Curated by Archirev Editorial | Published December 15, 2025 | Source: Foster + Partners
PROJECT TYPOLOGY: COMMERCIAL (OFFICE)
Project name: 1 St James’s Square
Location: St James’s, London, UK
Architect: Foster + Partners
Client/Developer: Not specified
Area: 11,000 m² (approx.)
Storeys: 10 office levels + 2 new upper levels with terraces
Status: Planning Permission Granted
Key Sustainability Targets: BREEAM Outstanding, NABERS 5.5*, WELL Platinum
Images: © Nigel Young/Foster + Partners
Westminster City Council has granted planning permission for the redevelopment of 1 St James’s Square, a prominent office building located in London’s historic and prestigious St James’s district. The project, led by Foster + Partners, focuses on adaptive reuse, façade renewal, and high-performance sustainability strategies aimed at extending the building’s lifecycle while significantly reducing its environmental impact.
Adaptive Reuse and Structural Retention
A central aspect of the approved scheme is the retention of more than 50 percent of the existing building structure. This approach prioritizes embodied carbon reduction and aligns with current best practices in sustainable retrofit design. Rather than demolishing and rebuilding, the project reuses substantial portions of the original frame, helping to prevent the asset from becoming obsolete while reducing construction waste and material demand.
This strategy supports the project’s ambition to exceed Greater London Authority (GLA) benchmarks for both embodied and operational carbon performance.
A Reimagined Façade for Performance and Context
The redevelopment includes a completely redesigned façade, crafted from Portland stone to reflect the architectural character of St James’s Square and its surrounding Georgian-era buildings. While rooted in local material tradition, the façade has been optimized for contemporary performance.
New chamfered window openings are designed to enhance air movement within the office spaces, supporting a mixed-mode ventilation strategy. This breathable envelope enables the building to operate with natural ventilation for approximately 40 percent of the year, thereby reducing its reliance on mechanical cooling systems.
Energy Efficiency and Environmental Performance
The building incorporates a mixed-mode ventilation system, combined with smart building controls, targeting an estimated 70% reduction in cooling-related energy demand. The scheme is entirely all-electric, supported by:
- Air-source heat pumps
- A high-performance building envelope
- On-site renewable energy generation through photovoltaic panels integrated into sloping canopies
Together, these measures aim to minimize operational energy consumption while improving indoor environmental quality.
The project is designed to achieve some of the highest sustainability benchmarks in commercial office development, including:
- BREEAM Outstanding
- NABERS 5.5 stars
- WELL Platinum
Workplace Design and Green Outdoor Spaces
The redeveloped building will provide approximately 11,000 square metres of premium office space across ten flexible floors, responding to evolving workplace needs. Two additional levels introduce landscaped terraces and green outdoor spaces, offering views across London and improving occupant wellbeing.
A green roof and planted terraces contribute to urban biodiversity, while also helping manage heat gain and stormwater runoff.