Chicago’s Sears Tower is getting a new name, later today the skyscraper will be re-christened the Willis Tower. But another, perhaps more significant, change is also on the way for the building. Its owners want to give it a $350-million green makeover.

Chicago’s Sears, soon to be Willis, Tower marks one of the great feats of modern architecture—when it opened in the 70s, it was the world’s tallest building. And now, its owners also want to make it a symbol of environmental sustainability. To do that, they have to do more than change a few light bulbs. John Huston is one of the building’s co-owners; we walk through an equipment room onto the too-windy-for-skirt-wearing 90th floor roof.

HUSTON: We’re looking at Lake Michigan to the east here and right in front of us is the beginning of a green roof.

Low growing red, green and white plants fill out the small test-planter box. Huston says it’s the highest green roof in the world; the plants don’t seem to mind the elevation. It’s neat, but it’s not where the real energy savings come from.

We turn to face the building…and look up…

HUSTON: The windows that are currently installed in the building are single glazed windows; that means they are not insulated glass. Our plan is to change all 16,000 windows to a triple glazed unit.

HILL: Now 16,000 windows is a lot.

HUSTON: It’s interesting what happens when you walk into a window vendor, when you say we’re interesting in ordering 16,000 windows you get a different level of attention.

The plan also includes replacing all the metal paneling on the outside of the building and upgrading some of the building’s mechanical systems. Cross

From the roof we trek into the guts of the building where huge engines and motors and other equipment whirs and hum.  Large multi-colored pipes twist around and above us.

HUSTON: This is one the boiler units, this large green box over here. It’s totally powered by electricity. It heats the water that heats the building. And it’s 8000 kilowatts, which is a very, very large unit.

There are 10 boilers. All of them will be replaced. They’ll also test wind turbines and add solar panels. All told they’re hoping to reduce electricity use by 80 percent.

Huston and his partners won’t say exactly how much of their own money they plan to kick in to accomplish that but they are hoping to get some public and private money for the project. One selling point: they say the rehab could create 3,600 green jobs. Scott Horst is with the US Green Building Council.

HORST: What’s exciting to see in buildings like this is that we’re seeing exactly what we mean when we talk about a green economy.

He says when iconic buildings like the Sears Tower and the Empire State Building, which recently announced a more modest, 20 million dollar overhaul, go green it could encourage other building owners to follow suit.

HORST : The potential that they represent as icons is really the potential of our country to rebuild itself in this green way.

There’s another reason building owners are looking to go green; it can make good business sense. Melissa Pionek is with retail real estate company CB Richard Ellis. She says from a building owner’s perspective, the market for office space is incredibly competitive as vacancy rates have been rising.

PIONEK: With the way the economy has been in the last couple of years and recently, buildings are really looking for a way to stand out in the world of leasing from their neighbor.

That can be a lure for a company that wants to up its green profile. Also, Pionek says, energy efficient buildings can be cheaper for tenants. Though she says the green-ness of a building isn’t the deciding factor for most tenants, it is something they say they care about. And she expects more big buildings to start responding to that interest.

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