An insole for footwear, characterised in that it comprises, in combination: - a first body having an upper surface comprising a first groove defining a first channel, extending close to at least part of an edge of said upper surface, and at least a second groove defining a second channel, extending between a central zone of said upper surface and an edge of the upper surface; - a second body having a first lower surface, in contact with the upper surface of the first body for closing said first and second channel (C1, C2), and a second upper surface, said second body comprising at least a first through opening, positioned, in use, at least at part of the first channel, and at least a second through opening, positioned, in use, at least at part of the at least a second channel; - an attachment, connected to said first body and second body, in turn comprising: at least a first conduit, in fluid communication with the first channel and with the outside environment, and at least a second conduit, in fluid communication with the at least a second channel and with the outside environment, wherein: - the at least a first conduit comprises two conduits, an inlet conduit and an outlet conduit, configured for the circulation in the first channel of fluid to and from the outside environment; - the attachment comprises a lower portion, having a plurality of grooves defining the at least a first conduit and the at least a second conduit, and an upper portion, configured for covering said at least a first and at least a second conduit (D1, D2); - and the attachment has a main axis of extension and wherein the attachment extends along said main axis of extension for a length of between 1 cm and 40 cm. - a first body having an upper surface comprising a first groove defining a first channel, extending close to at least part of an edge of said upper surface, and at least a second groove defining a second channel, extending between a central zone of said upper surface and an edge of the upper surface; - a second body having a first lower surface, in contact with the upper surface of the first body for closing said first and second channel (C1, C2), and a second upper surface, said second body comprising at least a first through opening, positioned, in use, at least at part of the first channel, and at least a second through opening, positioned, in use, at least at part of the at least a second channel; - an attachment, connected to said first body and second body, in turn comprising: at least a first conduit, in fluid communication with the first channel and with the outside environment, and at least a second conduit, in fluid communication with the at least a second channel and with the outside environment, - the at least a first conduit comprises two conduits, an inlet conduit and an outlet conduit, configured for the circulation in the first channel of fluid to and from the outside environment; - the attachment comprises a lower portion, having a plurality of grooves defining the at least a first conduit and the at least a second conduit, and an upper portion, configured for covering said at least a first and at least a second conduit (D1, D2); - and the attachment has a main axis of extension and wherein the attachment extends along said main axis of extension for a length of between 1 cm and 40 cm.