ENERGY EFFICIENT BUILDINGS

THE GHERKIN

INTRODUCTION

The building THE GHERKIN is an iconic symbol of London and is one of the city's most widely

recognized examples of contemporary architecture.

30 St Mary Axe (widely known informally as The Gherkin and previously as the Swiss Re

Building) is a commercial skyscraper in London's primary financial district, the City of London.

It was completed in December 2003 and opened in April 2004. With 41 storeys, it is 180 meters

(591 ft) tall and stands on the former site of the Baltic Exchange, which was extensively

damaged in 1992 by the explosion of a bomb placed by the Provisional IRA in St Mary Axe, the

street from which the tower takes its name.

After plans to build the 92-storey Millennium Tower were dropped, 30 St Mary Axe was

designed by Norman Foster and Arup Group and it was erected by Skanska, with construction

commencing in 2001.

Site :

The building stands on the former site of the Baltic Exchange, the headquarters of a global

marketplace for ship sales and shipping information.

The United Kingdom government's statutory adviser on the historic environment, English

Heritage, and the City of London's governing body, the City of London Corporation, were keen

that any redevelopment must restore the building's old façade onto St Mary Axe. The Exchange

Hall was a celebrated fixture of the ship trading company.

After English Heritage later discovered the damage was far more severe than initially thought,

they stopped insisting on full restoration, albeit over the objections of the architectural

conservationists who favoured reconstruction. The Baltic Exchange sold the land to Trafalgar

House in 1995. Most of the remaining structures on the site were then carefully dismantled, the

interior of Exchange Hall and the façade were preserved, hoping for a reconstruction of the

building in the future. Parts of its stained glass are displayed at the National Maritime Museum.

The tower's topmost panoramic dome, known as the "lens", recalls the iconic glass dome that

covered part of the ground floor of the Baltic Exchange.

The Gherkin name was applied to the current building at least as far back as 1999, referring to

that plan's highly unorthodox layout and appearance.

Planning process

THE ARCHITECTURAL FORM:

The shape of the tower is influenced by the physical environment of the city.

The smooth flow of wind around the building was one of the main considerations.

A net office floor area within the building of around 500,000 ft2 (46,450 m2).

The enhancement of the public environment at street level, opening up new views across the

site to the frontages of the adjacent buildings and allowing good access to and around the

new development.

Minimum impact on the local wind environment.

Maximum use of public transport for the occupants of the building.

Flexibly serviced, high specification ‘user-friendly’ column free office spaces with

maximum primary space adjacent to natural light.

Good physical and visual interconnectivity between floors.

Reduced energy consumption by use of natural ventilation whenever suitable, low façade

heat gain and smart building control systems.

PLANS:

1. Ground Floor Plan 2. Sixth Floor Plan

3. Twenty-First Floor Plan 4. Fortieth Floor Plan

1. Entry

2. Lobby

3. Retail

4. Core

5. Office Modules

6. Light Well

7. Private Dining

8. Elevator / Stair

30 St Mary Axe has a radical approach - technically, architecturally, socially and spatially.

Idea of having a city within a city.

An instantly recognizable addition to the city’s Skyline.

The site was special because it needed development, was not on any of the "sight lines"

(planning guidance requires that new buildings do not obstruct or detract from the view of St

Paul's dome when viewed from a number of locations around London), and it had housed the

Baltic Exchange.

The plan for the site was to reconstruct the Baltic Exchange. GMW Architects proposed a new

rectangular building surrounding a restored exchange—the square shape would have the type of

large floor plan that banks liked. Eventually, the planners realised that the exchange was not

recoverable, forcing them to relax their building constraints; they hinted that an "architecturally

significant" building might obtain a favourable reception from city authorities. This gave the

architect a free hand in the design; it eliminated the restrictive demands for a large, capital-

efficient, money-making building, whose design was per the client's desire.[17]

Swiss Re's low level plan met the planning authority's desire to maintain London's traditional

streetscape with its relatively narrow streets. The mass of the Swiss Re tower was not too

imposing. Like Barclays Bank's former City headquarters in Lombard Street, the idea was that

the passer-by in neighbouring streets would be nearly oblivious to the tower's existence until

directly underneath it.

Design and construction

The building was constructed by Skanska, completed in December 2003 and opened on 28 April

2004. The primary occupant of the building is Swiss Re, a global reinsurancecompany, which

had the building commissioned as the head office for its UK operation. The tower is thus

sometimes known as the Swiss Re Building, although this name has never been official and has

more recently fallen out of favour since the company's main headquarters is in Zurich and the

Gherkin name has become more popular.

The building uses energy-saving methods which allow it to use half the power that a similar

tower would typically consume. Gaps in each floor create six shafts that serve as a natural

ventilation system for the entire building even though required firebreaks on every sixth floor

interrupt the "chimney." The shafts create a giant double glazing effect; air is sandwiched

between two layers of glazing and insulates the office space inside.

30 St Mary Axe under construction

Architects promote double glazing in residential houses to avoid the inefficient convection of

heat, but the tower exploits this effect. The shafts pull warm air out of the building during the

summer and warm the building in the winter using passive solar heating. The shafts also allow

sunlight to pass through the building, making the work environment more pleasing, and keeping

the lighting costs down.

The primary methods for controlling wind-excited sways are to increase the stiffness, or increase

damping with tuned/active mass dampers. To a design by Arup, its fully triangulated perimeter

structure makes the building sufficiently stiff without any extra reinforcements. Despite its

overall curved glass shape, there is only one piece of curved glass on the building—the lens-

shaped cap at the very top.

On the building's top level (the 40th floor), there is a bar for tenants and their guests featuring a

360° view of London. A restaurant operates on the 39th floor, and private dining rooms on the

38th. Whereas most buildings have extensive lift equipment on the roof of the building, this was

not possible for the Gherkin, since a bar had been planned for the 40th floor. The architects dealt

with this by having the main lift only reach the 34th floor, and then having a push-from-below

lift to the 39th floor. There is a marble stairwell and a disabled persons' lift which leads the

visitor up to the bar in the dome.

Shown

here where it opens into the office floor at the base of one of the six-story atriums, the Abluft enclosure

sandwiches blinds and encased diagrid struts between the exterior curtain wall and an inner curtain wall

of rectangular glass sheets

The building is visible over long distances: from the north, for instance, it can be seen from

the M11 motorway, some 32 kilometres (20 mi) away, while to the west it can be seen from the

statue of George III in Windsor Great Park.

The mixed-mode ventilation that would allow the building to be cooled mechanically or through

natural ventilation depending. The Gherkin is enclosed by a unique curtain wall that combines

two systems. For most of its circumference on any given office floor, the building is encased by

an exterior curtain wall of clear diamond-shaped double-glazed panels as well as an interior

curtain wall of rectangular single-glazed panels fitted with blinds. In this Abluft or exhaust

façade, heat that builds up in the airspace between the two curtain walls is exhausted to the

outside by vents at the top of each one- or two-story zone. Where the enclosure adjoins the

spiraling atria, the interior curtain wall is omitted and the exterior curtain wall is tinted to reduce

solar heat gain as well as fitted with some operable windows that tilt open to admit fresh air.

When weather permits, a computerized building management system can selectively open these

windows, using the pressure differentials at atria thirty degrees apart around the façade to draw

air in and through the building.

After completion

In April 2005, the press reported that a glass panel two-thirds up the tower had fallen to the plaza

beneath. The plaza was sealed off but the building remained open. A temporary covered

walkway, extending across the plaza to the building's reception, was erected to protect visitors.

Engineers examined the other 744 glass panels on the building. The cost of repair was covered

by main contractor Skanska and curtain-wall supplier Schmidlin (now called Schmidlin-TSK

AG). Since its completion, the building has won a number of awards for architecture.

Plan view from a simulation of air flow and velocity through the sixth floor was among the many

documents generated by environmental consultants BDSP during the design of 30 St Mary Axe to model

the building’s environmental performance. BDSP, Swiss Re HQ, 2009. Presentation.

Like the previous image, this perspective view of a simulation of air velocities in Atrium 6 framed

expectations about energy consumption at 30 St Mary Axe. BDSP, Swiss Re HQ, 2009. Presentation.

FACTS AND FIGURES DIMENSIONS:

Height to top of dome: 179.8 m

Height to highest occupied floor level: 167.1 m

Number of floors above ground: 40

Number of basement levels: single basement across whole site

Largest floor external diameter (lvl 17): 56.15 m

Site area: 0.57 hectares (1.4 acres)

Net accommodations areas:

Office 46,450 m2

Retail 1,400 m2

Office floor-floor: 4.15 m

Gross superstructure floor area (incl. lightwells): 74,300 m2

Tower Structural Steelwork

Total weight of steel (from Arup Xsteel model): 8,358 tonnes of which:

29% is in the diagrid

24% core columns

47% beams

Total number of primary steel pieces: 8 348

Total length: 54.56 km

Diagrid column sizes:

Ground – level2: 508mm f, 40mm thick

Level 36–38: 273mm f, 12.5mm thick

Hoop design tension at level 2: 7 116 kN

Perimeter column maximum design load: 15,460 kN

Core column maximum design load: 33,266 kN

Foundations 750mm diameter straight-shafted piles into London Clay

Number of piles: 333

Total length of piles: 9 km

Total design capacity: 117,000 Tonnes

SUSTAINABLE BUILDING:

The tower is aerodynamically designed to reduce wind load on the structure, whilst the

lower part tapers so that wind wraps around the tower.

The six fingers of accommodation on each floor, configured with light wells in between,

maximize daylight penetration.

The façade design with advance glazing technologies, ventilated cavities and blinds ,

provides up to 85% solar protection.

Gas is the main fuel used hence it will only generate half the carbon emission.

Overall energy serving is up to 50%.

AWARDS:

2004 RIBA Stirling Prize . For the first time in the prize's history, the judges reached a

unanimous decision. In December 2005, a survey of the world's largest firms of architects

published in 2006 BD World Architecture 200voted the tower as the most admired new building

in the world. However, Ken Shuttleworth, who worked for Foster and Partners on the design of

the building, said in 2011 that he believed the style was now out-moded: "I was looking at the

glass all around and [thought], 'Why on earth did we do that?' Now we would do things

differently".

CONCLUSION

Working on this project, we have studied about the various energy efficiency

methods and techniques that have been used in The Gherkin Tower building.

This report will always help me in my design projects and help me in

contributing to the environment. We should also try our best to save energy

and lessen the carbon foot print of all the designs we do.

Bibliography

www.designbuild-network.com

www.fosterandpartners.com

krg2uf.wordpress.com

wikipedia.org