Cal. Civ. Code § 173

  § 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.