The mixed-use scheme, for General Projects with Henderson Park, will raise the building’s gross area by 40% to over 236,000 sq ft.
It includes the complete refurbishment of the existing eight-storey office building, located at 242 Marylebone Road in Westminster.
Jim Knowlton, ISG project director, said: “Originally constructed in the 1950’s, Woolworth House is an exemplar of how a low carbon approach can transform our cities’ dated building stock.
“Underpinned by environmental, social and governance considerations, the scheme shows how adapting assets into smarter office and retail environments, with more green spaces for occupants, can future proof London’s commercial property market.”
Renamed Metropolis, the new building will offer new stepped green roof terraces across every floor.
An events auditorium, rooftop-bar, on-site coffee shop, cyclist zone as well as new health and wellbeing amenities complete the revamp.
A new extension will significantly increase outdoor and green space, adding over 6,000 sq ft of new landscaped gardens.
To achieve this, the existing courtyard area will be infilled to the seventh floor, providing tiered planted terraces and the structure will be extended with various additions across floors three to eight using a steel frame with cross laminated timber (CLT) slabs.
In addition, the existing roof plant enclosures will be removed and consolidated, allowing the creation of rooftop office pavilions on level five and eight.
Designed by London architect AHMM, the environmental performance of the refurbished building will be boosted to a BREEAM rating of Outstanding.
Careful retention of existing building material will result in over 4,500 tonnes of carbon saved during the construction process and diverted from landfill.
The use of engineered timber floors to all building extensions has dramatically reduced embodied carbon, equating to a 73% improvement against RIBA 2030 targets.
The masonry facades, concrete frame and cores will also be retained while CLT will be used for all new floors forming the building’s extension.