Permit file for a biomass boiler in Luxembourg: the documents that prove EcoDesign and EN 303-5 Class 5

EcoDesign and EN 303-5 Class 5: what actually needs to be proven in the file?

Two European rules govern any new biomass boiler: EU Regulation 2015/1189 (EcoDesign), in force since 2020, sets minimum efficiency and emission thresholds for any boiler ≤ 500 kW sold in the EU. EN 303-5 Class 5 goes further: efficiency ≥ 90 % and low emissions (CO, NOx, OGC, particulates) measured under standard test conditions.

For a permit in Luxembourg, the administration does not accept a generic label. It wants proof that the chosen boiler reaches at least Class 5, not just the baseline EcoDesign level. Practically, the architect must submit three documents: the manufacturer's CE declaration of conformity, the EN 303-5 Class 5 test report (less than 5 years old), and the technical sheet with the guaranteed emission values.

The 5 documents that speed up permit review

A complete technical file avoids back-and-forth with the commune and the Klima-Agence. Here is the list to include from the sketch design stage:

• CE declaration of conformity (EU 2015/1189) issued by the manufacturer
• EN 303-5 Class 5 test report (accredited laboratory, < 5 years)
• Technical sheet: output, efficiency, emissions (CO, NOx, OGC, particulates) at 10 % and 100 % load
• Hydraulic schematic + buffer tank volume (≥ 20 l/kW recommended)
• Fuel quality commitment: ENplus A1 pellets

Pellets only: what Klimabonus 2026 changes in the technical choice

Klimabonus 2026 is reserved for wood pellet boilers: log or chip boilers are not eligible. The amount reaches up to €8,000 for a single-family home (with replacement of an old installation) or €4,000 without replacement, and €6,000 per unit in multi-family buildings, capped at €40,000.

The permit file can mention this choice at the design stage. Two technical levers open bonuses: a buffer tank adds +15 % to the grant, and a coupling with solar thermal adds €1,000 flat. Local communal aids may stack on top, varying by commune, and the official simulator can confirm the total.

Three design decisions that lock in compliance before submission

Three choices made at the drawing stage close the compliance gap without surprise at handover:

• Silo location: truck delivery access, safety distance < 10 m, volume sized for winter autonomy (about 6-8 m³ for 100 m²).
• Boiler room: high and low ventilation, direct combustion air inlet, maintenance clearance ≥ 60 cm around the boiler.
• Flue gas evacuation: flue compliant with EN 14471 or masonry, with limited deviations (≤ 2 bends at 90°).