BNK/BNG Certification

A streamlined certification system for residential buildings, focused on subsidy-compliant implementation and construction quality. It is one of the accredited supporting systems for the QNG seal, providing a path to KfW subsidy conditions while keeping administrative effort to a minimum.

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BNK-BNG-Zertifizierung

The System at a Glance

Rating Levels
Good · Very Good · Excellent
Areas of Application
BNK – Sustainable Small Residential Building Assessment System (1 to 5 units) · BNG – Sustainable Building Assessment System (more than 5 units)
System Provider and Certification Body
System provider: Bau-Institut für Ressourceneffizientes und Nachhaltiges Bauen (BiRN) GmbH

Testing body: BiRN conformity assessment
Validity
unlimited
Einordnung

Classification

A streamlined certification system for residential buildings. It verifies whether funding requirements and construction quality standards are met, without aiming to provide a comprehensive ESG assessment. Those seeking both should choose a different system.

A distinction is made based on building size: BNK covers small residential buildings with one to five units, while BNG covers everything above that. In combination with the QNG seal, this provides access to KfW funding.

Grant security with a low barrier to entry

Low barrier

Compared to other accredited system providers, the effort is lower, while the security of funding remains the same. This is the key argument for this system.

Access to KfW funding

Combined with the QNG seal, your residential property becomes eligible for funding according to the requirements of the Kreditanstalt für Wiederaufbau (KfW). The calculation behind this can be found on the QNG website.

Basis for depreciation

The certificate is a prerequisite for the declining-balance depreciation in residential construction and can be combined with the special depreciation for new rental housing under Section 7 (5a) of the German Income Tax Act (EStG).

Serial construction without individual effort

BiRN evaluates construction series and model ranges based on prototype designs. For developers of prefabricated and modular homes, as well as serial construction methods, this significantly reduces the effort required per building.
Wann ein anderes System besser passt

When another system is a better fit

The market does not recognize this process as equivalent to the DGNB. It is less comprehensive regarding indoor environmental quality, long-term value, biodiversity, and documentation, providing future buyers with less information about the building's quality. If you need these indicators because you are selling early or targeting institutional buyers, please talk to us about the DGNB.

The system also reaches its limits when dealing with multiple geometrically separate structures: ensemble certifications are not provided for, and each individual section requires its own process.

The path to certification

Project check

Is BNK or BNG a good fit, which rating level is realistic, and what are the funding benefits?

Strategy

Goals, priorities, and roadmap to BiRN registration

Measures

Life cycle assessments, material ecological audits, dismantling and recycling concepts, support during planning and construction

Certificate

Documentation up to BiRN conformity assessment

Duration

Preliminary design to completion

including 6 months to 2 years for planning and procurement, 1-2 years for construction
 
at least 18 months, up to 4 years

Completion to certification

 
3-4 months

What we handle

Auditing throughout the entire process
Life Cycle Assessments (LCA)
Material ecological assessments
Dismantling and recycling concepts
Project registration with BiRN, including QNG requirements
Coordination of documentation and liaison with the inspection body

Frequently Asked Questions

How do we register for a combined BNK/BNG and QNG certification?

An energy efficiency expert applies for the KfW loan on behalf of the client. In parallel, the BiRN auditor registers the project with BiRN for the QNG requirements. One person can hold both roles, but need not.

Does the market recognize this process as equivalent to the DGNB standard?

No. It is less comprehensive when it comes to criteria such as interior quality, long-term value, biodiversity, and documentation, which means future buyers learn less about the quality of the building.

Can we certify multiple buildings as a single ensemble?

No. Buildings that are not physically connected each need their own process. But there is another option: BiRN rates building series on the basis of type samples. You rate similar buildings through one sample, which saves much work for prefabricated, standard and serial construction.