Pellets or wood chips for a new collective housing project in Luxembourg: what the architect must lock in at sketch stage

Pellets or wood chips for a new collective housing project in Luxembourg?

For a new multi-unit building in Luxembourg, pellets win almost every time: only wood pellets qualify for Klimabonus 2026. Wood chips remain technically viable, but with no direct state subsidy and heavier urban logistics. This first decision drives the technical room layout and the delivery scheme, so it belongs in the sketch stage, not after the permit.

Three criteria that tip the balance from day one

Grant, logistics, and technical room: the three angles the architect must raise at the design meeting. Pellets tick all three boxes for a 5-30 unit building, urban or peri-urban.

• Grant: up to €6,000 per unit (cap €40,000) + +15% with a buffer tank + €1,000 with solar thermal.
• Logistics: ENplus A1 pellets delivered by blower truck into a sealed silo (15-40 m³ depending on size); wood chips need a tipper truck, a conveyor, and a much larger bunker.
• Technical room: a pellet silo fits in roughly 2.5-3 m × 2.5 m × 2.5 m for 10 tonnes — compatible with a basement car park; wood chips usually require a 30-60 m³ bunker.

What the architect must lock in at sketch stage

The silo + buffer tank pairing is decided on paper, not on site. Three items to settle with the MEP engineer before the building permit.

• Blower-truck access: a fill port in the façade or kerbside, max 12-15 m from the silo, with a DN 100 duct and a connection shaft.
• Buffer tank: 200 L/kW minimum (e.g. 10,000 L for 50 kW), Class C insulation, flow/return sensors.
• Safety: CO/CO2 detector in the silo room, high and low vents, accessible inspection hatch.

Spec and service plan: the four lines to lock down

A biomass spec for a new collective building must lock down four requirements with no wiggle room.

• EcoDesign EU 2015/1189: seasonal efficiency ≥ 75%, PM ≤ 60 mg/Nm³, NOx ≤ 200 mg/Nm³, CO ≤ 700 mg/Nm³ (at 10% O2).
• EN 303-5 Class 5: standard requirement for solid fuel boilers ≤ 500 kW.
• ENplus A1 pellets: 6 mm diameter, moisture ≤ 10%, net calorific value ≥ 4.6 kWh/kg, batch-by-batch certification.
• Service contract: annual, chimney sweep 1×/year, heat exchanger cleaning 1×/year, silo and auger checks.