A reinforced organic natural fiber composite material having a lambda value in the range 15-35 mW/m·K is disclosed which comprises 25-85% by weight hydrophobic nanoporous particles calculated on the total weight of the composite material, at least 10% by weight organic natural fibers having isocyanate reactive groups calculated on the total weight of the composite material and 1-15% by weight binder selected from a polyurea/polyurethane comprising binder made from emulsifiable polyisocyanate, water and surfactants.