GEG compliance documentation

GEG compliance documentation confirms that a building meets the statutory requirements for energy efficiency and thermal insulation. The related German term Wärmeschutznachweis refers specifically to documentation of the building’s thermal performance.

Depending on the building and the project, a GEG calculation may consider annual primary energy demand, the energy performance of the building envelope, summer thermal protection, and building systems, among other factors.

Current information:

On 29 July 2026, the German Building Energy Act (Gebäudeenergiegesetz, GEG) was renamed the German Building Modernisation Act (Gebäudemodernisierungsgesetz, GModG) and amended. The established term “GEG compliance documentation” continues to be used in practice and in search queries. Legally, it now refers to documentation demonstrating compliance with the requirements of the GModG.

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Why is GEG compliance documentation important?

• Documenting statutory requirements: The documentation shows whether a building meets the applicable energy requirements.
• Supporting reliable planning: The building envelope and technical systems are assessed as one integrated energy system.
• Making energy efficiency transparent: Key figures such as primary energy demand and transmission heat loss are calculated transparently.
• Supporting construction and refurbishment projects: Different forms of documentation or declarations may be required depending on the project.
• Creating reliable building data: Geometry, component areas, and technical properties provide the basis for a reliable calculation.

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What does GEG compliance documentation assess?

The requirements that must be demonstrated depend on factors including the type of building, whether the project concerns a new or existing building, and the specific measure involved.

Annual primary energy demand

Annual primary energy demand accounts not only for the energy required within the building but also for upstream processes involved in extracting, converting, and supplying the energy sources used.

For residential buildings, this may include the energy required for:

• Heating
• Domestic hot water
• Ventilation
• Cooling

For non-residential buildings, installed lighting is also taken into account, among other factors.

For new residential buildings, the permitted annual primary energy demand is determined using a reference building.

Thermal performance of the building envelope

Another important component is the energy performance of the building envelope.

For residential buildings, the specific transmission heat loss H'ₜ plays a particularly important role. It describes heat losses through the building envelope in relation to the heat-transferring envelope area.

Relevant components include:

• External walls
• Roof
• Windows
• External doors
• Ground floor slab
• Basement ceilings
• Thermal bridges

Summer thermal protection

Buildings must also be designed to limit excessive indoor temperatures during the summer.

Relevant factors include:

• Window areas
• Orientation
• Glazing
• Solar shading
• Thermal mass
• Room geometry

Building systems

Technical building systems also influence the energy assessment.

Depending on the building, the following systems may be considered:

• Heating system
• Domestic hot water system
• Ventilation
• Cooling
• Control systems
• Renewable energy systems
• Lighting in non-residential buildings

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What data is required?

The quality of energy compliance documentation depends significantly on the input data used.

Building geometry

Required information may include:

• Floor plans
• Building dimensions
• Room heights
• Usable floor areas
• External wall areas
• Window and door areas
• Roof areas
• Floor and ceiling areas
• Building orientation

Outdated or incomplete plans can create uncertainty, particularly in existing buildings.

Building envelope data

Information about the construction and energy-related properties of thermally relevant building components is required.

This may include:

• U-values
• Building materials
• Insulation
• Window performance
• Thermal bridges
• Component build-ups

Building systems data

Information about the building’s technical systems is also required, including:

• Heat generation
• Heat distribution
• Domestic hot water
• Ventilation
• Cooling
• Controls
• Renewable energy systems

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How is GEG compliance documentation prepared in practice?

1. Capture the building data

The building’s geometry, components, and technical systems are recorded first.

For existing buildings, a digital building survey can provide up-to-date data on floor areas and room geometry.

2. Define the thermal building envelope

The components that enclose the heated or cooled part of the building are identified.

This classification is essential for the subsequent energy balance.

3. Assess the energy performance of building components

External walls, the roof, windows, doors, and other components are described based on their thermal properties.

4. Record the building systems

Heating, domestic hot water, ventilation, cooling, and other technical systems are incorporated into the energy assessment.

5. Calculate the energy balance

The relevant energy performance indicators are calculated using the building data and compared with the statutory requirements.

6. Document the results

The calculations and required information are documented. The documents that must be submitted to the authorities also depend on the enforcement rules of the relevant German federal state.

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GEG compliance documentation for new buildings

Under the current legal framework, documentation for new residential buildings covers requirements relating in particular to:

• Overall energy performance
• Thermal performance of the building envelope
• Heating systems
• Summer thermal protection

The permitted annual primary energy demand is determined using a reference building with the same geometry, usable floor area, and orientation.

DIN V 18599 is currently used in particular for calculating the energy balance of residential buildings.

Under certain conditions, a simplified model building procedure may also be used for residential buildings.

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Compliance documentation for existing buildings

For existing buildings, the documentation requirements depend heavily on the specific measure.

If external building components are renovated, replaced, or installed for the first time, requirements may apply to their thermal transmittance.

This may affect:

• External walls
• Windows
• External doors
• Roof areas
• Ceilings
• Floor areas

For certain works, the contractors carrying them out must confirm compliance with the statutory requirements by issuing a contractor’s declaration.

For more extensive alterations, an overall energy assessment of the building may also be relevant.

There is therefore no single standardised form of “GEG compliance documentation” for every measure in an existing building. The decisive factors are the type and scope of the project and the applicable federal and state-level requirements.

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GEG compliance documentation and digital building data

Especially for existing buildings, a substantial part of the work takes place before the energy calculation itself: the necessary building information must first be captured completely and reliably.

A possible digital workflow is:

Digital building survey → floor plans and geometry data → building envelope model → component areas and thermal properties → energy balance → compliance documentation

Precise geometry data is particularly useful when determining:

• External wall areas
• Window and door areas
• Roof and floor areas
• Room volumes
• Building orientation
• The thermal building envelope

Digital geometry data does not replace the building physics assessment. U-values, component build-ups, and technical systems must still be determined by qualified professionals.

However, it reduces uncertainty in one of the calculation’s essential foundations: the building’s actual geometry.

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GEG compliance documentation vs. energy performance certificate

Both documents relate to a building’s energy performance, but they serve different purposes.

GEG compliance documentation or documentation under the GModG:

• Demonstrates compliance with statutory energy requirements
• Relates to a specific project or measure
• Is particularly relevant to new construction and certain building alterations
• Contains detailed calculations and supporting documentation

Energy performance certificate:

• Provides information about a building’s energy performance
• Is required particularly when a building is sold, rented, or leased
• Can be issued as either a calculated energy demand certificate or a measured energy consumption certificate
• Is primarily intended to provide information and enable comparisons

An energy performance certificate does not therefore automatically replace statutory energy compliance documentation.

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GEG compliance documentation vs. heating load calculation

GEG compliance documentation and a heating load calculation also serve different purposes.

Energy compliance documentation:

• Assesses compliance with statutory energy requirements
• Considers annual primary energy demand and thermal performance, among other factors
• Calculates the building’s energy balance using defined usage profiles and boundary conditions

Heating load calculation:

• Determines the required heating output
• Is performed for the building and individual rooms
• Is used in particular to size heat generators and heat emitters

The two calculations use some of the same building data, but they are not equivalent.

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GEG compliance documentation and transmission heat loss

Transmission heat loss describes heat losses through the thermal building envelope.

For new residential buildings, the specific transmission heat loss H'ₜ is an important indicator for assessing the thermal performance of the building envelope.

Its calculation depends on data including:

• The size of the component areas
• U-values
• Thermal bridges
• The thermal building envelope

There is therefore a direct relationship between precise building geometry and reliable energy compliance documentation.

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What is the declaration of compliance?

The declaration of compliance confirms to the competent authority that the statutory energy requirements have been met.

It is particularly relevant to new buildings and, in certain cases, alterations to existing buildings.

The relevant federal state legislation may specify who is authorised to issue the declaration, which supporting documents must be submitted, and when the declaration is due.

In practice, the term “GEG compliance documentation” therefore often refers to the underlying energy calculations and documents, while the declaration of compliance may serve as the formal instrument confirming that the requirements have been met.

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Current legal framework: GEG becomes GModG

On 29 July 2026, the former German Building Energy Act (Gebäudeenergiegesetz, GEG) was renamed the German Building Modernisation Act (Gebäudemodernisierungsgesetz, GModG) and amended in several areas.

The term GEG remains relevant to existing content, planning documents, and search queries. However, new publications should make it clear that the GModG is now the current legal basis.

For this glossary entry, the following distinction is therefore appropriate:

GEG compliance documentation = established search and industry term

Compliance documentation under the GModG = current legal classification

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Common mistakes and misunderstandings

• Treating GEG compliance documentation and an energy performance certificate as the same document: They have different functions and use cases.
• Considering only the building envelope: Building systems and other energy requirements may also be relevant.
• Using outdated plans: Incorrect areas affect the energy calculation.
• Simplifying the building geometry: Actual component areas and the building’s orientation are relevant to the energy balance.
• Confusing heating load with energy compliance: A heating load calculation does not replace statutory energy compliance documentation.
• Treating existing and new buildings in the same way: Requirements differ depending on the building and the measure.
• Considering federal law without state law: Details relating to enforcement, declarations of compliance, and authorisation to issue documents are partly regulated by the German federal states.
• Continuing to refer exclusively to the GEG as the current legislation: Since 29 July 2026, the legislation has been called the German Building Modernisation Act (GModG).

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