Five stars for sustainability

Almost ten years ago, the world’s first city hotel with a zero energy balance opened in Vienna, and it’s still setting the standard today. Not only have the technical systems continued to perform, but the owner remains as committed as ever.

Seen from the road, the six-story building seems unremarkable. That makes it all the more surprising when you enter the inner courtyard. Flowering on the flat roof are roses and lavender, and climbing plants creep up the façade, their path broken only by gleaming blue-black solar collectors. Everyone can see that the Boutique Hotel Stadthalle in Vienna’s 15th district has a green heart. What visitors can’t see is the complex building control technology that makes its heart beat – and turned the three-star premises into the world’s first city hotel capable of demonstrating a zero energy balance.


The story began in 2007 when Michaela Reitterer, the owner and manager, decided to put her energy into refurbishing and enlarging the then 140-year-old hotel. She’d bought the family business from her parents a few years earlier. Her planned expansion would almost double its capacity, from 42 to 80 rooms. And in terms of its energy needs, it would set new standards. The goal was to create a building that would generate all the energy it needed by itself.

Building control technology plays a key role

The project involved almost all the technology that was available at the time for energy-efficient construction. Electricity comes from a 94 square-meter photovoltaic system. Solar thermal collectors covering another 130 square meters ensure heat and the hot water supply. The building also uses a water-to-water heat pump, because the solar plant doesn’t always supply enough power.


“There are three huge cisterns in the cellar,” says Reitterer. They’re filled using groundwater from a well on the property. The water is then heated using the solar plant and the heat pump. The power is used for plate exchangers that heat fresh water as needed to supply the hot water for the hotel’s faucets and showers.


Instrumentation and control play a key role: At the heart of the system is the Desigo building automation system from Siemens, which ensures that the components work together seamlessly and that the guests are comfortable at all times.

The first hotel in Vienna designed as a passive building

In addition to power generation systems, good heat insulation is needed to achieve a zero energy balance. “Our extension meets the ‘passive building standard,” says Reitterer. That includes triple-glazed windows, for example, and controlled room ventilation with heat recovery.


The work of refurbishing the existing building didn’t go that far. “It would have been unaffordable,” Reitterer explains. But even so, the venerable original building still plays an important part in the overall energy strategy, providing the new part of the hotel with additional power at peak load periods.


Although the solar plant and heat pump cover the needs of the extension throughout the year, an occasional bottleneck still occurs: “For example, if a large number of guests want to take a hot shower at the same time on a Sunday morning in winter,” says Reitterer. “In this case, the building automation system automatically draws on the district heating from the original building.” Electricity can also be pulled from the old building, if necessary. And in return, the new building supplies hot water to the old section.

It isn’t always easy to maintain a balance between comfort and the environment. Reitterer recalls that this became evident during the planning stages. “If we’d gone along with what the engineers wanted, we wouldn’t have been able to open the windows now. The art lies in combining sophisticated technology and a maximum comfort factor for the guests.”

System pays off

Ten years is a long time when it comes to technological development: In 2008, just the idea of using LEDs for the entire hotel’s lighting system was enough to cause a stir, but it’s now become the norm. “Compared to what’s possible now, we were in the Stone Age back then," Reitterer recalls. And she’s all the more proud of the fact that the solution she opted for at the time still works perfectly. “For me, that’s also a kind of sustainability.”


The numbers speak for themselves, too: While energy costs make up five to six percent of total expenditures for other city hotels, for Reitterer’s business they range from two to 2.4 percent. “My colleagues are green with envy,” she says.


The installed technology may have remained essentially the same, but the hotel itself has continued to develop. “We’re constantly looking for new opportunities to reduce our environmental footprint even more,” Reitterer says. For example, she’s introduced a discount for guests who arrive by public transport rather than by car. And the breakfast buffet now consists entirely of regional organic products.


Reitterer’s commitment has drawn a lot of attention to her hotel since it opened. It features in reports throughout the German-speaking region, and it still draws praise today. It has also won various prizes, including the Austrian National Award for Tourism, the Environmental Award of the City of Vienna and the prestigious Climate Protection Award, a public prize offered by the Austrian Broadcasting Corporation.

Very happy guests

More important than any award, however, is guest satisfaction. And that’s high, if the excellent ratings that Reitterer’s business receives on platforms like TripAdvisor can be believed. The most recent comments guests have posted also leave no doubt: “They really seem to take their efforts to offer quality food and energy sustainability seriously,” writes one guest. And another says, “The hotel and its underlying ‘green strategy’ continue to be a winner.” Clearly, the investment in a sustainable building pays off not only financially but also in long-lasting success.

  • 94 m² photovoltaic system
  • 130 m² solar heating system
  • Concrete core activation
  • Desigo building automation system with PXC controllers and web operation


Picture credits: Boutique Hotel Stadthalle

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