Enerphit is the Passivhaus standard for retrofitting existing buildings.

Enerphit makes sense when you are doing a major renovation, as a deep retrofit is required to install the energy saving measures required.  The energy demand target depends on the location – London is classified as a warm temperate climate, with the heating demand target of 20 kilowatt hours per square metre per year. [kWh/(m²yr)]  More typically northern climates are classified as cool temperate requiring heating demand of 25 kWh/(m²yr).  

For this current Victorian terrace house project in London E15, we are the architects and passivhaus consultant.  It is being done in two phases – with Phase 1 currently under construction.

Phase 1 Enerphit

The entire Phase 2 project is modelled in PHPP, with the intention of achieving Passivhaus Enerphit precertification on the completion of Phase 1.   Phase one works include external wall insulation EWI, mechanical ventilation heat recovery MVHR, a new air source heat pump heating system ASHP (no gas),  new triple glazed windows, and air tightness measures.

An insulated enclosure has been built in the attic for the MVHR to be within the thermal envelope of the house.

The Phase 2 works will include a rear ground floor extension incorporating the family kitchen diner with excellent access to the garden, along with a bathroom and WC in the centre of the house,  and the floor will be lifted and insulated. Further information on ‘staged retrofit’.

Enerphit Retrofit
Phase 2 of the staged Enerphit retrofit.


The MVHR and the new triple glazed Rationel windows are mostly installed.

Passivhaus Enerphit retrofit

External Wall Insulation commences next week, with the Air Source heat Pump being installed within a month before the cold weather sets in.  That will conclude Phase 1.

passivhaus enerphit retrofit
Intake and exhaust MVHR flues through the pitched roof
passivhaus enerphit retrofit
Roof gable extension for EWI
passivhaus enerphit retrofit
Aerogel thermal bridge mitigation at party wall
  • MVHR:  Williams Energy Design, with Mango Projects for installation.
  • ASHP & EWI:  Pyramid Solution South East Ltd
  • General contractor:  Monogreen Renovation
  • Windows:  Citi Homes Windows, Rationel windows
  • Passivhaus Certification: Zero Energy + Passivhaus
  • Architects & Passivhaus Consultant: Cayford