In the late 1950s and early 1960s, Washington's real estate image started changing. After 150 years of classically derived architecture, modernism arrived, although often politely.

Architectural journals of that period showed the Geico headquarters complex completed in 1959 in Chevy Chase, designed by Vincent Kling; and housing in the Southwest urban renewal area designed by I.M. Pei, Charles Goodman, Chloethiel Woodard Smith, and Keyes, Lethbridge and Condon.

In 1961, Harry Weese designed Arena Stage, a building sculpted by the shaping of its interior. Eero Saarinen's Washington Dulles International Airport terminal, its shape symbolizing its purpose, was under construction, while Edward Durrell Stone's genteel National Geographic building was on its way to completion.

These and many other projects, although differing substantially in appearance, embodied the increasingly convolink to traditional pre-industrial building imagery.

Evisceration of vertical building surfaces and the creation of soaring external towers to house them did not originate with Kahn. Other modern architects in the United States and Europe had been exploring the sculptural potential of stair towers, elevator shafts and mechanical equipment pulled through building skins for functional and expressive purposes.

Nevertheless, this design strategy must have seemed too radical for Washington's taste. Unlike Philadelphia, Bostith a combination of round columns, projecting floor slabs, and circular and rectilinear air ducts. The heating, ventilation and air conditioning system components are black, as is the "mansard" roof. The circular metal air ducts decrease in diameter at each story as they proceed vertically downward from giant horizontal manifolds. The ductwork size change is logically motivated, for the volume of air flow diminishes as air from the descending ducts is diverted at each level.

Conversely, the circular, structural columns increase in diameter from top to bottom, signaling the increase in compressive forces accumulating floor by floor as the columns descend from roof to foundations. Because the loading on horizontal floor slabs and beams is constant at each level and the spans between columns remain unchanged, the horizontal structural elements expressed on the facade don't vary.

This pattern of revealed structure and ductwork on the south and west facades has another purpose. With the glass infill walls substantially recessed, they are shaded from hot southern and western sun in summertime, while in winter the lower-angled sun is able to penetrate.

However, on the shady north facade facing H Street, the architects have chosen to pull the glass wall out to the surface of the structure. Recessing the north-facing windows would reduce the amount of natural light inside and reducing rentable floor area. Here, the structural and mechanical elements are behind a smooth, flush skin, although the structural pattern is still apparent in the curtain walls' composition.

National Permanent, despite its innovative but conceptually sympathetic use of necessary building systems, seemed for a while to represent the limit of what Washington could abide. But not for long. An Australian architect, John Andrews, soon would design the Intelsat building on Connecticut Avenue, a structure whose expressionistic image would not be at all "Washingtonian."