NYC developers are stacking residential units on higher-than-ever mechanical floors—stuffed with things like heating and AC—to get around height restrictions in the race for air rights.

Why does this work? The mechanical floors don't count when it comes to zoning restrictions, providing a nice loophole to add more height the new supertalls, Crain's reports.

Groups like the Municipal Art Society already say supertalls disrupt the skyline, and the loophole only stokes the flames. "It's like a booster chair," says Municipal Art Society VP Mary Rowe. "This is not living up to the intention of the zoning."

But developers like Arthur Zeckendorf say the giant mechanical rooms are necessary to house the high-end, complex systems of modern luxury buildings. "It's like a battleship in these spaces—there's a ton of equipment," Arthur says.

This practice has become widely adopted in recent years. For instance, Vornado's 950-foot condo tower at 220 Central Park South houses six floors of mechanical spaces at its base, while condos start on the 21st floor—about 190 feet above street level. [Crain's]