There is increasing interest in indoor air quality studies. The effect of exhaled radon from soil, walls and ceilings has well-known consequences on human health, so the importance of modelling has been established. The present paper examines radon exhalation, on the one hand, only in the case of diffusion and, on the other hand, diffusion and advection. Comparing the results of the two test types, we can determine how significant the effect of temperature gradients on radon exhalation is. For a broader investigation, we performed the parametric tests on several types of material, wall thickness and radon concentration.