'Nearly Passivhaus' is a false economy
A recent Passivhaus Trust position paper points out the financial and performance risks associated with not fully implementing ALL eight Passivhaus principles.
The 8 core Passivhaus principles
The Passivhaus Trust defines eight Passivhaus principles: not only the well-known building principles of insulation, airtightness, ventilation, minimised thermal bridging, and high-performance windows, but also the three core principles of approach: detailed performance and comfort criteria, accurate modelling in PHPP, and rigorous quality assurance. Together, these eight principles form an integrated whole that reliably delivers performance, comfort and durability.
Nearly Passivhaus
Applying some but not all the principles of Passivhaus carries the risk of poor outcomes and significant costs.
Phrases like “Passivhaus lite”, “inspired by Passivhaus” or “based on Passivhaus principles” sound impressive and tempting when budgets and constraints are tight. However, such terminology lacks clarity and is likely to be misleading. These labels create the illusion of rigour, giving the impression that the project in question will perform like a Passivhaus, without meeting all the criteria and requirements.
In Claiming Passivhaus (PHT, 2025), we provide guidance on using the word Passivhaus correctly, and on the legal context in the UK. Download the guide for free at: https://pht.guide/claiming Passivhaus.
Financial risk
In Misunderstanding Passivhaus Principles: Being Aware of the Risks (PHT, 2025) we looked at two project case studies where the clients were ambitious in their intention to provide reduced operational carbon emissions and lower energy bills for residents. However, the projects did not require Passivhaus performance in their contracts, and an ill-defined brief, absence of Passivhaus Planning Package (PHPP) energy modelling, and lack of attention to key design aspects and build quality led to poor outcomes and significant costs. On one of these projects, the cost of rectification, to make the homes comfortable and cost-effective to run, amounted to £16,000 per dwelling.
The performance gap
The performance gap between design and in-use energy performance in the UK is well-documented and, conservatively, is found to result in a 60% increase in space heating demand in residential buildings on average and often considerably more in non-residential. Passivhaus offers an integrated approach encompassing the principles of detailed performance and comfort criteria, accurate modelling, and quality assurance. The evidence shows that Passivhaus buildings, unlike most UK new buildings, reliably perform as designed and avoid the ‘performance gap’.
De-risking projects & cutting costs
It is easy to assume that cutting Passivhaus certification and quality assurance will result in cost savings. However, the examples cited in Misunderstanding Passivhaus Principles demonstrate that omitting these is often a false economy and may cost you more in the long run.
A fundamental principle of construction projects should be to provide a clear brief to the project team. Referring to ill-defined ‘Passivhaus principles’ or a design ‘inspired by the Passivhaus standard’ does not establish clear deliverables in a brief or contract and can create ambiguity and increased risk. Without defined criteria, there’s ample room for misinterpretation and disputes. Clear, measurable targets aligned with the Passivhaus standard reduce this risk and support deliverability within existing professional frameworks such as Professional Indemnity Insurance.
True value engineering
Every Passivhaus project must be modelled using the Passivhaus Planning Package (PHPP) for precise energy balance calculations and comfort assessments, creating a tailored solution for each building. As well as an invaluable design aid, PHPP should be recognised as a powerful value engineering tool. For example, PHPP encourages good building form factor to reduce heat loss in proportion to internal area, which also maximises the asset in terms of valuable floor area enclosed within the thermal envelope. Similarly, careful consideration of the proportion of glazed areas on each elevation optimises the capital spend on a relatively expensive component, while minimising running costs of space heating and risks of overheating.
Passivhaus certification is independent and impartial and provides a “golden thread” of considered input throughout the design and construction process. Ultimately, it can save clients money, reducing project risks and identifying mistakes early - while they can still be remediated at low cost - ensuring the building will perform as designed.
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Further information
PHT Position Paper: Misunderstanding Passivhaus Principles - May 2025:
PHT Primer - Misunderstanding the principles - a primer - May 2025
PHT Technical Briefing: Claiming Passivhaus - June 2025
Inside Housing: Don't fall into the 'nearly Passivhaus' trap - 22 July 2025
4th March 2026
Get involved with the UK Passivhaus community
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