Muntins are any kind of vertical divider for anything from windows to furniture, whereas mullions are specifically dividing bars between the sections of a window. The major distinction is that mullions were traditionally employed for support, whereas mullions simply divided the window into smaller, less expensive panes of glass.Continue Reading
Until the mid-1800s, muntins were an economic necessity, because larger panes of glass were more expensive to produce and generally used for mirrors. Builders have varied the thickness of the muntins they employed throughout history, ranging from thick widths in the 17th and early 18th centuries to very slim versions in 19th-century Greek revival buildings. In the modern era, architects sometimes place decorative structures made of wood or metal called "grills" over single panes of glass to emulate the appearance of muntins.
Although muntins are most common in western styles of architecture, mullions supported windows in Armenian, Sexon, and Islamic architecture before the 10th century, although they did spread across Europe in the form of Romanesque design. Gothic architecture featured larger windows that included multiple mullions, especially in the designs of stained glass in churches. In modern architecture, mullions are often paired with "transoms," which are supporting elements that lie horizontally.Learn more about Doors, Windows, & Locks