Improving your energy rating by two classes: where to start

The energy performance certificate affects comfort, bills, letting and resale. Improving the rating by two classes is often possible, provided the work is carried out in the right order.

Understanding the energy performance certificate classes

The certificate rates the house according to two criteria: its primary energy consumption and its greenhouse gas emissions, per square metre per year. The weaker of the two results determines the class. The thresholds are as follows:

• A: up to 70 kWh and 6 kg of CO2;
• B: up to 110 kWh and 11 kg;
• C: up to 180 kWh and 30 kg;
• D: up to 250 kWh and 50 kg;
• E: up to 330 kWh and 70 kg;
• F: up to 420 kWh and 100 kg;
• G: above that.

Since 1 January 2026, the calculation treats electricity more favourably (a coefficient of 1.9 instead of 2.3), which reduces the displayed consumption of electrically heated houses by around 17%. The thresholds themselves have not changed.

Why two classes make a big difference

The energy performance certificate now determines whether a home can be let:

When selling, an energy audit has been compulsory for houses rated F and G since 2023, and for houses rated E since 1 January 2025. Finally, improving the rating by at least two classes is the condition for obtaining MaPrimeRénov' for a whole-house renovation.

Starting from an audit

An energy audit identifies where the house loses heat and proposes costed work scenarios, with the number of classes each one gains. It is compulsory to sell a house rated E, F or G, and required for a grant-funded whole-house renovation. It is the best basis for avoiding unnecessary work.

According to Ademe, the French environment and energy agency, in an old uninsulated house heat escapes first through:

Next come the windows (10 to 15%), the ground floors (7 to 10%) and thermal bridges (5 to 10%). The order of work that follows stems from this.

1. The roof and the loft

Heat rises: a poorly insulated roof is often the main source of heat loss. Insulating an unconverted or converted loft is generally the most cost-effective measure.

2. The walls

Whether from the inside or the outside, wall insulation greatly reduces heat loss. External wall insulation deals with thermal bridges and preserves the living space, but it alters the façade and requires a prior declaration. On a stone house, insulation materials that allow the wall to breathe are chosen.

3. Windows, doors and floors

High-performance, airtight windows limit heat loss and draughts. Insulating the ground floor, above a crawl space or a cellar, also noticeably improves comfort.

4. Ventilation

A better-insulated, more airtight house must be well ventilated, otherwise damp sets in. Suitable mechanical ventilation is an integral part of an energy renovation.

5. Heating and hot water

Once the needs have been reduced, a heating system sized for the renovated house is chosen: heat pump, high-efficiency boiler or wood-burning stove, depending on the case. Doing this before the insulation often leads to an oversized appliance.

Heating also weighs on the rating through greenhouse gas emissions. A house heated with oil can be rated F because of its emissions, even after insulation. Replacing oil with a lower-emission energy source is often part of the programme to gain two classes; it is in fact compulsory, in a detached house, to obtain MaPrimeRénov' for a whole-house renovation.

Mistakes to avoid

• Starting with the windows alone: they account for only a limited share of heat loss, and are almost never enough to gain two classes.
• Changing the heating before insulating: the appliance will be too powerful for the renovated house.
• Insulating without ventilating: damp sets in, with condensation and mould.
• Using a vapour-tight insulation material on an old stone wall: moisture remains trapped in the wall.
• Carrying out the work piecemeal without an overall plan: each measure can hinder the next, for example windows fitted before external wall insulation.

A coherent programme rather than a list of measures

Gaining two classes rarely comes down to a single measure. We coordinate all the work in the right order, with a single point of contact, in line with the audit and the available grants.

Sources : Arrêté du 31 mars 2021 relatif au diagnostic de performance énergétique (seuils des classes A à G) · Arrêté publié au Journal officiel du 26 août 2025 (coefficient de conversion de l’électricité du DPE, applicable au 1er janvier 2026) · Code de la construction et de l’habitation, article L. 126-28-1 (audit énergétique à la vente) · Loi n° 2021-1104 du 22 août 2021 « Climat et résilience » (calendrier des logements indécents E, F et G) · Ademe, guide « Isoler sa maison » (répartition des pertes de chaleur d’une maison non isolée) · france-renov.gouv.fr