01The window assembly
The window assembly| Term | Plain-language meaning |
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| Frame | The outer assembly secured within the opening. |
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| Sash | The framed glass section; it may be fixed or operable. |
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| Sightline | The visible width or alignment of frame and sash elements. |
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| Insulating glass unit | Panes assembled with sealed cavities, spacers and edge seals. |
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| Low-E | A glass coating used to control radiant heat transfer. |
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| Argon fill | Gas specified within a sealed cavity between panes. |
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| U-factor | A measure of heat transfer for the rated product. |
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| SHGC | Solar heat gain coefficient; a measure of admitted solar heat. |
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Installation and doors
Installation and doors| Term | Plain-language meaning |
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| Retrofit / insert | Replacement that retains suitable existing framing. |
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| Full frame | Removal of the old frame and installation of a new assembly. |
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| Brickmould | Exterior trim profile at the perimeter of the frame. |
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| Jamb extension | A component extending the frame finish toward the room surface. |
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| Threshold | The lower part of a door opening that forms the floor transition. |
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| Sidelite | Glazed section alongside an entrance door. |
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| Transom | Glazed section above a door or window. |
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| Egress opening | An opening assessed for the required emergency-exit function. |
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Measurements that should not be confused
Measurements that should not be confused| Term | Meaning in the project |
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| Rough opening | The building opening prepared to receive the assembly. |
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| Frame size | The outside dimensions of the supplied frame. |
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| Clear opening | The unobstructed space available when the selected configuration is open. |
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| Sightline | The visible framing around or between glass areas. |
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| Frame depth | The dimension through the profile toward the inside and outside. |
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| Jamb extension | A finishing component extending toward the interior wall surface. |
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| Mullion / joining detail | The division or connection between adjacent units, with system-specific support requirements. |
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Glass and entrance terminology
Glass and entrance terminology| Term | How to use it |
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| Insulated glass unit (IGU) | A sealed multi-pane assembly, distinct from the complete window. |
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| Spacer | The component separating panes around the edge of the sealed unit. |
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| Low-E | A coating feature that must be specified with the full glass package. |
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| Sidelite | A glazed section beside an entry door. |
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| Transom | A section above the door or window. |
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| Active leaf | The door leaf normally used for everyday passage. |
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| Handing | The agreed opening orientation, described from a specified viewing side. |
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| Threshold | The lower entrance transition that coordinates support, access and water management. |
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Use the terms on the quote
If two estimates use different words, ask what physical components and work each one includes. A clear drawing and opening schedule are more reliable than assuming that insert, retrofit or complete replacement means exactly the same scope to every provider.
