D.C. Mun. Regs. tit. 14, § 1309
1309.1 Each room used for high density occupancy shall have at least twenty-five percent (25%) more natural light than is required by § 502 of this subtitle.
1309.2 Each room used for high density occupancy shall have at least twenty-five percent (25%) more ventilation than is required by § 506 of this subtitle.
SOURCE: The Housing Regulations of the District of Columbia, 5G DCRR § 7302, Commissioners' Order 53-1503 (August 11, 1955).