation.We obtained the optimum thickness of a facade insulation layer, which is 100 mm. It provides up to a 100 % freeze protection of pipelines even when a heat-transfer agent movement stops for more than 24 hours. We established that an increase in the thickness of a facade heat insulation contributes to the additional drainage of a building structure, which leads to improvement of thermal characteristics of the thermomodernized building. The study showed that the developed innovative design and construction-technological solutions lead to a significant reduction in the energy consumption of existing buildings and structures of the housing stock, which has been in operation for longer than 30 years, and contribute to maintaining comfortable living conditions.