GS Architecture retrofits Hampstead Passive House with fabric-first approach

London studio GS Architecture has completed the renovation and extension of a semi-detached Victorian home in Hampstead Heath, London, upgrading it to meet the rigorous Passivhaus EnerPHit low-energy standard. Named Hampstead Passive House, the project employed a fabric-first approach with wood fibre insulation, traditional lime plaster, triple-glazed windows, solar panels, low-energy lighting, and a mechanical ventilation heat recovery system. A new timber-framed rear extension topped with a wildflower green roof replaced existing conservatories, housing an open-plan kitchen and dining space with timber doors opening to the garden. Reclaimed materials include snooker-table slate for worktops, salvaged floorboards for the ceiling and door facings, and former cheese-manufacturing boards for cupboard doors. Clay from the garden was mixed into lime-based wall paint. Designer Boris Vervoordt introduced a Wabi-sabi-inspired palette. Original features like the curving timber staircase were preserved. The bathrooms feature dark Tadelakt plaster. Photography is by Matt Clayton.