Last week, 461 Dean became the world's tallest modular building. Designed by New York architecture firm SHoP, the Brooklyn residential tower consists of 363 pre-fab apartments that stack like Tetris blocks into a 32-story building. It's an impressive architectural feat, to be sure—but 461 Dean is also an important test of modular design's potential to make cities more affordable.

The results of that experiment look to be mixed. The building is part of a commercial and residential development project in Brooklyn called Pacific Park. When construction on 461 Dean began in 2012, developer Forest City Ratner said the structure would be ready 18 months sooner and cost 20 percent less than a conventional tower, making its units more affordable. The good news is that half of the building's units will be priced below market rate, as originally planned. Studios will start at $559 a month, one-bedrooms at $600 a month, and two-bedrooms at $727 a month—in a neighborhood where the median rent on a one-bedroom is $2,700.

The bad news? The building took more time and money to build than originally promised. Conflicts between Forest City and its manufacturer, Skanska, caused construction to run two years over schedule and tens of millions of dollars over budget. If modular buildings like 461 Dean are going to help stem the rise of housing prices, designers and developers will need to work out some kinks first.

SHoP

Not that those kinks are unusual when architects and developers explore new building methodologies. "I think modular architecture is very smart, and I think it's something we're going to start to see more of in the future," says Carol Galante, director of the Terner Center for Housing Innovation at UC Berkeley. "But there are absolutely barriers to getting it scaled up."

In the case of 461 Dean, one of the biggest obstacles was developing the building's "library" of 960 modules. Modular architecture's promise is the idea that it can take a linear operation—constructing a building wall by wall, room by room, floor by floor—and divide it into parallel processes. Ideally, construction teams assemble 90 percent of a modular building off-site, all at once. "You can begin building a whole building at the same time,"says Chris Sharples, a principle at SHoP. The more units you build, the more predictable and efficient modular building becomes. But you have to design and manufacture the components first.