Where the extra cost comes from
| Item | Extra cost against standard | Why |
|---|---|---|
| Envelope insulation | EUR 25 - 45/m2 | Greater thicknesses, systematic thermal bridge correction |
| Windows | EUR 60 - 120/m2 of glazed area | Triple glazing, thermally broken frames, sealed installation |
| Mechanical ventilation with heat recovery | EUR 4,000 - 9,000 lump sum | A system absent from current construction |
| Air-tightness and blower door test | EUR 2,000 - 5,000 | Taping, membranes, instrumental testing |
| Design and certification | EUR 4,000 - 10,000 | Dynamic calculation, detail verification, certification process |
On the 120 m2 house of the reference article, the total extra cost typically sits between EUR 22,000 and 34,000. Note the least intuitive item: the cost of the heating system falls, because the reduced thermal load allows smaller generators and in some cases the elimination of traditional distribution systems. Part of the envelope's extra cost thus self-finances through the services.
The payback
The calculation must cover three components, not the energy bill alone. The three act over different time horizons.
Energy savings. A passive house consumes a fraction of a code-compliant house for heating: on a 120 m2 house, the annual energy spending differential generally sits between EUR 800 and 1,500 depending on climate zone and energy prices. With an extra cost of EUR 28,000, payback on energy alone falls between 19 and 35 years: a long horizon that does not justify the choice on its own.
Property value. Here the calculation changes. Energy rating has entered market valuation criteria and European building performance rules: a highly efficient property holds value while inefficient stock depreciates and faces upgrade obligations. On this front the extra cost is more an insurance premium than a yielding investment.
Comfort. Not monetisable but decisive in real decisions: uniform temperature, no draughts, constant air quality thanks to controlled ventilation, silence. It is the reason clients cite most often after living in the building.
Where not to save
Three errors cancel the passive investment and should be known before signing. Cutting on the windows while keeping heavy insulation: the windows' thermal bridge becomes the bottleneck of the whole envelope. Skipping the blower door test: without instrumental verification, the designed air-tightness remains a hypothesis, and defects are discovered through mould. Entrusting execution to untrained crews: in passive construction the quality of installation matters more than the quality of materials, and the details (taping, insulation continuity, junctions) decide the outcome.
Note: the figures shown are 2026 orders of magnitude for the Italian market, for guidance only. Payback calculations depend on climate zone, energy prices and project characteristics.