Expanding Solar Coverage on Buildings with Load Constraints

How can the energy efficiency of buildings be improved when conventional photovoltaic panels cannot be installed due to limited roof load capacity? One solution is the use of lightweight and flexible solar modules. We have already implemented this technology on two properties within our portfolio.

Enhancing energy efficiency and reducing operating costs are long-standing priorities within the sustainability strategy of ZDR Investments. Photovoltaic systems (PV) are one of the key tools that help us achieve these goals. However, during project preparation we sometimes encounter technical constraints — for example, roofs with insufficient load-bearing capacity for conventional glass PV panels.

When Conventional Panels Are Not an Option

Before installing a PV system, a structural assessment of the roof is always required to determine whether it can safely support the weight of standard modules. In several cases, feasibility studies revealed that certain buildings in our portfolio have lower roof load capacity, making conventional panels unsuitable. We therefore sought an alternative that would allow us to use the available roof space effectively while maintaining the necessary electrical output.

Lightweight and Flexible Polymer-Based Panels

In cooperation with our suppliers, we selected an innovative solution: lightweight and flexible photovoltaic panels made from composite polymer material that replaces the traditional glass front sheet.

• Up to 70% lower weight while delivering the same performance
• High durability and resistance to weather conditions
• Suitable for roofs with limited load-bearing capacity
  

For example, a panel measuring 2100 × 1100 × 2 mm with an output of 430 W weighs only 7–8 kg, which is considerably less than a conventional glass module. Another advantage is rapid installation using adhesive techniques, which avoids roof penetration and eliminates the need for additional mounting structures.

In 2025, we completed and commissioned the first two PV systems using this technology. The installation at the Rakovník retail park has a total capacity of 49.92 kWp, while the system at Flex-space Plzeň reaches 318.2 kWp. These projects clearly demonstrate the potential of lightweight modules to unlock solar capacity on buildings where standard installations would not be structurally feasible.

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Maximising Solar Potential Across Our Portfolio

Thanks to these innovations, we can increase the number of buildings equipped with PV systems across our portfolio, including those where installation was previously not possible. Lightweight polymer modules help reduce reliance on fossil fuels, lower energy expenses for tenants and building operations, improve the energy self-sufficiency of retail parks and industrial facilities, and strengthen the long-term sustainability of property management.