New collective build in Luxembourg: pellets, plant room and silo — design methodology
Practical guide for architects and developers: integrate pellet boiler, silo, buffer tank and Klimabonus 2026 from the design phase of a new multi-unit project.
Pellets or wood chips in collective housing — what works in Luxembourg?
In new collective projects, the question arises: pellets or chips? In Luxembourg, only pellet boilers qualify for Klimabonus 2026. Wood chips may work technically, but without state subsidy.
- Pellets: blower-truck delivery, ENplus A1 certification, 1–2 deliveries per year
- Wood chips: +30–50% larger storage, manual or pneumatic handling, no Klimabonus grant
- Collective: central pellet boiler (15–50 kW) or per-unit boilers — logistics decides
Plant room and silo: what dimensions to allow?
The plant room must be fixed before the building permit. Boiler, buffer tank and silo need space that schematic plans often miss if not integrated from the start.
- Minimum 8–12 m² floor area for boiler + buffer + maintenance zone (1 m clear in front of door)
- Silo: 2.40 m ceiling height, 60–80 cm width for fill hose delivery
- Buried silo: 4–8 m³ for 4–8 dwellings — fix before excavation works
- Flue: 150–200 mm diameter, 3–5 m length, no 90° bends
Buffer tank and Klimabonus: how to maximise the grant?
The buffer tank is not just a technical choice: it triggers a +15% Klimabonus bonus. With solar thermal, +€1,000 flat rate applies. In collective housing: €6,000 per dwelling, €40,000 cap.
- Buffer: 20–30 litres per kW installed (BBC: 50–80 L for 5 kW)
- Klimabonus collective: up to €6,000/dwelling, €40,000 cap
- Municipal grants: variable, stackable — simulator at aides.klima-agence.lu
- Solar thermal: +€1,000 flat rate, one tank for two energy sources
Seasonal efficiency and maintenance: what to plan for?
A BBC building needs 3–5 kW, not 12 kW. An oversized boiler cycles too often and drags down seasonal efficiency. EN 303-5 Class 5 and ENplus A1 pellets are the baseline. Maintenance access and flue cleaning must be built into the plans.
- Annual service: 1 visit, €150–250 — 80 cm clearance in front of boiler required
- Seasonal efficiency: ≥ 90% with EN 303-5 Class 5, modulation 30–100%
- EcoDesign 2015/1189: new model must be compliant — declaration in project file
- Flue cleaning: external access or via roof — cannot be added later
Sources
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