Additional costs for efficiency house and passive house standards

The German Effizienzhaus levels describe annual primary energy demand relative to a reference building defined in the Buildings Energy Act. An efficiency house 55 needs at most 55 per cent, an efficiency house 40 at most 40 per cent of the reference value.

Here lies the first pitfall. The statutory minimum for new buildings is itself 55 per cent of the reference building. The phrase "additional cost for efficiency house 55 against the statutory standard" is therefore misleading in new build: the funding level demands further evidence beyond primary energy demand, particularly on the building envelope and on excluding fossil heat generators. The additional cost arises from those extra requirements, not from the primary energy figure alone.

In existing buildings the system works differently: there the same levels describe a retrofit target and represent a genuine step from the starting condition. The levels are therefore not comparable between new build and existing stock.

Studies of the additional cost of moving to the efficiency house 40 standard produce values between roughly 1.0 and 19.9 per cent. That range is not the result of varying care but has two identifiable causes.

The data basis. What matters is which starting standard the calculation runs from. Comparing against an older statutory standard yields a far larger step than comparing against today's minimum.

The plant strategy chosen. A building reaching the standard through a very good envelope costs differently from one reaching it through elaborate plant. Both satisfy the same level.

Rule for cost estimating: a premium figure without a stated baseline standard and technical concept is unusable. Both belong in the same line as the percentage.

For a detached house of around 150 square metres of habitable area, premiums of the order of 12,000 to 20,000 euros are quoted for level 55, and considerably higher amounts with correspondingly wide scatter for level 40. The dispersion of published figures is considerable here too.

Passive house figures diverge particularly widely, because that standard is not a funding level but a separate certification system with different evidence quantities. Comparison with the funding levels is therefore not admissible.

The building envelope carries the largest share: greater insulation thicknesses at external wall, roof and ground slab, more careful thermal bridge detailing, and demonstrated airtightness.

Windows are the most sensitive area. They typically make up 15 to 25 per cent of the envelope, and the higher levels demand thermal transmittance values reachable only with triple glazing and matching frame systems.

Ventilation. Above a certain airtightness, mechanical ventilation with heat recovery becomes effectively necessary, not as a comfort feature but to prevent moisture damage.

The heat generator. Fossil main heat generators are excluded at the funding levels. In practice heat pumps or renewable district heating are used.

Evidence effort. Energy consultancy, calculations, airtightness testing and site supervision fall in cost group 700 and are precisely not inside the building cost benchmark. Where an additional sustainability certificate is sought, a dedicated assessor is added whose fee runs into four or five figures.

That last point is routinely overlooked because it does not sit within construction cost. The system is set out in the article on ancillary construction costs under KG 700.

Funding for energy-efficient new build runs through subsidised loans with credit ceilings per dwelling, higher where an additional sustainability certificate is obtained. Interest rates in spring 2026 sat well below market level.

For a viability appraisal three quantities must be kept apart. They are routinely conflated in comparison calculations.

1. The construction premium, which is fixed and sits in cost groups 300 and 400
2. The interest advantage, arising over the term and dependent on market rates
3. The running cost saving, arising over the service life

Only the first belongs in the cost estimate. The second and third belong in the viability appraisal. Mixing them is the commonest error on this topic: an interest advantage does not reduce construction cost, it reduces financing cost.

Note too that the programme landscape is in motion. A time limit to mid-2026 was published for funding level 55 in new build, and the total funding envelope for buildings is capped. A cost estimate premised on a particular grant must therefore carry an explicit reservation.

• Detached house construction costs per m² of gross floor area
• Energy retrofit: costs by element
• Ancillary construction costs under KG 700
• Residential construction costs in Germany
• German building regulations and standards