Buildings are responsible for about 30 % of total energy consumption of Latvia. Specific heat consumption is 200-225 kWh/m2 per annum, for its part average consumption of one household is about 1000-1200 kWh per annum. Due to growing requirements for comfort and increasing glased areas of building, as well as intensified interest about ensuring of good microclimate in buildings, more and more paying atention on cooling load of buildings and related heat transfer and exchange processes. Thermal inertia and thermal mass of building envelope are main factors, who substantially influence deviation amplitude and period of internal temperature depending on external temperature.