Passivhaus Affiliate

Cake & debate! It's another PHT Anniversary

Earlier this month, seeing so many faces at the Trust’s twelfth anniversary at the Museum of London, was fantastic. The event was sponsored by PHT Patrons Aluprof UKATTMAGreengauge and Passivhaus Homes 

The Trust has accomplished much in twelve years, accelerating in the past few years. Jon Bootland gave an overview of some of the most recent activities before we began our light-hearted debate, which you can watch. An edited recording of the proceedings is now freely available to all.


Don’t have 2.5 hours to catch up? Below we summarise the debate with a few highlight comments, and you can follow #PHTparty22 for more.


New build & net zero

2022 Passivhaus Anniversary: Sarah Lewis - The case for Passivhaus buildings
2022 PHT Anniversary: Pragya Gupta - The case for Net Zero buildings 2022 PHT Anniversary: David Adams - The case for net zero for major housebuilders

Fabric-first approaches are essential for slashing energy use, assisting grid capacity, and addressing the climate crisis. Anything less than Passivhaus for a new build is negligence! 

Fabric first efficiency is the starting point, but we need ‘Active Buildings’ that maximise on-site renewables to create localised energy solutions. Anything less than Net-Zero for newbuild is inappropriate. 

Large housebuilders are looking for the most cost-optimal option. They currently build 750 homes/ day, and the government wants that to increase to 1200. Zero carbon fuel supply must be considered in the equation. 

PHT Anniversary: Passivhaus, Net Zero & Retrofit - Sarah Lewis PHT Anniversary: Passivhaus, Net Zero, & Retrofit - Pragya Gupta PHT Anniversary: Passivhaus, Net Zero & Retrofit - New build panel

The panel & most delegates agreed that anything less than net zero for newbuild is no longer acceptable. 86% of delegates agreed we need Passivhaus for all new buildings and we need to set that future target now to allow the industry to be in a position to deliver this as soon as possible. The approach to realistically reaching net-zero is where speakers differed – with costs a key area of contention.

David argued that we must quickly find a language that engages housebuilders, who are influential with policymakers, into the conversation, along the net-zero journey. He emphasised it was important to avoid bunfights between those who want to go strong and those who want to do the minimum to comply. Housebuilders are building more new homes in a a few days than the current total of UK-certified Passivhaus schemes!

A question  posed by Lynne Sullivan: "How can we properly seek cost optimal when the government is 'silent' on the real costs of generation – it is obvious housebuilders will prefer a supply-side solution because taxpayers and customers will pay through bills rather than they (housebuilders) forking out for better quality fabric without a performance gap." 

"Should it be the major commerical housebuilders who are dictating that conversation?" asks Sarah. Scotland's Citizens Climate Assembly Committee recently saw a 97% vote in favour for Passivhaus to be mandated for all new builds within the next 5 years, with a proposed Private Members Bill out for consultation now. A policy for new schools linking funding to building performance, implemented by the Scottish Futures Trust, has been a game-changer in driving uptake of Passivhaus as its quality assurance deems it a risk-adverse option.

What is the cost of connecting to the grid? 8,500 new homes, built to building regulations in the South of England, cost £90 million. That is £10k per dwelling. Where do these infrastructure costs factor into cost-optimal options? 

Is it too late to bring people on the journey? The climate crisis is now. It does not wait. Pragya stated that ultimately, we must come together as an industry if we have any chance of solving this. Contractors often think cutting fabric costs is the answer – with monitoring & accountability for performance, that is no longer the answer. We must educate everyone.


Poll Results

PHT Anniversary: Passivhaus new build & net zero - poll results
PHT Anniversary: Passivhaus, Net Zero & Retrofit - delegates
PHT Anniversary: delegates



Retrofit & net zero

2022 PHT Anniversary: Chris Twinn - the case for average decarbonisation targets
2022 PHT Anniversary: Andy Simmonds - The case for targets & exemptions and individual building scale 2022 PHT Anniversary: Ann-Marie - The case for Passivhaus as your retrofit approach

Intermediate retrofit standards are required to start decarbonising existing building stock. LETI retrofit lite highlights EnerPHit is in the mix but may not a step too far for a large portion of building upgrades.

The AECB retrofit standard is based upon the Passivhaus methodology offering more relaxed criteria and self-assessment. Shallow retrofits prioriting zero carbon fuel sources may be the way forward to flatten the carbon curve. We must build up a library of solutions for different building typologies.  

A deep dive into case studies adopting an EnerPHit-informed Retrofit Programme, including detailed design decisions from the Entopia building and Edinburgh City Council, undertaking EnerPHit analysis at an estate-wide level.

PHT Anniversary: Passivhaus, Net Zero & Retrofit - Chris Twinn PHT Anniversary: Passivhaus, Net Zero & Retrofit - Andy Simmonds PHT Anniversary: Passivhaus, Net Zero & Retrofit - Ann-Marie

The retrofit presentations showcased fascinating research with many overlaps and tangents between speakers. What is apparent – there are no clear answers but many crucial questions. How far, how deep, and at what cost?

Is EnerPHit scaleable or even feasible for a large portion of the UK’s building stock? What measures are most impactful when rapidly decarbonising and flattening the carbon burp? We heard of a couple of new ‘lite retrofit’ standards underpinned by Passivhaus methodology, as a baseline.

Fabric first or heat pump first? AECB analysis showed that installing heat pumps & moving off fossil fuels as soon as possible helps flatten the carbon burp curve. However, Architype's research on a non-domestic building found that switching to heat pumps, with no additional fabric improvements, would jump from 19 radiators to 77! A big concern is whether electric heat pumps meet the householders' expectations of comfort & bills. Installing heat pumps, with no energy efficiency improvements, will increase most people’s energy bills - this cannot be overlooked at a time of increasing fuel poverty and the cost of living crisis. Prioritising efficiency measures results in far smaller heating demand. Replacing an 'oversized' heat pump once the building fabric is upgraded is a concern. COP efficiencies & install optimisation all need to be factored in.

What is crucial is advocating for a whole house plan and the all-important quality assurance to verify building performance. Retrofit lite, with the ability to deeper retrofit later, could be a helpful phased approach to kick-start decarbonising buildings at a national scale. Ann-Marie said that a no regrets approach must address the fabric and clients need to understand there are various infrastructure impacts beyond the building boundary if we do not do that. Building performance evaluation & feedback mechanisms would help.

Green financing models such as those researched by the Green Finance Initiative may provide the additional funding to allow house builders to build higher spec. Chris Herring commented that only political will can drive this agenda. If there is a level platform for all developers they will comply. When government intervenes on a long-term basis, the landscape changes; This can already be seen in places like Vancouver & Brussels.

Poll Results

PHT Anniversary: Passivhaus retrofit and net zero - Poll results
PHT Anniversary: Passivhaus retrofit and net zero - polls PHT Anniversary: Passivhaus retrofit and net zero - delegates


As usual, there was so much to unpick; The conversations continued over drinks and cake. The Trust hope to facilitate further debates soon, particularly exploring net-zero retrofit.


PHT Anniversary: Passivhaus, net zero, & retrofit - photo compilation

Save the date for our next hybrid event - the UK Passivhaus Conference 2022, in person in Exeter (and online): Wednesday 26 October. If you are not already, please consider becoming a PHT Member:

Once again, thanks to the sponsors and a special shout-out to Peter Hearle, Museum of London, who made our first transition to a hybrid event seamless!



Thank you to PHT Patrons Aluprof UKATTMAGreengauge and Passivhaus Homes for providing sponsorship for refreshments.

Aluprof   ATTMA Greengauge Passivhaus Homes


All images unless otherwise stated © Passivhaus Trust.

Further Information

2022 Passivhaus Anniversary: Passivhaus, Net Zero, & Retrofit

PHTparty22 media pack

PHT Passivhaus Primers

Passivhaus Retrofit

Passivhaus: the route to Zero Carbon

Passivhaus & Embodied Carbon

Getting to Net Zero: on-demand tutorials

Previous PHT story: The case for MVHR - 29 April 2020

UK Passivhaus Conference 2022 - Exeter & Online

Passivhaus Plus & Premium

Passivhaus Benefits

15th July 2022

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