A coated insulation material comprising an insulation material substrate and a coating on at least part of a surface of the insulation material substrate and wherein the coating comprises 20 to 65 wt % alkali silicate based on the total weight of the cured coating and the alkali silicate comprises potassium silicate. Also described is an aqueous coating composition useful in providing the insulation material coating, a potassium silicate coating, methods of producing the coated insulation material and potassium silicate coating and kit of parts including an insulation material substrate and either the aqueous coating composition or the potassium silicate coating.