Use of waste materials is an actual topic that corresponds to current trends associated with the decreasing of power exigency and sustainable development. The possibility to reduce depletion of natural resources and decrease the produced waste lies in an efficient and possibly repeated use of resources. An important subgroup of waste is formed by materials from petroleum derivatives - polymers (PP, PE, HDPE etc.). Polymers and their composite materials can be used as a base material for most products including products used in civil engineering. One of these products is an insulation block for elimination of thermal bridges in wall footing. During design of this product the MAP method (modelling-analysis-prediction) has been used together with experimental testing. This paper deals with the description of long term behaviour of an insulation block made of recycled polymers using full scale testing. Experimental data is compared to different rheological models.