London hospital building - world's tallest - to get badly needed renovation

Guy’s Tower in London, the tallest hospital building in the world, is getting a much needed renovation. In recent years, the 143-meter-high (about 470 feet) building—actually two towers connected by a bridge—has been falling apart. Small pieces of concrete have started to fall off the towers, endangering pedestrians. 

The design team led by Arup addressed issues such as how much of the façade to reclad, how to deal with cold bridging, and how to do the work while the building is operational. Each option was modeled and plotted on a graph of cost versus energy efficiency to see where the greatest green gain could be achieved while keeping costs reasonable. The most cost-effective solution was to fit a new façade in front of the existing columns of one tower, and to fully clad the other tower with an aluminum rainscreen.

(http://www.forumforthefuture.org/greenfutures/articles/world%E2%80%99s-tallest-hospital-gets-makeover [2])