The study aimed to analyse the basic properties of polystyrene thermal insulation products made from recycled materials, using laboratory tests to analyse the basic properties of polystyrene thermal insulation products made from recycled materials. The thermal insulation mortar mixture examined in this series of tests consists of a mixture of recycled EPS, water and cement. In addition to the heat conduction property, tests were performed to evaluate the compressive force, water absorption, and dimensional stability parameters at 10% compression, based on these parameters. The utilisation of secondary raw materials recycled from demolition and construction waste in the circular economy can be fully realised if the products’ basic properties meet the minimum requirements prescribed by the relevant product standards. Based on the results, it is possible to set further directions for product development.