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Structures like the Empire State Building become icons because their architecture stands the test of time. But what lies beneath those historical facades is not always efficient, according to an article on the National Geographic website.

When the Empire State Building was built, concepts like sustainability and climate change were not part of the blueprints.

Thankfully, aging buildings can now be updated with new windows, lighting, plumbing fixtures, and heating and cooling systems, ultimately saving money while they conserve energy, the article said.

When the Empire State Building unveiled new LED lights in 2012, not only did the color options increase from nine to millions, the new lights used a quarter of the electricity of its original floodlights.

The owners of the building also needed to deal with complaints from its office tenants. In summer, the building is hard to cool. Powerful chillers with a $17 million price tag were rejected for changes that would reduce energy use.

After dozens of energy-saving ideas were cut to eight, the most practical were chosen. Upgrades ranged from heating and cooling components to lights that automatically dim during the day to barriers that prevent heat from radiators escaping through the walls, the article said.

For instance, the Empire State's 6,500 double-pane windows were huge energy wasters. Instead of replacing them, they were removed and a gas-filled film, which acts as an insulating third pane, was added. The refurbishment was done on-site and the windows were reinstalled after hours. The new windows reduce summer heat gain and winter loss by more than 50 percent.

The Empire State Building is not the only historic facility shifting toward sustainability. Fenway Park has made great strides. For example, in addition to the famous Green Monster, the park features Fenway Farms, an agriculture project that grew nearly 6,000 pounds of organic food for the park in its rows of irrigated, repurposed milk-crate planters.

Fenway was also the first major league ballpark to install solar panels. According to the National Geographic reports, the investment reduced reliance on natural gas, used to heat water, by 37 percent.

Yet another program, called the Green Team, sends volunteers into the stands between innings to collect recyclables. It's reported that the initiative saves almost 400 tons of waste from landfills.

Inroads have been made to improve sustainability in other popular and historic buildings, too. Click here to learn more about how the Eiffel Towel installed rain collectors that funnel water to toilets, saving water and cutting the workload of pumps; how the Sidney Opera House traded corrosive chemical cleansers for natural ones (which has also lead to better indoor air quality) and implemented a comprehensive waste diversion program; how Reichstag became one the world’s greenest parliament buildings; and how the Transamerica Pyramid achieved the highest "green building" rating for its practices.