Passivhaus retrofit

How existing buildings can be upgraded to be warm, healthy, and have very low energy bills.

Passivhaus retrofit, the approach demonstrated by Guy Martin on Channel 4's "House Without Bills", shows how existing homes can be upgraded so they use very little energy, cut heating and running costs, and deliver healthy, comfortable indoor environments.

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Retrofitting the UK’s existing buildings is essential to improving comfort, cutting energy use, and reducing carbon emissions. By transforming cold, leaky buildings into warm, healthy, low-energy homes built to last, Passivhaus retrofit provides a proven, performance-based pathway for upgrading existing buildings with confidence.

Many people have discovered Passivhaus retrofit through Guy Martin's House Without Bills. The Channel 4 programme highlights how existing homes can be upgraded to dramatically reduce energy use and running costs. Passivhaus retrofit provides the performance-based approach behind many “house without bills” outcomes. It has been successfully applied to a range of buildings from private homes and non-domestic projects, to large scale social housing projects.

The Passivhaus Trust is an independent, non-profit organisation providing trusted, evidence-based guidance rather than commercial retrofit services. Our resources are designed to help build understanding and confidence at every stage. This page introduces what high‑quality retrofit looks like, why it matters, and how you can take the next step with tailored guidance for homeowners, professionals, and decision‑makers. Find your pathway.

Passivhaus Retrofit projects © project owners and photographers

Why Passivhaus retrofit is a "house without bills" approach

A “house without bills” typically refers to a home that uses so little energy for heating that running costs are extremely low. This is achieved by keeping heat inside the building, ensuring fresh air without heat loss, and avoiding common problems like draughts and damp. Passivhaus retrofit applies these same principles to existing homes, not just new builds.

What is Passivhaus retrofit?

Passivhaus retrofit is a performance‑based approach to upgrading existing buildings to deliver much higher levels of comfort, healthier indoor environments and lower energy demand. It focuses on keeping heat in, fresh air flowing, and energy use very low. Passivhaus retrofit provides a framework for improving building performance. Retrofit projects can be delivered by meeting the full Passivhaus Classic standard, or, more commonly, via the specialist retrofit standard, EnerPHit. Works may be completed in a single phase or carefully planned in stages over time.

Passivhaus retrofit

✔ Passivhaus retrofit is a proven way to upgrade existing buildings so they use very little energy while staying comfortable all year round.

✔ It focuses on keeping heat in, letting fresh air circulate, and avoiding common problems like draughts, damp, and overheating.

✔ The energy-efficient retrofit approach is based on accurately modelled performance, and on verified construction.

Built on verified performance

Passivhaus provides performance you can trust. Certified buildings are independently verified against strict energy, comfort and quality standards.

Independently checked through modelling and testing
Used worldwide to deliver buildings that perform as designed
Based on over 30+ years of internationally proven building science.

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Homeowners

What Passivhaus retrofit means for your home and where to start.

Industry professionals

Training, guidance, and certification to strengthen your expertise & skills.

Housing providers & policy makers

Retrofit at scale, estate-wide and regional.

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Why Passivhaus retrofit matters

Warmer, healthier homes: No more cold spots, draughts, or mould. Passivhaus retrofit creates stable indoor temperatures and excellent air quality.

Lower energy bills: Passivhaus alone cannot guarentee a 'house with no bills', it does give proven reductions in heating demand by up to 80%, protecting households from rising energy costs.

Comfort in every season: Warm in winter, cooler in summer, resilient in heatwaves.

Climate action at scale: Immediate carbon emissions reductions from existing buildings. The UK cannot meet its climate targets without upgrading existing buildings. Passivhaus retrofit provides a robust, evidence‑based pathway now.

Future‑proofing our building stock: Designed to perform as built, these retrofits are tested and verified to last decades, reducing maintenance costs.

Discover more benefits here, and why Passivhaus is the proven route to healthy homes.

Akerman Road occupant quote: You could hear the raspiness in my baby daughter’s cough, and a constantly runny nose. She doesn’t suffer from that anymore since we’ve been here, she doesn’t cough in the night.

Where does Passivhaus fit?

EnerPHit

The building physics behind Passivhaus apply to any building. With an existing building you can't change 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 Guidance: Passivhaus Retrofit in the UK

UK homes are among the oldest and least efficient in Europe. Even the majority of new homes built today are not nearly efficient enough. A Passivhaus retrofit to an existing home can make it more comfortable and energy efficient than a brand new home built to the latest standards.

Why Passivhaus retrofit is in the spotlight

With rising energy costs and the climate emergency, attention is turning to proven approaches that reduce bills and improve comfort. Passivhaus retrofit has been featured on Channel 4's 'House Without Bills' as an example of how homes can achieve very low energy demand.

Guy Martin House without Bills. Image credit Channel 4

Retrofit without regret: Why a performance-based approach matters

Research reinforces that retrofit should be guided by measurable performance, not just checklists. Avoid costly consequences by implementing a whole house approach from the start. Get a clear understanding of potential impacts & how components affect core principles such as ventilation and moisture. Passivhaus offers a safe choice:

✔ Designed & checked before work begins, reducing costly surprises

✔ Avoids unintended consequences like damp and overheating

✔ Based on accurately modelled performance and verified construction

✔ Clear sequencing reduces wasted spend

✔ Long-term comfort and energy savings are built in

✔ Trusted by housing providers, local authorities, and homeowners

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. This is a significant undertaking which is often staged over several years. Getting the sequence right and decisions in the early phases will ensure that the full potential of the retrofit is realised and that the project doesn’t inadvertently result in ‘carbon lock-in’, wasting opportunities and money. The EnerPHit process, therefore, includes tools to structure the retrofit in a step-by-step way, ensuring that the implications of each step are understood and properly planned out right at the start of the project.

		5 top tips for affordable Passivhaus retrofit
01		Work with an experienced Passivhaus Designer/ Consultant and independent Certifier.
02		Get the retrofit modelled in PHPP (Passivhaus Planning Package).
03		Develop a whole-house plan for the retrofit, even if all the measures can’t be undertaken at once.
04		Consider a component-based route, which offers greater flexibility in achieving Passivhaus retrofit certification.
05		Consider a step-by-step approach, with the retrofit implemented in stages, alongside other home improvements.

Learn more about the Passivhaus Trust's recommendations on assessing whether Passivhaus retrofit is right for you. ~ coming soon.

Advanced training for professionals

The retrofit transition is happening now. Stay ahead with live Passivhaus training for professionals delivering low-energy, high-quality buildings. Build the skills and gain expertise through our live Masterclass and Passivhaus training.

Training

2026 Passivhaus retrofit Masterclass series: Across six focused, expert-led sessions, you’ll gain the practical insights and technical know-how you need to drive ambitious Passivhaus retrofit projects forward.
2026 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.
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.
Become a Passivhaus retrofit expert: Passive House Designers/Tradespeople can proof their knowledge and skills regarding the highly energy-efficient retrofit of small projects. Take a further online exam to gain an additional retrofit qualification.

Go deeper: on-demand courses, guidance and tools

Visit the Passivhaus Learning Hub which brings together retrofit guidance, technical resources, and on-demand learning.
Managing Moisture: An on-demand Passivhaus retrofit Masterclass session from the authors of the research paper, Moisture & EnerPHit.
RIBA Passivhaus retrofit Series: An on-demand 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.

Retrofit success stories

Passivhaus retrofit can be applied to many contexts. The handful of selected schemes below show a variety of buildings certified to the standard, from bespoke homes, large residential developments, 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.

Step-by-step Passivhaus retrofits

Residential Passivhaus retrofits





Non-domestic Passivhaus retrofits

Project Sectors I Project Gallery I Project Map

Passivhaus retrofit FAQs

Homeowners, industry professionals, policymakers and more - Below are a few common starter queries, but check our Passivhaus retrofit FAQ's page for more.

Is Passivhaus the same as a “house without bills”?

Many homes described as “houses without bills” are built or retrofitted using Passivhaus. The Passivhaus standard focuses on reducing energy demand so dramatically that heating costs become very low or negligible.

How does Passivhaus retrofit reduce risk?

By using modelling, testing, and independent certification, Passivhaus retrofit reduces performance gaps and delivery risk compared to approaches based solely on specification or assumptions.

Is Passivhaus retrofit expensive?

Costs vary widely depending on the building and the scope of work. While deep retrofit involves upfront investment, it delivers long-term value through comfort, health, durability, and reduced energy demand. High-quality Passivhaus retrofit is cost-comparable with other deep retrofit standards. Costs will vary based on your project specifics, which are best discussed with a Passivhaus designer or consultant.

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.

PAS2035 as a compulsory retrofit requirement will result in better standards and hopefully a greater degree of trust from homeowners.

If you’ve seen Passivhaus retrofit on Channel 4's 'House Without Bills' and want to know what it could mean for your home, start here: Passivhaus retrofit for homeowners.

Join our case-study led introductory webinar series exploring how Passivhaus retrofit works in practice, featuring real homes and expert teams.

The Trust's activities

The Passivhaus Trust’s retrofit activities 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

Further Information

Passivhaus retrofit

Passivhaus retrofit FAQs

Passivhaus retrofit presentation - Passivhaus Trust, January 2026

Passivhaus retrofit YouTube playlist

OutPHit - Deep retrofits made faster, cheaper and more reliable

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

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

EuroPHit

Healthy Homes:

Passivhaus Benefits Guide

The Warm Homes Plan - Passivhaus Trust response - 22 January 2026