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UK’s first Passivhaus retrofit


greentomatoenergy was engaged by Octavia Housing to provide engineering design and project management services for the retrofit of this solid brick Victorian terraced house in a conservation area.

greentomatoenergy worked with builders Ryder Strategies (now Princedale Ecohomes), architects Paul Davis and Partners, energy consultants Eight Associates

The house comes equipped with over a dozen low energy innovations including greentomatoenergy’s Passisash windows, super wall insulation, ESE solar thermal panels and a heat exchange system that recycles energy from waste air and water. The home has no gas boiler, radiators or conventional heating system and uses these innovations to keep the house at a comfortable temperature with a healthy air-flow all year round.

The retrofit resulted in a building that is warm and comfortable without condensation or moisture problems. It now produces 85% less CO2 emissions and uses 92% less energy than before, making it the UK’s first retrofitted Passivhaus.

  • Street view of the Passisash triple-glazed windows at the UK's first Passivhaus retrofit
  • Close-up view of the Passisash triple-glazed windows at the UK's first Passivhaus retrofit
  • Internal view of the tilt-and-turn Passisash triple-glazed windows
  • The Genvex Combi Unit provides MVHR ventilation, air-source heat pump and domestic hot water
  • An assessment of where cold and warm air could escape from the Passivhaus retrofit pre-renovation
  • Solar thermal technology on the roof providing hot water to the Passivhaus retrofit