Polyester-ether polyols were prepared by a clean method, consisting of PET wastes glycolysis with common diols (diethylene glycol and a mixture diethylene gycol/dipropylene glycol) and a diol derived from biomass (isosorbide) followed by mono-esterification of the glycolyzed products with phthalic anhydride and subsequent propolglation, under relatively mild conditions. The polyester-ether polyols were characterized by chemical methods, dynamic viscosity measurements, gas chromatography and H-1-MNR spectroscopy. Experiments, conducted in order to test the polyester-ether polyols in rigid polyurethane (PUR) foams formation, showed that the chemical composition of the experimental polyester-ether polyols is fully suitable for reaction with di-isocyanate. The physico-mechanical and flame retardant properties of PUR foams, prepared by using the experimental polyester-ether polyols up to 30% wt. of the polyol component in the foam formulations, were at least similar to the properties of the foam obtained from PET wastes by classical recycling methods. The synthesis method is in agreement with the principles of clean technologies and green chemistry, in the sense that no by-products and no wastes results.