Abstract: Disclosed is a spacer for a disposable formwork for the construction of a wall, with first and second panels. The spacer mutually couples the first and second panels at a certain distance one from the other. The spacer includes: a first connecting portion coupled, in use, with the first panel; a second connecting portion opposite the first and coupled, in use, with the second panel; and at least one pipe with at least one lateral opening communicating, in use, outside the formwork. In the pipe a through hole communicates, in use, with the formwork interior, allowing air passage from the outside towards the inside part and liquid outflow from inside towards the outside of the formwork. Also disclosed is a disposable formwork for the construction of a wall, including two panels and at least one such spacer, arranged between the two panels and coupling the two panels.