The high cost of fossil raw materials is leading to the partial replacement of polyurethane raw materials with solid fillers. A promising modifier is fly ash (FA) added to rigid polyurethane foam (PUR) at 10 wt%. An unsolved problem concerns the recycling of this material. Therefore, in the present study, composites of PUR were produced with 2.5, 5.0 and 7.5 wt% shredded foam containing 10 wt% of FA. The paper presents the results of apparent density, morphology and thermal conductivity of obtained materials. Furthermore, the results of the hot plate test were presented. The addition of the filler resulted in a reduction in cell diameter and partial opening of the cells. As the filler concentration increased, there was an increase in density and thermal conductivity. The highest coefficient value was obtained for PUR+ 7.5%PUR and was 0.0037 W/(m⋅K). The effect of the shredded foam added to the new polyurethane system on the thermal conductivity coefficient was confirmed in the hot plate test, with the PUR+ 7.5% PUR sample achieving the highest surface temperature and the PUR the lowest. As part of the comparison of insulation properties, numerical calculations of the heat demand were carried out for a partition built with the materials received and pure foam. For a house with walls insulated with a 15 cm layer of PUR, the annual energy demand is 11.30 kWh/(m²·year), for PUR+ 2.5%PUR it is 11.59 kWh/(m²·year), for PUR+ 5.0%PUR it is 12.46 kWh/(m²·year), and for a wall with PUR+ 7.5%PUR it is 13.55 kWh/(m²·year).