The invention provides a pre-insulated duct having a length and comprising a tube having a foam layer. The pre-insulated duct has an interior face and an exterior face and a thickness defined as a distance between the interior face and the exterior face. The interior face of the pre-insulated duct bounds an airflow space. In the present group of embodiments, the pre-insulated duct has a mounting rail system extending along the length of the pre-insulated duct. The mounting rail system includes at least one mounting rail, and preferably a plurality of mounting rails, positioned on (e.g., positioned on an exterior of) the pre-insulated duct.