A short guide to radical retrofit

21° has just launched a film which goes through the key principles of undertaking a radical retrofit of a home. The 10 minute film uses two real-life projects in West Yorkshire to illustrate the key principles for whole house retrofits, drawing on principles from the Passivhaus low energy building standard.

The film emphasises the importance of paying attention to insulation, airtightness, continuity of insulation and ventilation when undertaking a radical retrofit. It also explores what to consider when choosing internal wall insulation (IWI) strategies for radical retrofit projects.

The film contains an interview with a homeowner of one of the radical retrofits who commented on the effects of the retrofit on the comfort and energy efficiency of the house:  “In the winter we used to start to hate the house because it was so cold and draughty and miserable. Since the retrofit, the place is far warmer than it ever was. It stays at a constant 20-21-22 degrees C all year round, day and night. Obviously now there are no draughts. The air is always fresh and clean in here because of the MVHR system that pumps around air and filters it and heats the incoming air. So..it’s a very different place indeed.”


A short guide to radical retrofit

21° Directors Chris Herring and Bill Butcher feature in the film as do 21° technical experts Paul Smith and Anna Marie Byrne.


The need to improve the energy efficiency and comfort of Britain’s existing housing stock is getting ever more urgent, to combat fuel poverty and tackle the threat of climate breakdown. Improving the energy efficiency of our existing housing stock is a lot more difficult than newbuild. However, the film shows that it really is possible. Using the Passivhaus standard and methodology we can bring our housing stock up to 21st century standards.

Chris Herring

The film complements other free resources on radical retrofit on 21°s website, including:

Life changing homes