An air control system 20 and associated methods including a flexible duct 30 having air exit holes 40, 42 and a flexible liner 50, 60 sheet within the duct 30 and extending longitudinally along the duct, the liner 50 sheet having opposite longitudinal edges 52, 54 connected to the duct 30 along the longitudinal length of the duct 30, the liner 50 sheet being permeable in one aspect and regulating air flow through the exit holes 40, 42 when the sheet is pressed against the portion of the duct having the exit holes. The duct 30 may also have multiple liner sheets 50, 60 arranged end-to-end and/or layered in various duct segments such that the different liners may be independently controlled to regulate the outflow of air from the duct as desired. The duct having a liner which closes or inhibits air flow from the exit holes may also be rotated to accommodate use of a single duct for different seasons and where the internal liner adjusts to assist with the downward control of air flow based on alignment of various perforations with the different exits holes.
