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From the S/G website:

The greening project at Sears — the tallest building in the United States and also one of the largest in terms of square footage — will demonstrate how to save a significant amount of energy and improve the occupant experience of an existing building during a large-scale 21st century modernization.

Key components of the greening/modernization project include:

• Efficiency improvements to the building’s exterior envelope and windows. The tower has 16,000 single-pane windows. Sustainability plans for the building call for a window replacement and glazing program. Strategies to achieve a thermal break of the curtain wall are also being investigated. These upgrades would achieve savings of up to 50 percent of heating energy.

• Mechanical systems upgrades in the form of new gas boilers that utilize fuel cell technologies, which generate electricity, heating and cooling at as much as 90 percent efficiency. Mechanical upgrades also will include new high-efficiency chillers and upgrades to the distribution system.

• The tower’s 104 high-speed elevators and 15 escalators that will be modernized with the latest technology to achieve 40 percent reduction in their energy consumption.

• Water savings that will be realized with conservation initiatives through upgrades to restroom fixtures, condensation recovery systems and water efficient landscaping, which will reduce water usage by 40 percent and save 24 million gallons of water each year.

• Lighting that will be upgraded through advanced lighting control systems and daylight harvesting, an advanced lighting control system that automatically dims lights in tenant spaces based on the amount of sunlight entering through the windows. Combined, these upgrades will save up to 40 percent of lighting energy consumption.

• Renewable energy like wind and solar, and technologies like green roofs that will be tested. Wind turbines will be tested to take advantage of the tower’s height and unique set-back roof areas. Solar hot-water panels will help heat water for the building. Green roofs that can sustain high- altitude conditions, and that will be among the tallest in the world, will be tested to reduce storm water runoff, improve insulation, help mitigate the urban heat island effect, and provide pleasant vistas for tenants overlooking the areas.

In concert with the new building construction, Sears Tower’s grade-level plazas and retail will undergo a transformation. A new park on Wacker Drive will feature a reflecting pool, landscaping and seating, creating an inviting public space. The Adams Street granite wall will be replaced with an interactive digital display and glass storefronts at Adams and Franklin. Trees will be planted along Adams to form an accessible planting terrace. The new hotel will feature a retail plaza level that complements the Sears Tower restaurant Level 2. The upper plaza will include an indoor connection to the hotel, outdoor seating and additional landscape elements.

A new skydeck entry will be located within the hotel building’s podium, integrated with retail along Jackson Street. Visitors will enter in the same location, but will be able to take escalators to the Skydeck attraction on LL2 in order to decrease wait times. The escalators will be underneath an attractive glass dome that connects Sears Tower to the new hotel. Direct access to the outdoor plaza and restaurants will be provided for skydeck visitors.

http://www.smithgill.com/#/work/sears_tower