Abstract: The disclosure embraces a method of spraying a binder composition of hybrid character containing both organic and inorganic materials into a fiber-forming hood or chamber onto glass fibers produced by a fiber-forming process, the disclosure embracing fibrous insulation products, such as pipe insulation and block insulation, the products embodying hybrid binder composition wherein the organic phase of the binder composition improves moldability and handleability of the fibrous product during processing and installation and which provides hardness and toughness characteristics in the products to resist or prevent handling damage and physical damage in use, the inorganic phase of the binder system providing high bond strength and improved thermal stability in the product particularly under high temperatures which may volatilize the organic binder, the inorganic phase of the binder system preventing or resisting fiber slump under high temperature conditions.