EnerPHit – The Passive House Standard for Retrofits

The best scenario for a building retrofit is to be performed all at once. However, the reality for most building owners is that it is financially and logistically not feasible to complete an entire deep energy retrofit in one step. In fact, 80-90% of all retrofits undertaken are partial retrofit measures rather than complete one-time deep energy refurbishments. These partial retrofit measures are completed over time when the respective building component needs to be renewed.

These events are a great opportunity to not just replace an old component by code, but to improve their performance at the same time to get the most benefit. For example, if the facade already needs to be renewed anyway, the extra effort to add optimal thermal protection of the exterior wall based on the Passive House Standard at the same time will be manageable.

The challenge is to have these single measures, that are performed over time, work together to a high-performance, whole house retrofit, step-by-step until the last step has been done.

Interdependencies exist between individual energy efficiency measures, e.g. making a building more airtight requires a ventilation strategy. Technical connection details must be developed that will work well during all phases, e.g. how to deal with old windows in a new exterior insulation layer and how to prepare for an optimal window placement once windows will be replaced in a subsequent step.

The Passive House Institute has researched and adjusted the Passive House Standard to the realities of retrofitting buildings; considering all the challenges that come with older buildings and, based on that research, developed EnerPHit.

The EnerPHit Standard provides a concept and planning tool that can be used for all-at-once or step-by-step renovations for all project locations with their specific local climate.

Of course, the EnerPHit Standard for existing buildings is based on the same principles as the Passive House Standard for new buildings, just the set of criteria vary due to the unique challenges of old, existing buildings.

Passive House is the world leading standard in energy efficient construction and it is way more than just a low-energy building. It is a building standard that achieves ultra energy efficient, comfortable, affordable, durable and ecological buildings, regardless of the regional climate.

Passive House is a design and construction concept that can be applied by anyone; it has withstood testing of performance for over 20 years.

For a building to be considered a Passive House building, it must meet a set of criteria, which can be achieved by the following 5 construction principles. These principles relate to new buildings as well as retrofits.

Passive House Principles

The EnerPHit Retrofit Plan

EnerPHit provides a toolset that allows to plan and manage a whole building Passive House retrofit over time, step-by-step. An overall plan will be prepared for the current and all subsequent modernization steps before starting. This is the only way to be sure that everything fits together, and the building owner can count on having an increasingly comfortable building with lower energy cost over time and once the final step is completed. An EnerPHit Retrofit plan is composed of

  • a calendar that provides an overview of the chronological sequence of normal necessary measures to repair/replace building systems over the buildings lifetime years based on wear and tear (e.g. new roof). The chronological measures and timeframes will look different based on each building’s specific current condition.
  • detailed information about the measures due to wear and tear and additional Passive House measures added on;
  • investment, maintenance, and energy cost for both sets of measures listed separately;
  • characteristic values of building components used (what type of products and their performance requirements);
  • reported achievement of EnerPHit criteria at each step;
  • matrix with interdependencies between both sets of measures at each step and over time;
  • detail drawings and explanatory notes.

The whole EnerPHit Retrofit plan is handed to the building owner for safekeeping. If certification is pursued, all EnerPHit documentation will be stored on the online Passive House Certification platform and can be accessed at any time and updated at each new retrofit step.

Here are some of the benefits an EnerPHit Retrofit Plan provides:

  • prepares for future steps with today’s measures will save costs overall and will ensure an optimal outcome for energy savings and comfort over time;
  • once the overall EnerPHit plan has been prepared, it is available as a guide for every further step and thus facilitates the planning process (you don’t have to start from the beginning every time).
  • high-performance results can only be achieved if each individual step is implemented with the appropriate quality and with consideration of interdependencies;
  • the energy demand is stated and energy savings can be determined for each step;
  • the approximate timelines for upcoming refurbishment measures are stated in the general plan. This serves as a valuable aid for personal financial planning.


A pre-certification can be pursued for quality assurance and recognition. A PHI accredited certifier will check the prepared EnerPHit Retrofit Plan for compliance with EnerPHit requirements and for completeness and consideration of all interrelations between all measures.

This way, unnecessary investment and energy cost can be avoided. After approval, the first set of measures can be implemented. Once the step is executed and approved by the certifier the building owner will receive a pre-certification for the building.

A preliminary certificate might increase the value of the building because its potential is clearly demonstrated with 3rd party validation. It also increases the credibility of the refurbishment concept in the context of talks with the bank e.g. because the achievable cost savings are available in a reliably calculated way. Apart from that, you can demonstrate to the outside world that you are committed to climate protection.

Passive House Principles

Key Aspects of a Passive House EnerPHit Project

 Here are some questions that are essential to be answered for a successful EnerPhit retrofit project:

  • What are the characteristics and remaining life expectencies of the current building components?
  • Which ones must be renewed now, and which ones later?
  • Where are the biggest opportunities to save energy cost?
  • Where are the biggest opportunities to increase comfort?
  • Which retrofit practices are most cost-effective and value-enhancing for the project at hand?
  • Where are interdependencies between individual energy efficiency measures and how should they be addressed?

Deep vs. Conventional Energy Retrofits

A word of clarification about the difference between a conventional, a deep energy retrofit and the Passive House Standard.

A deep energy retrofit is based on a whole-building analysis including all building assemblies and systems. It achieves much larger energy savings than a conventional retrofit.

Deep energy retrofits can be applied to both residential and commercial buildings. A deep energy retrofit can result in savings of 50 percent or more, perhaps spread over several years, and may significantly improve the building value, comfort and durability.

Conventional energy retrofits focus on isolated system upgrades without any regards to the impact on other assemblies and systems and the performance of a building as a whole.  (HVAC equipment without impact analysis of possible airtightness and insulation measures ). These retrofits are generally simple and fast, but they often miss opportunities for larger and more cost-effective energy savings, increased comfort and durability. They can even be damaging to comfort and the health of the building (e.g. more airtight windows can lead to mold if additional ventilation is not considered).

Of course, the Passive House EnerPHit Standard looks at the whole building as an interdependent system and supports only deep energy retrofits.

The Passive House EnerPHit Standard provides tools and guidelines for ultra high performing deep retrofits based on the local climate of each project. EnerPHit can be used in any local climate around the world.