- Grids (muntins)
- The bars that divide glass into smaller panes. Patterns include Colonial, Prairie, Craftsman, Victorian and Queen Anne.
- True divided lites (TDL)
- Separate small panes of glass held by real muntins, as in original wood windows.
- Simulated divided lites (SDL)
- Bars fixed to both faces of a single insulated glass unit, often with a spacer between, so it reads like true divided lites from the street.
- Grids between the glass (GBG)
- Bars sealed inside the insulated glass unit. Easy to clean, but flatter looking than SDL.
- Insulated glass unit (IGU)
- Two or three panes sealed together with a gas-filled space between them.
- Low-E coating
- A microscopically thin metal coating on the glass that reflects heat and blocks UV. Different coatings suit foggy or sunny exposures.
- Argon and krypton
- Inert gases sealed between the panes that insulate better than air.
- Warm-edge spacer
- The strip that separates the panes around the edge, made of materials that conduct less cold than old aluminum spacers, which helps reduce condensation.
- Tempered glass
- Safety glass that breaks into small, blunt pieces. Required by code in doors, near doors, near tubs and showers and close to the floor.
- Laminated glass
- Two layers of glass bonded to a plastic interlayer. It stays in place when broken, blocks more noise and UV, and adds security.
- Obscure glass
- Textured or frosted glass for privacy in bathrooms and street-facing rooms.
- Triple-pane
- Three panes instead of two, for more insulation and quiet. Most useful in foggy, windy or noisy rooms.
- Seal failure
- When the seal of an insulated glass unit breaks and moisture gets in, leaving fog between the panes that can’t be cleaned.