The EnerPHit Component/ Elemental route is an alternative approach that helps get Passivhaus retrofit projects across the certification line! Greengauge Director & Passivhaus Certifier Paul Smith highlights the under-used route to retrofit certification, with examples of when it might be used.
The EnerPHit (Passivhaus retrofit) standard often has a reputation of being too difficult for the majority of existing buildings in the UK to achieve. It is often depicted as out of reach and impossible for most projects.
And yet the Passive House Institute already has an existing route to certification developed which contradicts this perception – with its alternative approach to EnerPHit certification that not many designers may be aware of – the EnerPHit component or elemental route.
The EnerPHit Component Method
Instead of certifying a retrofit based on space heating demand, the component route focuses on the thermal performance of individual building elements and their component-specific requirements (e.g. U-values). To access this method simply select the appropriate drop downs in the Energy standard / Criteria on the PHPP verification page and away you go. The PHPP will then align itself with checking compliance against the appropriate criteria.
For UK projects (Cool-temperate climate), this sets an alternative goal to hit with specific targets like walls ≤ 0.35 W/(m²K), windows ≤ 1.10 W/(m²K), and roofs ≤ 0.15 W/(m²K) instead of those demanding space heating targets.
The focus of this certification route becomes more about maintaining comfort and hygiene requirements for the occupants rather than the energy needed to heat the building. As we’re all aware, in the UK our heating patterns for existing dwellings are typically intermittent anyway. Airtightness requirements are the same at ≤1.0 1/h but overall space heating demand can exceed the normal EnerPHit space heating route – often coming in over the standard 25kWh/m2/year limits (which is always calculated in the PHPP as maintaining a constant indoor temperature of 20 degrees C for certification). It is liberating!
Flexibility & exemptions
At the heart of the Component method is the understanding that retrofit of existing buildings is more complicated than newbuild, with many more constraints. Historic conservation requirements, orientation, form and window sizes are all limiting factors.
Dealing with solid wall construction will affect the suitability and thickness of insulation materials. Moisture accumulation risk – particularly crucial for internal wall insulation projects – is a valid reason for exemptions.
So, although requiring pre-determined U values there is further flexibility and understanding that there may need to be exemptions.
Passivhaus Certifiers will consider if the exception is justified and would then approach the Passive House Institute to get final approval – requiring written confirmation from PHI that is specific to your building.
Typical EnerPHit Component method projects
Low TFA: If TFA (treated floor area) to surface area ratio is low (for example in an open plan barn conversion with minimal upstairs floor area) then the space heating certification method is unlikely to be possible, and the component approach will be the best route to certification.
Internal wall insulation: EnerPHit projects that require an internal wall insulation strategy will often need to go down the EnerPHit component route. This is because using internal wall insulation limits the amount of insulation that can be applied, both from a space and moisture risk perspective.
Heritage buildings: Where conservation requirements fundamentally limit your insulation options, the component route acknowledges these real-world constraints, while still driving performance improvements.
Buildings with unavoidable thermal bridges: Where eliminating thermal bridges isn’t economically or practically feasible, the component method provides a pathway forward.
Certifying an EnerPHit Component project
From a Certifier’s point of view, certification of EnerPHit elemental/ component projects is different to usual PHPP modelling and requires that the Certifier checks that the core values are achieved. These core values – covering everything from U-values to MVHR efficiency to glazing performance – are all clearly defined in the Building Criteria document and automatically calculated by the PHPP when you select the component route.
Documentation requirements remain comprehensive – you’ll still need thermal bridge calculations (although more emphasis will be placed on the internal temperatures and Frsi values than the Psi value), component specifications, and construction manager declarations – but the focus shifts from energy demand verification to component performance verification.
For the complete technical picture – including all core values, exemption criteria, and process details – the Building Criteria document and PHPP User Manual contain everything you need. Your Certifier can guide you through the specifics relevant to your project.
This route enables a wider range of projects to achieve EnerPHit certification, so next time you think EnerPHit certification is out of reach, think again!
