Chicago landmark plans to become a green giant
The Willis Tower, the iconic 110-storey office building in Chicago, USA, is now undergoing a five-year renovation to become environmentally efficient.  The plan includes the construction of a 50-storey hotel right beside the 1,450 ft. (443-metre) tower, which will also be built with the environment in mind.

The Willis Tower, formerly known as the Sears Tower, was built in the early 1970s and is the tallest building in the Western Hemisphere and the eighth tallest in the world.  It is the premier corporate office building in Chicago, housing more than 100 companies, including prominent law, insurance, transportation and financial service firms.  The Willis Tower encompasses more than 4.5 million sq. ft., including its Skydeck and 103rd-floor glass viewing platform (called  The Ledge) which attracts over 1.3 million visitors every year.

The renovation project now underway has been designed by Chicago-based Adrian Smith and Gordon Gill Architecture.

Costing $350 million, it will result in 80 per cent less electricity consumption.  There will be changes involving the tower’s exterior walls, mechanical systems, lighting, vertical transportation, water supply, roofs and maintenance.  The most visible changes will be noticed on the roofs of the building, where between 30,000 and 35,000 sq. ft. of gardens will be planted  to create green roofs, aimed at reducing storm-water run-off.

The surroundings of the tower are being altered as well. The granite wall on Adams Street will be replaced by a digital display of news and upcoming or current events.
Accompanying that, more trees will be planted around the tower and a landscaped terrace will be built, which will help in the natural filtration of carbon dioxide.

“The changes made and benefits realised through the bold sustainable initiatives at the tower serve as an example that a sustainable future is more than a concept, it is within our reach,” said John Huston of American Landmark Properties, representing the building’s ownership. As part of the renovation plan, the amount of heating energy consumed  by the building is to be reduced  by 60 per cent by replacing the 16,100 single-paned windows with double-paned windows that have insulating film in between.
The installation of solar panels on the roofs will help bring in more of the natural energy to run the mechanical systems in the building and save 40 per cent of lighting energy in the process.  Just as much water usage will be reduced through water-efficient fixtures that will be included.  Even the 104 elevators and five escalators will be upgraded to cut their energy usage by half.

Along with the solar panels on the roofs, several wind turbines will be installed which will  contribute to the electric supply for the tower.

On a clear day, visitors to the Willis Tower can have views of four states (Illinois, Indiana, Wisconsin and Michigan) from the 103rd-floor Skydeck, which is 1,353 ft. (412 metres) above the ground.

The Ledge’s four glass boxes, each weighing 7,500 lb., extend out 4.3 ft. from the Skydeck;  they are comprised of  three layers of  half-inch-thick glass laminated into one seamless unit. The Ledge has what  is called ‘heat tracing’ to melt snow off  the glass.

Geetha  Balachandran

From bull ring to commercial complex
A 19th century bullring in the Spanish city of  Barcelona left to decay with the fading interest in bullfighting has been transformed by London-based architects Rogers Stirk Harbour + Partners into a mixed use commercial facility, reigniting interest in this formerly significant landmark in the city’s heritage.

Recently completed, the Las Arenas complex was opened to the public in March, offering commercial, entertainment and health and leisure facilities, arranged around a central event space. It encompasses 47,000 sq. metres in its cylindrical form and is located at the foot of Montjuic, a hill near the centre of Barcelona. The entire complex has been raised above the streets at ground level, with ramps and stairs providing access.  The lengthy construction project involved the excavation of the base of the façade and the insertion of composite arches to support the existing wall and create new spaces for shops and restaurants.  Similar amenities will also be provided in the nearby ‘Eforum’ building.

Las Arenas’ signature domed roof measures 76 metres in diameter, is structurally independent from the façade, and floats above a 100-metre-diameter habitable ‘dish’, creating a magnificent viewing platform for visitors to the complex. The domed roof itself  has been finished with a plastic coating to reduce solar glare.  Orientation within the facility is afforded using a variety of  stairs, escalators, bridges and walkways, with four passenger lifts split into pairs on either side of the circular atrium. Structural columns are contained within the stairs, lifts and bridges, allowing for an open, column-free space at level 4 and obviating the need for any structural members to pass through the cinema spaces below at levels 2 and 3.  The cinema spaces are formed by large steel cantilevered boxes that effectively constitute a separate, self-contained structural system within the building and rest on a concrete base at level 2.

All the constituent parts – the façade, the roof-level spaces, the four internal segments and the adjacent Eforum building – are structurally independent, allowing for future flexibility and change to encourage a wide variety and rotation of activities, including sports events, fashion shows and exhibitions.

Achal Narayanan  

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