Your syndic partner for boiler-room renovation

Technology options for a co-ownership in 2026

A boiler-room renovation in an apartment building is not a simple boiler swap — the technical choices affect efficiency, comfort quality, the regulatory context and financing over 15-25 years. These are the 4 most common configurations we install:

Option 1: Cascade of condensing gas boilers

The classic and still most common upgrade: three to five Buderus GB212 condensing boilers coupled in cascade control. The cascade self-regulates: at low demand one boiler runs on low modulation, at peak demand the others join in rotation. Benefits: proven tech, short install time (1-2 weeks), relatively low cost (€25,000-€50,000 for buildings of 10-20 flats). Drawbacks: gas dependency, 21% VAT since 01/07/2025, limited future-proofing. For buildings where a full heat-pump switch is not (yet) feasible, this remains the realistic choice.

Option 2: Collective heat pump (air/water)

A large air/water heat pump (40-200 kW) feeds the collective grid. Required: sufficient roof space for outdoor units (about 2-3 m² per 20 kW), electrical supply upgraded to 3-phase 250-500A, and a sufficiently insulated building. Benefits: heavily reduced CO2 (-70% vs. gas), no VAT shock, future-proof, optionally combined with a smaller peak boiler as backup. Investment: €60,000-€150,000 for mid-sized buildings, but with collective subsidies often €10,000-€30,000 recovered.

Option 3: Collective geothermal heat pump

Vertical boreholes (80-150 metres deep, 2-6 bores depending on scale) with a central heat pump in the boiler room. Highest efficiency (SCOP 4.5-5.5), completely silent for residents, 50+ year lifespan for the boreholes. Drawbacks: highest upfront investment (€100,000-€250,000), requires drilling permit, install time 4-8 weeks. Ideal for full renovations or new-build apartment buildings.

Option 4: Hybrid cascade (gas + collective heat pump)

The "safe" compromise for co-ownerships wanting to transition without investing everything at once: a heat pump covers 60-75% of annual use, a matched gas-boiler cascade handles peak cold. Benefits: presentable at AGM (lower risk), phased execution, immediate efficiency and CO2 gains. Drawbacks: slightly lower SCOP than pure HP, still gas-dependent for part of the year.

How we work with syndics and AGMs

A boiler-room renovation is rarely a pure technical decision — it is a democratic decision where, as syndic, you must persuade the co-owners. Our approach is specifically designed to support you, not push our own agenda.

Step 1: Technical audit (free, 2-3 hours)

We visit the existing boiler room, inventory the emitter system (radiators, underfloor, DHW production), measure the current annual use and identify bottlenecks. We talk with the syndic and possibly one or two owners to get context on past decisions.

Step 2: Scenario document for the AGM (2-3 weeks)

You receive a 10-15 page technical and financial analysis with:

• Current state (installation, efficiency, CO2, consumption)
• 2-3 scenarios for the renovation (usually: condens, hybrid, full HP)
• For each scenario: technical spec, cost, schedule, lifespan, annual savings, CO2 impact
• Subsidy overview (Prime Renolution, collective Mijn VerbouwPremie, EPC Label premium)
• Allocation key: cost per apartment (based on share or actual consumption)
• Comparison table for fast AGM decision-making

Step 3: AGM support

On request our project manager attends your AGM to answer technical questions. We stay neutral — we present the scenarios and let the owners decide. We also provide communication templates (resident letter, FAQ) you can use before and after the decision.

Step 4: Execution with minimal disruption

The old boiler stays active while we build the new installation. Changeover happens in a short window (1-2 days), usually in spring or late summer when heating demand is low. If needed we rent a temporary mobile boiler. Residents are informed 2 weeks in advance with a concrete schedule.

Step 5: Handover and follow-up

Full subsidy-application file: inspection certificate, CE-certificates, photos, invoices with correct VAT structure. First-year consumption monitoring to verify that the theoretical efficiency gain is actually realised. Annual maintenance via our OGP contract.

Individual metering: why and how?

Until recently, heating costs in co-ownerships were split by share (tantièmes). Simple but unfair: a family heating to 18 °C paid the same as one heating to 22 °C in the same building. Individual metering fixes this.

Technical options

• Calorimeters (splitters): a small electronic device (5 × 5 cm) attached to each radiator that measures the temperature difference between water and room. Read remotely annually (radio or wired). Typical cost: €30-€50 per radiator, install €20-€40 per unit.
• Per-flat heat meters: an ultrasonic meter on the riser entering each apartment. More accurate than calorimeters but requires an accessible meter location. Cost: €250-€450 per flat.
• Hybrid: heat meter on DHW + calorimeters on radiators. Best value for buildings with central DHW production.

Legal framework

Since 2019, individual metering is required for new-build and major renovations in all three Belgian regions. For existing buildings it is recommended but not mandatory — unless a boiler-room renovation takes place and it is technically feasible.

Expected effects

Studies show residents heat 15-25% less on average after installing individual metering — simply because cost becomes visible. For the co-ownership: lower shared bill, fairer split, and higher per-flat resale value (apartments with separate meters typically sell 2-4% higher).

Retrofit in existing buildings

Yes, possible in most cases. We renovated a 24-apartment building in Schaerbeek in 2024: from tantièmes system to individual calorimeters on all 216 radiators, in 3 days per stairwell (residents scheduled, 30-45 min access per flat). Total cost: €18,500 for 24 flats, so €770 per apartment. Payback typically 3-5 years for larger flats.

References from our region

FAQ — co-ownerships and syndics