160.2(c)2 Natural Ventilation - 2022

• Natural ventilation. Naturally ventilated spaces shall be designed in accordance with Sections 160.2(c)2A through 160.2(c)2C and include a mechanical ventilation system designed in accordance with Section 160.2(c)3:
• Exception 1 to Section 160.2(c)2: The mechanical ventilation system shall not be required where natural ventilation openings complying with Section 160.2(c)2 are either permanently open or have controls that prevent the openings from being closed during periods of expected occupancy.
• Exception 2 to Section 160.2(c)2: The mechanical ventilation system shall not be required where the zone is not served by a space-conditioning system.
  
  1. Floor area to be ventilated. Spaces or portions of spaces to be naturally ventilated shall be located within a distance based on the ceiling height, as specified in 1, 2 and 3. The ceiling height (H) to be used in 1, 2 or 3 shall be the minimum ceiling height in the space, or for ceilings that are increasing in height as distance from the operable openings is increased, the ceiling height shall be determined as the average height of the ceiling within 20 ft from the operable opening. [ASHRAE 62.1:6.4.1]
  2. Single side opening. For spaces with operable opening on one side of the space, the maximum distance from the operable opening shall be not more than 2H. [ASHRAE 62.1:6.4.1.1]
  3. Double side opening. For spaces with operable openings on two opposite sides of the space, the
     maximum distance from the operable opening shall be not more than 5H. [ASHRAE 62.1:6.4.1.2]
  4. Corner opening. For spaces with operable openings on two adjacent sides of a space, the maximum distance from the operable openings shall be not more than 5H along a line drawn between the two openings that are the farthest apart. Floor area outside that line shall comply with 1 or 2. [ASHRAE 62.1:6.4.1.3]
  5. Ceiling height. The ceiling height (H) to be used in Sections 160.2(c)2A1 through 160.2(c)2A3 shall be the minimum ceiling height in the space.
     Exception to Section 160.2(c)2A4: For ceilings that are increasing in height as distance from the opening is increased, the ceiling height shall be determined as the average height of the ceiling within 20 feet from the operable openings. [ASHRAE 62.1:6.4.1.4]
• Location and size of openings. Spaces or portions of spaces to be naturally ventilated shall be permanently open to operable wall openings directly to the outdoors. The openable area shall be not less than 4 percent of the net occupiable floor area. Where openings are covered with louvers or otherwise obstructed, the openable area shall be based on the net free unobstructed area through the opening. Where interior rooms, or portions of rooms, without direct openings to the outdoors are ventilated through adjoining rooms, the opening between rooms shall be permanently unobstructed and have a free area of not less than 8 percent of the area of the interior room or less than 25 square feet. [ASHRAE 62.1:6.4.2]
• Control and accessibility. The means to open the required operable opening shall be readily accessible to building occupants whenever the space is occupied. Controls shall be designed to coordinate operation of the natural and mechanical ventilation systems. [ASHRAE 62.1:6.4.3]

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