Every year, more green buildings are added to the New York skyline, each one a testament to the financial and environmental benefits of sustainable design. But yesterday, I traveled to the Empire State Building to welcome an even more remarkable development: an old landmark is getting a makeover that will not only reduce energy use by 38 percent but will pay for itself in energy savings in just three years.

I am thrilled that owner Tony Malkin, the president of Wien & Malkin and the husband of long-time NRDC Trustee Shelly Malkin, is showing the world that existing buildings can become more efficient. Many states have strong efficiency codes for new buildings, but by 2030, the majority of commercial spaces will still have been built before the codes took effect.

That means existing buildings provide an enormous, cost-saving vein of energy efficiency that we need to learn how to tap.

The Empire State Building is pointing the way. After all, the Empire State Building is 78 years old. It was built in the Great Depression, and is made of Art Deco infused concrete, not the sleek glass and steel of new buildings popping up around Manhattan.  Its retrofit reminds us that even gray towers can become greener.

At yesterday's press conference, Mayor Bloomberg told the crowd that 78 percent of New York global warming pollution comes from the city's buildings, much of it from using electricity and natural gas. Reducing that energy use through more efficient windows, heating and cooling systems, and better insulation is a critical climate solution.

President Bill Clinton also spoke to the crowd. His organization, the Clinton Climate Initiative, has been helping the Malkins design the retrofit. He emphasized that in addition to policies that explain why we should make efficiency improvements, we need to actually figure out how to make them. The Empire State Building project, he said, is all about the how.

The Malkins and their partners are not going to hide their efficiency discoveries as proprietary knowledge. They are making this project as transparent as possible so others to learn from their experience. This includes bringing the tenants into the effort. They will have access to a web-based database that gives feedback about how much energy they are using and where their big drains are.

During the question and answer period of the event, people asked if the owners were concerned about making this kind of capital outlay during an economic crisis. The answer was clear: efficiency measures are cost-saving investments that pay for themselves in lower utility bills and eager tenants.

These energy efficiency plans will turn the Empire State Building into a green beacon. I couldn't think of a better addition to our famous skyline.