Not all buildings can be renovated to the Passive House Classic Standard without great difficulty and cost. EnerPHit is a building standard that was developed by the Passive House Institute for existing buildings with such limitations due to unavoidable thermal bridges.
EnerPHit is the established Standard for refurbishment of existing buildings using Passive House components or the energy demand method via climate zone. Through the use of Passive House components, EnerPHit certified buildings offer nearly all the advantages of a Passive House building to the residents – while at the same time offering optimum cost-effectiveness.
The EnerPHit seal provides assurance that optimum thermal protection has been implemented for the respective existing building. An EnerPHit retrofit includes the insulation of the floor, exterior walls and roof with Passive House insulation thicknesses, installing Passive House windows and reducing air leaks. A ventilation system with heat recovery ensures reliable fresh air. Thermal bridges are reduced to a reasonable extent.
Advantages of Certification
A significant energy savings of between 75 – 90% can be achieved even in existing buildings, for which the following measures have proved to be particularly effective:
- Improved thermal insulation (based on the principle: if it has to be done, do it right)
- Reduction of thermal bridges
- Considerably improved airtightness
- Use of high quality windows (there is no reason why Passive-House-suitable windows should not be used whenever the opportunity arises)
- Ventilation with highly efficient heat recovery (again, Passive-House-suitable systems are very recommendable)
- Efficient heat generation
- Use of renewable energy sources
Certification is a way to ensure quality control during the design and planning processes. It is also a way to make it easier for the designer to specify adequate components, since they have been independently tested and certified.
Different Certification Levels and Criteria:
For a building to be certified as a Passive House, it must meet the following main criteria:
Table 1: EnerPHit criteria for the building component method
Table 2: EnerPHit criteria for the energy demand method (as an alternative to Table 1)
Table 3: EnerPHit primary energy criteria for the building component and energy demand method
To start the certification process you will need to engage a certifier approved by the Passive House Institute, ideally at the start of a project, as any problems identified early can be easily corrected. Enerphit certification can be achieved by completing all of the renovations at once, including the air tightness testing and ventilation commissioning, or via a step-by-step process.
Step-by-Step Retrofit Process with the EnerPHit Retrofit Plan
Many building owners cannot undertake a complete renovation all at once, but may rather upgrade each building component as repairs are required. It is often possible to reach a high level of energy efficiency with low additional costs using Passive House components. Before renovations begin, an overall plan should be completed ahead of time for the current step as well as all future retrofit steps which will be undertaken. This is the only way to be sure that everything will fit together, that there are not unintended health and safety situations created by the renovation steps, and that the owner can count on having a comfortable building with low energy costs once the final step is completed.
The EnerPHit Retrofit Plan (available with PHPP) provides a methodology for this type of overall planning to take into account important interrelationships between the different energy saving measures. For additional quality assurance, the Passive House Institute offers a pre-certification as an EnerPHit Retrofit Plan project. This requires a carefully prepared EnerPHit Retrofit Plan showing that the first retrofit step has been implemented achieving at least 20% energy savings. The pre-certification provides assurance to the building owners and planners that upon completion of all of the steps of their plan, they will achieve the desired EnerPHit certification class that they are aiming to meet.
Title illustration of an EnerPHit Retrofit Plan for an end-of-terrace house showing the heating demand and generation of renewable energy (right-hand axis) in the existing building and after the four steps.
Exemptions for EnerPHit
The limit values in Table 1 (above) for the heat transfer coefficients of the exterior envelope building components may be exceeded if absolutely necessary based on one or more of the following compelling reasons:
- If required by the historical building preservation authorities
- If the cost-effectiveness of a required measure is no longer assured due to exceptional circumstances or additional requirements
- Due to legal requirements
- If implementation of the required standard of thermal insulation would result in unacceptable restriction of the use of the building or adjacent outer areas
- If special, additional requirements (e.g. fire safety) exist and there are no components available on the market that also comply with the EnerPHit criteria
- If the heat transfer coefficient (U-value) of windows is increased due to a high thermal transmittance (psi value) of the window installation offset to the insulation layer in a wall that has interior insulation
- If reliably damage-free construction is only possible with a smaller insulation thickness in the case of interior insulation
- If the thickness of the thermal insulation is restricted due to any of the reasons mentioned above, and an exemption is applicable, then the insulation thickness that is still possible must be implemented with a high-performance insulation material with a thermal conductivity λ ≤ 0.025 W/(mK) if this can be implemented cost-effectively and in a damage-free way (in the case of interior insulation). In this case, the additional application of a surrounding insulation skirt should be considered in the case of floor slabs and basement ceilings. The measure should be implemented if this is economically viable.
- If other compelling reasons relating to construction are present