- A window pane's infiltration level refers to the amount of air it accidentally leaks, either through the glass itself or through its surrounding frame, according to the Consumer Energy Center.
- Glazing refers to the number of glass panels installed in a window pane. Double-glazed, triple-glazed and quadruple-glazed windows provide greater insulation than single glazing.
- A window pane's U-value describes its ability to resist the flow of heat energy through it. Pumping inert gases into the space between pane layers can improve the pane's U-value.
- Modern window panes sometimes include a thin coating of metal oxide called low-emissivity, or "low-E," coating. This coating helps the window pane retain indoor warmth in winter while deflecting excess sunlight for cooler summertime performance.
- Tinted window panes, with or without low-E coatings, can reduce energy requirements by up to 30 percent. Installers refer to the amount of solar heat from a window as its shading coefficient.