Building physics, energy performance and sustainability
Building physics, energy performance and sustainability
This domain tests how Luxembourg’s performance rules interact with real physics: insulation, airtightness, thermal bridges, moisture and ventilation. The exam rewards candidates who can explain why a compliant U-value can still produce a failing building.
Core rules
- The energy-performance law and the 2021 grand-ducal regulation set requirements for new buildings and major renovations, moving toward nearly zero-energy buildings. The CPE (certificat de performance énergétique) communicates the calculated rating.
- LENOZ is Luxembourg’s sustainability certification for housing; Klimabonus supports eligible energy renovations. Subsidy eligibility depends on the measure and the existing building, not on a verbal promise.
- Design must control the sequence: continuous insulation, minimised thermal bridges, an airtight layer, controlled ventilation and moisture-safe construction. Airtightness without adequate ventilation raises indoor humidity and mould risk.
Worked example
A roof is insulated at ceiling level but the eaves are left unsealed and the vapour barrier is interrupted at the wall junction. The U-value of the field may pass, but the junction becomes a thermal bridge and a condensation risk. The fix is a continuous insulated and airtight line, with a ventilated cold roof or a properly placed vapour control layer.
Traps
Confusing R and U; quoting manufacturer lambda values without ageing or moisture correction; ignoring junctions in the CPE model; and installing mechanical ventilation without commissioning or filters.