Exclusive study — wave 1
Summer comfort barometer 2026
4 in 10 homes poorly rated — but the official risk map misleads
Three heatwaves in summer 2026 and talk of a future "summer comfort rating" put home overheating in the spotlight. OneDpe analysed 11.2 million EPCs: 40.2% of homes are rated "insufficient", and 46.5% would be if the rule were applied to the letter. Crucially, the official indicator — blind to location — names the North, while the real risk concentrates in the South and Paris.
Figures frozen on · Source: OneDpe.fr
Key figures
- 40,2 %
- homes rated "insufficient"
- 43.2% "average", 16.6% "good"
- 11 183 219
- EPCs analysed
- mainland France, houses + flats, excluding EPCs generated from a building-level one; indicator present on 86.4%
- 68,2 %
- in Roubaix, worst city on the declared indicator
- old dense stock — but cool climate (Summer Score 64)
- 16,4 %
- of verdicts inconsistent with their own criteria
- annex 9 rule re-applied to the 5 recorded parameters: 46.5% "insufficient" instead of 40.2%
Infographics
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Methodology
Published in full so anyone can check, replicate or challenge it.
Scope, definition, sources and limits
Scope
11,183,219 mainland EPCs (houses + flats), excluding EPCs generated from a building-level one. The declared indicator is measured as a full census; the OneDpe Summer Score and the annex 9 recomputation run on a 2.4-million EPC sample.
What the figure means
Summer comfort indicator = insufficient / average / good rating from Annex 9 of the order of 31 March 2021 (building only). OneDpe Summer Score = 0-100 rating crossing the building, the department’s climate and the address’s urban heat. The lower the score, the more exposed the home (national median: 67).
Sources
- ADEME open database — EPCs completed since July 2021
- Climate: CLIMADIAG Commune / DRIAS-TRACC (Météo-France), aggregated at department level
- Urban heat: Local Climate Zones (LCZ, WUDAPT), at address level
Limits — what this study does NOT say
- Unweighted statistics, not representative of the entire stock (completed EPCs only).
- 13.6% of EPCs do not fill in the indicator; the direction of the resulting bias is not established (coverage is identical for houses, 86.5%, and flats, 86.4%).
- No aggregate published under 100 homes; rankings limited to towns with more than 3,000 filled-in EPCs.
The data
Map 1 — declared indicator: the North on top
| City | "Insufficient" homes | Median Summer Score |
|---|---|---|
| Roubaix | 68,2 % | 64 |
| Hazebrouck | 61,8 % | 67 |
| Tourcoing | 61,7 % | 67 |
| Armentières | 59,7 % | 67 |
| Paris | 59,6 % | 53 |
The top five. Old dense stock but cool climate: the Summer Score stays near the median (67) — except in Paris. Nine of the ten worst-rated towns are in the Nord and Pas-de-Calais; Paris (5th) is the only exception, and the only one also topping Map 2.
Map 2 — Summer Score (building + climate + urban heat): the South and Paris
| City | Median Summer Score | "Insufficient" homes (declared) |
|---|---|---|
| Aix-en-Provence | 52 | 33,5 % |
| Paris | 53 | 59,6 % |
| Perpignan | 54 | 27,0 % |
| Nice | 58 | 24,2 % |
| Montpellier | 58 | 24,7 % |
A panel of major cities, not a ranking: here climate dominates. The Summer Score is an integer, so ties are frequent — Nice and Montpellier belong to a group of 14 towns tied at exactly 58, occupying ranks 15 to 28 as a block. The strictly lowest scores belong to smaller towns: Agde, Apt and Roquebrune-sur-Argens are also at 54, tied with Perpignan.
Ranking, town by town
The two measures side by side for every ranked town. Search yours, or browse the rankings.
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Quotes
Attributable and ready to publish. For an interview, see the contact below.
« The official indicator tells someone in Montpellier their home is fine, and someone in Roubaix theirs is insufficient. The reality of overheating is often the reverse: it is not only build quality that counts, it is where the home stands. »
About OneDpe
OneDpe.fr is an independent platform of analysis tools for the French energy performance certificate (DPE). It offers free tools — certificate consistency checks, discount estimation, 3CL simulation, 2026 reform simulation, renovation works estimation — built on the analysis of several million certificates from the ADEME open data, cross-referenced with French property transaction data (DVF). OneDpe is published by RIANN SAS (Paris).
Going further
Journalist? Detailed figures, interviews and custom breakdowns: presse@onedpe.fr — reply within 24 hours.