The goal of this doctorate study is to develop a method to calculate a constructive solution for heating systems with in-built heaters using low-temperature sources of heat. In order to reach this goal, the following tasks were put forth: the current standard regulations for the installation of heaters built into walls was evaluated; a calculation method was prepared; during practical experiments, the suggested calculation method was tested; the practicality of an in-built heating system was supported economically; the system was compared with the traditional heating system, with several heat sources; the heat-pump system and geothermal energy were evaluated, as possible sources of heat in low temperature heating systems with in-built heaters.