"Вестник МГСУ"

Reduction of energy consumption by devices designated for cooling residential buildings in the hot and dry climate of Central Asia is a most important challenge. The author uses a large apartment building (105 series), built in the 1980ies in the city of Khujand, to study the energy consumption required to cool the building after its renovation and modernization. Basic methods of reducing energy consumption for cooling buildings in hot, dry climates were applied. According to the findings of the research performed using a model residential house, ambient solar heat gain is reduced by 65 % during the hot season lasting from April to September. To cool the building, old windows are replaced by new insulated ones having a low solar heat gain coefficient (SHGC — 0.4) and external awnings are installed to protect windows looking to the West.The typical internal room temperature of +25 °C is assumed for the thermal calculations in the summer conditions. In summer, the outside temperature exceeds 40 °C in the northern regions of Tajikistan. A typical difference between the inside and outside air temperature is 15 °C. This extensive temperature difference has a negative effect on the human body. Frequently, the human body has no time to adapt to rapid temperature changes. Aged and sick people are especially sensitive to rapid temperature changes. They are more likely to experience headaches, exacerbated hypertension, atherosclerosis and other diseases. Moderate fluctuations of the air temperature are preferable, as they reduce pressure on the body's thermoregulatory mechanisms.It is noteworthy that people who remain inside buildings are not isolated from the external environment, and they must be careful to avoid sudden temperature changes. In the European regulations aimed at warm, rather than hot summer conditions, internal residential air temperature of +25 °C is considered comfortable. On the contrary, the internal temperature in residential buildings in northern Tajikistan varies from +27 °C to +28 °C. High temperatures can cause significant discomfort in the hot and dry climate like the one in Tajikistan.It is recommended to remain indoors during the day, to keep the windows open at night, and to run air conditioners in residential buildings in summer at certain time intervals.The author proposes a method of optimization of the design temperature of residential rooms using PMV and PPD indices. Optimal air circulation through open windows at night is identified to ensure comfort in modernized residential buildings.

The energy demand of a 5-storey residential building (a 105 series design structure built in 1980), located in the city of Khujand, Tajikistan, was simulated at the Fraunhofer Institute of Building Physics in Germany using WUFI+ software. The purpose of the simulation was to reduce the energy demand for its heating and cooling, as well as to ensure thermal comfort inside the building in the course of its reconstruction and modernization. Reconstruction and modernization of this residential building includes the construction of POLYALPAN ventilated façade, application of mineral wool insulation sheets, aerated concrete blocks, and replacement of old windows by the sealed double glazing.The analysis of micro-climatic parameters of this residential building is performed in furtherance of Category II of EN 15251 "Indoor environmental input parameters for design and assessment of energy performance of buildings addressing indoor air quality, thermal environment, lighting and acoustics", and it is based on the comprehensive assessment of the values of heat indexes PMV (Predicted Mean Vote) and PPD (Predicted Percentage of Dissatisfied). The research is based on the modeling pattern limiting the air temperature values on the premises during the heating period and reducing the energy demand for its heating through the employment of a heat exchanger. The findings prove that the analysis of micro-climatic parameters of buildings would benefit from the comprehensive and integrated assessment of the values of thermal comfort indexes PMV and PPD and from the evaluation of thermal insulation properties of clothes. Moreover, the findings demonstrate the need for development of national standards of the microclimate inside residential buildings. The research was based on the data simulating the climatic conditions in the northern region of Tajikistan during an extremely hot summer season and the optimum indoor air temperature of +24,3 °C instead of 20—22 °C. The research has proven that it is advisable to record the cooling data for five hottest months (May through September) instead of three, which is a common practice. The energy savings of 47,5 % were achieved using a 90 % efficient heat recovery procedure during the winter period when mechanical ventilation systems are in operation. Using heat exchangers after the renovation and modernization of residential buildings can significantly reduce the load on the heating system of a building.