Abstract: In a sectional overhead garage door assembly, the problem of inefficient and/or insufficient insulation of a garage door assembly that comprises a door for closing an entrance is solved by covering joints and openings of the door assembly with isolating members so that the joints and openings of the door assembly other than the entrance remain close when the door is opened. For example, an embodiment of an insulation system includes a lateral insulating assembly to be secured to a door frame or wall adjacent the garage door; and a resilient insulating assembly is secured to at least one of the garage door along the lateral edge thereof and the lateral insulating assembly for defining an enclosure with the garage door and the lateral insulating assembly. In some embodiment, each door panel is provided with a door panel insulating assembly.