Bygningsreglementets vejledning om efterisolering – Danish Building Regulations Guidance on Retrofit Insulation
Issued by BUILD for the Bolig- og Planstyrelsen (Danish Authority for Social Services and Housing), this guidance document details the requirements for retrofit insulation during the renovation of existing buildings in Denmark. It took effect on July 1, 2022, replacing previous guidance regarding profitable constructions. The document functions within the framework of Bygningsreglementet 2018 (BR18), specifically focusing on sections § 274 and § 279, which govern energy consumption and climate impact through thermal efficiency improvements.
The regulatory scope encompasses a wide range of building components, including exterior walls, cellar walls, lofts, roof constructions, and floors. It provides a structured methodology for determining when insulation is mandatory based on the nature of the work, categorized into Reparation (Repair), Ombygning (Renovation/Conversion), and Udskiftning (Replacement). Technical annexes, such as Bilag 1, provide specific examples for typical building parts like massive brick walls, timber-framed walls, and various floor types, while Bilag 2 offers a standardized scheme for calculating economic profitability.
Professional users can reference this document to determine maximum U-values and linear loss coefficients required for compliance, as well as the specific conditions under which technical or architectural exemptions may be granted by municipal authorities.
Classification of Renovation Activities
The building regulations distinguish between three levels of intervention, each triggering different requirements for thermal insulation:
- Reparation: Minor changes such as replacing a few roof tiles or patch-repairing a facade. These do not trigger requirements for profitable energy savings.
- Ombygning: Renovation of a building component where the existing material layer is replaced but structural elements remain. Insulation is mandatory if the measure is deemed rentabel (profitable).
- Udskiftning: Full replacement where a component is demolished and rebuilt. In these cases, insulation to the levels specified in § 279 is mandatory, regardless of profitability.
Maximum Thermal Transmittance (U-values) and Linear Loss
Section § 279 defines the maximum allowed heat loss coefficients for retrofitted components. If full compliance is not profitable, insulation must be performed to the highest level that remains profitable.
- Exterior and cellar walls: 0.18 W/m²K (typically requiring 200 mm of insulation).
- Loft and roof constructions: 0.12 W/m²K (typically requiring 300 mm of insulation).
- Ground floors and crawl spaces: 0.10 W/m²K (typically requiring 350 mm of insulation).
- Foundations (Linear loss): 0.12 W/mK.
- Joints (Windows/Doors): 0.03 W/mK.
Profitability Assessment Methodology
For renovation categorized as Ombygning, the measure is considered profitable if the investment is paid back within 75% of the expected lifespan of the insulation. The guidance sets the standard lifespan at 40 years.
- Simple Payback Period: The investment must be recovered within 30 years (75% of 40 years).
- Calculation formula: (Annual energy price × annual heat savings) × 40 years × 75%.
- Included costs: Only the additional costs (merudgifter) directly related to the insulation work and its immediate secondary tasks (e.g., moving a walkway in the loft) are included.
Exemptions and Documentation Responsibilities
Exceptions to the insulation requirements are permitted under specific moisture-related, technical, or aesthetic conditions.
- Moisture risks: Insulation can be avoided if it creates a risk of internal condensation or mold, particularly in internal insulation of heavy walls.
- Architectural preservation: Requirements may be waived if the building's architecture or basic geometry must be preserved.
- Documentation: Property owners are responsible for documenting compliance. This may include a profitability calculation or proof that the project follows the standard examples in Bilag 1.
Frequently Asked Questions
What is the standard payback period for profitable insulation in Denmark?
An insulation measure is considered profitable if the investment is repaid within 30 years, which represents 75% of the standard 40-year lifespan defined in the building regulations.
Does replacing a few roof tiles require extra insulation?
No, minor repairs like replacing a few roof tiles or individual facade boards are categorized as Reparation and do not trigger mandatory energy saving requirements.
What is the maximum U-value for retrofitting an exterior wall?
The maximum U-value requirement is 0.18 W/m²K, which generally corresponds to a total insulation thickness of 200 mm when using standard materials.
Are there exemptions for internal insulation of masonry walls?
Yes, requirements can be waived if internal insulation poses a significant risk of condensation or mold, as is often the case with heavy masonry structures.
Is a building permit required for retrofit insulation?
Generally, no permit is required unless the exterior insulation on a single-family house adds more than 25 cm to the thickness, which affects the calculated floor area.
What is the required U-value for loft and roof constructions?
The requirement is a maximum U-value of 0.12 W/m²K, which typically necessitates a total insulation thickness of 300 mm.
