Legal Framework (GModG)
The Building Modernisation Act (Gebäudemodernisierungsgesetz, GModG) – until July 2026 the Building Energy Act (Gebäudeenergiegesetz, GEG) – forms the legal basis for energy-efficient construction and renovation in Germany. Here you will find the most important information on the current situation.
- Legal requirements
- Current version since 29 July 2026
- Focus on energy efficiency
All services are carried out in accordance with the Building Modernisation Act (Gebäudemodernisierungsgesetz, GModG – formerly the Building Energy Act, GEG) and the standards it specifies – in particular DIN V 18599 or DIN/TS 18599, DIN 4108 and DIN EN 12831-1 with DIN/TS 12831-1.
What does the GModG regulate?
The Building Energy Act (Gebäudeenergiegesetz, GEG) came into force on 1 November 2020 and merged the previous regulations – the Energy Saving Ordinance (EnEV), the Energy Saving Act (EnEG) and the Renewable Energies Heat Act (Erneuerbare-Energien-Wärmegesetz, EEWärmeG) – into a single law. Following the reform of 23 July 2026, it has been called the Building Modernisation Act (Gebäudemodernisierungsgesetz, GModG) since 29 July 2026.
The GModG regulates the energy requirements for new and existing buildings, the installation of heating systems and the energy performance certificate. The so-called 65 per cent rule has been abolished, as have the obligation to seek advice before installing a gas or oil heating system and the ban on operating boilers after 30 years. Owners therefore once again have more freedom in choosing their heating – however, newly installed gas and oil heating systems must use gradually increasing shares of biomethane, bio-oil or hydrogen from 2029.
The aim of the law remains to make a significant contribution to achieving the national climate protection targets: the energy demand of buildings is to fall and the share of renewable energy is to rise. Further parts of the reform – including those on the energy performance certificate and on new buildings – will come into force in stages from 1 January 2027.
What applies when?
- 29 July 2026
New heating rules
The 65 per cent rule, the obligation to seek advice before installing a gas or oil heating system and the obligation to replace boilers after 30 years no longer apply. The so-called “bio ladder” (Bio-Treppe) applies to newly installed gas and oil heating systems in existing buildings.
- 1 January 2027
Energy certificate & new builds
Energy performance certificates go digital and contain new information, for example on greenhouse gas emissions. For residential buildings, owners can choose between a demand-based and a consumption-based certificate. Calculations follow DIN/TS 18599:2025-10.
- 1 January 2029
First stage of the bio ladder
New gas and oil heating systems must generate at least 10% of their heat from biomethane, bio-oil or hydrogen – rising to 15% from 2030, 30% from 2035 and 60% from 2040.
- 1 January 2030
Zero-emission buildings
All new buildings must be built as zero-emission buildings. They state their life-cycle greenhouse gas emissions in the energy performance certificate – large new buildings over 1,000 m² from as early as 2028.
Excerpts from the legal text
Version in force since 29 July 2026 (BGBl. 2026 I Nr. 226). From 1 January 2027, § 11 refers to DIN 4108-2: 2026-05 and DIN 4108-3: 2024-03. Unofficial translation – only the German text is legally binding.
§ 1 Purpose and aim
(1)The aim of this Act is to make a significant contribution to achieving the national climate protection targets. This is to be achieved through economically viable, socially acceptable and efficiency-enhancing measures to save greenhouse gas emissions, and through the increasing use of renewable energy or unavoidable waste heat for the energy supply of buildings.
§ 11 Minimum thermal insulation
(1)In a building to be constructed, building components that separate it from the outside air, the ground or parts of the building with significantly lower internal temperatures shall be designed in such a way that the requirements for minimum thermal insulation in accordance with DIN 4108-2: 2013-02 and DIN 4108-3: 2018-10 are met.
§ 12 Thermal bridges
A building shall be constructed in such a way that the influence of structural thermal bridges on the annual heating demand is kept as low as possible in accordance with the generally recognised rules of technology and the measures that are economically justifiable in each individual case.
§ 13 Airtightness
A building shall be constructed in such a way that the heat-transferring envelope, including the joints, is permanently sealed airtight in accordance with the generally recognised rules of technology. Public-law provisions on the minimum air exchange required for the purposes of health and heating remain unaffected.
§ 43 Installation of a heating system fired by gas, heating oil or liquefied petroleum gas
(1)If a heating system fired by gas, heating oil or liquefied petroleum gas is newly installed in an existing building after 29 July 2026, the owner of the building shall ensure that at least 10 per cent of the heat provided by the system from 1 January 2029, at least 15 per cent from 1 January 2030, at least 30 per cent from 1 January 2035 and at least 60 per cent from 1 January 2040 is generated from biomethane, bio-oil, biogenic liquefied petroleum gas, or green, blue, orange or turquoise hydrogen, including derivatives produced from them.
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As a certified energy efficiency expert, I will be happy to advise you on all questions relating to the Building Modernisation Act and to support you in meeting its requirements.
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