Robert Venturi and Denise Scott Brown have never been known to go quietly over anything, much less an extensive alteration to one of their most acclaimed projects. On Monday, the National Park Service sent out a press release describing plans—not of Venturi and Scott Brown’s design—for “the ambitious and exciting rehabilitation” of the underground museum at Franklin Court in Philadelphia’s Independence National Historical Park.

Also known as the Ghost House, Franklin Court and the museum dedicated to Benjamin Franklin’s life and work were designed by Venturi Scott Brown and Associates (VSBA) in 1976 as a kind of Harold-with-a-purple-crayon version of the great man’s mansion and print shop. It is arguably one of the most gratifying projects of the postmodern period in successfully integrating historicist subtleties with modernist clarities.

The Park Service’s press release, which said that the Washington, D.C. firm Quinn Evans Architects has designed a new glass entry pavilion with gift shop, staircase, and elevator leading to the underground museum, came somewhat belatedly considering that the project has been in the works for two years and that , Venturi and Scott Brown write that “the Neomodern aesthetic seems confusingly close in character to the Ghost structure and out of keeping with the mellow brick, stone, and wood of the site elements.” They also take issue with the lack of sheltered waiting space, the sudden plunging stairs that replace a ramp meant to invoke a Colonial road and provide a processional experience through the building, and the absence of inviting colors, communicative signs, and hangings in the lobby.

More offensive still, they write, is how the addition alters the original museum entry experience, which was tied into former urban planner Edmund Bacon’s greenway plan for Society Hill. “They don’t realize all the thinking that went into this,” said Scott Brown in a phone interview.

The current project was initiated as part of the National Park Service Centennial and its challenge program. The Pew Foundation is committing $6 million and raising $6 million more for the renovation project that is expected to go into construction this fall and be completed within 18 months. “They keep telling us they think we’re wonderful,” Scott Brown said. “And they want a letter saying we love the scheme. But it’s a whole other ball game.”