Abstract: A weatherstrip having a backing member and a pair of rows of pile of different height above said backing strip. A flexible fin is disposed between said rows and has a height equal or slightly greater than the height of the higher row. When sash members, such as those of a horizontal sliding window move into closing relationship, the fin bends causing bending of the higher row forming a seal between the sash members while the row of lower height is not substantially compressed and provides a springlike force opposing the mechanism which holds the sliding sash.

Abstract: A weatherstrip has a backing strip on which is attached two longitudinal rows of pile. An air infiltration membrane is secured near one end to the backing strip and is supported in upright position between the two rows of pile. When the weatherstrip is disposed in sealing engagement with a closure member, such as a window or door, it provides controlled air infiltration therethrough without increased stiffness which would make movement of the closure member, as in opening or closing the window or door, difficult.