Constructional element and constructional element system

A constructional element system (12) for a building comprises a composite panel (14) of thermally insulating material, which has a recess (24a, 24b, 24c) in an outer face thereof, and first and second fixing means (34, 44, 49) for fixing the panel (14) to a purlin (18) at the interior of the building and for fixing a facing (16) at an outer side of the panel respectively. In one embodiment, the respective heads (50) of the first and second fixing means are both received in a lipped channel section (46) in the recess, with a stem of the first fixing means (34) passing through a thermal break (36), the channel section (46) and the panel (14) to extend to the purlin (18). A threaded stem (54) of the second fixing means (49) extends out of the recess between the lips of the channel section (46) and through an opening in a bracket (56) attached to the facing (16).