"The most environmentally friendly building is the one that already exists," he remains convinced today. By preserving the reinforced concrete structure alone, he has been able to save 416,000 kilograms of CO2, he has calculated. Innovative energy technology has added a minus of 317,000 kilograms of CO2 since the building opened in 2014.

Hotel manager Voit grew up spending time with his grandmother in the kitchen of the Casselsruhe restaurant. Later, he helped build today's Dorint Hotel, and brought daughter Christina Voit on board for his new project. The fact that she is an art historian can be spotted in many corners of the V-Hotel. Both of them focused on sustainability from the very beginning.

In keeping with that, the Voits wanted to preserve the greenery around it as much as possible. "We only had to cut down two trees on the entire property," says Harald Voit, who built a “passive house” 25 years ago. "I have always been interested in the subject. For many, the rethinking is just starting now."

Because only the shell of the old youth work center remained, the Voits were able to install many things that are not visible at first glance, such as the cost and CO2-saving hot water supply. It takes the shortest route directly to the 45 rooms, so that only about 200 liters need to be kept warm in the water circuit, instead of about 1800 liters as in a conventional water circuit. In the meeting rooms, air meters indicate when it is time to ventilate so that the windows are not left open all the time. Photovoltaics, a combined heat and power unit and buffer storage are also part of the equipment, as is a smart energy management system that always calculates the most favorable energy source.

"Sustainability must also be economical," says Harald Voit. That's why, for example, the special bread on the breakfast buffet is wrapped in thin foil. Otherwise, it would have to be thrown away every day. Some of the furniture was repurposed, such as the Voits' old kitchen bench, which now stands in the breakfast room, along with lamps from a ship.

The artist Thomas Baumgärtel, known as the banana sprayer, designed the staircase and incorporated graffiti from the remains of the old building. The artwork is as unique as it is long-lasting. Photos of Bonn as capital city by Camillo Fischer hang in the hallways, "a nice reference to Bonn," finds Christina Voit. Its colorful mix of design and vintage is a bit reminiscent of the 25 Hours Hotel in Berlin, and the guests like it too.

Right next to the hotel, the Voits built three tree houses named “Rotkäppchen” (“Little Red Riding Hood”), “Waldgeist (“Forest Spirit”) and “Rostlaube” (something like “Rusty Bucket”), anticipating the tiny house trend. These separate accommodations weren't only popular during the pandemic, they remain so. Families come from Bonn to spend a weekend nestled in fragrant pine walls.

This year, the V-Hotel was the winner in the sustainability category of the Ludwig 2022, the medium-sized business award of the Bonn/Rhein-Sieg Chamber of Industry and Commerce. But the Voits are not resting on their laurels, they are planning to expand the solar power system. Printing is now done only on grass paper, if at all. "We are also working on the small adjusting screws," says Christina Voit.

Orig. text: Bettina Köhl

Translation: ck