Renovating existing buildings to achieve high performance can be far more complex than designing a new one from scratch. Structural limitations, existing materials, and budget constraints often make it difficult to meet the strict requirements of the Passive House standard. To address this challenge, the EnerPHit certification was developed, bringing the benefits of Passive House performance to retrofit projects in a cost-effective way.
EnerPHit is a certification framework created by the Passive House Institute (PHI) specifically for the energy-efficient retrofit of existing buildings. It applies many of the same Passive House principles such as super insulation, airtight construction, high-performance windows, thermal bridge – free design and mechanical ventilation… but adapts performance targets to the realities of renovation.
The EnerPHit approach is suitable for a wide range of projects, including residential homes, apartment buildings, schools, and commercial buildings undergoing major renovations. Rather than requiring every project to meet new-build criteria, EnerPHit standards provide flexible pathways that allow existing buildings to reach very high levels of energy efficiency.
EnerPHit vs Passive House
Both EnerPHit and the Passive House standard, created by the international Passive House Institute, aim to dramatically reduce energy demand and improve indoor comfort.
Passive House certification is generally intended for new buildings, where orientation, structure, and envelope design can be optimized from the start. EnerPHit, on the other hand, adapts those goals to retrofit conditions, recognizing that some constraints, such as existing foundations or structural geometry, cannot be (easily) changed.
In practical terms, EnerPHit standards maintain the same philosophy as the Passive House standard but allow slightly higher energy demand limits or alternative compliance methods to ensure renovations remain feasible.
Performance Targets & Energy Demand
EnerPHit projects must still meet strict performance requirements, particularly in terms of heating demand, airtightness, and thermal performance. However, these targets are lighter.
Key areas of performance include:
Heating demand: Refers to the amount of energy required over one year to heat the building during winter, in order to maintain a comfortable indoor temperature of 20°C. The heating demand limit for EnerPHit buildings is ≤ 25 kWh/(m²·a) (climate-dependent), while for new Passive House buildings it is ≤ 15 kWh/(m²·a).
Space cooling demand: Refers to the amount of energy required over one year to keep the building comfortable during summer, typically by maintaining indoor temperatures below 25°C. The cooling demand limit for EnerPHit buildings is ≤ 15 kWh/(m²·a), although this value is climate-dependent and may be higher in warmer regions.
As an alternative, when no air-conditioning system is installed and only passive cooling strategies are used, compliance can be demonstrated through the overheating frequency. This limits how often indoor temperatures exceed a comfort threshold (typically 25°C). For EnerPHit, the requirement is ≤ 10% of annual hours above 25°C.
Airtightness: Measured through a blower door test, where the building is pressurized and depressurized to a pressure difference of 50 Pa and the resulting air leakage rate is recorded. For EnerPHit projects, the maximum allowed air leakage is 1.0 air changes per hour (ACH), while for Passive House it is 0.6 ACH.
Primary energy demand (PER): Represents the total annual energy use of the building, including heating, air-conditioning, domestic hot water, lighting, and appliances, weighted according to the energy source. The EnerPHit requirement is ≤ 60 kWh/(m²·a) and in some climates the PER can be higher.
Despite these differences, EnerPHit houses still achieve substantial reductions in energy use, often cutting heating demand by 70–90% compared with pre-renovation conditions.
Building Component Method
One of the defining features of EnerPHit standards is the Building Component Method. This approach allows individual construction elements – such as windows, walls, roofs, or ventilation systems – to meet specified performance criteria rather than requiring the entire house to meet a single energy demand target of 25kWh/m2/year for cool-temperate climates. When certifying to the building component method, each component should meet certain technical parameters – for example, the Mechanical Ventilation with Heat Recovery (MVHR) systems are mandatory for EnerPHit Passive House components certification, with a minimum efficiency of 75% and strict limits on electrical consumption.
This method is especially useful in cases where:
Structural constraints limit insulation thickness
Heritage or protected façades must be preserved and insulated internally
Budget or phasing requires step-by-step renovation
The Building Component Method makes EnerPHit particularly practical for complex or historic buildings, while still providing superior thermal comfort in EnerPHit retrofits, eliminating draughts and ensuring stable temperatures.
Benefits of EnerPHit Retrofits
The EnerPHit concept provide many of the same advantages associated with Passive House construction, particularly in terms of comfort and performance.
Reduced energy consumption is one of the most significant benefits. By upgrading insulation, improving airtightness, and installing heat recovery ventilation, buildings require far less energy for heating and cooling.
Comfort is another significant improvement. Eliminating drafts, cold surfaces, and uneven temperatures transforms the indoor environment. Rooms remain consistently warm in winter and comfortable in summer, even in existing homes that previously suffered from poor thermal performance.
Good air quality indoors also improves substantially. MVHR systems provide a steady supply of filtered fresh air, reducing humidity, pollutants, and allergens while maintaining a healthy indoor environment.
Long-term building durability is an often-overlooked benefit. Better moisture control, improved detailing, and higher-quality materials can extend the lifespan of the building envelope and reduce maintenance costs over time.
Because the EnerPHit concept focuses on whole-building performance, similarly to all Passive Houses, these benefits are not isolated improvements but part of an integrated strategy that enhances the building as a system.
When Is EnerPHit the Right Choice?
The EnerPHit concept is particularly suitable in situations where achieving full Passive House certification is impractical or impossible.
Typical scenarios include:
Modernization of older residential existing houses
Historic or protected structures where façade changes are limited
Apartment blocks undergoing deep energy retrofits
Existing schools and public buildings with structural constraints
Projects retrofitted in stages over time
Attempting to meet the full Passive House standard in most existing homes would require disproportionate costs or major structural interventions. This is because it is often not possible to fully eliminate all thermal bridges or achieve the same level of airtightness as in new construction.
Overcoming Technical Challenges
Retrofitting existing buildings presents several technical challenges, and EnerPHit standards are designed to address them systematically.
Airtightness is often the most challenging step during the retrofit journey. Existing buildings typically contain many potential air leakage paths – such as cracks in masonry, poorly installed windows, service penetrations, leaky connections between walls and floors, or unsealed attic and basement interfaces. All of these must be carefully addressed without damaging the existing structure, which is not always fully achievable. For this reason, the airtightness requirement for retrofits is slightly more relaxed than for new-build Passive House projects.
Thermal bridges – areas where heat can bypass insulation are another common issue in older buildings. Structural elements such as balconies, slab edges, or junctions between walls and floors often create major heat losses and surface condensation risks.
A common example is an exposed concrete balcony slab that penetrates the thermal envelope. Since removing the balcony is usually not feasible, the solution is often to wrap the slab with high-performance external insulation and, where possible, add internal insulation at the slab junction to reduce heat flow and improve surface temperatures. In new houses, on the other hand, thermal breaks can be used and in most cases, which can significantly reduce thermal bridging and surface heat losses.
System integration also requires careful planning. Installing efficient mechanical ventilation, improving insulation, and upgrading windows must be coordinated to ensure that all components work together effectively.
Certification & the EnerPHit Retrofit Plan (ERP)
EnerPHit certification is a quality assurance that the building meets defined performance criteria through energy modeling, documentation, and on-site testing.
A key tool in this process is the Passive House Planning Package (PHPP), part of which is the EnerPHit Retrofit Plan (ERP). The ERP allows building owners to plan renovations in stages while maintaining a clear long-term strategy. Each phase of work is designed to be compatible with future improvements, preventing costly rework or performance conflicts.
This long-term planning approach is particularly valuable for large buildings or projects where renovation must occur over several years. It ensures that each step contributes to the final energy efficiency targets rather than creating obstacles.
The certification of EnerPHit projects can be carried out by any accredited body recognized by the international Passive House Institute such as Passive House School.
Summary & Key Takeaways
EnerPHit provides a practical pathway for bringing the benefits of Passive House design to existing buildings. While it is closely related to the Passive House standard, it adapts performance targets and compliance methods to the realities of retrofit projects.
Key points to remember:
Enerphit standards are specifically designed for retrofits and renovations by the Passive House Institute.
They apply many Passive House principles, including airtightness, insulation, and heat recovery ventilation.
The Passive House performance targets are adjusted to reflect structural and technical constraints.
The Building Component Method allows flexibility when full performance targets are difficult to achieve.
EnerPHit retrofits deliver major improvements in energy efficiency, comfort, and indoor air quality.
The EnerPHit Retrofit Plan supports long-term, phased renovation strategies.
For building owners, architects, and developers, EnerPHit offers a realistic way to transform existing houses into high-performance spaces combining practicality with ambitious energy efficiency goals.
