See this item for the LeDroit Park Historic District, next door to Bloomingdale, from his permit review today:
338 U St. NW: Conversion of this LeDroit Park rowhouse into a two-unit dwelling, with separate HVAC, hot water and electric services.
Note that this property – 338 U St NW – is being converted to a two-family flat.
Note that the Historic District designation status of LeDroit Park does NOT impact the R-4 zoning for the neighborhood, which allows for multiple dwelling units per lot. The neighborhood Historic District designation does not prevent the property owner from converting away from a single family dwelling.
Of course, if the front of the property were to be changed -- or side of the house if at a corner or abutting an alley -- then such renovations WOULD need to go before the Historic Preservation Review Board.