Effizienzhaus 40, 55 and 70 – what is behind them
Not a funding programme, but the calculation every funding programme hangs on. We explain how the levels are derived and what they mean for design and execution in timber construction.
What an Effizienzhaus level actually is
An Effizienzhaus is neither a building type nor a funding programme — it is the outcome of a calculation. For every building a standardised reference building is defined: same geometry, same orientation, same floor area, but with a legally fixed specification for envelope and building services. Your planned building is then calculated against that reference, and the number after the word Effizienzhaus states what percentage of the reference building's annual primary energy demand your design may consume at most. Effizienzhaus 40 therefore means 40 percent, Effizienzhaus 55 means 55 percent. A second requirement applies in parallel to transmission heat loss — the heat escaping through walls, roof, floor slab and windows. Only when both figures are met is the level actually reached. Because every federal funding programme builds on these levels, the expert's calculation decides which funding your project can access at all.
Who the levels matter to
The Effizienzhaus levels concern anyone building new, retrofitting an existing building or buying a newly completed property. In new construction they determine whether funding flows at all and how much; in refurbishment they additionally set a target that defines the scope of work. Even without any funding intention the level is a useful figure: it condenses thermal protection, building services and thermal bridging into a single number, which makes competing offers comparable. For clients planning with a timber construction firm it is the shared language between design, expert and financing.
Which level unlocks which funding
In new construction, Effizienzhaus level 40 is the decisive threshold: it is the prerequisite for the Klimafreundliches Wohngebäude levels in the Klimafreundlicher Neubau programme (KfW 297/298) and for the family loan KfW 300. Adding the QNG sustainability certificate raises the available loan amounts. Effizienzhaus 55 was reintroduced in Klimafreundlicher Neubau for a limited period and is tied to a capped budget. Effizienzhaus 70 no longer plays a role in new-build funding, but it does in refurbishment: existing buildings have their own levels within the federal BEG funding, on different terms.
What the calculation is made of
Annual primary energy demand is compared with that of a standardised reference building; the level number states the permitted percentage.
The second metric is transmission heat loss through the building envelope, for which each level has its own permitted percentage.
Component U-values and a thermal bridging surcharge enter the balance; carefully designed junction details reduce that surcharge.
Airtightness of the envelope is verified with a blower door test and enters the calculation as the air change rate n50.
Building services count too: heat generator, hot water, ventilation and any cooling directly affect the primary energy demand.
The calculation and the verification are produced by an energy efficiency expert from the federal list, using the applicable standard method.
From target level to verification
Agree the target level up front
We discuss which Effizienzhaus level suits your project, your plot and your budget, and what funding it unlocks. That conversation determines whether you plan towards Effizienzhaus 55 or Effizienzhaus 40.
Calculation and comparison of variants
The energy efficiency expert calculates variants: wall build-up, insulation thicknesses, windows, heat generator and ventilation. Only this balance shows which level the design really reaches and what getting there costs.
Apply before work begins
The expert issues the pre-application confirmation, with which you apply for funding through your financing institution. The application must be in place before any supply or works contract is signed.
Execution and airtightness test
We build wall, roof and junction details to the verified design. The airtight layer is installed and checked with a blower door test while corrections are still possible without major effort or cost.
Confirmation and proof of use
After completion the energy efficiency expert confirms the level achieved. You submit the proof of use to the funding body within the deadline — only then is any funding finally secured.
Why timber insulates better at the same wall thickness
At equal wall thickness, timber frame construction achieves better U-values than a monolithic solid wall. The reason is thermal conductivity: insulation in the stud bays — mineral wool, wood fibre or cellulose — sits well below even highly insulating clay blocks, which have to carry load and insulate at once. In timber construction the studs take the load and insulation fills the gap. The honest qualification: studs conduct heat better than insulation, so the timber fraction of the wall area enters the U-value calculation and reduces the advantage without cancelling it. Extra insulation layers can be added without the wall becoming disproportionately thick. Specific build-ups are fixed with your expert.
Services we carry out for this
We carry out the construction work. Evidence and applications go through independent experts.
Our role — and the expert's role
An Effizienzhaus level is not awarded on site; it is calculated and verified. That is the job of an independent energy efficiency expert from the federal list — only they may issue the pre-application and post-completion confirmations. MAIER & PARTNER INNOVATIVBAU is the timber construction contractor: we translate the verified design into the actual building, execute insulation layers, the airtight layer and junction details so the calculated values genuinely materialise, and provide the construction records for inspection. We cannot warrant calculated values or funding approvals.
Effizienzhaus levels at KfWFrequently asked questions about funding
Is an Effizienzhaus 40 the same thing as a KfW 40 house?
The same thing is meant, but KfW 40 house is colloquial shorthand from earlier generations of the programmes. The official term for the metric is Effizienzhaus level. Because both the requirements and the programme structures have changed repeatedly over the years, older information found online should never be applied to a current project unchecked.
What exactly does the number after Effizienzhaus mean?
It states the permitted share of the corresponding reference building's annual primary energy demand. Effizienzhaus 55 may therefore reach at most 55 percent of that demand, Effizienzhaus 40 at most 40 percent. The smaller the number, the stricter the requirement. In addition, each level has its own limit for transmission heat loss that must be met.
Does the Gebäudemodernisierungsgesetz change the Effizienzhaus levels?
The Gebäudemodernisierungsgesetz was passed in July 2026, replaces the Gebäudeenergiegesetz and enters into force in stages. The reference building method remains as the calculation approach, but the reference buildings themselves have been amended. What that means for your project is calculated by the expert under the version in force at the time.
Does an Effizienzhaus always need a ventilation system?
A system as such is not prescribed, but a ventilation concept for the airtight envelope is. In practice the route to the stricter levels almost always runs through mechanical ventilation with heat recovery, because primary energy demand can otherwise hardly be pushed low enough. Which solution works is shown by your expert's calculation.
Clarify the target level for your project
Before deciding on funding, you should know which Effizienzhaus level your design realistically reaches. We assess that for your timber project and set out the next steps.
Status: July 2026. Requirements and funding conditions can change at short notice — what binds is the building energy law in force and the current KfW programme information.
All information on funding programmes is provided to the best of our knowledge, without guarantee and without any claim to completeness. It does not replace legal, tax or energy consulting. Terms and budgets change constantly; only KfW, BAFA, NBank and the responsible funding bodies are binding. Applications must generally be filed before work begins.