Use of a mineral wool product comprising mineral fibers bound by a binder resulting from the curing of a binder composition comprising a phenol-formaldehyde-based resin, and/or a carbohydrate containing component; and a hydrophobic agent comprising: (i) at least one silicone compound, such as silicone resin, such as a reactive silicone resin, such as a reactive silicone resin chosen from the group of polyalkylethoxysiloxane, polymethylethoxysiloxane, polyphenylethoxysiloxane, polyphenylsiloxane, polyphenylmethylsiloxane; (ii) at least one hardener, such as silane, such as alkyltriethoxysilane, such as octyltriethoxysilane; and (iii) at least one emulsifier; as insulation of a metallic structure, said structure having an operating temperature between 70-650 °C, wherein the hydrophobic agent comprises (i) in an amount of 20 to 90 percent by weight, in particular 30 to 60 percent by weight, based on the weight of the hydrophobic agent, and (ii) in an amount of 0.5 to 10 percent by weight, in particular 1 to 5 percent by weight, based on the total weight of the hydrophobic agent, and wherein the mineral wool product comprises the hydrophobic agent in an amount of 0.05 to 2 percent by weight, such as 0.10 to 1 percent by weight, such as 0.15 to 0.8 percent by weight, based on the weight of the mineral wool product. a phenol-formaldehyde-based resin, and/or a carbohydrate containing component; and a hydrophobic agent comprising: (i) at least one silicone compound, such as silicone resin, such as a reactive silicone resin, such as a reactive silicone resin chosen from the group of polyalkylethoxysiloxane, polymethylethoxysiloxane, polyphenylethoxysiloxane, polyphenylsiloxane, polyphenylmethylsiloxane; (ii) at least one hardener, such as silane, such as alkyltriethoxysilane, such as octyltriethoxysilane; and (iii) at least one emulsifier; as insulation of a metallic structure, said structure having an operating temperature between 70-650 °C, wherein the hydrophobic agent comprises (i) in an amount of 20 to 90 percent by weight, in particular 30 to 60 percent by weight, based on the weight of the hydrophobic agent, and (ii) in an amount of 0.5 to 10 percent by weight, in particular 1 to 5 percent by weight, based on the total weight of the hydrophobic agent, and wherein the mineral wool product comprises the hydrophobic agent in an amount of 0.05 to 2 percent by weight, such as 0.10 to 1 percent by weight, such as 0.15 to 0.8 percent by weight, based on the weight of the mineral wool product. (i) at least one silicone compound, such as silicone resin, such as a reactive silicone resin, such as a reactive silicone resin chosen from the group of polyalkylethoxysiloxane, polymethylethoxysiloxane, polyphenylethoxysiloxane, polyphenylsiloxane, polyphenylmethylsiloxane; (ii) at least one hardener, such as silane, such as alkyltriethoxysilane, such as octyltriethoxysilane; and (iii) at least one emulsifier; as insulation of a metallic structure, said structure having an operating temperature between 70-650 °C, wherein the hydrophobic agent comprises (i) in an amount of 20 to 90 percent by weight, in particular 30 to 60 percent by weight, based on the weight of the hydrophobic agent, and (ii) in an amount of 0.5 to 10 percent by weight, in particular 1 to 5 percent by weight, based on the total weight of the hydrophobic agent, and wherein the mineral wool product comprises the hydrophobic agent in an amount of 0.05 to 2 percent by weight, such as 0.10 to 1 percent by weight, such as 0.15 to 0.8 percent by weight, based on the weight of the mineral wool product. as insulation of a metallic structure, said structure having an operating temperature between 70-650 °C, wherein the hydrophobic agent comprises (i) in an amount of 20 to 90 percent by weight, in particular 30 to 60 percent by weight, based on the weight of the hydrophobic agent, and (ii) in an amount of 0.5 to 10 percent by weight, in particular 1 to 5 percent by weight, based on the total weight of the hydrophobic agent, and (i) in an amount of 20 to 90 percent by weight, in particular 30 to 60 percent by weight, based on the weight of the hydrophobic agent, and (ii) in an amount of 0.5 to 10 percent by weight, in particular 1 to 5 percent by weight, based on the total weight of the hydrophobic agent, and wherein the mineral wool product comprises the hydrophobic agent in an amount of 0.05 to 2 percent by weight, such as 0.10 to 1 percent by weight, such as 0.15 to 0.8 percent by weight, based on the weight of the mineral wool product.