09 January 2025
On 1 January 2025, Section 32a of the Lower Saxony Building Regulations, adopted in December 2023, comes into force with stricter requirements for mandatory solar roofs.The solar installation requirement applies to all buildings constructed from 2025 onwards with a roof area of at least 50m2.
Solar installations must then cover 50% of the total roof area, provided this does not conflict with another obligation under public law and is technically feasible and economically viable.
A solar thermal system does not provide an exemption from this requirement. However, the area it occupies is deducted from the area required for solar installations.
Installation is technically unfeasible on thatched or glass roofs and on existing buildings with insufficient load-bearing capacity.
Systems that do not pay for themselves within a typical service life of 20 years are considered economically unviable. Depending on electricity demand, this does not necessarily rule out north-facing roofs!
It is advisable to have a solar adviser carry out a site-specific analysis. Our solar advisers use PV-Sol or Aurora to prepare an analysis that includes a financial viability calculation. The PV system is sized according to the anticipated energy demand. Feeding too much surplus electricity into the grid reduces financial viability. The analysis is included in the system documentation.
The client commissioning the building is responsible for compliance.
The solar roof requirement has applied to newly built commercial buildings since 2023 and to all new public buildings since 2024. However, all new buildings have already been required to be constructed in such a way that a photovoltaic system can be retrofitted without additional structural reinforcement. Since the beginning of 2025, the solar installation requirement has also applied to all new publicly accessible car parks and parking decks with more than 25 parking spaces.
North Rhine-Westphalia has a regulation similar to that in Lower Saxony. Section 42a of its state building regulations stipulates that a solar system must be installed if the building application was submitted after 1 January 2025. This applies where the building's usable floor area exceeds 50 square metres. A solar installation requirement for the renovation of commercial roofs is also planned for 2026.