Abstract
In the paper, the heat transfer inside a building block with cavities is analyzed and a brief overview of the relevant physical problem is given. The equations governing the heat exchange processes are presented and a numerical model is derived with the help of ANSYS software. The role of radiation and convection inside the cavities is emphasized throughout the work. The results show that in such cavities the radiation mechanism of heat transfer is dominant. The authors also examine the dependence of the effective heat conductivity on the properties of clay material. Using the numerical model, attempts have been made to improve the heat resistance of a building block. Possibilities of practical application of numerical modelling in the heat insulation material engineering are discussed.