An insulating element for thermally insulating spaces, including closed cells, in which a first and a second group of closed cells are formed by first or second recesses in a first or second flat element and the first and the second flat elements form first or second connection regions between recesses adjacent to the edges of the openings, to which respectively a flat covering element closing the openings of a plurality of first recesses is bonded on a front side of the flat element. The second recesses are arranged between the first recesses on a rear side of the first flat element and the first recesses are arranged between the second recesses on a rear side of the second flat element such that the space remaining of the first and second recesses between the first and the second flat elements amounts to less than 50% of the space enclosed by the first and second recesses.