Clapham Retrofit

This project is a deep retrofit of a 170-year-old Grade II listed Victorian townhouse. It was the first listed building in England to meet the AECB Silver Performance Standard and the project won the CIBSE Building Performance Award - Residential Building of the Year in recognition of achieving such a high energy performance whilst protecting the historic character of a listed building.

Using Passivhaus methodology, the estimated Space Heat Demand of the 170sqm building has been reduced by over 75% from 180kWh/m2/yr (5,631 kgCO2e) to 40kWh/m2/yr (1,251 kgCO2e) and the air leakage reduced from 9.6ach to 1.8ach.

The solid brick building has been internally retrofitted with nine types of insulation material, each a bespoke solution to localised performance requirements respecting the historic significance of the existing fabric. The existing sash windows and doors have been upgraded through the installation of double-glazed secondary glazing. High performance insulation materials together with careful airtightness and thermal bridge detailing have resulted in a historic building that is both highly energy efficient and more comfortable to live in.

Prior to the application of internal insulation, wireless sensors (connected to an internet gateway) were installed into the walls of the building. The monitoring of the building fabric moisture is on-going and was presented at the 18th International Passivhaus Conference.


  • CIBSE Building Performance Award - Residential Building of the Year 2016.

  • AJ Retrofit Awards 2014 (Nominated)