Nowadays energy resources saving problem is extremely important, especially for heating in buildings. The aim of the paper is to simulate indoor air temperature depending on heating rate, solar heat gains, infiltration rate and outdoor air temperature. In order to get the desired result dynamic model of the room was created in EnergyPlus program, which is a widely used building energy simulation program. Based on the developed model and modified IWEC weather data the series of simulations were performed for inside air temperature calculation depending on internal and external factors changes. The analysis of individual and aggregate factors influence on inside air temperature change is performed. The multiple linear regression model structure is analysed and background of factors change over the past three days is chosen. Regression models for daily average inside air temperature dependence on each of the factors and all of them are created. Results verification is performed for prognosis values of temperature in comparison with simulation for December weather data from IWEC. Regression models can be used for complex analysis of problems connected with selecting heating rate, influence assessment of climatic conditions on indoor air temperature, qualitative and quantitative heating system regulation.