Section 3280.103 - [Effective 3/17/2025] Light and ventilation(a)Lighting. Each habitable room shall be provided with exterior windows and/or doors having a total glazed area of not less than 8 percent of the gross floor area.(1) Kitchens, bathrooms, toilet compartments, laundry areas, and utility rooms may be provided with artificial light in place of windows.(2) Rooms and areas may be combined for the purpose of providing the required natural lighting provided that at least one half of the common wall area is open and unobstructed, and the open area is at least equal to 10 percent of the combined floor area or 25 square feet whichever is greater.(b)Whole-house ventilation. Each dwelling unit of a manufactured home must be provided with a whole-house mechanical ventilation having the capability to provide a minimum capacity of 0.035 ft3 /min/ft2 of interior floor space or its hourly average equivalent. This ventilation capacity must be in addition to any openable window area. In no case shall the installed ventilation capacity of the system be less than 50 cfm. The following criteria must be adhered to:(1) The ventilation capacity must be provided by a mechanical ventilation system or a combination natural and mechanical ventilation system.(2) The ventilation system or provisions for ventilation must exchange air directly with the exterior of the home, except the ventilation system, or provisions for ventilation must not draw or expel air with the space underneath the home. The ventilation system or provisions for ventilation must not draw or expel air into the floor, wall, or ceiling/roof systems, even if those systems are vented. The ventilation system must be designed to ensure that outside air is distributed to all bedrooms and main living areas. The combined use of undercut doors or transom grills connecting those areas to the room where the mechanical system is located is deemed to meet this requirement.(3) The ventilation supply system or a portion of the ventilation supply system is permitted to be integral with the home's heating or cooling system. The supply system must be capable of operating independently of the heating and cooling modes. A mechanical ventilation supply system that is integral with the heating and cooling system is to be listed as part of the heating and cooling system or listed as suitable for use with that system.(4) A mechanical ventilation system, or mechanical portion thereof, must be provided with a manual control, and must be permitted to be provided with automatic timers or humidistats.(5) A whole-house ventilation label must be attached to the whole-house ventilation control, must be permanent, and must state: "WHOLE-HOUSE VENTILATION".(6) Instructions for correctly operating and maintaining whole-house ventilation systems must be included with the homeowner's manual. The instructions must encourage occupants to operate these systems whenever the home is occupied, and must refer to the labeled whole-house ventilation control.(c)Additional ventilation.(1) At least half of the minimum required glazed area in paragraph (a) of this section shall be openable directly to the outside of the manufactured home for unobstructed ventilation. These same ventilation requirements apply to rooms combined in accordance with § 3280.103(a)(2) .(2) Kitchens must be provided with a local exhaust system that is capable of exhausting 100 cfm to the outside of the home. The local exhaust system must be located as close as possible to the range or cook top, but in no case farther than 3 feet horizontally from the range or cooktop.(3) Each bathroom and separate toilet compartment must be provided with a local exhaust system capable of exhausting 50 cfm to the outside of the home. A separate toilet compartment may be provided with 1.5 square feet of openable glazed area in place of a local exhaust system, except in Uo value Zone 3.(d)Optional ventilation provisions. As an option to complying with the provisions of paragraphs (b) and (c) of this section, ventilation systems complying with ANSI/ASHRAE 62.2 (incorporated by reference, see § 3280.4 ) may be used.(e)Airflow rating. During the design stage, the airflow rating at a pressure of 0.25 inch water column may be used, provided the duct sizing meets the prescriptive requirements of table 5.3 in ANSI/ASHRAE 62.2 (incorporated by reference, see § 3280.4 ) or ventilation system manufacturer's design criteria.58 FR 55003, Oct. 25, 1993, as amended at 70 FR 72042 , Nov. 30, 2005; 86 FR 2517 , Jan. 12, 2021 86 FR 2517 , 3/15/2021; 89 FR 75744 , 3/17/2025