Muntins and Mullions

Muntin is an age-old term used to describe spacing inside windows, doors and other building structures such as interior paneling and exterior siding. The term is even used in the design of furniture. Today we mostly refer to muntins in windows and doors as “grids“. These separations in the glass can be on the outside of the glass or in between the layers of glass. Most often we see newer windows built today with grids inside double-paned glass.

Grids in windows and doors provide a certain level of safety for fast moving children and pets. Glass becomes more visible with grids. Birds especially are helped with highly visible grids viewed from the outside on a bright and sunny day. Grids also provide a certain esthetic appeal to the overall design of a home. Grids can be built into the upper or lower window sash only if desired. Grids are available in different designs as well. The grid color matches the window frame color for a great look.

Mullion or mull, also referred to as a “mulled” window, is the spacing that holds two or more windows together in a single unit. It is the strip of window material that runs vertically between windows most often seen in single or double hung window units. Mulled windows are also quite common using a single or double hung window on each side of a picture window. Theoretically, mulls can be installed on any set of windows. Window units can be installed with mulls at the factory or at the job site by the window installer.