Environmental Leader

As the tallest building in the Western Hemisphere readies itself for a major energy efficiency overhaul, engineers have developed what may be the world’s tallest green roof.

The Willis Tower, formerly known as the Sears Tower, is spending about $200 million to $300 million to upgrade its energy efficiency and become more “green” overall, reports the Chicago Tribune.

The building might have one of the tallest green roofs in the world. Set on the 90th floor, the feature required the use of metal meshing to prevent sod and plants from blowing away.

The skyscraper, which was constructed in 1973 and has 110 stories and stands 1,450 feet tall, is starting to show its age. Single-pane windows leak around the edges. Lighting is excessive and inefficient. Outdated electric heating is incorporated throughout.

Willis Tower has had upgrades through the years but still uses enough electricity each year to power 9,000 homes. It uses about 50 percent more energy than a new office building of the same scale would use, according to the article.

Adrian Smith + Gordon Gill Architecture in Chicago is handling the building retrofit, which was announced earlier this year.

A new skin of 16,000 energy efficient windows is expected to be installed late next year. The building also will benefit from automated lighting that reduce lighting when enough natural light is available, or turn off lights when not in use. The window project alone is estimated to cut energy required to heat the building by half.

Plumbing improvements are estimated to save 24 million gallons of water a year.

The steep price tag does not have a quick ROI. All told, the retrofit likely will take 26 years to pay for itself.