D.C. Mun. Regs. tit. 11, r. 11-1722
Except for a building located in the Principal Intersection Area, as described in § 1723.1, or a building located on Lot 158 in Square 515 for which a building permit has been received within nine (9) months prior to or after [the effective date of this section], or any portions of a building that existed on the [effective date of this section] that is subsequently designated a historic landmark or is included within a historic district, this Section together with § 1701.3, shall apply to each building with frontage on:
Each building shall devote not less than fifty percent (50%) of the surface area of the streetwall(s) at the ground level of each building to display windows with clear or clear and/or low-emissivity glass, except for decorative or architectural accent, and to entrances to commercial uses or to the building.
Each building shall devote not less than fifty percent (50%) of the surface area of the streetwall between twelve (12) feet and fourteen (14) feet above grade to clear or clear and/or low-emissivity glass.
Each building shall be designed so as not to preclude an entrance every forty (40) feet on average for the linear frontage of the building; excluding vehicular entrances, but including entrance to ground floor uses and any main lobby.
The ground floor level of each new building or building addition shall have a minimum clear floor-to-ceiling height of fourteen (14) feet for a distance of at least thirty-six (36) feet perpendicular to the ground floor's front building line.
D.C. Mun. Regs. tit. 11, r. 11-1722