Abstract: Background radiation in space is largely determined by the radiological properties of materials and structures used in the construction of buildings. Mineral raw materials in the manufacture of building materials and structures are often subjected to heat treatment. Studied theoretically and experimentally increase radon emanation mineral raw materials as a result of the heat treatment. Analytical expressions for the activity concentration of radon and its rate of exhalation of mineral grains isometric form. On an example plagiogranites experimentally investigated the variation of the surface structure of samples and increase its radon emanation by increasing their porosity. The empirical dependence of the concentration of radon activity on temperature. The results of theoretical and experimental studies are qualitatively consistent with each other and indicate that the radon emanation of building constructions depends not only on the radiological properties of the original mineral but also on the heat treatment technology.