An insulating construction element comprising: - a first skin adopting the shape of a panel; - a second skin, adopting the form of a panel, made of an insulating material, parallel to the first skin, positioned in front this first skin and at a determined distance from said first skin; - a core, interposed between the two skins (6; 7), and including a plurality of flat plates each made of an insulating material, parallel to these two skins (6; 7), and applied against these two skins (6; 7); - fastening means for making the flat plates of the core integral with the two skins (6; 7); - at least one longitudinal cavity (11, 11'), on the one hand, delimited by the two skins (6, 7) as well as by at least one flat plate of the core, on the other hand, extending parallel to these two skins (6, 7), perpendicularly to a first side of the insulating construction element, and to a second side of this insulating construction element, opposite this first side, as well as between these two sides (3, 4) and, yet on the other hand, communicating with at least one opening (12; 12') these two sides (3; 4) include; - this insulating construction element being characterized in that it includes at least one transverse cavity (15, 15'), on the one hand, delimited by the two skins (6, 7) as well as by at least two flat plates of the core, on the other hand, extending parallel to these two skins (6, 7), between the first side and the second side, while including an acute angle with this first side and/or with this second side and, yet on the other hand, communicating with at least one of the openings (12; 12') these two sides (3; 4) include. - a first skin adopting the shape of a panel; - a second skin, adopting the form of a panel, made of an insulating material, parallel to the first skin, positioned in front this first skin and at a determined distance from said first skin; - a core, interposed between the two skins (6; 7), and including a plurality of flat plates each made of an insulating material, parallel to these two skins (6; 7), and applied against these two skins (6; 7); - fastening means for making the flat plates of the core integral with the two skins (6; 7); - at least one longitudinal cavity (11, 11'), on the one hand, delimited by the two skins (6, 7) as well as by at least one flat plate of the core, on the other hand, extending parallel to these two skins (6, 7), perpendicularly to a first side of the insulating construction element, and to a second side of this insulating construction element, opposite this first side, as well as between these two sides (3, 4) and, yet on the other hand, communicating with at least one opening (12; 12') these two sides (3; 4) include; - this insulating construction element being characterized in that it includes at least one transverse cavity (15, 15'), on the one hand, delimited by the two skins (6, 7) as well as by at least two flat plates of the core, on the other hand, extending parallel to these two skins (6, 7), between the first side and the second side, while including an acute angle with this first side and/or with this second side and, yet on the other hand, communicating with at least one of the openings (12; 12') these two sides (3; 4) include.