2301.1 An "existing window" means a windows existing at the time of designation, if supported by documentary evidence, or a window that has been changed subsequent to designation pursuant to a valid permit reviewed by the Board.

2301.2 A "historic window" means:

(a) A window that appears to date from the construction of the historic building, as determined with a reasonable degree of certainty by professional evaluation;

(b) A window that is of a type characteristic of the building when constructed, as supported by documentary evidence which may include typologies of similar buildings in similar periods and styles; or

(c) A window that was incorporated into the building by a major alteration undertaken within the period of significance of the historic landmark or district, as supported by documentary evidence.

2301.3 A "special window" means a window that creates a special architectural effect, or is a custom design, not typically found in a manufacturer's catalogue. These windows may or may not be repetitive, and usually involve one or more of the following attributes:

(a) Non-rectilinear frame or sash;

(b) Transom or side light configuration;

(c) Multi-pane configuration with twelve or more panes in a single sash;

(d) Curved glass;

(e) Stained, leaded, or artistically crafted glazing;

(f) Decorated, carved, or embellished sash, frame, or surround; or

(g) Projecting bay or oriel.

SOURCE: Notice of Final Rulemaking published at 51 DCR 7447 (July 30, 2004).