Biaxially oriented polyester films formed from a crystallizable polyester having increased diethylene glycol content and/or increased polyethylene glycol content, and/or increased isophthalic acid content, preferably polyethylene terephthalate. The films of the invention further include at least one IR-reflective pigment and one UV stabilizer. The inventive films feature adjustable mattness, diffuse scattering power for visible light, high light transmittance and IR reflectance and good thermoformability, and are suitable for thermally protective coatings or thermally protective packaging.