KfW 40: Requirements at a Glance
The Efficiency House 40 standard is one of the most demanding new-build targets. This guide explains the key values for primary energy demand and heat loss. It distinguishes the technical standard from the funding and explains the 40-NH label. That way you understand the KfW 40 requirements for 2026.
The Efficiency House 40 standard is among the most demanding targets in new construction – and is a precondition for the most attractive funding programmes. But what exactly must a KfW 40 house meet technically? This guide explains the central key figures on primary energy demand and heat losses, distinguishes the technical standard from the funding and shows which additional requirements apply for the “40-NH” label.
Short answer: A KfW 40 house may at its core consume only around 40 percent of the primary energy demand of a legally defined reference building, and the transmission heat loss escaping through the building envelope may amount to at most about 55 percent of the reference value. These two key figures are the decisive target quantities; for the addition “40-NH”, the Sustainable Building Quality Seal (QNG) is added in 2026.
What does the KfW 40 standard actually mean?
Short answer: The number 40 denotes the Efficiency House standard: compared to a legally defined reference building, a KfW 40 house consumes only about 40 percent in primary energy. The lower the number, the more efficient the building. The standard therefore does not describe a particular component, but the overall energy result from insulation, plant technology and airtightness.
The Efficiency House standard is the common language of the legislator and the development bank. What a KfW 40 house looks like in everyday life and what distinguishes it from the legal minimum standard is shown by the house-type page KfW 40 house. Which funding programmes are tied to this standard is explained by our overview of KfW in house building.
Which technical key figures must a KfW 40 house achieve?
Short answer: Two key figures are decisive: the annual primary energy demand, which may amount to at most around 40 percent of the reference building, and the transmission heat loss of the building envelope, which must lie at about 55 percent of the reference value. Both are demonstrated by calculation in the energy performance certificate. Complementarily, an airtight envelope and, as a rule, a ventilation system with heat recovery are needed.
Core requirements for an Efficiency House 40 (target values)
| Key figure | Requirement | Reference |
|---|---|---|
| Primary energy demand | ≈ 40 % of the reference value | total annual energy demand |
| Transmission heat loss | ≈ 55 % of the reference value | heat loss of the envelope |
| Airtightness | proof via blower door | tight building envelope |
| Ventilation | usually with heat recovery | controlled domestic ventilation |
| Proof | energy certificate / confirmation | by an energy efficiency expert |
The calculation is handled by a qualified energy efficiency expert; the values are interconnected and can only be achieved in the overall concept. How the standard fits into the legal framework is closely linked to the Buildings Energy Act (GEG).
Compare providers capable of KfW 40
Not every provider achieves the standard 40 as standard. Request offers free of charge and with no obligation and have the Efficiency House standard confirmed in writing.
What is the difference between KfW 40 and KfW 40-NH?
Short answer: “40-NH” stands for sustainability: in addition to the energy key figures of the Efficiency House 40, the building must meet the Sustainable Building Quality Seal (QNG). In doing so, ecological, economic and socio-cultural criteria are assessed over the entire life cycle and certified by an accredited body. The NH standard is thus more demanding and a precondition for higher funding levels.
- The Efficiency House 40 meets the core energy key figures (primary energy, heat loss).
- 40-NH additionally requires the QNG seal with sustainability criteria.
- The QNG assesses the entire life cycle, not only the energy demand.
- Certification is carried out by an accredited, independent body.
- Higher funding levels as a rule require the NH proof.
Standard and funding are two different things
The Efficiency House standard describes the technology, the funding the financing. Whether and to what amount a KfW 40 or 40-NH house is funded in 2026 depends on the funding programme in force at the time. Check the current conditions in the guide KfW funding 2026.
How are the KfW 40 standard and funding connected?
Short answer: The structural standard is the entry ticket to the funding – but not identical with it. Anyone who achieves the Efficiency House standard 40 or 40-NH and provides all the proofs can apply for subsidised loans or grants. The specific programmes, amounts and deadlines change regularly, so you should always prepare the funding application before the start of construction and with an energy efficiency expert.
An overview of the current programmes is given by the guides KfW funding 2026 and funding at a glance. What characterises an energy-efficient prefabricated house overall is explained by the guide sustainable prefabricated house.
How is the KfW 40 standard achieved in practice?
Short answer: The standard is achieved through the interplay of several measures: strong insulation of the roof, wall and base slab, triple-glazed windows, an airtight envelope, a ventilation system with heat recovery and efficient heating technology – usually a heat pump, often combined with photovoltaics. No single component suffices on its own; the proof is carried out via the overall balance.
Prefabricated houses often achieve the standard 40 as standard, because the prefabricated walls are highly insulated from the outset. Nonetheless, have the Efficiency House level achieved confirmed in writing in the building description and calculate the budget in advance with the cost calculator.
Conclusion: two key figures, one overall concept
The KfW 40 standard stands and falls with two key figures – around 40 percent primary energy demand and about 55 percent transmission heat loss of the reference building – which can only be achieved in the overall energy concept. The addition 40-NH raises the bar further via the QNG seal. Anyone who aims for the standard cleanly separates technology and funding and has both demonstrated by experts. Neutral programme information is provided by the KfW.
Compare a KfW 40 house for free
Have offers drawn up by providers capable of KfW 40 and match the efficiency standard, fittings and prices – free of charge and with no obligation.
What does your dream house really cost?
Request suitable quotes from vetted manufacturers for free and compare the prices per square metre for your construction project.
Compare house prices nowImportant questions briefly explained
The most common price questions around KfW 40 – answered concisely by the Prefabricated House editorial team (as of 2026).
