It’s true that density requires an efficient use of energy, which has obvious benefits for the way we employ resources. Also, urban density makes possible those chance encounters that contribute to the creative energy celebrated by commentators such as Richard Florida. Still, is greater density always green? Is it more livable? For the public, the second may be the more pressing question.

From my trips to Washington, D.C., I have become more aware of an ongoing debate about the city’s historic height limit. Although for many years something like that existed in Philadelphia (no building should be higher than the hat that William Penn’s statue wears on top of City Hall), it was a gentlemen’s agreement, rather than a planning principle codified by law. When, by community consent, the agreement was breached, Philadelphia gained a new skyline and an economic shot in the arm.

If the number of cranes on the horizon is any indication, our nation’s capital doesn’t need a financial stimulus. So the argument here is that a denser city will be more lively and green. For the community and developers, this seems like a clear win-win. The case seemed closed, in my mind—at least until I read a thoughtful op-ed piece in The New York Times by Robert A.M. Stern, FAIA.

Stern was responding to a study released last summer by New York’s Department of City Planning that calls for doubling the developable floor area on some sites around Grand Central Terminal. The rationale is green in both senses of the word—a more sustainable city and more square footage to keep New York competitive with its Asian rivals. But then Stern asked, “What happens at the end of the workday when all the new tenants power down their laptops and head back home? I’ve been on the Lexington Avenue line at rush hour. How could the existing system accommodate the hordes of new straphangers?”

Far too often we have reached for the holy grail of new construction without first preparing for the infrastructure to support it—water, sewage, and transportation, to name the most obvious. Far too often infrastructure arrives after development, not before. As the current expensive efforts to untangle the gridlock of Northern Virginia’s Tysons Corner (a suburb of Washington) suggests, greater density by itself may not yield the kind of green dividend we’re looking for. The first, and necessary, step is to invest in the infrastructure that will support it.

Mickey Jacob, FAIA, 2013 President