All occupiable rooms shall be ventilated by natural or mechanical means, or by a combination of both. Natural ventilation may be provided except where mechanical ventilation is required by article seven or eight of this subchapter.
All habitable rooms shall be provided with natural ventilation complying with the provisions of this subchapter except as provided in section 27-750 of this article.
An alcove or room opening off another room or space shall be considered as a separate room in determining its requirements for ventilation. However, for dwellings classified in occupancy group J-3, where the opening between the alcove and the room or space is at least eighty percent of the area of the common wall and the floor area of the alcove does not exceed twice the area of the opening, the alcove and the room opening into the alcove may be considered as a single space.
Where an interior balcony or mezzanine opens to form part of another room or space, its area shall be added to the area of the room or space in which it is located to compute the ventilation required for both spaces.
Natural ventilation, when required, shall be provided by windows, skylights, monitors, doors, louvers, jalousies, or other similar ventilating openings. Such ventilating openings shall open to the sky or a public street, space, alley, park, highway, or right of way, or upon a yard, court, plaza, or space above a setback, where such yard, court, plaza, or space above a setback is located on the same lot and is of the dimensions required by the applicable provisions of the zoning resolution.
Ventilating openings in all habitable rooms or spaces shall have a free openable area of at least five percent of the floor area of the room or space ventilated and where there is an enclosed or partially enclosed balcony or space above a setback complying with section 27-733 of article three of this subchapter the ventilating openings shall have a free openable area of at least five per cent of the combined floor area of such room and portion of the balcony or space directly adjoining and in front of such room. Each required ventilating opening shall have a minimum openable area of six square feet. Where fresh air is furnished in any habitable room or space by mechanical means supplying a minimum of forty cfm the free openable area of the openings may be reduced to one-half of the above requirements but not less than five and one-half square feet in aggregate. In all occupiable rooms or spaces, the free openable area shall be used to calculate the index for ventilation (section 27-753 of article seven of this subchapter), which shall determine the minimum requirements for supplementary mechanical ventilation.
Habitable rooms shall have a minimum clear width of eight feet in any part; a minimum clear area of eighty square feet and a minimum clear ceiling height of eight feet for the minimum area, except:
(a) A room which complies with the requirements for natural light and ventilation and in addition has an opening of not less than sixty square feet into an immediately adjoining room may have a minimum floor area of seventy square feet and a least horizontal dimension of seven feet;
(b) A dining space which has legally required ventilation, and in which the window has an area of at least one-eighth the floor area of such dining space;
(c) One-half the number of bedrooms in a dwelling unit containing three or more bedrooms may have at least minimum dimension of seven feet;
(d) A room in a class B multiple dwelling as defined in section four of the multiple dwelling law which may have a minimum floor area of sixty square feet and a least horizontal dimension of six feet.
(a) A room which complies with the requirements for natural light and ventilation and in addition has an opening of not less than sixty square feet into an immediately adjoining room may have a minimum floor area of seventy square feet and a least horizontal dimension of seven feet;
(b) A dining space which has legally required ventilation, and in which the window has an area of at least one-eighth the floor area of such dining space;
(c) One-half the number of bedrooms in a dwelling unit containing three or more bedrooms may have at least minimum dimension of seven feet;
(d) A room in a class B multiple dwelling as defined in section four of the multiple dwelling law which may have a minimum floor area of sixty square feet and a least horizontal dimension of six feet.