New passive project in Luxembourg: how to size a pellet boiler from the design brief
Practical guide for architects: sizing, silo, buffer tank and Klimabonus 2026 to integrate a pellet boiler from the design stage of a new project.
What power do you need for a new passive or BBC project?
A BBC or passive home in Luxembourg typically drops to just 20-40 W/m² of heat load. The pellet boiler must be sized correctly, not oversized: too much power kills seasonal efficiency and shortens equipment life.
A dynamic thermal simulation (DTS) at the design brief stage lets you quantify the real load and target 6-12 kW for a single-family home, 15-25 kW for a small collective.
- BBC/passive: 20-40 W/m²
- Single-family home: 6-12 kW
- Small collective (5-10 units): 15-25 kW
- Modulation range: ideally 1:3 or higher
- Compliant with EU Regulation 2015/1189 (EcoDesign) and EN 303-5 Class 5
Silo and buffer tank: how to integrate them into the plan?
The pellet silo drives delivery logistics: allow 3-5 m³ of useful volume for a single home, enough for a full heating season. Place it near a truck-accessible façade with an auger or vacuum feed to the boiler.
A buffer tank is mandatory for modern pellet boilers: it lengthens combustion cycles, lifts seasonal efficiency and triggers the +15 % Klimabonus bonus.
- Tank volume: 20-30 L/kW (≥ 500 L for a home, ≥ 1,000 L for a collective)
- Silo-to-boiler distance: < 15 m with auger, < 20 m with vacuum
- Plan an inspection hatch of 600 x 600 mm
- Level sensor for automatic delivery scheduling
- ENplus A1 pellets: less dust, higher net calorific value
Seasonal efficiency and maintenance: what to plan early
A well-sized pellet boiler paired with a buffer tank reaches 85-92 % seasonal efficiency. Architects must plan a ventilated plant room with access for chimney sweeping and ash disposal (about a 20 L bag per tonne burned).
On maintenance: one professional service per year is usually enough for residential use; a maintenance contract is often required by the commune to validate the Klimabonus.
- Chimney sweep: 1-2 times/year
- Ash: ~1-2 % of pellet weight burned
- Annual service contract: strongly recommended
- Clearance to heat exchanger and burner: ≥ 60 cm
- Tatano manufacturer warranty: confirm conditions at the quote stage
Klimabonus 2026 and municipal aids: what's the net cost?
The Klimabonus 2026 explicitly funds pellet boilers (not logs or wood chips). A single-family home can receive up to €8,000 (€4,000 without replacing an old installation), a collective €6,000/unit capped at €40,000, a heating network €6,000 capped at €24,000.
A +15 % bonus is added when a buffer tank is installed, plus a flat €1,000 when the boiler is paired with solar thermal. Communal top-ups vary and can stack with the state aid.
- Single-family home: up to €8,000 (with replacement)
- Collective: €6,000/unit (cap €40,000)
- Buffer tank bonus: +15 %
- Solar thermal bonus: +€1,000
- Communal aids: variable, check via the Klima-Agence simulator
Sources
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