# Handover — post S0380.81..84 (Table 32 default + Table 12a Grid 2 CO2 + RR fold-in)

Branch: `feature/per-cert-mapper-validation`. **HEAD `49622f55`**.
Predecessor: [`HANDOVER_POST_S0380_80.md`](HANDOVER_POST_S0380_80.md).

## Slices committed this session (S0380.81..84)

Four spec-cited slices, two clean closures + one extractor data-completion
+ one structural RR fix that surfaces the next named gap.

| Slice | Commit | Spec | Cert 000565 outcome |
|---|---|---|---|
| **S0380.81** | `9338914f` | RdSAP 10 §19.1 (PDF p.80-81) — "use Table 32 prices (not Table 12) for §10a/§10b" | sap_score 28 → **29 EXACT** at the (28.5) rounding boundary. Cost residual £+3.62 → £−2.39. |
| **S0380.82** | `27ead127` | SAP 10.2 Table 12a Grid 2 (p.191) + Table 12d/12e (p.194-195) — "All other uses" off-peak dual-rate | CO2 residual −8.92 → **−3.08 kg/yr** (65% closed). Lighting + pumps_fans + electric_shower CO2/PE factors now blend Table 12d/12e high-rate × low-rate codes per Grid 2 fraction on off-peak certs. |
| **S0380.83** | `ed8fdc6a` | RdSAP 10 §3.10 + Summary PDF §8.1 schema | Extractor recognises `"Exposed"` + `"Connected"` `gable_type` (was Party / Sheltered / "Connected to heated space" only). Mapper elif extended to preserve cert 9501. Pure data-extraction completion; zero cascade impact. |
| **S0380.84** | `49622f55` | RdSAP 10 §3.9.2 + §3.10 + Table 4 (p.22) | Mapper drops Connected gables, routes Exposed → `gable_wall_external` with lodged U, surfaces Common Walls, applies spec area formula `L × (0.25 + H)` and `Σ` per-common-wall gable correction. Cascade adds `common_wall` kind handler. **11 per-BP RR surface areas EXACT vs worksheet PDF**. Cascade walls 322 → 443 W/K (43% closer to worksheet 604); party 153 → 93 (68% closer to worksheet 65). cert 000565 sap_score temporarily regressed 29 → 26 — see §"Why the regression is the correct signal" below. |

**Test baseline at HEAD `49622f55`:** 555 pass + 9 expected
`test_sap_result_pin[000565-*]` cascade-gap fails. Pyright net-zero on
every touched file. Cohort + golden + cert 9501 unaffected.

## Cert 000565 state (HEAD `49622f55`)

| Pin | Cascade | Worksheet | Δ | Cause |
|---|---:|---:|---:|---|
| sap_score (int) | 26 | 29 | **−3** | RR fold-in (S0380.84) exposed BP main-wall gap; see §"BP main-wall residual −161 W/K diagnostic" |
| sap_score_continuous | 26.4972 | 28.5087 | −2.01 | Downstream of HTC over-count via space_heating +2591 |
| ecf | 5.5970 | 5.3866 | +0.21 | Downstream of cost +£182.6 |
| total_fuel_cost_gbp | 4862.88 | 4680.26 | +182.6 | Downstream of space_heating fuel cost |
| co2_kg_per_yr | 6684.52 | 6447.63 | +236.9 | Downstream of HP electricity over-fuel-use |
| **space_heating_kwh** | **61599.61** | **59008.35** | **+2591.3** | **BP main-wall cascade gap** (Curtain Wall −112 W/K + thin-wall alt −47 W/K — see diagnostic below) |
| main_heating_fuel | 36235.07 | 34710.79 | +1524.3 | Follows space_heating via 1/COP |
| **hot_water_kwh** | **3755.03** | **3755.03** | **✓ 0 EXACT** | §4 cascade fully closed (S0380.77..80) |
| lighting | 1387.02 | 1384.84 | +2.19 | Sub-spec |
| pumps_fans | 255.00 | 252.52 | +2.48 | MEV PCDB record missing (external data) |

### §4 HW cascade line refs (all EXACT, unchanged)

| Line | Cascade | Worksheet | Δ |
|---|---:|---:|---:|
| (45)m sum energy_content | 1286.3266 | 1286.3266 | ✓ 0 |
| (46)m sum distribution_loss | 192.9490 | 192.95 | ✓ <1e-3 |
| (57)m sum solar_storage | 596.9725 | 596.9725 | ✓ <1e-4 |
| (59)m sum primary_loss | 1176.77 | 1174.79 | +1.98 |
| (61)m combi_loss | 0.00 | 0.00 | ✓ 0 |
| (62)m sum total_demand | 3060.07 | 3060.07 | ✓ <1e-3 |
| (64)m sum (after solar) | 2778.72 | 2778.7213 | ✓ <1e-4 |
| (64a)m electric shower | 702.94 | 702.94 | ✓ <1e-4 |
| (217)m water-heater eff | 0.74 | 0.74 | ✓ EXACT |
| (219) HW fuel kWh | 3755.03 | 3755.0288 | ✓ <1e-3 |

### Per-BP RR surface areas (all EXACT after S0380.84)

Verified against the cert 000565 U985 worksheet "External Walls" + "Party
Walls" sections at 4 d.p. precision:

| BP | Surface | Spec formula | Worksheet | Cascade |
|---|---|---|---:|---:|
| 0 | Main GW1 Exposed | 4 × 2.45 (Simplified, no CW) | 9.80 | 9.80 ✓ |
| 0 | Main GW2 Sheltered | 6 × 2.45 | 14.70 | 14.70 ✓ |
| 1 | Ext1 CW1 | 9 × (0.25 + 1.0) (Simplified + CW) | 11.25 | 11.25 ✓ |
| 1 | Ext1 CW2 | 5 × (0.25 + 1.8) | 10.25 | 10.25 ✓ |
| 1 | Ext1 GW2 Exposed | 8 × (0.25+9) − ((9−1)²+(9−1.8)²)/2 | 16.08 | 16.08 ✓ |
| 2 | Ext2 GW2 Exposed | 3 × 8 (Detailed) | 24.00 | 24.00 ✓ |
| 3 | Ext3 CW1 | 5 × (0.25 + 1.5) (Simplified + CW) | 8.75 | 8.75 ✓ |
| 3 | Ext3 CW2 | 7.5 × (0.25 + 0.3) | 4.13 | 4.13 ✓ |
| 3 | Ext3 GW1 Exposed | 9 × (0.25+7) − ((7−1.5)²+(7−0.3)²)/2 | 27.68 | 27.68 ✓ |
| 4 | Ext4 CW1 | 4 × 1 (Detailed) | 4.00 | 4.00 ✓ |
| 4 | Ext4 CW2 | 3.5 × 0.6 (Detailed) | 2.10 | 2.10 ✓ |

### Cumulative cert 000565 closure (S0380.77 → .84)

| Pin | .77→ | .78→ | .79→ | .80→ | .81→ | .82→ | .83→ | .84 |
|---|---:|---:|---:|---:|---:|---:|---:|---:|
| hot_water_kwh | +1399 | +260 | −238 | **✓0** | ✓0 | ✓0 | ✓0 | ✓0 |
| sap_score (int) | +1 | −1 | 0 | −1 | **✓0** | ✓0 | ✓0 | **−3** ⚠ |
| sap_score_continuous | +0.60 | −0.04 | +0.06 | −0.04 | +0.03 | +0.03 | +0.03 | −2.01 ⚠ |
| ecf | −0.06 | +0.00 | −0.01 | +0.00 | −0.00 | −0.00 | −0.00 | +0.21 ⚠ |
| total_fuel_cost_gbp | −53 | +3 | −5 | +4 | −2 | −2 | −2 | +183 ⚠ |
| co2_kg_per_yr | (n/a) | (n/a) | −58 | −9 | −9 | **−3** | −3 | +237 ⚠ |

S0380.84 ⚠ rows are the documented BP main-wall surfacing (NOT a
regression of S0380.84's RR fix itself).

## Why the regression is the correct signal

S0380.84 closed the RR cascade routing to spec correctness. The 11
per-BP RR surface areas pin EXACT vs worksheet at 4 d.p. The cascade
walls subtotal moved 322 → 443 W/K (worksheet 604, 43% closed); party
153 → 93 (worksheet 65, 68% closed).

Pre-S0380.84 the cascade had two ~equal-magnitude bugs of opposite
sign that mostly cancelled at the SH-pin level:

  - **RR cascade**: Exposed gables wrongly routed to party_walls at
    U=0.25 (cascade over-counts party_walls by ~88 W/K)
  - **BP main-wall cascade**: Curtain Wall + thin-wall alt missing
    (cascade under-counts walls by ~161 W/K)

S0380.84 closed the first one. The second is now exposed as a +2591
kWh space_heating residual. Per `[[feedback-spec-citation-in-commits]]`
and `[[feedback-spec-floor-skepticism]]` the spec-correct fix ships
even when the test pin temporarily regresses; the diagnostic signal
is sharper now.

## BP main-wall residual −161 W/K diagnostic

Probed per-BP at HEAD `49622f55`:

| BP | Cascade U | Worksheet U | Δ contribution | Spec gap |
|---|---:|---:|---:|---|
| 0 Main | 0.32 | 0.35 | −1.6 W/K | sub-spec (Solid Brick A age, 75mm External insulation) |
| 0 Main alt1 | 0.32 | 2.34 | **−46.5 W/K** | `_insulation_bucket(thk=120, ins_present=False)` returns 100 not 0 (docstring intent vs current code) + thin-wall §6.6/§6.7 for U=2.34 |
| 1 Ext1 | 1.70 | 1.70 | ✓ 0 | ✓ Spec-correct (Stone Granite E age, Unknown insulation) |
| 2 Ext2 (Curtain Wall) | 0.60 | 1.40 | **−112.2 W/K** | `WALL_CURTAIN=9` defined `rdsap_uvalues.py:116` but no `_ENG_WALL` table entry; `u_wall` falls through to default Cavity table |
| 3 Ext3 (basement) | 0.45 | 0.45 | ✓ 0 | ✓ Spec-correct |
| 4 Ext4 (basement) | 0.35 | 0.35 | ✓ 0 | ✓ Spec-correct |

Total: **−160.3 W/K** (matches the observed −161 W/K).

### Gap #1 — Curtain Wall (largest, −112 W/K)

**Where:** [domain/sap10_ml/rdsap_uvalues.py:116](../../sap10_ml/rdsap_uvalues.py) — `WALL_CURTAIN: Final[int] = 9` is defined but has no entry in `_ENG_WALL` and is not in the `known_types` set at `u_wall:373-376`. When the cert lodges `wall_construction=9`, `u_wall` falls through to `_DEFAULT_WALL_BY_AGE` (default cavity) and returns the cavity-wall U for that age band.

**Cert 000565 BP[2] Ext2** lodges `Type: CW Curtain Wall` + `Curtain Wall Age: Post 2023` per Summary PDF §7. The "Curtain Wall Age" is a separate per-BP attribute from the dwelling-wide `construction_age_band` — the BP is age `H` (1991-1995) but the curtain wall itself was installed Post-2023. Worksheet uses Curtain Wall Post-2023 U=1.40.

**Slice span:**

1. Extractor (`backend/documents_parser/elmhurst_extractor.py`) — currently doesn't surface "Curtain Wall Age" from Summary §7
2. `datatypes/epc/surveys/elmhurst_site_notes.py` — add `curtain_wall_age` to `WallDetails`
3. `datatypes/epc/domain/epc_property_data.py` — add `curtain_wall_age` to `SapBuildingPart`
4. `datatypes/epc/domain/mapper.py` — thread through both API + Elmhurst paths
5. `domain/sap10_ml/rdsap_uvalues.py` — Curtain Wall U-value lookup by age; add `WALL_CURTAIN` to `known_types`

**Spec citation needed:** RdSAP 10 Table 6 or related — locate the canonical Curtain Wall U-values per age category. The worksheet says 1.40 for Post-2023; need to verify the full table.

### Gap #2 — Thin-wall alt stone granite (−47 W/K)

**Where:** Two coupled bugs.

1. `domain/sap10_ml/rdsap_uvalues.py:160 _insulation_bucket` ignores `insulation_present=False` when `thickness_mm > 0`. Docstring says "when not present, the as-built (bucket 0) row applies regardless" but the code falls through to thickness-bucket selection. For BP[0] alt1 with `wall_insulation_type=4` (None) but `wall_insulation_thickness='120'`, bucket returns 100 not 0.

2. The `wall_insulation_thickness='120'` on `SapAlternativeWall` is actually the **WALL thickness** lodged in Summary §7 ("Alternative Wall 1 Thickness: 120 mm"), NOT an insulation thickness. Per [[feedback-no-misleading-insulation-type]] this should land on a new `SapAlternativeWall.wall_thickness_mm` field (mirror of `SapBuildingPart.wall_thickness_mm`).

3. Even with bucket 0, `_TYPICAL_STONE_UNINSULATED[0] = 1.7` + dry-lined adjustment = 1.32. Worksheet wants 2.34. This is the RdSAP 10 §6.6/§6.7 "thin-wall" formula for stone walls below typical thickness — needs implementing in `u_wall`.

**Slice span:**

1. Extractor — surface "Alt 1 Thickness" as wall thickness (currently mapped to `wall_insulation_thickness`)
2. `datatypes/epc/domain/epc_property_data.py` — `SapAlternativeWall.wall_thickness_mm: Optional[int]`
3. `datatypes/epc/domain/mapper.py` — populate `wall_thickness_mm` from Elmhurst extractor's alt-wall-thickness field
4. `domain/sap10_ml/rdsap_uvalues.py:160 _insulation_bucket` — short-circuit `if not insulation_present: return 0` per docstring intent (audit cohort for any cert with insulation_present=False AND thickness>0)
5. `domain/sap10_ml/rdsap_uvalues.py:329 u_wall` — RdSAP §6.6/§6.7 thin-wall formula keyed on `wall_thickness_mm` for stone constructions

## Open work — prioritised next slices

### S0380.85 — Curtain Wall (highest impact, −112 W/K of −161)

Extract `curtain_wall_age` per BP + add Curtain Wall U-value lookup keyed
on age. Multi-layer (extractor + datatypes + mapper + cascade); a single
slice if the spec lookup is tractable.

Spec citation candidate: RdSAP 10 Table 6 row for "CW Curtain Wall"
across age categories. The worksheet (cert 000565) gives Post-2023 →
U=1.40 as the empirical ground truth.

Expected impact: cert 000565 cascade walls 443 → 555 (worksheet 604).
HTC fabric 795 → 907. SH residual +2591 → +~800 kWh. sap_score should
move 26 → ~28 (still 1-2 short of 29 due to remaining alt1 gap).

### S0380.86 — Thin-wall alt stone granite (−47 W/K)

Two coupled bugs in `rdsap_uvalues.py`:
1. `_insulation_bucket` short-circuit on `not insulation_present`
2. Thin-wall §6.6/§6.7 formula keyed on a new `wall_thickness_mm`
   field on `SapAlternativeWall`

Plus extractor + datatype + mapper plumbing for the wall_thickness
field. After both gaps close: cascade walls 555 → ~610 (matches
worksheet 604). HTC → ~960. SH should close to ~−72 (or smaller —
the original residual pre-S0380.84).

### Deferred (unchanged from post-S0380.80 handover)

- MEV PCDB Table 4f component for pumps_fans +2.5 (blocked on external
  data acquisition; PCDF 500755 record needed)
- HP SAP code → main_heating_category=4 mapper extension (couples with
  MEV; ship after MEV record acquired)
- 12 gas-combi PV certs at +0.5..+1.6 PE (no worksheets)
- 5 SAP-residual API-only certs (no worksheets)

## How to run the baseline

```bash
PYTHONPATH=/workspaces/model python -m pytest \
    backend/documents_parser/tests/test_summary_pdf_mapper_chain.py \
    backend/documents_parser/tests/test_elmhurst_extractor.py \
    backend/documents_parser/tests/test_elmhurst_end_to_end.py \
    domain/sap10_calculator/worksheet/tests/test_e2e_elmhurst_sap_score.py \
    domain/sap10_calculator/worksheet/tests/test_appendix_h_solar.py \
    domain/sap10_calculator/rdsap/tests/test_cert_to_inputs.py \
    domain/sap10_calculator/rdsap/tests/test_golden_fixtures.py \
    --no-cov -q
```

Expected: **555 pass + 9 expected `test_sap_result_pin[000565-*]` fails**.

The 9 expected fails (verbatim):
```
sap_score
sap_score_continuous
ecf
total_fuel_cost_gbp
co2_kg_per_yr
space_heating_kwh_per_yr
main_heating_fuel_kwh_per_yr
lighting_kwh_per_yr
pumps_fans_kwh_per_yr
```

(was 8 + sap_score EXACT at HEAD `27ead127`; sap_score moved into the
fail list at HEAD `49622f55` per "Why the regression is the correct
signal" above).

## Files touched this session

| File | Slices | Change |
|---|---|---|
| `domain/sap10_calculator/rdsap/cert_to_inputs.py` | S0380.81, .82 | Added `RDSAP_10_TABLE_32_PRICES`; switched default; new `_other_use_co2_factor_kg_per_kwh` + `_other_use_primary_factor` helpers; wired into pumps_fans / lighting / electric_shower CO2 + PE fields |
| `domain/sap10_calculator/rdsap/tests/test_cert_to_inputs.py` | S0380.81, .82 | 2 new tests + 3 re-pinned scalar assertions to Table 32 |
| `backend/documents_parser/elmhurst_extractor.py` | S0380.83 | Added "Exposed" + "Connected" to `gable_type` recognition set |
| `backend/documents_parser/tests/test_summary_pdf_mapper_chain.py` | S0380.83, .84 | 2 new tests (extractor gable_type + mapper RR routing/areas) |
| `datatypes/epc/domain/mapper.py` | S0380.83, .84 | Mapper RR routing per §3.10 Table 4; drops Connected, routes Exposed external, surfaces Common Walls with §3.9.2 spec area formula |
| `datatypes/epc/domain/epc_property_data.py` | S0380.84 | `SapRoomInRoofSurface.kind` docstring extended with `common_wall` |
| `domain/sap10_calculator/worksheet/heat_transmission.py` | S0380.84 | Added `common_wall` kind handler (walls += area × U) |

## Spec source quick-reference

- **SAP 10.2 full specification**: `domain/sap10_calculator/docs/specs/sap-10-2-full-specification-2025-03-14.pdf`
  - Table 12a (p.191) — Grid 1 SH + WH + Grid 2 "All other uses" high-rate fractions
  - Table 12d (p.194) — monthly CO2 factors for electricity
  - Table 12e (p.195) — monthly PE factors for electricity
- **RdSAP 10 specification**: `domain/sap10_calculator/docs/specs/RdSAP 10 Specification 10-06-2025.pdf`
  - §3.9 + §3.10 (p.30-35) — Simplified Type 1/2 + Detailed RR
  - Table 4 (p.22) — RR surface variants (gable_wall U-value rules)
  - §19.1 (p.80-81) — Table 32 prices for §10a/§10b
  - Table 32 (p.95) — RdSAP unit prices + standing charges
  - Table 6 — wall U-values by construction + insulation bucket (Curtain Wall entry needed for S0380.85)
  - §6.6 / §6.7 — thin-wall stone formula (S0380.86)
- **SAP 10.3 at** `domain/sap10_calculator/docs/specs/sap-10-3-full-specification-2026-01-13.pdf`: **DO NOT reference** ([[feedback-sap-10-2-only-never-10-3]])

## Memory updated this session

- `project_cert_000565_recovery_state` — S0380.81/.82/.83/.84 entries
  + post-S0380.84 BP main-wall diagnostic table localising the −161
  W/K residual to Curtain Wall + thin-wall alt
- `MEMORY.md` — index entry refreshed at HEAD `49622f55`