The present invention relates to a composition comprising a binder comprising one or more siloxane polymers, silicone resins, silicone based elastomers, and mixtures thereof, wherein said binder optionally comprises one or more cross-linker components comprising a silane and/or a siloxane containing silicon-bonded hydrolysable groups; and a hydrophilic powder and/or gel selected from one or more amorphous, porous hydrophilic silica (s) having a thermal conductivity at 20° C. and atmospheric pressure of 0.001 to 0.15 W/m·K and a surface area (SBET) of between 200 and 1500 m2/g, one or more hydrophilic aerogel (s) and mixtures thereof, wherein the binder is a solution, an emulsion, or a dispersion in water. The invention also relates to the use of the composition as or in thermally or acoustically insulating materials and to coated substrates, products and articles made by using the composition.