How to Improve Your EPC Score in Brussels

In Brussels, 28.5% of residential properties still carry a label G — the worst energy performance rating. The average primary energy consumption stands at 254 kWh/m²/year, far above the target needed to reach label D or better. With the 2033 deadline approaching, improving your EPC score is no longer just about value — it's a legal obligation. This guide tells you which works have the greatest impact, in what order to tackle them, and how to fund them.

Understanding Your EPC Score

The EPC score (called the "Ew" score in Brussels) measures the primary energy consumption of a property in kWh/m²/year. The lower the score, the better the label:

• Label A: ≤ 45 kWh/m²/year — nearly zero-energy building
• Label B: 46–95 kWh/m²/year — very good performance
• Label C: 96–150 kWh/m²/year — good performance
• Label D: 151–250 kWh/m²/year — minimum 2033 target
• Label E: 251–340 kWh/m²/year — below target
• Label F: 341–450 kWh/m²/year — poor performance
• Label G: > 450 kWh/m²/year — very poor performance

The EPC score is determined by the combination of the building envelope (insulation of roof, walls, floors, glazing) and the technical installations (heating, hot water, ventilation, solar). Improving any of these elements reduces the score and can move you up one or more labels.

High-Impact Works

The following works have the greatest impact on your EPC score. The order given here is the one most commonly recommended by Brussels EPC certifiers, but the optimal order depends on your specific property type and layout.

1. Roof and Floor Insulation

Heat loss through the roof can account for 25–30% of a building's total energy loss. Insulating the roof (from the inside via the attic, or from the outside) is consistently the single most effective intervention. Similarly, insulating the ground floor (above a cold basement or crawl space) prevents significant heat loss that is invisible to occupants but directly measured by the EPC.

• Typical impact: reduction of 20–35% in primary energy consumption
• Recommended insulation thickness: ≥ 14 cm (roof), ≥ 10 cm (floor)

2. Wall Insulation

Walls represent 20–25% of total heat loss in older Brussels properties. External insulation (EWI) is the most effective option as it eliminates thermal bridges, but it requires planning permission. Internal insulation is simpler but reduces living space slightly and must be done carefully to avoid condensation issues.

• Typical impact: reduction of 15–25% in primary energy consumption
• Recommended insulation values: U-value ≤ 0.24 W/m²K

3. Heating System Upgrade

Replacing an old gas boiler (efficiency 60–70%) with a high-efficiency condensing boiler (efficiency >95%) or a heat pump (COP 3–4) directly reduces primary energy consumption. The EPC calculation accounts for the heating system's efficiency, so an upgrade has an immediate and measurable impact on your score.

• Condensing boiler: reduction of 10–20% in primary energy consumption
• Air-to-water heat pump: can reduce heating energy by 50–70%

4. Window Replacement

Windows (including balcony doors) account for 15–20% of heat loss in typical Brussels apartments. Replacing single or old double glazing with modern high-performance double or triple glazing (U-value ≤ 1.1 W/m²K) significantly reduces heat loss and can move you up one label.

• Typical impact: reduction of 10–15% in primary energy consumption
• Bonus: improved acoustic comfort and reduced condensation on cold glazing

Summary Table: High-Impact Works

Work	Impact on EPC	Estimated cost (€)	Renolution grant
Roof insulation	Very high (−20–35%)	€3,000 – €15,000	Yes (check current conditions)
Floor insulation	High (−10–20%)	€2,000 – €8,000	Yes
Wall insulation (external)	High (−15–25%)	€8,000 – €25,000	Yes
Heating system upgrade	High (−10–70%)	€3,000 – €15,000	Yes (heat pump especially)
Window replacement (HR glazing)	Medium (−10–15%)	€5,000 – €20,000	Yes

Moderate-Impact Works

These works have a smaller individual impact on the EPC score but are valuable as part of a comprehensive renovation strategy:

• Mechanical ventilation with heat recovery (VMC double-flux): required for new builds and major renovations. Improves air quality and reduces ventilation heat losses.
• Solar thermal panels: for domestic hot water. Covers 40–60% of annual hot water needs and directly reduces the EPC's hot water contribution.
• Photovoltaic solar panels (PV): produce renewable electricity and can be counted in the EPC calculation, but the Brussels methodology limits the credit. Most effective as a complement to a well-insulated building.
• Air tightness improvement: sealing gaps around windows, doors, electrical sockets and pipe penetrations. Low cost, immediate impact on comfort and energy bills.
• Smart thermostats and heating controls: reduce heating waste without modifying the building fabric. Impact on EPC is limited but reduces real-world energy bills.

Renolution Grants 2026

The Renolution programme offers financial support for energy renovation in Brussels. Key principles:

• Grants are available for both owner-occupiers and landlords.
• Grant rates vary depending on income level (higher grants for lower-income households).
• Works must be carried out by a registered contractor.
• Application must be made before starting the works (or at most at the start, depending on the measure).
• Certain measures require an energy audit prior to application.

Which Works to Start With Depending on Your Budget

Getting Recertified After Renovation

After carrying out significant renovation works, you should book a new EPC assessment to obtain an updated certificate reflecting the improved energy performance. This is important for three reasons:

1. Legal compliance: for sale or rental, the EPC must reflect the current state of the property. Carrying out works without updating the certificate means your improved performance is not officially recognised.
2. Property value: a better energy label increases the property's market value and rental appeal. Buyers and tenants increasingly factor the EPC label into their decisions.
3. Renolution compliance: some grants require a post-renovation EPC to confirm that the improvements meet the required standards.

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Frequently Asked Questions

Last updated: April 2026