Composite pipe for air conditioning and ventilation technology, comprising - an oval cross-section -- with first wall portions (1, 2; 1d, 2d) arranged opposite to each other; -- with second wall portions (3, 4; 3d, 4d) arranged opposite to each other for interconnecting the first wall portions (1, 2; 1d, 2d); -- with a short main axis penetrating the first wall portions (1, 2; 1d, 2d); and -- with a large main axis penetrating the second wall portions (3, 4; 3d, 4d); - a corrugated external pipe (8; 8d) which has -- peaks (14, 15; 14a, 15a; 14b, 15b; 14c, 15c; 14d); and -- first troughs (16; 16a; 16d) which are in each case arranged between directly adjacent peaks (14, 15; 14a, 115a; 14b, 15b; 14c, 15c), --- wherein the first troughs (16; 16a; 16d) are welded to the internal pipe (7; 7d) at the circumference of the composite pipe, characterised in that between adjacent peaks (14, 15; 14a, 15a; 14b, 15b; 14c, 15c; 15d) and between the first troughs (16; 16a; 16d), first trough portions (18, 19; 18a, 19a) are formed at the first wall portions (1, 2; 1d; 2d), the first trough portions (18, 19; 18a, 19a) being welded to the internal pipe (7; 7d) only in the region of the first wall portions (1, 2; 1d, 2d). - an oval cross-section -- with first wall portions (1, 2; 1d, 2d) arranged opposite to each other; -- with second wall portions (3, 4; 3d, 4d) arranged opposite to each other for interconnecting the first wall portions (1, 2; 1d, 2d); -- with a short main axis penetrating the first wall portions (1, 2; 1d, 2d); and -- with a large main axis penetrating the second wall portions (3, 4; 3d, 4d); -- with first wall portions (1, 2; 1d, 2d) arranged opposite to each other; -- with second wall portions (3, 4; 3d, 4d) arranged opposite to each other for interconnecting the first wall portions (1, 2; 1d, 2d); -- with a short main axis penetrating the first wall portions (1, 2; 1d, 2d); and -- with a large main axis penetrating the second wall portions (3, 4; 3d, 4d); - a corrugated external pipe (8; 8d) which has -- peaks (14, 15; 14a, 15a; 14b, 15b; 14c, 15c; 14d); and -- first troughs (16; 16a; 16d) which are in each case arranged between directly adjacent peaks (14, 15; 14a, 115a; 14b, 15b; 14c, 15c), --- wherein the first troughs (16; 16a; 16d) are welded to the internal pipe (7; 7d) at the circumference of the composite pipe, characterised in that between adjacent peaks (14, 15; 14a, 15a; 14b, 15b; 14c, 15c; 15d) and between the first troughs (16; 16a; 16d), first trough portions (18, 19; 18a, 19a) are formed at the first wall portions (1, 2; 1d; 2d), the first trough portions (18, 19; 18a, 19a) being welded to the internal pipe (7; 7d) only in the region of the first wall portions (1, 2; 1d, 2d). -- peaks (14, 15; 14a, 15a; 14b, 15b; 14c, 15c; 14d); and -- first troughs (16; 16a; 16d) which are in each case arranged between directly adjacent peaks (14, 15; 14a, 115a; 14b, 15b; 14c, 15c), --- wherein the first troughs (16; 16a; 16d) are welded to the internal pipe (7; 7d) at the circumference of the composite pipe, characterised in that between adjacent peaks (14, 15; 14a, 15a; 14b, 15b; 14c, 15c; 15d) and between the first troughs (16; 16a; 16d), first trough portions (18, 19; 18a, 19a) are formed at the first wall portions (1, 2; 1d; 2d), the first trough portions (18, 19; 18a, 19a) being welded to the internal pipe (7; 7d) only in the region of the first wall portions (1, 2; 1d, 2d). --- wherein the first troughs (16; 16a; 16d) are welded to the internal pipe (7; 7d) at the circumference of the composite pipe, characterised in that between adjacent peaks (14, 15; 14a, 15a; 14b, 15b; 14c, 15c; 15d) and between the first troughs (16; 16a; 16d), first trough portions (18, 19; 18a, 19a) are formed at the first wall portions (1, 2; 1d; 2d), the first trough portions (18, 19; 18a, 19a) being welded to the internal pipe (7; 7d) only in the region of the first wall portions (1, 2; 1d, 2d).