Pioneering project upgraded to Passive House Plus

DARMSTADT, GERMANY – The world’s first Passive House building has increased its already high energy efficiency level and now relies on renewable energy.

A year ago, a photovoltaic system was installed on the roof of a row house built in 1991 in Darmstadt. Since then, this pioneering Passive House project has been producing its own electricity, thus fulfilling the criteria of a Passive House Plus building. The official certificate was recently issued.

The certificate was accepted by Dr. Wolfgang Feist and his wife Witta Ebel (left). Photos: Passive House Institute

“Passive House buildings are perfectly equipped to utilize renewable energy. With their extremely low heating energy demand, it is even possible to derive as much energy from the sun on-site as is consumed in the house over a year,” explains Dr. Wolfgang Feist. Together with his wife Witta Ebel he recently accepted the Passive House Plus certificate.

Photovoltaic system for the anniversary
Twenty-five years ago, building physicist Dr. Wolfgang Feist built the world’s first Passive House, and with it established this energy-efficient, construction standard. Since then, the founder and director of the Passive House Institute and his family have lived in the terraced housing complex in the Darmstadt city district of Kranichstein. In the year of its 25th anniversary, the Feist family installed a photovoltaic system on the roof of their house in order to utilize the sun’s energy.

Efficiency plus renewable energy
With the Passive House Plus Standard, Passive House has contributed to the second step of the energy revolution. In addition to being highly energy efficient, it also generates on-site renewable energy. What matters here is that the energy demand of a building is considered and optimized separately from the energy generation.

The details:

Good basis for Passive House Plus –
In a Passive House Plus building, the upper limit for the total demand for renewable primary energy is 45 kWh/(m²a). At the same time, at least 60 kWh/(m²ta) of renewable energy must be generated based on the projected building footprint. From the very beginning, the Feist family equipped their house with extremely efficient devices. The electricity consumption is therefore very low, even with the operation of the ventilation system.

Heat pump with reduced energy use –
The same also applies for the air-to-air heat pump that was recently installed for test purposes this past autumn, which is used for heating as well as ventilation in the Passive House. This electrically operated heat pump should use approximately 30 percent of the energy consumption that was previously required with natural gas for the gas heating system.

Electricity surplus into the grid – 
In the summer the surplus electricity produced by the photovoltaic system in Darmstadt-Kranichstein is fed into the public grid. In theory, the produced amount would suffice for supplying the whole house for one year, and the surplus electricity in summer could be stored for the winter.

Saving in network is useful
“For a single household, this kind of seasonal storage is not a reasonable option, but in the network, this “gap” becomes smaller and storage becomes much more cost-effective. This is what needs to be done in future”, explains Dr. Wolfgang Feist.


In 2015, the Passive House Institute introduced the Passive House Plus and Passive House Premium building classes which combine the classic Passive House Standard with renewable energy.  Both classes provide building owners with reliable orientation for combining energy efficiency and renewable energy.  Energy generation and energy demand are balanced separately. 

Direct accounting of the electricity generated by a photovoltaic system in the summer to the heating energy required in winter falls short of the reality since seasonal storage is always associated with losses.  The PER (Primary Energy Renewable) concept forms the basis of this calculation: PER factors are specified for the individual energy applications.  These state the number of kilowatt hours of renewable primary energy that are required to generate one kilowatt-hour of energy. 

In a Passive House Plus, the upper limit for the total demand for renewable primary energy is 45 kWh/(m²a). At the same time, at least 60 kWh/(m²ta) of renewable energy must be generated based on the projected building footprint.  In a Passive House Premium the energy demand is limited to 30 kWh/(m²a) while the energy generated must amount to at least 120 kWh/(m²ta).

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