20-Story Building Takes Passive House to New Heights

An office tower shows even a massive building with a glass façade can achieve Passive House certification—in Austria, at least.

A 20-story office building in Vienna recently became the world’s first high-rise building to be certified under the international Passive House standard. With a glass façade 262 feet (80 m) high and office spaces for 900, the RHW.2 building—home to the Austrian Raiffeisen-Holding Group—could be a counterpoint to those arguing that all-glass buildings popular with developers are inherently wasteful (see “Rethinking the All-Glass Building”).

Andreas Benzing, board member of New York Passive House, which is affiliated with the Passive House Institute, told EBN that it did not surprise him that an all-glass building could meet the stringent energy and air-leakage criteria. “The amount of glass does not really matter as long as you are meeting your heating and cooling loads. Besides,” he added, “we are no longer dealing with your grandfather’s curtainwall.”

Highly efficient mechanical systems and optimized shading equipment reduced the RHW.2 building’s heating and cooling demand by 80% compared to that of conventional high-rise buildings, according to a press release. The project description explains that triple glazing of the glass façade prevents heat loss and promotes solar gain, but occupants can also open windows on the upper floors and take advantage of cool breezes from the nearby Danube River.

Although Benzing thinks a similar project would be feasible in the U.S., he admitted that Austria’s cooler, less humid climate must have made it easier to increase glazing while managing the greater burden on cooling loads.