Abstract: A replacement parting stop installed in a double-hung window frame has a top groove on one side and a bottom groove on the other side. The grooves are equal in length to the top sash and bottom sash respectively. A pile weatherstrip has a base with protruding resilient ridges on each side along its length. The pile weatherstrip, cut into lengths equal to the top groove and bottom groove, is pressed into the grooves compressing the ridges with an airtight friction fit with the parting stop installed in place on the window frame. The weatherstrip is easily pulled out of the grooves and replaced as necessary with weatherstrip of a desired pile height to fill the gap between the parting stop and the sash.