Section 173. Windows in rooms

1. Except as provided in subdivision four of
  section one hundred seventy-seven every living room shall  have  one  or
  more windows opening directly upon a street or upon a yard or court with
  dimensions   conforming  to  those  specified  in  section  one  hundred
  seventy-two, or upon an inner court or shaft three feet nine  inches  or
  more in width and eight feet or more in length.
    2.  Such windows shall be so located as to light properly all portions
  of the room and in each room shall have an aggregate glazed area  of  at
  least  one-tenth of the floor area of the room, unless in the opinion of
  the department such room is already adequately lighted  and  ventilated.
  The  top  of at least one window in each living room shall be seven feet
  or more above the floor except when such room is in the basement  or  on
  the top story, in which case the top of at least one window shall be six
  feet  or  more above the floor. Every such window shall be twelve square
  feet or more in area, and shall be so constructed that one-half or  more
  of  its  area  may  be  opened.  However, such window need not be twelve
  square feet in area provided that each  room  shall  have  an  aggregate
  glazed  window area of at least one-eighth of the superficial floor area
  of the room.
    3. Whenever a basement conforming to  the  provisions  of  subdivision
  four  of  section  one hundred seventy-seven is permitted to be occupied
  for  living  purposes,  every  living   room,   bathroom,   water-closet
  compartment,  kitchen  and  cooking space therein shall have one or more
  windows opening directly upon a street; or upon a yard which is at every
  point at least fifteen feet in depth and, above the window sill level of
  the first story above the basement, at least  twenty  feet;  or  upon  a
  court  at  least two feet in width and extending the entire depth of the
  lot from the street to the yard. All such  yards  and  courts  shall  be
  measured  at  the  ground  level  from the lot line to the building line
  opposite on the same lot. The windows in each such room  shall  have  an
  aggregate  glazed area of at least one-eighth of the total floor area of
  the room, and in no event less than twelve square feet. The top edge  of
  the  glazed  area of every window shall be nine inches or more below the
  finished ceiling and one foot or more above the level of  the  adjoining
  ground.  Every such window shall be so constructed that one-half or more
  of its area may be opened, and shall be  so  located  as  to  light  and
  ventilate adequately all portions of the room.
    4. Any room on a top story may be lighted and ventilated by a skylight
  of  the  dimensions  specified  for  windows  and  arranged  to  provide
  ventilating openings of six square feet or more. Such a  skylight  shall
  be  accepted  in  lieu of a window. Nothing in this subdivision shall be
  construed to prohibit the installation of a skylight without ventilating
  openings of six square  feet  or  more,  provided,  however,  that  such
  skylight  shall  be equipped with at least one hundred forty-four square
  inches of ventilation and provided that the glazed area of such skylight
  together with the glazed area of any existing window shall be  not  less
  than one-eighth the superficial floor area of such room.
    5.  When required by the department transoms, or louvres, or partition
  sash to private halls or to adjoining rooms in the same apartment  shall
  be  provided  to  secure  thorough  ventilation,  but no such transom or
  louvres or partition sash shall be required in rooms having two  windows
  opening  to the outer air if each window contains at least twelve square
  feet of area nor in rooms having a mullioned window  with  an  aggregate
  area of at least twenty-four square feet.