Germany implements new Building Modernization Act

The Building Modernization Act (GModG), published in the Federal Law Gazette on July 28, 2026, has begun replacing central provisions of the previous Building Energy Act (GEG). While public debate has focused on the removal of the 65% renewable energy requirement for heating systems, the new law introduces extensive changes regarding heating installations, new constructions, building automation, energy efficiency requirements, solar mandates, rental law, and combined heat and power (CHP).

In addition to heating regulations, legal requirements for the airtightness of the building envelope remain in effect for both new builds and renovated existing buildings. To ensure energy efficiency, new constructions must be built so that the building envelope remains permanently airtight. Technical compliance is often verified through a blower-door test, which measures the n50 value (the air exchange rate at a pressure difference of 50 pascals). Documenting airtightness is frequently a prerequisite for energy efficiency subsidies and required for certain energetic calculations.