Muntin

A muntin (also spelled munting, or called a glazing bar or sash bar) is the vertical or horizontal bar that divides a window into individual panes. In traditional windows, muntins were structural — each pane of glass was separately set into the muntin grid because large sheets of glass were unavailable or prohibitively expensive. In modern windows, muntins are almost always decorative.

True Divided Lights vs. Simulated Divided Lights

• True divided lights (TDL) — each pane is a separate piece of glass set in its own glazing channel within the muntin framework. Traditional, authentic look. Significantly more expensive to manufacture and repair (each pane must be individually replaced if broken).
• Simulated divided lights (SDL) — a single large IGU with muntin grilles glued to the interior and exterior glass surfaces, plus a spacer bar grid inside the IGU cavity for a 3D appearance. Looks like TDL from a distance; the IGU has all the insulation benefits of a single sealed unit.
• Between-glass grilles (BGL) — muntin strips suspended inside the IGU cavity between the glass panes. No grilles on the glass surfaces (easy cleaning); can look slightly flat compared to SDL.
• Snap-in grilles — plastic or wood grilles that clip onto the interior face of the sash. The cheapest option; can be removed for cleaning; least authentic appearance.

Muntin Profiles

Muntin width and profile vary by architectural style. Colonial/traditional windows typically have 1¼–1¾ inch wide flat or ogee-profile muntins. Contemporary windows use narrow aluminum muntins (under ¾ inch). The profile affects both aesthetics and the amount of visible light.

Repairing Muntin Grilles

Snap-in and between-glass grilles can often be replaced individually. SDL grilles glued to the glass cannot be removed without damaging the IGU. If an SDL grille is damaged, the entire IGU typically needs replacement.