Watch Anthony E. Malkin in a video in which he offers advice for owners and developers of any size buildings as well as to policy makers.

What’s the key to making an 80-year-old building more energy efficient and transforming it into one of the greenest in the city?

“Windows,” says Anthony E. Malkin, president of New York City–based real estate firm Wien & Malkin, with a portfolio of 8 million square feet (744,000 sq m) in the Big Apple that includes the Empire State Building.

Malkin’s plan for the greening of one of America’s most iconic buildings involved preserving 96 percent of the Empire State Building’s 6,514 windows, including the original frames and 26,000 panes of glass. The window replacement is one of eight components in the retrofit that, when finished in two years, is expected to reduce energy use in the structure by 38 percent, save $4.4 million annually, and avoid 105,000 metric tons of carbon dioxide emissions over the next 15 years.

Built in 1931, the 102-story, 2.6 million-square-foot (241,800-sq-m) art deco structure at 34th Street and Fifth Avenue is an example of how older buildings can be retrofitted to the highest energy standards and reduce their greenhouse gas emissions.

“When you look at energy savings, start with the building envelope before you work on mechanical systems,” says Malkin, a nationally recognized real estate entrepreneur. “By making the windows more resistant to temperature change, and adding insulation between the perimeter heating units, we reduced our heating and cooling loads, which meant smaller HVAC demands for our plant. The Empire State Building is no different. Size may matter. It’s about making an integrated plan, utilizing life-cycle cost analysis, and implementing.”

Never has a structure so old and so tall gone so green, says Malkin, whose plan wasn’t to simply shut down the building while refurbishing it. Instead, his team turned to Sunnyvale, California–based Serious Materials to create a window workshop on the fifth floor of the Empire State Building. Serious Materials employees transformed the building’s dual-pane windows after hours into super-insulated panes to avoid interfering with tenants.

There’s nothing greener than reusing existing glass, he adds, noting that the new energy-efficient windows will reduce the solar heat gain of the Empire State Building by over 50 percent, saving an estimated $500,000 a year. Workers carefully separated the windows’ components and rebuilt them with items including new spacers and a layer of coated film. The double-hung window retrofit cost about $700 per window—about a third of what it would cost to replace the structure’s 12-year-old windows with new ones, making the retrofit the less expensive, more eco-friendly one. Of greater importance, he adds, the project did not create tons of waste for landfills.

“We created an innovative solution, bid it out, and had a great, qualified vendor in Serious Materials do the job for us,” says Malkin. “It wasn’t rocket science; it was transparently bid and won. Overall, we created a system that allows for analysis of costs and benefits and payback. We did this for tenants as well. Our plan is not proprietary; anyone can use it. The key is that we did not try to be ‘green,’ we tried to conserve energy without compromise to function and to make it about dollars spent and saved.”

The project, Malkin adds, is all about breaking down challenges into digestible pieces and finding cost-effective solutions. “Anyone can utilize our innovative window retrofit now,” he continues. “We didn’t patent it. It’s free to others.

The Empire State Building’s energy retrofit is already gaining the attention of building owners in New York City and the rest of the country. Although the retrofit of the iconic skyscraper was specifically designed for the energy-efficiency improvements, it can serve as a model for other office buildings around the world.

“All portfolio managers and real estate owners to some extent have been concerned with energy efficiency, and they’ve done small things,” Malkin continues. “What we did was to show that it makes sense to make large and significant energy-efficiency improvements. People associate greening with expense and compromise. We proved: no compromise and payback. The building system work is done. We just bought two years’ [worth] of clean power from a vendor that was the low bidder overall. We are assisting large tenants with energy-efficient installations now. We have become the catalog for everyone to draw from on successful energy-efficiency work.”

See the Empire State Building energy retrofit website to learn more about the multitude of changes made, those decided against and to avail yourself of the free, open source tools created to help other developers and owners assess energy retrofit steps under consideration on their own projects.