Passivhaus Affiliate

Passivhaus Retrofit

EnerPHitWhere does Passivhaus fit?

Step-by-step for a whole house approach

The Trust's activities & what’s going on now?

Retrofit case studies

Passivhaus retrofit - an introduction

The full Passvhaus retrofit masterclass lecture series is available to watch on demand - book now.


The retrofit challenge

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. Read the Trust's recommendations on how to sensibly approach Passivhaus retrofit & assess whether it is right for your building here. 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.

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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.

UK housing stock breakdown by space heating demand and building form - PHT Primers: Retrofit


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

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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

Passivhaus RetrofitThe Passivhaus Trust's recommendations on assessing whether Passivhaus retrofit is right for you


What’s on now?

The Trust is currently involved in the following retrofit projects:

  • 2024 Passivhaus Retrofit Delivery: An online training course delivered by PHT preferred training partner Coaction. Understand the delivery of deep fabric retrofits and what is needed to ensure projects are a success on site.

  • 2024 Good practice guide - Moisture and EnerPHit: Uncover key insights for resolving moisture risks, ensuring a safer, healthier environment. The guide is a must-read for designers and clients providing a crucial starting point for mastering moisture-safe design in any retrofit. Hear directly from the authors in an on-demand masterclass.

Managing Moisture Webinar On-demand

  • 2024 Enhanced Retrofit Fabric Improvement Training (ERFIT) Programme: This precursor course founded on the Passivhaus pillars, supports the need for growth in the retrofit supply chain.  The ERFIT Programme aims to deliver trained practitioners with the technical knowledge and expert skills to install, advise and troubleshoot existing and new retrofit projects.

  • 2023 Research report: EnerPHit and PAS 2035/2030EnerPHit is an established energy standard for refurbishment of existing buildings using Passive House components.  PAS 2035/2030 is a process for the retrofit of dwellings and does not set any energy targets to meet.  However, there are more similarities than one might think and the two standards complement one another.

  • 2023 RIBA Passivhaus Retrofit Series: A series of 8 webinars, jointly organised by the Trust & RIBA, will offer an introduction to the benefits of Passivhaus retrofit and discuss how to communicate with clients. Delve into the retrofit processes and various toolkits, and discuss the differences between Passivhaus and Energiesprong retrofit.

RIBA Passivhaus Retrofit Series: 8 modules


  • 2021 Passivhaus retrofit in the UK: The Trust has issued a Passivhaus Retrofit position paper which sets out how EnerPHit fits into the wider net-zero retrofit agenda.

  • 2021 LETI Retrofit Guidance: The Trust has lead a retrofit Workstream in partnership with LETI, RIBA and the AECB, to jointly publish cross-industry retrofit guidance, identifying common building typologies & proposed upgrade works to help reach net-zero carbon targets.

  • 2021 Technical Guidance - Modelling existing dwellings in PHPP Periodic Heating: The Passivhaus Trust has developed guidance accompanied by a PHPP plugin to calculate more representative monthly average internal temperatures for existing buildings and an overall average for the heating season.

Passivhaus Retrofit Position Paper
Retrofit Guide Front Cover Modelling existing dwellings in PHPP Periodic Heating EuroPHit: Step by step retrofits

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Retrofit case studies

As with the Passivhaus Standard, EnerPHit 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 search for inspiration further afield in the  International Passivhaus Buildings Database.

The Barrel Store Bowman's Lea ©Agnese Sanvito Zetland Road facade photo © Rick McCullagh
New Forest EnerPHit Erneley Close
Modernist EnerPHit Plus
Mildmay Community Centre Passmore Street Cre8 Barn
Carlton Chapel House Greenfield Passivhaus Plus. © AD Practice, Matthew Smith Architectural Photography
River Studio EnerPHit
Shepherds Barn EnerPHit, Image credit: Mark Siddall Niddrie Road, Image credit: John Gilbert Architects Harpenden EnerPHit Plus

Project Sectors    I   Project Gallery   I   Project Map


Further Information

Previous PHT story: Estate-wide EnerPHit-informed retrofit planning - 1 August 2022

Previous PHT story: Renfrewshire retrofit programme aims for EnerPHit - 20 June 2022

Previous PHT story: Passivhaus Retrofit Masterclass series wrapped - 29 April 2022

Previous PHT story: Retrofit: The 'EnerPHit' in the room - 22 October 2021

Previous PHT presentation: Passivhaus Retrofit - 2019

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

EnerPHit & how it fits into the zero carbon agenda

Previous PHT story: Passivhaus on-demand training - 14 July 2022

SHRA Podcast: Energiesprong & Passivhaus - 09 November 2021

Homebuilding & Renovating: Why do we still not have a national retrofit strategy? - 17 November 2021

outPHit - Raising awareness for prefabricated and streamlined renovation concepts throughout Europe

outPHit: Analysis reveals energy savings potential of EnerPHit approach - 5 May 2023


Sustainable Renovation Guide - SEDA publication

Retrofit with Passivhaus Components

AECB CarbonLite Retrofit Training