1. The annex 9 rule, step by step
The summer comfort indicator (French order of 31 March 2021, annex 9, consolidated by the order of 8 October 2021) rests on five criteria, split into two families:
- Two eliminatory criteria: external solar protections and roof insulation.
- Three secondary criteria: thermal inertia, dual-aspect layout and fixed ceiling fans.
The level is then derived in two steps:
- If either eliminatory criterion is not satisfied → the level is "insufficient", whatever the secondary criteria.
- If both eliminatory criteria are satisfied → count the secondary criteria: at least two out of three → "good"; otherwise → "medium".
This rule is informative only: it does not change the energy or climate label of the DPE.
2. Source hierarchy per criterion
For each criterion, the tool uses the most reliable available source, in this order of priority:
- XML file — the flags declared in the DPE's official XML output (summer comfort block) prevail whenever the file is uploaded.
- ADEME data — the technical characteristics found from the DPE number or address (roof insulation quality, inertia class).
- Declared answers — your answers to the complementary questions (solar protections, dual-aspect, ceiling fans) when no data is available.
- Regulatory convention — the 1975 convention for roof insulation when neither data nor answer is available (see below).
When a criterion remains unknown, the tool never invents a value: it returns an honest range (worst case / best case) instead of a clear-cut verdict.
3. The 1975 convention
When the roof insulation quality is unknown, the tool applies a regulatory convention based on the construction year: a home built before 1975 (the first French thermal regulation) is deemed poorly insulated on its roof, and a home built in 1975 or later is deemed insulated. If the exact year is missing, the construction period label is used (upper bound of the range); if both are absent, the criterion stays unknown and feeds the range.
4. Roof criterion neutralised for flats
For a flat on the ground floor or an intermediate floor — with no roof or top floor above the dwelling — the roof insulation criterion does not apply (annex 9). It is displayed as "not assessed" but treated as satisfied in the calculation, since there is no deperditive upper floor. A flat on the top floor or under the roof is, on the contrary, treated like a house and subject to the 1975 convention.
5. Buildings and overseas territories
- Whole-building DPE (annex 9.1): the official indicator is not assessed for a DPE established at building level. The tool still computes an estimate, clearly labelled "OneDpe estimate", but points out that the official indicator does not exist for this document.
- Overseas territories (postal codes 97x / 98x): the annex 9 indicator is defined for metropolitan France. Overseas, the tool returns no verdict and displays a dedicated message — a hygrothermal indicator adapted to those climates is under study.
6. Scope and limits of version 1
Scope: DPE of existing dwellings (ADEME base dpe03existant). New-build DPE and tertiary/commercial DPE are out of scope in version 1.
- Solar protections are declarative in version 1: the ADEME flat file does not carry the presence of external shading, so this eliminatory criterion relies on your answer (or the XML file). We recommend uploading the XML to firm up the verdict.
- The estimate is not a DPE: only a DPE issued by a certified assessor is authoritative.
7. Regulatory status
A "summer comfort letter" was announced on 15 July 2026, but no text has been published to date. The annex 9 indicator remains in force and this tool stays valid: should an official text be published, we will update the method and the related articles accordingly.
8. Attribution & version
- DPE data: ADEME (Open Licence 2.0).
- Summer climate data (hot days, tropical nights, 2030 projection): Météo-France, CLIMADIAG Commune / DRIAS-TRACC (Open Licence 2.0), by commune and department.
- Rule version: 1.1.0
Score Été OneDpe 0-100 — proprietary method
Beyond the official 3-level indicator above, OneDpe computes a proprietary 0-100 score (class A-G, A = best summer comfort) that grades the building and crosses it with the local climate and the urban heat island effect. It is indicative and non-official, distinct from the annex 9 indicator and from the future 2028 indicator.
Formula: Score = 100 − (0.65 × building penalties + 0.35 × climate exposure), bounded 0-100.
- Building: graded penalties on the annex 9 criteria — solar protection −30 and roof −20 (eliminatory), inertia −15, dual-aspect −10, ceiling fans −5, plus solar overheating 0-10.
- Climate: summer severity of the department (Météo-France CLIMADIAG: tropical nights + very hot days), weighted present 0.7 / 2030 0.3.
- Calibration: class thresholds set on the national septiles of the score (199,875 DPE), validated by median monotonicity (declared insufficient < medium < good) and a healthy A-G distribution. Positioning: more reliable than the declared indicator, 16.4% of which diverges from the criteria recorded on the certificate itself (OneDpe measurement, 9,663,670 EPCs).
- Current limits: a criterion answered "I don't know" is not penalised (optimistic score — a confidence index is shown); the climate component is at department level, while the urban heat island effect (LCZ) is resolved at address level since score 0.5.0.
- Score version: 0.5.0
Full parameters — reproduce the score yourself
Every number the score uses is published below. Nothing else enters the computation.
Class thresholds (on the 0-100 score): A ≥ 84 · B ≥ 77 · C ≥ 70 · D ≥ 65 · E ≥ 61 · F ≥ 52 · G < 52. These are the national septiles measured on 199,875 DPE (2026-07-22). They were unchanged by the addition of the floor factor (0.4.0) and by the activation of the urban heat island (0.5.0, recalibrated on 1,999,249 DPE).
Floor factor (flats only): top floor +6 × severity (penalty), ground floor −4 × severity (bonus), applied to the building component. No regulatory method models this; the magnitude is an expert setting, not a measured one.
Urban heat island (LCZ → offset): applied to the climate component, then multiplied by the local severity (so it is null in a cool climate). Reference is LCZ 6 (open low-rise, the dominant fabric) at 0.
| LCZ (WUDAPT) | Offset |
|---|---|
| 1, 2 — compact high / mid-rise | +8 |
| 3 — compact low-rise | +5 |
| 10 — heavy industry | +5 |
| 8 — large low-rise | +4 |
| 4, 5 — open high / mid-rise | +1 |
| 6, 7, 9, 15, 16 — open low-rise, lightweight, sparse, paved, bare | 0 (reference) |
| 13 — bush, scrub | −2 |
| 12, 14 — scattered trees, low plants | −3 |
| 11, 17 — dense trees, water | −4 |
Solar overheating (0-10): ratio of south-equivalent glazed area to living area, mapped linearly between the 75th and 90th percentile of the climate zone: H1a 0,85–1,29 · H1b 0,76–1,02 · H1c 0,73–0,96 · H2a 0,80–1,04 · H2b 0,76–1,03 · H2c 0,74–0,98 · H2d 0,68–0,88 · H3 0,76–1,06 (default 0.78–1.00 when the zone is unknown).
Climate component: composite severity = 0.6 × tropical nights + 0.4 × very hot days, weighted present 0.7 / 2030 0.3, then renormalised from 0-80 to 0-100. When the climate cannot be resolved, it is dropped entirely and the building weight is renormalised to 1 — the score is never lowered by missing data.
Confidence index: (number of the 5 annex 9 criteria actually known ÷ 5) × 0.7 if the climate is missing × 0.5 if the certificate is a whole-building or overseas one. A criterion answered "I don't know" is not penalised — the score is optimistic, and the confidence index is what tells you so.
How often the declared indicator is wrong
We re-applied the annex 9 rule to the five parameters recorded on each certificate, and compared the result with the verdict the assessor actually wrote. Below is the full comparison — rows are what the certificate declares, columns what the rule gives.
| Declared ↓ / Recomputed → | Insufficient | Medium | Good |
|---|---|---|---|
| Insufficient | 869 125 | 49 357 | 43 457 |
| Medium | 100 338 | 904 631 | 23 017 |
| Good | 133 217 | 39 844 | 206 471 |
The diagonal is agreement. Off it, 16.4% of certificates display a verdict that contradicts their own recorded criteria. The asymmetry matters: an "insufficient" verdict is confirmed 90.4% of the time, a "medium" one 88.0%, but a "good" one only 54.4% — and 35.1% of certificates declared "good" turn out to be "insufficient" once the rule is applied. Overall the recomputed share of "insufficient" is 46.5%, against 40.2% declared.
Measured on a 25% sample (2,413,909 certificates) of the 9,663,670 that carry the indicator; 44,452 could not be decided because a parameter is missing and are excluded rather than forced. As an external check, the Pouget Consultants / IGNES study of 16 June 2026 publishes the same recomputation on its own extraction and reaches 46.39% "insufficient", 42.17% "medium", 11.44% "good" — our figures are 46.54 / 41.94 / 11.52.
Sources: LCZ map WUDAPT Europe 100 m (Demuzere et al. 2019, CC BY 4.0); climate Météo-France CLIMADIAG Commune / DRIAS-TRACC (Open Licence 2.0). Published on 2 August 2026 — if you reproduce the score and find a discrepancy, the engine is the reference and we want to know.