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68 lines
3.8 KiB
Markdown
68 lines
3.8 KiB
Markdown
# Follow-ups from the full-SAP baseline-downgrade work (ADR-0037)
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Open items surfaced while fixing the full-SAP mapper / portfolio-796 downgrades.
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Each is **separate from** the full-SAP fix (`fix/baseline-downgrades`).
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## 1. RdSAP ventilation mapping is inconsistent across schemas
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**Severity: accuracy bug for MEV/MVHR dwellings.** The mappers handle
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`sap_ventilation` four different ways:
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- `17_0` + full-SAP — build via `_sap_17_1_ventilation`, which **maps**
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`mechanical_ventilation_kind`. ✅
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- `21_0_1` — rich inline `SapVentilation(...)` incl. the kind. ✅
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- **`17_1` / `18_0` / `20_0_0`** — built `SapVentilation(sheltered_sides=…)` and
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**dropped** the kind. **Fixed in this PR** (mirror `_api_mechanical_ventilation_kind`).
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- **`19_0` / `21_0_0`** — set **no `sap_ventilation` at all** → the dataclass
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default empty object. They drop the **entire** ventilation block (sheltered
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sides + kind + everything), not just the kind. **Still open** — a bigger,
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separate consistency fix (give them a proper `sap_ventilation` construction,
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mirroring 21.0.1), not a one-liner.
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Either way, an MEV/MVHR cert (`mechanical_ventilation ≠ 0`) is treated as
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**natural** by the affected mappers — wrong §2 ventilation cascade (and heat
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recovery). Natural certs (code `0`/`5` → `None`) are unaffected.
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- For **natural-ventilation** certs (`mechanical_ventilation = 0`, e.g. UPRN
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100020603823 / property 726605) it's **benign** — unmapped → `None` defaults to
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natural in the §2 cascade.
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- For **MEV/MVHR** certs (`mechanical_ventilation ≠ 0`) the calculator treats the
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dwelling as **naturally ventilated**, getting the SAP §2 ventilation cascade
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(and any heat recovery) wrong → mis-scored SAP.
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The granular **counts** (fans/flues/vents) are *not* a bug: older RdSAP open-data
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certs don't lodge them, and the calc correctly uses RdSAP Table-5 age defaults.
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`percent_draughtproofed` is mapped (top-level) and read by the calc.
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**Remaining fix (19.0 / 21.0.0):** give them a proper `sap_ventilation`
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construction mirroring 21.0.1. **Calc-facing → validate** with the RdSAP-21.0.1
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corpus (must hold 73.3% / MAE 0.774) plus an **Elmhurst-anchored MEV/MVHR
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`RealCertExpectation`** (the corpus is natural-vent-dominated, so the kind change
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isn't exercised by it). Quantify blast radius: count older-RdSAP certs with
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`mechanical_ventilation ≠ 0`. The 17.1/18.0/20.0.0 fix in this PR is guarded by a
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mapper-level MVHR test + the corpus/mapper-corpus staying green, with the Elmhurst
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MEV/MVHR anchor as the SAP-accuracy fast-follow.
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## 2. FE "Main Fuel: Unknown" is FE-side, not a Model mapper gap
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`main_fuel_type` (the gov fuel **code**) **is** populated Model-side — UPRN
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10093412452 (709791) → `1`, UPRN 100020603823 (726605) → `26` — and is persisted
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(`epc_main_heating_detail.main_fuel_type`). So the panel's "Main Fuel: Unknown"
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is the **front-end** either not mapping the code → fuel name or reading a field we
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don't populate. Needs an FE-repo (Drizzle/Next) check, not a Model change.
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## 3. Survivor clusters from the post-fix population sweep
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`scripts/hyde/case_a_population_sweep.py`: the representative sample rebaselined
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cleanly (0 survivors), but the worst-old-drop sample held **28 survivors**
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(lodged A/B → new C/D, 15–25 SAP) in tight UPRN clusters (new-build blocks),
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spanning multiple schemas (16.0/16.1/17.1/18.0.0) and heating types. No single
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mapper-gap signature → likely genuine SAP-2012→10.2 drops for very-high-lodged
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new-builds, but **triage one in Elmhurst** to confirm genuine vs a residual calc
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issue before trusting the cohort.
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## 4. Predicted-property display path (e.g. property 721167)
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721167 has **no lodged EPC** (predicted). Its Heating-Control / Main-Fuel /
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Ventilation Unknowns come from the prediction + landlord-override **overlay** not
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populating the display fields — a separate path from the lodged-cert mappers.
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