A heating, ventilation and air conditioning (HVAC) system may include one or more ducts and each duct may include one or more sections. A duct section, for example, may include a flange, which may help increase the ease and efficiency of installing the duct section. The flange may also help provide a seal between portions of the duct section and other structures. A duct section may include a cover, which may advantageously help prevent animals, debris and the like from entering and/or passing through the duct section. A duct section may also include a barrier, which may also help prevent animals, debris and the like from entering and/or passing through the duct section. The barrier may also include one or more air-permeable portions through which at least some air may advantageously pass.