Abstract: Hydrophobic thermal insulation fiberglass flexible blanket using a textile grade fiberglass is produced by impregnating a hydrophobic polymer (e.g. a fluoropolymer) dispersion into a fiberglass blanket/mat, such as a needle felted fiberglass (FG) blanket/mat. The preferred FG needle felt blanket is a mechanically, rather than organically, bound glass fiber insulating blanket. The hydrophobic polymer dispersion forms a hydrophobic coating on the surface of the fiberglass filaments. Integral hydrophobicity is achieved and maintained without the need to add commonly-used hydrophobic inorganic particles, such as treated silica aerogels or fumed silica. Optionally, to enhance overall hydrophobicity and to inhibit fibrous surface lofting, a super-hydrophobic coating of fluoropolymer and inorganic particles such as silica particles may be dispersed onto one or more surfaces of the blanket.