The building was designed by Lord Foster, his then business partner Ken Shuttleworth, and Arup engineers, and was constructed by Skanska of Sweden in 20012004. The Swiss Re Headquarters at 30 St Mary Axe,popularly known as the Gherkin, won the Stirling Prize for 2004. 30 St Mary Axe is London's first environmental skyscraper, located in the heart of the City of London. A comprehensive range of sustainable measures mean that the building will use 50% less energy than a traditional prestige office building. Fresh air is drawn up through the spiralling light-wells to naturally ventilate the office interiors and minimise reliance on artificial cooling and heating. The light-wells and the shape of the building maximise natural daylight, moderate the use of artificial lighting and allow views out from deep within the building. The exterior cladding consists of 5,500 flat triangular and diamond shaped glass panels, which vary at each level. The glazing to the office areas consists of a double-glazed outer layer and a single-glazed inner screen that sandwich a central ventilated cavity which contains solar-control blinds. The building is currently the 6th tallest in London.