Nowadays, waste management represents a big issue, especially in less developed countries. The cradle-to-cradle philosophy gives potential solutions for these wastes, basically reintegrating them into any stage of life-cycle of a product. Therefore, post-industrial PET and HDPE was used to create a new added value material which would be the feedstock necessary to produce new roof panels. Their production costs and sale price would be reduced, pointing to a low socioeconomic status. The aim of this study is to design a roof panel made from a polymer matrix 70 wt.% of rPET and 30 wt.% of rHDPE, adding Ethylene Glycidyl Methacrylate copolymer and benzotriazole derivate additives as plastic compatibilizer and UV absorber, respectively. This recycled blend composite was melted using a single-screw extruder. The pelletizer compound was processed via injection molding to obtain tensile specimens. Low mold temperatures were used to minimize crystallization and consequently weakness. From a previous work the polymer matrix with EGMA presented the highest balance of rigidity/deformation for potential structural applications. Deformation and stresses were under the maximum admissible defined by construction standards. A roof design was selected to produce low cost, easy installation, high thermal insulation and feasible process. The mechanical analysis of the design was performed based in International Building Code using ANSYS mechanical modelling. Finally, this study proved the viability of the roof panel, offering an innovative idea characterized by being highly sustainable.