A glazed crown on top of the building, spanning from level 10 up to 14, will become the eyecatcher of the new One Fen Court in the City of London. The closed cavity façade (CCF) with its kinks and inclinations features dichroid glass which offers an array of colours changing in dependence of daylight and weather conditions. Daylight enters the large office rooms from all four sides. The building also offers spaces open to the public, such as the unique rooftop garden with exceptional 360-degree views of the City, numerous retail space at the lower levels and a new public passageway at street level.
In February 2019, the rooftop garden on the 69-meter high building was opened to the public – one of the largest roof gardens in London. Eric Parry Architects designed the iconic building which is characterized by minimal yet sharp geometries. The façades even increase the overall complexity by an inclined and folded CCF and a diversity of façade types and materials.
Josef Gartner GmbH, a company of the Permasteelisa group, designed, engineered and produced for One Fen Court a 10 meter high steel mullion-transom façade at ground level using precast concrete cladded pillars. In the unitized main façade more than 20,000 terracotta plates with 30 different shapes were integrated. Its appearance changes due to the flip-flop paint that reflects light at different angles from the metallic painted surface of the brise soleil profiles used as sunscreen louvres.
For the first time, dichroic glass has been used for the outer pane of a CCF façade. Iridescent strips of the CCF are producing colourful effects both inside and outside the building. Even the inclined and kinked individual panels have been fitted with complex aluminum sunscreen louvres inside the closed cavity of the façade. As a closed double-skin curtain wall, this CCF technology provides excellent noise protection (Rw= 48 dB) as well as thermal insulation (Ucw= 1.3W/m2K and Ug= 1.1W/m2K).
One Fen Court lies at the heart of the City of London’s banking, insurance and commercial sector near to the Lloyd´s building, which incidentally also features a Gartner façade, the building is 300 meters from 20 Fenchurch (affectionately known as the Walkie Talkie), with a main façade designed and produced by Permasteelisa and the roof construction for the Skygarden realized by Gartner. Generali Real Estate as owner of the site at 116- 120 Fenchurch Street and 10-14 Fenchurch Avenue hired architect Eric Parry in 2006, who proposed a tower of similar height to 20 Fenchurch Street. But Parry had to find a compromise between the client and the City of London planners. So he cut down the scheme. A park on the roof and open space below with extra room for pedestrian movement through the City, should compensate the uncomfortable height of the building for this site.
“One Fen Court is an iconic building with a dynamic urban presence, it’s visible down the City´s many lanes and streets; a building of a hundred views“, explains Eric Parry, who therefore suggested a glass crown for this iridescent building. “One Fen Court is a building that represents a sustained dialogue between the planning authority, the client and the architect to create a building that is more than the sum of its architectural parts. It is a civic as well as a commercial building and it creates a new convivial horizon within the emerging taller buildings of the Eastern cluster.”
The project is subdivided into three superimposed parts. Vertically, it is structured by pre-cast concrete and terracotta tile cladded pillars and horizontally, by iridescent brisesoleil profiles and the gleaming strips of dichroic foils. The ground level offers a prominent street presence with shops, bank offices and a HQ style entrance solely for floors 1 and 2. A spacious through-passageway retains a historic link between Fenchurch Street and Fenchurch Avenue. Inside there is a curated art space featuring a 1,900 sq ft LED ceiling that displays a live feed of the view from roof level and video art, as well as stylish retail units. From here, vistors can catch a lift to the restaurant and the roof. Three units face into the hall, two have prominent street corner locations. It will be “a city blockbuilding that speaks to the street”, Eric Parry.
The commercial office space of the main building starts on the first floor, which is 9 meters above ground level. The glass crown, from levels 10 to 14, which is set back from the main building, is used for offices and a restaurant on the 14th floor. Office floors with a ceiling height of 2.75 m are virtually column-free and offer large, efficient and flexible offices with natural light on all four sides. Fen Court offers a total of 39,000 sqm of office space on 13 floors as well as 2,500 sqm retail space.
2,800 sqm of free public rooftop garden with a 360-degree panorama
The free public rooftop garden on the 15th floor is one of the most exhilarating vantage points in the City of London and allows for stunning views in the open air with a 360-degree panorama on 2,800 sqm. Designed by German architects Latz + Partner this garden includes plants inspired by English country gardens with espaliered fruit trees, 79 wisteria trees, 5,000 bulbs and a 200 ft long recessed flowing water feature.
For members of the public, the rooftop garden is free to visit with no booking required. The 207-capacity garden will even open every Saturday and Sunday. Chris Hayward, Chairman of the Planning and Transportation Committee at the City of London Corporation, said: “I especially look forward to the warmer months when the garden will be in full-bloom, complementing the success and popularity of the SkyGarden at 20 Fenchurch Street and the roof terrace at One New Change (which also features a Gartner façade, J.Wax) as a weekend destination for Londoners and visitors alike. Fen Court is an example of the type of developments that the draft local plan ‘City Plan 2036’ proposes for the future of the City. With a free public space, a pedestrian route between Fenchurch Street and Fenchurch Avenue creating more space at ground level, and the garden, which goes above and beyond our urban greening proposals”.
Also, Tina Paillet, Senior Executive at Generali Real Estate, was excited, when the garden opened in February 2019: “The garden is the crowning achievement of Fen Court, an innovative development where new technologies blend with tradition and nature to create a unique office and retail environment that will benefit both occupiers and visitors. The building is recognisable at a glance and destined to become a landmark.in the City of London”.
One Fen Court will hold the now-standard mix not only of a green location with free public space and the roof garden but also for the mix of office and retail spaces. The building is designed to achieve the BREEAM Excellent certification thanks to sustainable façade types, with high thermal and acoustic insulation and a high level of comfort.
Gartner has clad Fen Court with a 17,930 sqm façade of various types which have been specifically designed for the individual parts of the building. A particular challenge for façade design, planning and engineering has been the complex geometry of the building with its sharp edges and the diversity of materials requested.
Intricate Technical Detail
The 3,650 sqm steel stick-system façade at ground level contains 10m long steel frames. The pillars have been clad with precast concrete parts in varying sizes and with a weight of up to 7 tons. Generally, these concrete parts are approx. 1m wide and 5m high. For the ground floor level, a number of different glass types have been used, partly with translucent PVB interlayer “Vanceva Artic Snow” or with black screenprint RAL 9004. In some areas, the glass is fixed with toggles. This representative large-volume façade achieves a heat insulation of Ucw= 1.01 W/m2K or Ug= 1.0 W/m2K and a noise protection of Rw= 42dB.
The 9,250 sqm main façade, from levels 1 to 9, is composed of panels with a standard size of 2.5 m x 3.8 m. This façade features more than 20,000 beige terracotta plates with 30 different shapes and a size of around 1m x 0.4m. Another highlight of this façade is its sun protection with horizontal aluminium brise soleil profiles and flip-flop paint between the vertical terracotta-cladded pillars. Thanks to this special paint they also change in color, between green-pink and orange-red as the sunlight changes. The main façade achieves a heat insulation of Ucw= 1.44 W/m2k or Ug= 1.0W/m2K and a noise protection of Rw= 42dB.
Inclined and folded closed cavity façade with dichroic glass
The must-see of One Fen Court is the closed cavity façade (CCF) of the crown, from levels 10 to 14. Initially, an open double-skin façade had been planned. In a collaborative approach with the architect and the client Gartner demonstrated the clear benefits and advantages a CCF would bring to the project and showed how they are increasingly requested for sustainable building construction – a façade type which is also being installed by Gartner at the 288m high 22 Bishopsgate building in London. As a closed double-skin façade, a CCF provides a high degree of energy efficiency by profiting from very good heat protection in summer and in winter with a Ucw-value of 1.35 W/m2K and a Ug-value of 1.1 W/m2K for the Fen Court building. As compared to an open multi-skin façade, there are no costs for service openings, additional frames or fittings. Furthermore, there is minimized cost for maintenance, no need for façade cavity cleaning and increased service life. In addition, the CCF allows for use of highly transparent glass in combination with a highly sensitive sun protection system in the façade cavity. Even complex geometries with kinks and inclinations can be realized, such as was used for the Fen Court building.
One Fen Court was clad with a 4,860sqm CCF with 21 differently inclined façade areas and folded panels. In order to produce these kinks and inclinations in the façade units (approx. 1.5m x 3.8m) the profiles had to be cut with individual dimensions and shapes. While the main façade was designed using proprietary digital design software PMF, the CCF was designed with parametric programming. It is the first time that dichroic foils have been incorporated in low-iron laminated glass with Sentry glass interlayer in the outer pane of the closed cavity façade. Like the flip-flop paint, the dichroic foil changes color depending on the light incidence and viewing angle. Despite varying inclinations and corners, the dichroic stripes run around the building perfectly, at the same height.
The closed façade cavity contain venetian blinds which accomodate the kinks of the units. These aluminium louvres run downwards vertically in guiding rails with varying distance to the glass panes. In general, the sunscreens are 1.4m wide and 3m high. They have been produced in a number of special sizes and in a trapezoidal shape.
The CCF designed and engineered for this project is one of the most complex the Gundelfingen based company have ever developed. Its complexity is due not only to the particular geometry of the panels, but also comes from the variety of materials and elements which have been specifically developed to meet the extremely high expectations of the architect and the clients. For the first time, such complex CCF units have been assembled on the new CCF production line at the Gartner HQ back in Gundelfingen/Germany, they have undergone cleaning in a special glass washing machine in order to safeguard quality, functionality and performance.
Logistics and installation of the façade have also been a challenging venture since a bank subsidiary had to remain in the building during the demolition of the old structure and the construction of the new building. For this reason, Gartner had to install the façade in several strategic steps in partnership with the local company Permasteelisa UK who presented a sophisticated site management system.
At first, only the left-side of the old building was pulled down so that the bank offices could remain operational on the right-side of the building. Then, the building shell of the leftside was constructed and the façade installed. After approx. one year, the bank could move into the newly built premises and the rightside part of the old building was pulled down and re-constructed. Due to the fact that the installation had to be done in several phases, the façade units had to remain stored at HQ in Gundelfingen for up to six months.
Transport from Gundelfingen to London was made by lorry and ship. Upon arrival in London the façade units were transported inside the building to the individual storeys with one of the tallest freight elevators (this area now accommodates the lifts to the roof garden) and carried to the respective points of installation.
Gartner was able to deliver the project in time. “Our performance throughout the construction phase was strongly influenced by the collaborative approach taken by main contractor SRM and all other stakeholders,” said John Linnell, Senior Project Manager of Permasteelisa UK. One of the many factors contributing to the smooth logistics and timely completion of this project was the good cooperation within the Permasteelisa Group who´s three brands are all currently cladding new developments each with unique façades in and around London, 22 Bishopsgate (Gartner), the International Quarter London (Scheldebouw) and Battersea Power Station Phase 3A (Permasteelisa), are to name but a few.
This article first appeared in IGS Magazine’s Spring 2019 Issue – Read the full Magazine here for more thought-leadership from those spearheading the industry
Owner: Generali Real Estate, London
Architect: Eric Parry Architects, London
Client and Main Contractor: Sir Robert McAlpine, London
Façade Consultant: FMDC, London
Development Manager: Greycoat CORE, London
More information: www.josef-gartner.de