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InfiltrationThe air or moisture that leaks through the cracks of a window or door from outside of a structure. A tight window (low infiltration rate) will prevent the loss of energy more than any other single factor.
Integral Fin WindowA window with a nailing fin. (See Nailing Fin)
Integral MullionA frame member trapped within the master frame to separate vents or fixed glass.
Interior GlazedGlass glazed from the interior of the building.
Interior Track Sliding Glass DoorAlso known as a flush track, it has no riser to protect against water infiltration.
InterlockA design feature of a window or door that provides a hooking action between the sash rail and the mid-rail, sill or jamb. This action reduces air infiltration and increases security to the unit.
Interlocking RailPortion of a door or window unit where the operating section meets and interlocks with the fixed portion.
Intermediate JambA vertical member in a window or door, with three or more panels, that is located in the central area of the unit, and acts as a jamb in receiving the moving panel.
Internal GainThe heat produced in the interior of a dwelling from the operation of lights, appliances, etc.
Internal MuntinsMuntin bars (grids), located between the sheets of glass in an insulated glass unit. These muntins are purely decorative and only give the appearance of a divided light window. (See Muntins)
