You are a tenant, your home shows a fine C or D rating on the DPE (Diagnostic de Performance Énergétique — the French Energy Performance Certificate / EPC), and yet, from the very first heatwave, the flat becomes an oven: 30°C at 10pm, impossible to sleep, weeks on end above the discomfort threshold. Millions of people in France live this every summer — and many wrongly believe their energy class was protecting them.
The summer of 2003 caused around 15,000 excess deaths in France, according to Santé publique France (the French public health agency); 2022, the deadliest since, caused nearly 2,816. With global warming, these episodes are becoming the norm. The DPE, for its part, mainly measures winter heating. Its summer comfort indicator does exist, but it is currently purely qualitative and does not affect the A-to-G rating. Here is what it is really worth, what changes by 2028, and what you can demand — or do — when your home cooks you in summer.
A good DPE does not guarantee a cool home in summer — the summer comfort indicator appears on the second page of the certificate (good, average or insufficient), but it does not enter the calculation of the A-to-G energy label. A home rated C can be "insufficient" for summer comfort.
What this article covers
How to read your DPE's summer comfort indicator and why it does not change the energy class, why a home well insulated for winter can overheat in summer, the strengthened summer comfort indicator planned for 2028 (PNACC-3, the degree-hour method inspired by RE2020), your rights as a tenant facing an "oven" home (decency, case law), and the measures that really cool a home: solar shading, thermal mass, night ventilation, external wall insulation.
Summer comfort in the DPE: an indicator that does not weigh on the label
Since the DPE reform that came into force on 1 July 2021 (ministerial order of 31 March 2021), every certificate includes a summer comfort indicator. It appears on the second page of the document and rates the home on three levels: summer comfort "good", "average" or "insufficient". This is useful information, but it stays separate: it does not enter the calculation of the A-to-G energy label, which aggregates only primary energy consumption and greenhouse gas emissions.
In practice, the same home can show a C rating — therefore considered acceptable for winter — and "insufficient" summer comfort. The indicator and the rating live side by side without speaking to each other. This is the first thing to understand: your energy class says almost nothing about what you will feel in July.
What the current indicator is based on
The DPE's summer comfort indicator is qualitative: it assesses only "passive" comfort, that is, without resorting to an energy-consuming cooling system (ceiling fans, however, are taken into account). It draws on a few input data points: the building's thermal mass (its capacity to dampen temperature swings), roof insulation, the presence of external solar shading (shutters, blinds, overhangs) and whether the home has cross-ventilation, which enables natural airflow.
A direct consequence: a home fitted with an air conditioner may well be judged "uncomfortable in summer" by the DPE, since active cooling is not taken into account. The indicator measures the building's ability to stay cool on its own, not the comfort actually obtained by burning kilowatt-hours.
Profile: a studio or one-bedroom flat under converted roof space, glazing facing west, with no shutters or external shading, in a hot climate zone (the south, the Rhône valley, the Mediterranean) — the typical profile of a C- or D-rated home that is "good for winter" but "insufficient" in summer.
Why a good winter DPE does not guarantee a cool home
Winter performance and summer comfort do not rely on the same levers. For winter, you want to retain heat: strong insulation, airtightness, low losses. But a highly insulating envelope can also trap the heat that came in during the day and prevent the home from cooling down at night, especially if it lacks thermal mass and ventilation. The worst overheating often affects recent, very well-insulated but lightweight homes, or roof spaces converted under a poorly shaded roof.
Three factors worsen overheating: solar gains (large unshaded glazed surfaces, west or south orientation), lack of thermal mass (lightweight walls that heat up fast) and the impossibility of ventilating at night (a non-cross-ventilated home, windows that do not open, nuisances that discourage opening them). A home can combine a good DPE rating with all three handicaps.
Strengthened summer comfort: what the 2028 reform plans
The crude nature of the current indicator is known to the authorities. The third French national climate-change adaptation plan (PNACC-3), launched on 10 March 2025 with 52 measures and more than 200 actions, plans to strengthen how summer comfort is taken into account in the DPE and the energy audit. The stated goal: a more reliable summer comfort indicator by 2028.
The direction taken is towards a quantitative indicator, no longer merely qualitative. A study led by the CSTB (Centre scientifique et technique du bâtiment — the French building science centre) is under way to evolve the 3CL-DPE method (the certificate's official calculation method), drawing on the degree-hour (DH) method already used in the RE2020 environmental regulation. This method measures, hour by hour, the number of degrees above a comfort threshold, and RE2020 calibrated it from data on the historic 2003 heatwave. The future DPE indicator would take the home's location into account, because a flat's summer discomfort is not the same in Lille as in Marseille.
⚠️ Warning: at this stage, the strengthened summer comfort metric is to remain an indicator distinct from the A-to-G rating — as at the date of this article, it is not planned to make a label tip on its own. Consultations are due to continue from 2026. The thinking also covers displaying this indicator in property listings, alongside the energy label.
Which homes will be most exposed
If the indicator becomes quantitative and location-based, certain home profiles will see their summer weakness highlighted far more clearly than today: roof spaces converted under poorly insulated roofs, homes with large west-facing glazing and no shading, properties in hot climate zones (the south of France and the overseas territories on the front line). For these homes, summer comfort could become a buying and renting criterion scrutinised as closely as the energy class.
For landlords as well as buyers, anticipation has a wealth interest: an "oven" home is likely to lose value as buyers factor summer comfort into their decision, exactly as green value already penalises thermal sieves. Our analysis of the EPC discount city by city shows how the rating already translates into euros on the sale price.
Your rights as a tenant facing an "oven" home
This is the question thousands of tenants ask every summer: is my landlord required to do anything if my home is unliveable during a heatwave? The legal answer is nuanced, and you need to know it precisely.
The law sets no maximum temperature
French law imposes a minimum heating temperature in winter, but it defines no ceiling temperature not to be exceeded in summer. No text makes a home automatically "illegal" because it reaches 30°C or 35°C in August. The landlord is therefore not required, under current law, to install air conditioning. That is the starting point: there is no enforceable heat threshold.
The home must nevertheless remain "decent"
Protection runs through the concept of a decent home. The Act of 6 July 1989 on improving rental relations requires the landlord to provide a decent home (article 6), and decree no. 2002-120 of 30 January 2002 sets out its characteristics: the home must not show manifest risks to the physical safety or health of occupants, and must protect the premises against runoff and rising water. Historically focused on cold, damp and safety, decency is evolving: protection against excessive heat is increasingly seen as a health issue in its own right.
To this framework is added the minimum energy performance criterion, built into decency: since 1 January 2025, a home rated G can no longer be offered for rent (the threshold moves to F on 1 January 2028, then E on 1 January 2034). A thermal sieve in winter is often a furnace in summer — the two issues converge.
What to do now: if your home becomes unliveable in summer, report it in writing (recorded-delivery letter) to your landlord, asking for passive solutions — fitting external shutters or blinds, roof-space insulation, a ceiling fan. Keep dated temperature readings. If you hit a wall, refer the matter to the departmental conciliation commission, then to the court.
Case law that is starting to move
In some cases, notably in the south, judges have already ordered the installation of solar shading to ensure the home's healthiness — case law favourable to the tenant, even if it remains isolated and assessed case by case. In addition, a private member's bill tabled in June 2025 aims to explicitly write summer comfort into the decency criteria, by requiring landlords to provide solar shading (shutters, blinds) or passive devices (ceiling fans). As of today, this text is not in force: you must therefore reason on existing law, not on a future obligation.
Case study: a C-rated one-bedroom flat under the roof in Lyon (illustrative)
To make things concrete, let's take an illustrative case — the orders of magnitude are indicative and replace neither a quote nor a simulation. You rent a 65 m² two-bedroom flat on the top floor of a Lyon building, rated C on the DPE, with large west-facing glazing, poorly insulated roof space and no external solar shading. In winter, the home is fine; in summer, it tops 30°C in the evening during heatwaves.
Scenario — Three passive measures to cut overheating
| Measure | Expected effect | Order of magnitude |
|---|---|---|
| External blinds or shutters on the west-facing glazing | Blocks solar radiation before it enters | a few hundred to a few thousand euros |
| Roof / roof-space insulation | Cuts heat gain through the roof, winter + summer gain | priority item in a house / top floor |
| Night ventilation (cross openings, ceiling fan) | Evacuates the heat accumulated at night | low-cost, high-impact measure |
| Combined effect | Move from "insufficient" to "average" or even "good" summer comfort, without air conditioning | |
The lesson is clear: it is not the most expensive measures that cool the most. External solar shading and night ventilation, both inexpensive, are often the most effective — well ahead of air conditioning, which treats the symptom by consuming energy and does not improve the DPE's summer comfort indicator.
The mistakes that turn a home into a summer oven
Mistake no. 1 — Relying on the energy label alone
A C- or D-rated home can be "insufficient" for summer comfort: the A-to-G rating does not measure summer overheating. Before renting or buying, read the second page of the DPE and look at the summer comfort indicator. It is a signal that most candidates ignore — and that will carry more and more weight with the 2028 reform.
Mistake no. 2 — Installing air conditioning before treating the passive side
Air conditioning brings immediate relief, but it consumes energy, is costly to run and does nothing to improve the DPE's summer comfort indicator (which only counts passive comfort). Before turning to it, address solar shading, night ventilation and roof insulation: you cut the cooling need at the source.
Mistake no. 3 — Fitting solar shading on the inside
A blind or curtain fitted indoors stops some of the light, but the solar radiation has already passed through the glazing and heats the room. Effective shading is external (shutters, awnings, brise-soleil): it blocks the heat before it enters. It is one of the most cost-effective levers against overheating.
⚠️ Warning: insulating internally (ITI) rather than externally (ITE) deprives the home of its walls' thermal mass, which dampens the heat. For summer comfort, ITE is almost always preferable — it keeps the wall mass on the lived-in side. See our comparison external or internal wall insulation: the choice that changes everything.
Mistake no. 4 — Believing heatwaves are a southern problem only
Heatwaves now move north and hit homes never designed for heat. The future location-based indicator will reveal the real exposure of each municipality. If you are in an overseas territory, the issue is even sharper: see our DPE obligations specific to the French overseas territories.
Simulate the works that cool your home
OneDpe 2026 renovation works and subsidies simulator
Build a bundle of "summer comfort" measures — solar shading, roof and roof-space insulation, external wall insulation to preserve thermal mass, ventilation — and see the estimated gain item by item, the indicative cost and the available 2026 subsidies (MaPrimeRénov' for full-scale renovations, CEE, the eco-PTZ loan) based on your income category, before committing to a single quote.
To go further: why summer comfort will be the certificate's next shock and the DPE rating simulator to place your home.
Conclusion
The DPE does not really protect tenants in summer — not yet. Its summer comfort indicator exists but stays qualitative and disconnected from the A-to-G rating: a well-rated home can be a furnace. The reform expected for 2028 promises a quantitative, location-based indicator that will change the picture, but in the meantime the tenant mainly has the lever of decency and dialogue with the landlord, in the absence of any legal maximum temperature.
The real answer lies in passive works, and it can be costed. The OneDpe 2026 renovation works and subsidies simulator lets you compare "summer" measures item by item — solar shading, roof insulation, external wall insulation, ventilation — and weigh their cost against the available subsidies, to turn an "insufficient" home into a liveable one without depending on air conditioning.
