Abstract: According to a method for applying an insulating layer to a surface fibers, of an inorganic material an sprayed onto the surface under simultaneous wetting of the fibers with water and/or a binder so that the fibers stick to the surface whereafter the layer is formed and dryed/hardened. Prior to or after the drying/hardening a binder can be sprayed to the surface for the purpose of achieving a dustless and mechanically resistant surface layer. A device for applying of an insulation to a surface of an object (10), making use of the method, comprises a store (41) of fibers of an inorganic material, a conduit (20) for the transfer fibers from the store (41) to a spray nozzle (21) and device for generating an air flow in the conduit (20) directed towards the nozzle (21).