The transformation of the former US Embassy in London into a five-star hotel by David Chipperfield Architects delivers an adaptive reuse with high-end luxury and BREEAM Outstanding sustainability credentials, despite whole life carbon compromises, says Stephen Cousins.
At a time when the ‘special relationship’ between the UK and the US is under pressure, due to differing security strategies and tensions over military operations in the Middle East, it is gratifying to report on the restoration and revamp of a building constructed when the partnership was at its zenith.
David Chipperfield Architects’ (DCA’s) transformation of the former US Embassy in Grosvenor Square, originally designed by famous Finnish-American architect Eero Saarinen between 1957 and 1960, takes great pains to protect and restore the Grade II-listed structure. It also dials up the ‘bling’ factor to 11, with plush new interiors masterminded by French designer Joseph Dirand to meet the high standards required of a 5-star luxury hotel.
Britain’s first modern embassy was created at the apotheosis of the US post-war embassy-building programme, its importance underscored by the fact it was the only such project designed through
a competition.
Not many hotels have stone facades decorated with gold anodized aluminium, and fewer still have a gold-plated eagle with a 35-foot wingspan perched on the rooftop. In creating a 137-bedroom hotel for The Rosewood Chancery, Chipperfield retained and restored these features, alongside other elements, including a signature diagrid ceiling of intersecting concrete beams, which was also expanded.
Doubling the building’s area from 25,000 m2 to 48,000 m2 nevertheless required significant interventions, including digging down 20 metres to expand the basement to house a gigantic new ballroom, spa complex with swimming pool and MVHR plant and ‘stretching’ the facade to add a much taller sixth storey.
Passive design and energy efficiency measures, including thermally upgraded facades, delivered a 20%+ improvement on Part L compliance in terms of carbon emissions, enabling the building to become the first five-star hotel in the UK to achieve a BREEAM Outstanding rating for sustainability.
Ryan Butterfield, project architect at DCA said: “Many of the BREEAM credits were achieved with seemingly invisible architectural provisions: enough basement space for larger, more efficient plant equipment, water efficient vacuum drainage, biodiverse rooftop garden planting, and detailed tracking and monitoring of waste and recycling streams during construction.”
Nerve centre
Grosvenor Square in Mayfair has always had a strong association with the US, during the Second World War Macdonald House at number 20 functioned as the nerve centre for the country’s armed forces in the UK.
Saarinen’s embassy, constructed across the full length of the western side of the square, exemplified a US post-war mission to ‘engender good will’ in host nations by creating distinctive architecture designed to be accessible, distinguishably American, but also to harmonise with the surroundings.
A fine example of mid-century modernism, the building is notable for its strongly-articulated design, dynamic chequerboard facade with ‘O’-shaped window surrounds and finely detailed stonework. The scheme was developed in collaboration with UK executive architects Yorke, Rosenberg and Mardall, with FJ Samuely as structural engineers.
Adaptive reuse has become a trend with Saarinen’s buildings, his bird-like terminal at John F. Kennedy International Airport in New York was resuscitated as a hotel in 2019 following an extensive renovation by Beyer Blinder Belle. More recently, another former US Embassy in Oslo was transformed into a mixed-use office complex.
When it opened in 1960, Saarinen’s US diplomatic base in the UK proved controversial from the start. The blocky white facade contrasted with the surrounding Georgian architecture, even though it was intended to darken over time to blend more harmoniously with local buildings. Critic Reyner Banham called it “monumental in bulk, frilly in detail.” Even Saarinen himself expressed some doubts, saying: “In my own mind the building is much better than the English think – but not quite as good as I wished it to be.”
Political events deepened negative sentiment towards the building. In 1968 it was the focus of violent anti-Vietnam war protests and 200 people were arrested. After the attack on the twin towers in 2001, a series of anti-terrorist devices were installed around the embassy and the road running along the front was completely closed to traffic, quashing the architect’s original intention – which was to promote a degree of openness and accessibility.
The security threat continued over subsequent years until, in 2017, operations were moved to a new modern embassy building in Nine Elms, Battersea.
The decision to reinvent the building as a luxury hotel dates back to 2015, when DCA, in collaboration with structural engineers AKT II, won a design competition run by client Qatari Diar, an arm of the Qatar Investment Authority. ReardonSmith Architects was later appointed as executive architect and work commenced on site in 2018.
Chipperfield’s proposal sought to strengthen the qualities that made Saarinen’s original design so special, and enhance the dialogue between the adapted building and its context.
Improving the ground floor connection to the street, by removing the existing traffic regulation order and all external security measures accrued over the years, including the perimeter defensive sloping stone bank, makes the building more open and accessible.
The existing entrances at the front and sides are retained and the ground and first floors feature a range of new public uses including restaurants, bars, lounges and meeting rooms overlooking Grosvenor Square.
Despite the Grade II listing, many aspects of the embassy were not considered worth keeping. Over the years, it had been modified for different office uses, partitions, finishes and furniture had been removed, changed or covered leaving only small areas that remained faithful to their original design.
The first floor grand rooms, originally including a library and consular offices, had completely lost their original architectural value with spaces sub-divided by partition walls and original features removed or covered by carpets, banners, blinds, etc.
Elsewhere, the fountain in the main lobby, the auditorium ceiling, office furniture designed by Saarinen, and ironmongery on the main and side entrances, were lost.
As a result of these alterations, and in order to accommodate all the modern services required in a high end hotel, the upper floors were largely demolished and re-built behind the existing facade to accommodate guest rooms.
The building’s original U-shaped block had a fourth side added as an extension to the rear to increase the sizes of hotel rooms on typical levels. This also enabled a new core layout with a central atrium, above the first floor, providing a visual connection between the first floor lobby and the hotel room levels above.
Saarinen’s early design studies included a pronounced cornice level on the street frontage in the same checkerboard pattern, which was never realised.
Chipperfield seized on this idea, extending the facade vertically to add a double-height sixth storey designed to complement the composition and language of the floors below. The new Portland stone O-frames are built to a different scale and rhythm to distinguish the floor from the levels below.
Above the building’s crown, and behind the winged form of sculptor Theodore Roszak’s gilded eagle, another two storeys were added and set back to create a golden rooftop pavilion featuring a bar and penthouse suites, each reported to cost up to £24,000 a night.
Grid-locked
Saarinen’s legacy on the interior is mostly evident on the first floor, where his unique concrete diagrid ceiling has been restored and extended at the rear, replacing an existing concrete beam ceiling.
Historic England’s Grade II listing entry for the embassy describes the diagrid as “an intelligent combination of structural expression and decorative motifs, which provides cohesion to the whole and illustrates Saarinen’s principles of marrying form to structure, interior to exterior – and his close involvement in detail and execution.”
All embassy-era office partitions were removed from the first floor, giving the diagrid an almost continuous horizontal plane, an open piano nobile aligning with Saarinen’s original intention for the building to appear as a “palace on the park.” The existing double-height cruciform columns on this level were also retained and extended to the rear.
Externally, a comprehensive refurbishment of the existing facades saw more than 4,000 individual elements disassembled for cleaning and restoration before being reinstalled.
Improvements to facade thermal performance were key to helping the building achieve a BREEAM Outstanding rating. “Upgrading windows and wall layers offered building fabric improvement to reduce the energy demand for internal spaces,” says Butterfield.
An insulation-packed Metsec subframe now runs in front of the new steel posts around the perimeter, the latter functioning as primary structural support for new post tensioned floor slabs. The upgraded facade is now 370 mm thick in section, resulting in a U-value of 1.14 W/m²K, down from 6.28 W/m²K.
Single-glazed windows on the ground and first floors are replaced by fixed double glazed units designed to match the existing. On the upper hotel levels, better performing but visually similar versions of the full-height, pivoting glass steel frame and rolled-steel cassette windows have been installed and the existing gold-anodised extruded aluminium central mullions refurbished.
Replacing the existing double-height aluminium framed glazing sections on the piano nobile level was a particular challenge. Saarinen’s 57 mm frames were embedded into the cruciform columns to make them invisible, but adding new secondary glazing frames set back from the originals would have interfered with the sight lines.
DCA opted instead to specify a new aluminium frame with double-glazed units, which copies the original central mullion detail, increasing the frame section to 82 mm. This elegant solution improved transparency and acoustic performance and cut the U-value from 6.04 W/m²K to 1.89 W/m²K.
The Rosewood Chancery is operationally very efficient, thanks largely to all the high tech plant in its basement, but on the first floor the listed diagrid ceiling could not be used to supply air conditioning so a complex displacement air system via a raised floor was required.
“These are normally used in galleries or museum buildings, to provide the best quality solution for heritage and sustainability,” says Butterfield.
Other factors helping boost the project’s BREEAM credentials include enhanced biodiversity, through the installation of an extensive green roof with a higher number of floral species known to be of ecological value to wildlife.
But class-leading operational performance is sadly not matched by the ability to cut embodied energy. Despite efforts to adapt and reuse parts of the building, critics have highlighted the extensive demolition work and decision
to ship in exotic stone from abroad to line the interiors.
Back when the design got underway in 2015, the impact of embodied carbon was less well understood by the industry and DCA has admitted that, at the time, its decision making was driven less by sustainability concerns than by heritage and conservation of architectural intent.
Were the project started again today, DCA has said embodied carbon would have been a more important part of the decision making process.
Ultimately, the Rosewood Chancery encapsulates both the promise and the contradictions of adaptive reuse. It demonstrates how heritage buildings can be sensitively reimagined to meet the highest standards of operational performance, but for future transformations to be truly sustainable, they must balance architectural legacy with a comprehensive plan to tackle whole-life carbon.