The Zwhatt district in Regensdorf, near Zurich, shows façade PV at work on a meaningful scale. The site, which hosted the 2025 Solar Building Symposium organised by Swissolar, is one of Switzerland's larger urban development areas, combining residential and commercial space. "Our approach is guided by sustainability principles for construction and building operation," says Martin Schriener, who heads project development at Pensimo Management.
Pensimo is developing around 650 apartments and 15,000 square metres of commercial space by 2030. Photovoltaic systems are central to the energy concept and will be deployed on the rooftops and façades. The two planned residential towers, each around 75 metres high, will use façade-integrated PV. “We need to produce electricity wherever possible to achieve near climate-neutral building operation,” Schriener says. “For high-rises, roof space alone is insufficient.”
Germany – colour films mark a step change in PV aesthetics
Splitting PV from the façade
The aim is to reach around 40 percent energy autonomy in operation, with the two towers illustrating different approaches to integrating photovoltaics into the façade. In high-rise H1, built using timber construction on a concrete base, PV elements are integrated as sun-shading components. The façade wraps around the building in red metal cladding, allowing floor-to-ceiling glazing behind the modules.
"We deliberately separated the solar power generation from the façade to allow for larger windows and ensure fire safety," says Marlene Hübel of Bolthauser Architekten. The modules are mounted on a steel support structure, with spacing designed to limit fire propagation between floors. Although not required, fire tests were carried out to confirm the concept, and wind and snow loads are distributed across the mounting system.
Yield and detailing
Bifacial modules are installed above each window. Changes in cell formats during the project required adjustments to the façade layout, but improved efficiency offsets the potential losses. The modules are angled gently towards the façade, which supports rainwater drainage and reduces the risk of ice formation, a relevant factor at this height. Detailing at this level also affects maintenance and long-term performance.
A second tower in the development takes a different route, drawing on local building forms. The façade incorporates angled elements beneath the windows that function as both design features and solar canopies, referencing the steep roofs of buildings in the surrounding Furttal valley. Material selection has shifted in the course of planning. Early concepts using coloured or structured modules were set aside due to performance and consistency issues. Ultimately, the developers opted for standard monocrystalline modules, as these were deemed to balance output, cost and appearance.
Lightweight modules unlock low-load roofs and facades
Operational experience
Experience from existing projects highlights the importance of operation and maintenance. The Solaris building on Lake Zurich, which has been fully clad with photovoltaic modules since 2017, has delivered sufficient energy to cover its consumption. Nevertheless, yields have fallen short of forecasts due to inverter and optimiser failures, a defective battery and installation issues. Such cases underline the need for ongoing monitoring as well as system redundancy. “A well-stocked spare parts inventory and thorough monitoring are vital for long-term reliability,” says Jamal Degen of Planeco, who worked on the Grosspeter Tower in Basel. At all times, redundant inverters and regular cleaning help keep operation stable.
From façade to system
Façade-integrated photovoltaics expand the surface available for generation, but they also bring added complexity. Fire safety, structural integration and maintenance access all need careful attention alongside energy yield. Today, solar façades are moving from optional add-on to integral building layer – no longer attached to architecture, but designed into it from the outset, where planning, operation and aesthetics matter as much as the modules. (TF)
