The EnerPHit Standard: Adapting Passive House Principles for Building Refurbishment
Technical summary · Retrofit
A professional summary and technical analysis of the retrofit energy efficiency standard that brings Passive House principles to existing buildings.
01Executive summary and context
The building sector is a primary driver of global energy demand and greenhouse gas emissions, accounting for approximately one-third of global final energy consumption. While modern architecture can use the ultra-low energy Passive House (Passivhaus) standard to reduce heating and cooling energy by up to 90% compared to legacy structures, applying these stringent baseline standards to existing building stock presents substantial practical and economic hurdles.
Factors such as unfavourable structural orientation, spatial constraints, unresolvable thermal bridges and architectural preservation guidelines often prevent retrofits from reaching the primary target of ≤ 15 kWh/(m²a) space heating and cooling demand.
To resolve this challenge, the Passive House Institute (PHI) introduced the EnerPHit Standard in 2010. EnerPHit establishes a practical, highly engineered framework tailored specifically to building refurbishment. It delivers superior occupant thermal comfort, structural longevity and radical energy efficiency, while allowing the flexibility needed to accommodate a building’s inherent limitations.
Core strategy
EnerPHit serves as an optimised compromise, offering building owners an authoritative, quality-assured certification pathway that yields the majority of Passive House performance benefits within realistic retrofitting constraints.
02Strategic pathways to compliance
Project teams seeking EnerPHit certification can pursue compliance through one of two methodological tracks: the Energy Demand Method or the Building Component Method.
The Energy Demand Method
Unlike new-build Passive House standards, which enforce a single global threshold, the Energy Demand Method sets maximum space heating demands that vary by regional climate zone, as calculated in the Passive House Planning Package (PHPP). This climate-dependent scale acknowledges the significantly higher heating demands of colder environments.
The Building Component Method
Where unalterable site factors (such as extreme overshadowing, complex building geometry or severe layout limitations) prevent a building from meeting the overall heating demand cap, this method offers an alternative. Certification is granted if all relevant elements, including exterior insulation, interior insulation, windows and heat recovery ventilation, meet stringent component-level criteria on average. Pre-certified components from the PHI Online Component Database can be used, or independent verification supplied for non-certified materials.
Table 1: Climate-specific maximum space heating demand under the EnerPHit Energy Demand Method.
03Universal criteria and performance classes
Whichever method is selected, every EnerPHit retrofit must satisfy universal baseline criteria for envelope airtightness and energy efficiency classification.
Airtightness
Recognising how complex it is to seal existing wall junctions and retrofit structural assemblies, EnerPHit permits a pressurisation test limit of n₅₀ ≤ 1.0 h⁻¹. This is slightly more lenient than the new-build requirement, yet still delivers exemplary airtightness and protection against interstitial moisture.
Performance classes
Projects are assigned a tier based on overall Primary Energy Renewable (PER) demand and on-site renewable energy generation.
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Source: “The EnerPHit Standard: How does it PHit in?”, International Passive House Association (iPHA) — blog.passivehouse-international.org
