The energy consumption of cooling systems comprises a significant part of the total energy consumption in residential and public buildings. One of the methods of reducing the energy consumption in air-conditioning process is application of evaporative water cooling where during constant enthalpy process evaporating water cools the heat exchange surface. Historically, this cooling method has been widely applied in hot and dry areas where in conditions of low air humidity water evaporation brings the highest cooling efficiency. However, alongside with the development of air conditioning sector and the growing popularity of “high temperature” cooling, this cooling method is becoming more appealing to be used in more humid temperate climate conditions. Because of the insignificant difference in dry and humid thermometer temperature, the evaporative cooling separately, in a “pure” way, cannot provide comfortable environment during the whole cooling season. Therefore in HVAC systems, used all around the world, the application of combined compression cycle and evaporative coolers becomes more common. For example, spraying water on the surface of Freon condenser significantly (by 10-15%) increases the efficiency of the cooler.In HVAC systems of Latvian construction sector cooling is not being frequently used. This may be explained by the sceptical attitude of the designers and other sphere specialists as well as greater capital investments which are necessary for purchasing such devices. The goal of the thesis is to establish the technical and economic aspects of indirect evaporative cooling system application in temperate Latvian climate evaluating the possibilities of reducing the energy consumption. The following research objectives have been brought forward: 1. To evaluate the existing calculation methods, develop methodology for seasonal energy consumption and economic calculation; to perform calculations for application of indirect evaporative water cooling system (KKCD) combined with compression cycle, in comparison with other cooling principles. 2. To verify the indirect evaporative cooling (IEC) method in action in experimental object during the cooling season. 3. To identify the correlation between IEC efficiency and outdoor humidity by using the data obtained in the research object. 4. To evaluate the availability of the useful temperature of water that has been cooled with the IEC method (coolant supply temperature, which can be applied in the cooling system) in laboratory conditions. The scientific novelty of the paper: the development of methodology for calculating the seasonal energy consumption in coolers based on the proportional power and energy efficiency ratio (EER) distribution according to a typical meteorological year. The methodology is approbated in calculations of energy consumption in cooling systems for the existing historical building in Latvian climate. The practical significance of the thesis: in order to increase the accuracy of economic and energy consumption calculations, it has been proposed to make changes in the European standard 14511:3-2007 which defines the procedure of seasonal efficiency for ESEER, taking into consideration the peculiarities of different objects and conditions of cooler climate. Technical and economic indicators have been established for application of evaporative cooling. The proposed evaluation of seasonal energy consumption methodology may be implemented in calculations of other historical reconstructed buildings. The results of the research are intended for energy efficiency improvement in air conditioning systems applying the principles of indirect evaporative cooling. They can be used by HVAC designers, architects and developers for evaluation of sustainable solutions in engineering systems. The results of the research have been announced in 4 full-text publications in international issues and 4 international conferences.