Abstract The problem of a strip containing an edge crack and an interior crack subjected to a thermal shock on one edge and insulated on the other is solved in order to analyze the difference between using temperature-dependent material properties and constant ones. For this purpose two brittle materials, ceramics and glass, are each subjected to a thermal shock. The results show that in general, using constant material properties over large temperature ranges can lead to considerable underestimation of the maximum stress intensity factors. The difference in the results is dependent on the variation of the thermal diffusivity and the thermal expansion coefficient with temperature for a given material. Also, this difference varies for different crack lengths and different thermal shock conditions at the boundary.