News Heidelberg’s Bahnstadt Passivhaus District Passes Energy Efficiency Test

An entire district built to the Passive House standard in the German city of Heidelberg has demonstrated its energy efficiency performance with flying colours, according to a new report.

Bahnstadt is regarded as one of the most significant ongoing Passive Projects, given the scale of the project, that’s hardly surprising; the scale of the regeneration is certainly ambitious, even without the Passive House energy efficiency element.

Rather than a singular building, it is the attempt to construct an entire city district to the energy efficiency principles. Built on the site of a former freight railway station, it provides a mix of residential and commercial buildings on an area covering 116 hectares.

Several office buildings and institutes have opened in the district, as well as a kindergarten; a school, shops, a community centre, and a cinema complex are currently being planned. Once Bahnstadt is entirely developed, up to 12,000 people will live and work there.

The report assessing recent measurements revealed that the values being strived for in relation to energy efficiency were met in full. In 2014, the average consumption of 1,260 housing units with a total living area of more than 75,000m² was 14.9 kWh/(m²a).

Compared with conventional new constructions, savings of around 80 % were achieved. The statistically high number of residential projects built by different property developers and architects convincingly shows that a successful large-scale implementation of the Passive House Standard is possible, according to the full report, which is now available online.

“The evaluation of the consumption data proves that the efforts made by the City of Heidelberg to design an entire city district to a high standard in terms of energy efficiency based on future-oriented specifications and corresponding quality assurance have been tremendously successful,” said Søren Peper of the Passive House Institute (PHI), based in Darmstadt, Germany.

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Peper was in charge of the monitoring project. The measurements were carried out on the basis of monthly meter readings of the total heat consumption in several blocks with over a hundred apartments in each. An average heating energy consumption lower than the Passive House limit value of 15 kWh/(m²a) was measured in the process.

The heating demand of a building is calculated mathematically. The actual consumption depends on many additional factors such as user behaviour and the weather. In the case of the present study, the PHI said it must be kept in mind that these measurements were predominantly performed during the first year of operation, in which consumption is usually higher than in subsequent years, due to work relating to tenants moving in and necessary adjustments. But even with these adverse influences, the Passive House buildings in Bahnstadt already “function faultlessly”. The consumption data showed consistently high conformity with the demand calculated in advance using the Passive House Planning Package (PHPP).

“The monitoring carried out in Heidelberg doesn’t just prove the reliability of calculations using the PHPP planning tool,” says Dr Wolfgang Feist, the PHI’s director. “The slight differences between the calculated balance and the actual measured values show that the Passive House Standard demonstrably and reproducibly results in extremely high savings of heating energy and thus, of course, also of costs. The much heard of ‘performance gap’, a divergence between expectations and reality, does not exist with the Passive House Standard.”

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