Abstract: An HVAC duct is provided. The duct includes an outer tube having a fully continuous external perimeter. The duct further includes an inner tube capable of conveying forced air. The inner tube extends within the outer tube longitudinally. The duct also includes a plurality of support elements spanning between the outer tube and the inner tube. The elements extends along the outer tube and the inner tube longitudinally. The elements define a plurality of channels between the outer tube and the inner tube. The outer tube, the inner tube, and the elements are fully unitary.