muntins

Muntins are slender strips of wood, metal, or vinyl that divide a window or door opening into multiple individual panes, or lites. They are used in both historical and contemporary sash windows to create a grid pattern, whether for structural support or decorative effect.

In traditional construction, muntins serve to hold small panes of glass in place. As glass manufacturing advanced and larger panes became common, muntins remained for stylistic reasons or to mimic the look of older divided-light windows. Modern windows can use muntins in several ways: true divided light, where each pane is physically separated by muntins within a single sash; and simulated or grilles, where muntin-like profiles are decorative or are installed between or on the glazing beads to imitate a divided-light appearance.

Muntins are distinct from mullions. Mullions are the larger framing members that divide a window into separate sash units or exterior walls, while muntins subdivide a single sash into multiple panes.

Materials and styles vary by product. Wooden muntins are common in traditional wood windows and can be crafted to various profiles. Aluminum and vinyl muntins are used in modern frames, often with finishes designed to resist weathering. Exterior muntins are visible from outside the building, interior muntins from inside, and some systems place muntins between the glass panes (between-glass grilles) to reduce maintenance.

Maintenance needs depend on the material and exposure. Wood muntins require painting or sealing; metal muntins may need corrosion protection, and decorative muntins between glass can complicate cleaning.