Renewable energy is the ideal complement to the efficiency of the Passive House Standard. In order to provide guidance for this combination, the Passive House Institute offers three tiers for its building certification: Classic, Plus and Premium. They classify the building in terms of their overall efficiency level and the renewable energy generation. The classes Plus and Premium were first introduced with PHPP version 9 (2015) as addition to the well-established Passive House Classic.

The functional definition of the Passive House and EnerPHit standards remain unchanged and is the same for all three classes (relating to useful energy demand for heating and cooling, as well as airtightness and comfort criteria). The assessment of the different classes is driven by the total primary energy demand, as well as renewable energy supply (on-site or nearby). The higher the achieved level of overall efficiency and of renewable energy generation, the higher the Passive House class.

PER limits for the three Passive House Classes. Plus and Premium classes call for increased overall efficiency (figures on the right) and also require a certain amount of renewable energy generation (figures on the left).

The Passive House Classes are assessed using the PER methodology (Primary Energy Renewable, see details below). In the case of the Passive House Classic category, the renewable primary energy demand must not exceed 60 kWh/(m²a). A building built to Passive House Plus is more efficient as it may not consume more than 45 kWh/(m²a) of renewable primary energy. It must also generate at least 60 kWh/(m²a) of energy in relation to the area covered by the building. In the case of Passive House Premium, the energy demand is limited to just 30 kWh/(m²a), with at least 120 kWh/(m²a) of renewable energy being generated.

The classification is available for newbuild Passive House buildings, as well as for EnerPHit retrofits. In the case of EnerPHit the PER targets are adjusted slightly to account for the higher heating energy demand limits.

There are different ways of achieving a higher Passive House class. This article shows examples of how to reach the different Passive House Classes.

Selected case studies:

• Passive House Premium – Erne Campus, Ireland (iPHA Project Spotlight, Sept 2023)
• EnerPHit Plus – High rise office buildings in Vienna, Austria (iPHA Project Spotlight, March 2022)
• Browse implemented projects worldwide in the online Passive House Database. Use the advanced search to filter for Passive House or EnerPHit by Class Classic/Plus/Premium.

Renewable energy generation in the context of buildings is typically assessed based on achieving a “net-zero” or even “positive” energy balance. The intention of these approaches is to generate at least as much energy as is being consumed over the course of the year in absolute terms, i.e. MWh per year. While this initially appears intuitive, this approach presents challenges and can be very misleading:

• In a “net” energy balance, effects of energy storage and distribution losses are neglected entirely. The additional energy needs to cover storage losses can, however, be quite significant (especially for heating demand, as shown by the PER methodology). For an honest “zero-energy” approach, these losses would need to be taken into account.
• It is easier to offset the absolute energy demand in the case of a single family home than it is for a multi-storey building. Multi-story buildings, however, have a lower impact in terms of space and material use and are therefore advantageous in terms of sustainable housing developments.

Instead of off-setting energy demand and energy generation, the Passive House concept rates both aspects independently of one another. The energy demand is measured against the value of the service, which is represented by the useful space of the building, the so-called “Treated floor area (TFA)”. The renewable generation is measured against the area that the building occupies and that is therefore longer available for other uses: the “Projected building footprint (PBF)”. This approach of independent assessment of the efficiency level (with respect to the living area) and the energy generation (with respect to the projected footprint area) encourages optimised solutions for both parameters. Regardless of whether the building is a bungalow or an office tower, it is ensured that the energy input needed for health and comfort is low and the energy output with respect to the locally available renewable resources is high. Bungalows will automatically become “plus-energy” houses in many cases, whilst high-rises will not be misguidingly downgraded for not achieving “net-zero”.

In both situations shown the total living space is the same, provided by three single family homes (left) or one multifamily building (right). It is much easier for a single family houses to achieve a net-zero energy balance because of the larger roof space, which puts the multifamily building at a disadvantage. In the PER methodology energy generation is assessed based in the individul building's footprinta area. Assuming the buildings have the same efficiency level, the multifamily can achieve the same PH Class rating as a single family house. © PHI

The sun and wind provide primary renewable electricity. Some of this electricity can be used directly. However, storage capacities are necessary for transferring surplus energy to time periods with lower energy gains. These supply secondary electricity as required, and this is associated with losses. Depending on the type of energy application, the proportion of primary and secondary electricity varies, as do the losses for providing energy. These specific energy losses of an energy application are described as the respective PER factor. The demand for domestic energy is quite constant throughout the year, which is why the share of direct electricity is high and the PER factor is low. In contrast with this, heating is necessary only in winter. In order to provide enough energy in winter, electricity must in part be produced in summer and stored with very high losses for the winter, which results in a high PER factor.

To learn about the PER methodology in detail, please visit the Passipedia landing page "Primary Energy Renewable" (PER).

Current building certification criteria including the categories Classic, Plus and Premium

Browse implemented projects worldwide in the online Passive House Database. Use the advanced search to filter for Passive House or EnerPHit Class Classic/Plus/Premium.

Classic, Plus, Premium: The Passive House classes and how they can be reached (Lecture given at the 19th International Passive House Conference 2015 by Dr. Benjamin Krick)

iPHA fact sheet No. 3: The new Passive House Classes based on the PER system and their implications

Passipedia landing page "Primary Energy Renewable" (PER)

We welcome any questions or comments regarding the Passive House categories, PER factors or building certification criteria. Please send them to info@passivehouse-international.org.