Bloomsbury House

Prewett Bizley Architects, London, 2015


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The 20th-century rear extension 

Adam Parker     Download Original

  • The 20th-century rear extension    
  • Exterior rear view    
  • Thermally insulating evacuated glass has been set into a slim timber frame    
  • The home has underfloor heating    
  • Emily Bizley designed the interiors    
  • The kitchen    
  • The house is refurbished to be a family home    
  • The home feels light and fresh throughout    
  • Proportions have a Georgian grandeur    
  • The renovation took 16 months    
  • Basement plan    
  • Ground floor plan    
  • First floor plan    
  • Second floor plan    
  • Third floor plan    
  • Roof plan    
  • Front elevation    
  • Rear elevation    
  • Isometric drawing    
  • Insulation detail    
  • Second floor insulation    
  • Third floor insulation    

Renovation of a Georgian house in central London to high sustainability standards.

After many years as an office, the five-floor building has been returned to use as a family home, suitable for seven occupants. Conversion work included upgrading and restoring the original 1820s features, along with updating a 20th-century rear extension. It focused on three key themes: improving the building’s energy performance; preserving the historic architectural characteristics; and pulling the home back into modern-day living.

The existing external walls are solid brick, becoming progressively thinner with increased height, but preservation of the streetscape ruled out external wall insulation. Using the Passivhaus Planning Package (PHPP) as a fundamental design tool, the energy strategy relies on intricately planned and installed internal wall insulation, which incorporates a number of different wall build-ups.

This upgrade of the building’s thermal performance meant the practice could remove conventional radiators, helping restore the rooms to their original character. They were replaced with a low-output underfloor heating system, driven by an air source heat pump (ASHP). Hot water is provided by another ASHP in combination with solar thermal panels. Mechanical ventilation systems with heat recovery (MVHR) minimise heat losses and provide a constant supply of fresh filtered air.

The newer rear extension has a very distinct feel from the old but continues the flow of spaces with a similar palette of colour and materials. It is flooded with daylight via cleverly designed lightwells and well-positioned light scoops.


  • Begun: Jun 2014
  • Completed: Oct 2015
  • Floor area: 400m2
  • Sector: Residential
  • Total cost: £1.6M
  • Procurement: JCT Intermediate
  • CO2 Emissions: 23kg/m2/year
  • Address: Bloomsbury, London, WC1, United Kingdom

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