Passivhaus Affiliate

Passivhaus Retrofit

EnerPHitWhere does Passivhaus fit?

Step-by-step for a whole house approach

What’s going on now (2020)?

Retrofit case studies


Retrofitting existing buildings is undoubtedly a colossal challenge in transitioning the built environment to net zero.  Even the majority of new homes built today are not nearly efficient enough, which means we will need to retrofit all 27 million homes, not just the older ones.

The sheer scale of this task is huge.  It’s one home every 35 seconds between 2020 and 2050.  Or, if every retrofit takes 4 people 6 months, it's 500,000 simultaneous retrofits needing 2 million people in the industry.

35 seconds to complete each retrofit | 500,000 simultaneous retrofits | 2m people needed in the retrofit industry

It’s also a complex undertaking.  Every home is different which means some efficiency measures that work on one project may not be appropriate for another.  Get it wrong and you could end up with damp and rot. Getting the right contractor with the right skills and experience is also a worry for most homeowners.


How can we make retrofit happen?

There are many issues surrounding retrofit at scale in the UK. The route to introducing higher standards and the associated costs are relatively clear for new-build properties. For retrofit, it is much more complex, and several interrelated issues must be addressed:

  • How can we legislate to ensure homes are retrofitted?
  • When should retrofit happen?
  • How far/deep should retrofit go?
  • How should it be financed?
  • How can we ensure retrofits are done to a good standard?
  • How do we make sure that a retrofit doesn’t result in damage to the building fabric?

We know how to safely retrofit buildings and we cannot afford to wait any longer. If we had spent all the money raised by quantitative easing in 2007/8 on retrofit, then we would have done it by now…

There were many good ideas in the Bonfield Review and the arrival of PAS2035 as a compulsory retrofit requirement will result in better standards and hopefully a greater degree of trust from homeowners.



Where does Passivhaus fit?

The building physics principles behind Passivhaus apply to any building – but you may not be able to get quite the same results from an existing building where you aren’t really in control of the building’s orientation, structure, shape or amount of glazing.  The Passivhaus standard, therefore, includes a retrofit standard called EnerPHit which takes these limitations into account and relaxes some criteria to reflect this.  However, it is still a very demanding standard and will typically result in a building that outperforms a new-build property both in terms of energy and comfort.  An introduction to the standard can be found on What is Passivhaus and there are some case studies below.


One step at a time

A radical whole house retrofit is likely to achieve the best results both in terms of energy reduction and comfort. However, this is a significant undertaking which could take place over several years. Getting the sequence right and decisions in the early phases are critical to ensure that the full potential of the retrofit is realised and that the project doesn’t inadvertently result in ‘carbon lock-in’. The EnerPHit process, therefore, includes tools to structure the retrofit in a step-by-step way, thus ensuring that the implications of each step are understood and properly planned out right at the start of the project.

Passivhaus step by step retrofit


The Trust's activities

The Passivhaus Trust’s activities relating to retrofit are intended to:

  • Support work to examine the technical barriers to retrofit and how they can be overcome
  • Support work to examine how retrofit at-scale can take place in the UK
  • Support work to determine the level/depth of retrofit that is feasible and practical across the range of UK housing stock
  • Lobby central government to introduce legislation to enable retrofit at scale
  • Support the sharing of best practice knowledge and experience in deep retrofit
  • Promote the building-physics principles of Passivhaus to support retrofit and, where appropriate, the EnerPHit standard


What’s going on now?

The Trust is currently involved in the following retrofit projects:


Retrofit case studies

As with the Passivhaus Standard, Passivhaus retrofit can be applied to many contexts. The handful of selected schemes below show a variety of building typologies from multi-home developments to one-off houses and even commercial schemes. For more examples in the UK please visit our Passivhaus projects gallery and map, or for international inspiration head over the Passivhaus buildings database.

Ernerley Close

Woodside Multi-storey

Zetland Road

Ernely Close Woodside multi-storey retrofit Zetland Road facade photo © Rick McCullagh

Refurbishment of 2 blocks of flats for One Manchester HA.

Tower block refurb & community regeneration for Queens Cross HA. 

A pair of Victorian semi-detached houses certified to EnerPHit Plus

The Barrel Store

Bowman's Lea

Wilmcote House

The Barrel Store Bowman's Lea ©Agnese Sanvito Wilmcote House ©ECD Architects

Historic Cotswold stone building converted into a Yourth Hostel.

Step-by-step retrofit of a 1970's 3-storey mid-terrace.

Step-by-step refurb of a council tower block with residents insitu. Part of the EuroPHit project.

Hiley Road

Passmore Street

Cre8 Barn

Hiley Road Passmore Street Cre8 Barn

Victorian mid-terrace to Passivhaus Standard.

Ugrade of privately rented historic grade II listed terrace in London.

Derelict cow byre transformed into an all-purpose educational centre.


Further Information

2020 Retrofit Workstream

Previous PHT story: Can EnerPHit at scale fight fuel poverty? - 27 November 2018

Previous PHT story: Bonfield Review: A step in the right direction? – 27 February 2017

Previous PHT presentation: Passivhaus Retrofit - 2019


Sustainable Renovation Guide - SEDA publication

AECB CarbonLite Retrofit Training