A retractable, flexible-panel door is mountable to a door frame attached to a building and includes a first side rail, a second side rail, a top rail mountable to and between the first and second side rails, a bottom rail mountable to and between the first and second side rails, a handle coupled to and between the top and bottom rails, a flexible panel extending between the handle and one of the first and second side rails, and at least one biasing member carried by at least one of the first side rail, the second side rail, the top rail and the bottom rail to apply a force to draw the handle toward the one of the first and second side rails, wherein the top and bottom rails are each expandable in length to accommodate mounting of the retractable, flexible panel door to door frames of different widths.