Concrete blocks are the primary building materials in Saudi Arabia, where temperatures can reach almost 50 °C. Concrete is a poor thermal insulator in such high-temperature conditions. To improve thermal insulation in these blocks, a common material used is Styrofoam. This paper examines the thermal insulation properties of concrete blocks when a mixture of wax and Styrofoam spheres is used as insulation materials. Four concrete blocks were filled with liquid microcrystalline wax at 60 °C, containing suspended 7 mm diameter Styrofoam spheres. These blocks were then left at room temperature until the wax solidified. The wax to Styrofoam- volume ratios were 0.4: 0.6, 0.6:0.4, 0.8:0.2. The blocks were then fixed to a (50 cm × 50 cm × 20 cm) wooden box with one side of the block facing the outer environment. The temperature of the opposite side (in the shade of the wooden box) was then recorded hourly for 24 h using a laser thermometer. The specific heat capacity of each block was also measured. The study showed that as the wax percentage in the specimen increases, the inner surface temperature decreases. The thermal inertia of the blocks filled with the mixture also showed a clear advantage over the control block. The specific heat of the blocks was found to be 0.972 kJ/Kg °C, 0.353 kJ/Kg °C, 0.359 kJ/Kg °C, and 0.620 kJ/Kg °C for the control block, 0.4: 0.6, 0.6:0.4, 0.8:0.2 wax to Styrofoam volume ratio, respectively.