N.Y.C. Admin. Code § 27-2061: § 27-2061 Lighting and ventilation of living rooms in old law tenements.

a. Required windows. Every living room in an old law tenement shall either have a window opening:

(1) On a street; or

(2) On a yard at least four feet in depth; or

(3) On a court or shaft at least twenty square feet in area open to the sky without a roof or skylight; or

(4) Above the roof of an adjoining building; or it shall meet the requirements of the multiple dwelling law. In the event that a window opens above the roof of an adjoining building and the light and air from the adjoining lot is thereafter diminished in any way, the department may determine that such a room is a noncomplying room and require compliance with the requirements of the multiple dwelling law. For a room located on the top story, a ventilating skylight opening to the outer air may be substituted for a window. At least one-half of every required window shall open.

b. Dining space. A dining space shall have at least one window which:

(1) Opens on a street, yard or legal court, and

(2) Has an area not less than one-eighth the floor area of such dining space.