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PROJECT REPORT: HOTELS, RESTAURANTS & BARS A SUSTAINABLE SUBSTITUTE
Double-glazed units have been installed on ground and fi rst fl oor facades, as well as better performing, but virtually identical looking units on upper stories Photos © Simon Menges
Grid-locked Saarinen’s legacy on the interior is mostly evident on the fi rst fl oor, 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 offi ce partitions were removed from the fi rst fl oor, 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 Butterfi eld.
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 fl oor 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 fi rst fl oors are replaced by fi xed 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
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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 effi cient, thanks largely to all the high tech plant in its basement, but on the fi rst fl oor the listed diagrid ceiling could not be used to supply air conditioning so a complex displacement air system via a raised fl oor was required.
“These are normally used in galleries or museum buildings, to provide the best quality solution for heritage and sustainability,” says Butterfi eld. 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 fl oral 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.
ADF SEPTEMBER 2026
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