Add SAP-16.2 schema coverage + single-glazing fix; flat party-wall fix; pin 2 certs

SAP-Schema-16.2 (datatypes/epc/domain/mapper.py):
- 16.2 is structurally an RdSAP-17.1 cert under a different name; add
  _normalize_sap_schema_16_2 (field renames + defaults) and dispatch to the
  tested from_rdsap_schema_17_1 mapper. uprn_100020933699 maps → SAP 71.
- Honour a "Single glazed" windows description when multiple_glazing_type="ND"
  (was defaulting to double) → RdSAP-21 code 5; eng 72→71 (lodged 70).
- 4 regression tests + sap_16_2.json fixture; 0 new pyright errors.

Flat party-wall fix (domain/sap10_calculator/worksheet/heat_transmission.py):
- Full-SAP flats carry flatness in dwelling_type, not property_type, so the
  party-wall default fell through to the 0.25 house value instead of the RdSAP
  Table-15 flat 0.0. Add _is_flat_or_maisonette_dwelling fallback + regression
  test. uprn_10093116529 80→81 (matches the cert's lodged party u_value 0).

Accuracy corpus pins (tests/domain/sap10_calculator/test_real_cert_sap_accuracy.py):
- uprn_10093116543 (SAP-17.1 gas-combi semi): engine 81 (Elmhurst 77; documented
  full-SAP→RdSAP residual — measured wall/floor U + PCDB boiler vs RdSAP defaults).
- uprn_10093116529 (SAP-17.1 g/f flat): engine 81 (Elmhurst 78).

devcontainer: add poppler-utils (pdfinfo) for the documents-parser PDF fixtures.

Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>

.claude/skills/expand-sap-accuracy-corpus/worklist.md

@@ -10,12 +10,26 @@ UPRN, tick it and annotate: `— <schema> · eng <X> / elm <Y> · <note>`.
 2020 new-build flat) — full loop proven: eng 77 / elm 78, engine-on-Elmhurst-
 inputs 79 (calculator faithful within ~1). Use it to sanity-check the pipeline.
 
+## E2E testing set
+
+UPRNs needed for end-to-end testing (also tracked in The 100 below).
+
+| UPRN | Schema | Status | Engine SAP | Notes |
+|---|---|---|---|---|
+| 10093116528 | SAP-17.1 | ✅ pinned | 82 (elm 81) | full-SAP semi; AP50 fix |
+| 10093116543 | SAP-17.1 | ✅ pinned | 81 (elm 77) | 2017 gas-combi semi |
+| 10093116529 | SAP-17.1 | ✅ pinned | 81 (elm 78) | 2017 gas-combi g/f flat; party-wall fix |
+| 100020933699 | SAP-16.2 | 🔧 mapper + glazing fix | 71 (lodged 70) | RdSAP-shaped; single-glazing fix; Elmhurst validation pending |
+| 44012843 | — | ☐ todo | — | not yet processed |
+| 10023444324 | — | ☐ todo | — | not yet processed |
+| 10023444320 | — | ☐ todo | — | not yet processed |
+
 ## The 100
 
 - [x] 🔧 10093116528 — SAP-17.1 (full-SAP semi) · eng 82 / elm 81 · 🔧 air-perm AP50 fix: q50 Blower-Door routed to (18)=AP50/20 not the AP4/Pulse formula (was eng 78). Residual +1 = lodged-U vs RdSAP age-band-U; FGHRS (60031) omitted both sides. Worked-ref 10092973954 re-pinned 77→80 by same fix.
-- [ ] 10093116543
-- [ ] 10093116529
-- [ ] 100020933699
+- [x] 10093116543 — SAP-17.1 (2017 gas-combi semi) · eng 81 / elm 77 (lodged 82) · PINNED engine 81. +4 = documented full-SAP→RdSAP residual, NOT a mapper bug: ~1.5 floor-U (cert lodges measured 0.11 vs Elmhurst RdSAP solid default 0.23; U-known override disabled) + ~1 boiler-eff (cert PCDB 17644 88.5% vs Elmhurst generic BGW combi 84%; PCDB search disabled, 89% cascade option is a regular boiler needing a cylinder) + ~0.5 roof band-L/infil. Conservatory leftover from prior cert cleared (worksheet 73→77). No mapper change.
+- [x] 🔧 10093116529 — SAP-17.1 (2017 gas-combi ground-floor FLAT, TFA 49) · eng 81 / elm 78 (lodged 81) · PINNED engine 81. 🔧 FIXED a real calc bug: full-SAP flats took the 0.25 house party-wall default instead of the RdSAP Table-15 flat 0.0 (flatness is in dwelling_type, not property_type) — heat_transmission._is_flat_or_maisonette_dwelling; +regression test. Cert lodges party u_value 0; Elmhurst worksheet 0.0; fix 80→81. Residual +3 vs Elmhurst = documented full-SAP→RdSAP gap (measured wall 0.184/floor 0.12 + PCDB 88.5% vs generic 84%). Calculator faithful: fed Elmhurst's Us, HTC 93.4 vs ~94. House→Flat Elmhurst switch (storeys→1, roof→another-dwelling-above). No mapper change.
+- [ ] 🔧 100020933699 — SAP-16.2 SCHEMA COVERAGE ADDED (end-terrace house, band G). 16.2 is structurally RdSAP-17.1 (reduced fields, glazed_area band, construction-code building parts) under a different name; mapped via `_normalize_sap_schema_16_2` (renames windows→window, main_gas→mains_gas, boiler_index_number→main_heating_index_number, wwhrs→instantaneous_wwhrs + defaults) → reuses from_rdsap_schema_17_1. 🔧 Also fixed: "Single glazed" description honoured when multiple_glazing_type="ND" (was defaulting to double; RdSAP-21 code 5) → eng 72→71. +4 regression tests, sap_16_2.json fixture, 0 new pyright errors. eng 71 / lodged 70. ⚠ Known gap: 16.2 lodges no party_wall_length → end-terrace party wall unmodelled (likely the residual +1). ⏳ Elmhurst build (partial: PropDesc/Dims/Walls/Roofs done) + pin still pending.
 - [ ] 44012843
 - [ ] 10023444324
 - [ ] 10092970673

.devcontainer/backend/Dockerfile

@@ -6,11 +6,14 @@ ARG USER_UID=1000
 ARG USER_GID=1000
 ARG DEBIAN_FRONTEND=noninteractive
 
-# 1) Toolchain + utilities for building libpostal, plus LazyVim deps
+# 1) Toolchain + utilities for building libpostal, plus LazyVim deps.
+# poppler-utils provides `pdfinfo`, required by backend/documents_parser (the
+# Elmhurst Input-Summary / SAP-worksheet PDF fixtures in the SAP corpus tests
+# shell out to it).
 RUN apt-get update && apt-get install -y --no-install-recommends \
     sudo jq vim curl git ca-certificates wget \
     build-essential pkg-config automake autoconf libtool \
-    ripgrep fd-find make unzip bash-completion \
+    ripgrep fd-find make unzip bash-completion poppler-utils \
  && rm -rf /var/lib/apt/lists/*
 
 # 1b) Headed-browser viewer stack for the hyde Elmhurst automation.

backend/epc_api/json_samples/real_life_examples/SAP-Schema-16.2/uprn_100020933699/elmhurst_inputs.md

@@ -0,0 +1,86 @@
+# Elmhurst RdSAP inputs — UPRN 100020933699 (cert 9548-2053-6299-9947-0950, SAP-Schema-16.2)
+
+**Lodged SAP:** 70   **Our engine:** 72 (continuous 72.29)   ← compare Elmhurst against the engine
+**Property:** End-terrace HOUSE, age band G (1983–1990), mains-gas regular boiler + cylinder, TFA 62 m²
+
+**Schema note:** SAP-Schema-16.2 is RdSAP-shaped (reduced-field) — mapped via `_normalize_sap_schema_16_2` → RdSAP-17.1 mapper. This is a REDUCED-FIELD cert (descriptions + glazed-area band, no measured U-values), so unlike the 17.1 new-builds the engine and Elmhurst should both use RdSAP age-band/description U-values — expect a TIGHTER agreement.
+
+**Known divergences / gaps to watch:**
+- **Party wall:** 16.2 does not lodge `party_wall_length`; the normalizer defaults it to 0, so the engine currently models NO party wall. An end-terrace HAS one party wall — Elmhurst will model it. **This is the likely main divergence; check the worksheet party-wall line.**
+- Age band G → Elmhurst on-screen band **G 1983-1990**.
+
+## Property Description
+| Elmhurst field | Value | Notes |
+|---|---|---|
+| Property Type | **House** | dwelling_type "End-terrace house" (switch from FLAT — prior cert) |
+| Built form | **End-Terrace** | built_form 3 |
+| Age band | **G 1983-1990** | construction_age_band G |
+| Storeys | 2 | floor 0 + floor 1 |
+| Habitable rooms | 4 | habitable_room_count 4 |
+
+## Dimensions
+| Elmhurst field | Value | Notes |
+|---|---|---|
+| Ground floor area | 31.06 m² | floor 0 |
+| First floor area | 31.06 m² | floor 1 |
+| Room height (ground / first) | 2.40 / 2.65 m | room_height |
+| Heat-loss perimeter (each) | 15.8 m | heat_loss_perimeter |
+| Party-wall length (each) | **see note** | 16.2 lodges none; for an end-terrace enter the real party-wall length if Elmhurst derives it from built-form, else note the divergence |
+
+## Walls
+| Elmhurst field | Value | Notes |
+|---|---|---|
+| Construction | Cavity | wall_construction 4 |
+| Insulation | **Filled** | wall_insulation_type 2 = filled cavity ("Cavity wall, filled cavity") |
+| Thickness | 280 mm | wall_thickness |
+| Party wall | Present (End-Terrace) — Unable to determine | built_form 3 |
+
+## Roofs
+| Elmhurst field | Value | Notes |
+|---|---|---|
+| Type | Pitched, access to loft | roof_construction 4 |
+| Insulation at | Joists | roof_insulation_location 2 |
+| Thickness | 100 mm | roof_insulation_thickness "100mm" |
+
+## Floors
+| Elmhurst field | Value | Notes |
+|---|---|---|
+| Location / type | Ground floor / Solid | floor_construction 1 |
+| Insulation | **None** | "Solid, no insulation (assumed)" |
+
+## Openings
+| Elmhurst field | Value | Notes |
+|---|---|---|
+| Windows | **Single glazed**, glazed-area band Normal | glazed_area 1, multiple_glazing_type ND, "Single glazed" |
+| Doors | **2 doors, uninsulated** | door_count 2, insulated_door_count 0 (high U — solid/older doors) |
+
+## Ventilation & Lighting
+| Elmhurst field | Value | Notes |
+|---|---|---|
+| Ventilation | Natural | no MV; no air-permeability test lodged (ap50/ap4 None) |
+| Extract fans / flues | 0 / 0 | none lodged; open chimneys 0 |
+| Sheltered sides | 1 | sheltered_sides 1 |
+| Air Pressure Test | **None** (do NOT enter Blower Door) | no test lodged — leave method blank |
+| Lighting | 22% low-energy | low_energy 2 / total 9 outlets |
+
+## Space Heating
+| Elmhurst field | Value | Notes |
+|---|---|---|
+| Main heating | Mains gas **regular boiler + radiators** | fuel 26, emitter 1, control 2106, fan-assisted flue, PCDB 10321. NOT a combi — has a cylinder → use the BGB regular condensing/non-condensing cascade option (per age band G, likely non-condensing) |
+| Secondary | None | secondary "None" |
+
+## Water Heating
+| Elmhurst field | Value | Notes |
+|---|---|---|
+| Water heating | From main (901), gas | water_heating_fuel 26 |
+| Hot water cylinder | **Present** — 110 L (Normal), Foam, 25 mm | has_hot_water_cylinder True, cylinder_size 2, insulation type 1 (foam) 25 mm |
+| Solar / WWHRS / FGHRS | None | — |
+
+## Fields to clear in Elmhurst (do NOT map)
+| Elmhurst field | Set to | Why absent |
+|---|---|---|
+| Flats page | (gone — House now) | switch from prior FLAT cert |
+| Conservatory | none / uncheck | not lodged |
+| Air Pressure Test method | **blank** | no test lodged (prior certs had Blower Door — CLEAR it) |
+| Main Heating 2 / Secondary | none | single system |
+| PV / Wind / Hydro | none | none lodged |

backend/epc_api/json_samples/real_life_examples/SAP-Schema-16.2/uprn_100020933699/epc.json

@@ -0,0 +1,310 @@
+{
+  "uprn": 100020933699,
+  "roofs": [
+    {
+      "description": "Pitched, 100 mm loft insulation",
+      "energy_efficiency_rating": 3,
+      "environmental_efficiency_rating": 3
+    }
+  ],
+  "walls": [
+    {
+      "description": "Cavity wall, filled cavity",
+      "energy_efficiency_rating": 4,
+      "environmental_efficiency_rating": 4
+    }
+  ],
+  "floors": [
+    {
+      "description": "Solid, no insulation (assumed)",
+      "energy_efficiency_rating": 0,
+      "environmental_efficiency_rating": 0
+    }
+  ],
+  "status": "entered",
+  "tenure": 2,
+  "windows": [
+    {
+      "description": "Single glazed",
+      "energy_efficiency_rating": 1,
+      "environmental_efficiency_rating": 1
+    }
+  ],
+  "lighting": {
+    "description": "Low energy lighting in 22% of fixed outlets",
+    "energy_efficiency_rating": 2,
+    "environmental_efficiency_rating": 2
+  },
+  "postcode": "SE18 2PE",
+  "hot_water": {
+    "description": "From main system",
+    "energy_efficiency_rating": 4,
+    "environmental_efficiency_rating": 4
+  },
+  "post_town": "LONDON",
+  "built_form": 3,
+  "created_at": "2013-01-14 15:52:33.000000",
+  "door_count": 2,
+  "glazed_area": 1,
+  "region_code": 17,
+  "report_type": 2,
+  "sap_heating": {
+    "wwhrs": {
+      "rooms_with_bath_and_or_shower": 1,
+      "rooms_with_mixer_shower_no_bath": 0,
+      "rooms_with_bath_and_mixer_shower": 0
+    },
+    "cylinder_size": 2,
+    "water_heating_code": 901,
+    "water_heating_fuel": 26,
+    "cylinder_thermostat": "Y",
+    "main_heating_details": [
+      {
+        "has_fghrs": "N",
+        "main_fuel_type": 26,
+        "boiler_flue_type": 2,
+        "fan_flue_present": "Y",
+        "heat_emitter_type": 1,
+        "boiler_index_number": 10321,
+        "main_heating_number": 1,
+        "main_heating_control": 2106,
+        "main_heating_category": 2,
+        "main_heating_fraction": 1,
+        "main_heating_data_source": 1
+      }
+    ],
+    "cylinder_insulation_type": 1,
+    "has_fixed_air_conditioning": "false",
+    "cylinder_insulation_thickness": 25
+  },
+  "sap_version": 9.91,
+  "schema_type": "SAP-Schema-16.2",
+  "uprn_source": "Energy Assessor",
+  "country_code": "EAW",
+  "main_heating": [
+    {
+      "description": "Boiler and radiators, mains gas",
+      "energy_efficiency_rating": 4,
+      "environmental_efficiency_rating": 4
+    }
+  ],
+  "dwelling_type": "End-terrace house",
+  "language_code": 1,
+  "property_type": 0,
+  "address_line_1": "1, Acland Close",
+  "schema_version": "LIG-16.1",
+  "assessment_type": "RdSAP",
+  "completion_date": "2013-01-14",
+  "inspection_date": "2013-01-14",
+  "extensions_count": 0,
+  "measurement_type": 1,
+  "total_floor_area": 62,
+  "transaction_type": 8,
+  "conservatory_type": 1,
+  "heated_room_count": 4,
+  "registration_date": "2013-01-14",
+  "restricted_access": 0,
+  "sap_energy_source": {
+    "main_gas": "Y",
+    "meter_type": 2,
+    "photovoltaic_supply": {
+      "percent_roof_area": 0
+    },
+    "wind_turbines_count": 0,
+    "wind_turbines_terrain_type": 2
+  },
+  "secondary_heating": {
+    "description": "None",
+    "energy_efficiency_rating": 0,
+    "environmental_efficiency_rating": 0
+  },
+  "sap_building_parts": [
+    {
+      "identifier": "Main Dwelling",
+      "wall_dry_lined": "N",
+      "wall_thickness": 280,
+      "floor_heat_loss": 7,
+      "roof_construction": 4,
+      "wall_construction": 4,
+      "building_part_number": 1,
+      "sap_floor_dimensions": [
+        {
+          "floor": 0,
+          "room_height": 2.4,
+          "floor_insulation": 1,
+          "total_floor_area": 31.06,
+          "floor_construction": 1,
+          "heat_loss_perimeter": 15.8
+        },
+        {
+          "floor": 1,
+          "room_height": 2.4,
+          "total_floor_area": 31.06,
+          "heat_loss_perimeter": 15.8
+        }
+      ],
+      "wall_insulation_type": 2,
+      "construction_age_band": "G",
+      "wall_thickness_measured": "Y",
+      "roof_insulation_location": 2,
+      "roof_insulation_thickness": "100mm"
+    }
+  ],
+  "low_energy_lighting": 22,
+  "solar_water_heating": "N",
+  "bedf_revision_number": 333,
+  "habitable_room_count": 4,
+  "heating_cost_current": {
+    "value": 370,
+    "currency": "GBP"
+  },
+  "insulated_door_count": 0,
+  "co2_emissions_current": 2.2,
+  "energy_rating_average": 60,
+  "energy_rating_current": 70,
+  "lighting_cost_current": {
+    "value": 66,
+    "currency": "GBP"
+  },
+  "main_heating_controls": [
+    {
+      "description": "Programmer, room thermostat and TRVs",
+      "energy_efficiency_rating": 4,
+      "environmental_efficiency_rating": 4
+    }
+  ],
+  "multiple_glazing_type": "ND",
+  "open_fireplaces_count": 0,
+  "has_hot_water_cylinder": "true",
+  "heating_cost_potential": {
+    "value": 296,
+    "currency": "GBP"
+  },
+  "hot_water_cost_current": {
+    "value": 106,
+    "currency": "GBP"
+  },
+  "mechanical_ventilation": 0,
+  "percent_draughtproofed": 100,
+  "suggested_improvements": [
+    {
+      "sequence": 1,
+      "typical_saving": {
+        "value": 27,
+        "currency": "GBP"
+      },
+      "indicative_cost": "\u00a3800 - \u00a31,200",
+      "improvement_type": "W",
+      "improvement_details": {
+        "improvement_number": 47
+      },
+      "improvement_category": 5,
+      "energy_performance_rating": 71,
+      "environmental_impact_rating": 73
+    },
+    {
+      "sequence": 2,
+      "typical_saving": {
+        "value": 26,
+        "currency": "GBP"
+      },
+      "indicative_cost": "\u00a335",
+      "improvement_type": "E",
+      "improvement_details": {
+        "improvement_number": 35
+      },
+      "improvement_category": 5,
+      "energy_performance_rating": 72,
+      "environmental_impact_rating": 74
+    },
+    {
+      "sequence": 3,
+      "typical_saving": {
+        "value": 33,
+        "currency": "GBP"
+      },
+      "indicative_cost": "\u00a34,000 - \u00a36,000",
+      "improvement_type": "N",
+      "improvement_details": {
+        "improvement_number": 19
+      },
+      "improvement_category": 5,
+      "energy_performance_rating": 74,
+      "environmental_impact_rating": 76
+    },
+    {
+      "sequence": 4,
+      "typical_saving": {
+        "value": 52,
+        "currency": "GBP"
+      },
+      "indicative_cost": "\u00a33,300 - \u00a36,500",
+      "improvement_type": "O",
+      "improvement_details": {
+        "improvement_number": 8
+      },
+      "improvement_category": 5,
+      "energy_performance_rating": 77,
+      "environmental_impact_rating": 80
+    },
+    {
+      "sequence": 5,
+      "typical_saving": {
+        "value": 236,
+        "currency": "GBP"
+      },
+      "indicative_cost": "\u00a39,000 - \u00a314,000",
+      "improvement_type": "U",
+      "improvement_details": {
+        "improvement_number": 34
+      },
+      "improvement_category": 5,
+      "energy_performance_rating": 89,
+      "environmental_impact_rating": 92
+    },
+    {
+      "sequence": 6,
+      "typical_saving": {
+        "value": 19,
+        "currency": "GBP"
+      },
+      "indicative_cost": "\u00a31,500 - \u00a34,000",
+      "improvement_type": "V",
+      "improvement_details": {
+        "improvement_number": 44
+      },
+      "improvement_category": 5,
+      "energy_performance_rating": 90,
+      "environmental_impact_rating": 92
+    }
+  ],
+  "co2_emissions_potential": 0.5,
+  "energy_rating_potential": 90,
+  "lighting_cost_potential": {
+    "value": 37,
+    "currency": "GBP"
+  },
+  "hot_water_cost_potential": {
+    "value": 72,
+    "currency": "GBP"
+  },
+  "renewable_heat_incentive": {
+    "water_heating": 2577,
+    "impact_of_loft_insulation": -309,
+    "space_heating_existing_dwelling": 5864
+  },
+  "seller_commission_report": "Y",
+  "energy_consumption_current": 189,
+  "has_fixed_air_conditioning": "false",
+  "multiple_glazed_proportion": 0,
+  "calculation_software_version": 8.0,
+  "energy_consumption_potential": 36,
+  "environmental_impact_current": 71,
+  "fixed_lighting_outlets_count": 9,
+  "current_energy_efficiency_band": "C",
+  "environmental_impact_potential": 92,
+  "has_heated_separate_conservatory": "false",
+  "potential_energy_efficiency_band": "B",
+  "co2_emissions_current_per_floor_area": 36,
+  "low_energy_fixed_lighting_outlets_count": 2
+}

backend/epc_api/json_samples/real_life_examples/SAP-Schema-17.1/uprn_10093116529/elmhurst_inputs.md

@@ -0,0 +1,88 @@
+# Elmhurst RdSAP inputs — UPRN 10093116529 (cert 8178-7436-5600-9809-0906, SAP-Schema-17.1)
+
+**Lodged SAP:** 81   **Our engine:** 80 (continuous 80.22)   ← compare Elmhurst against the engine
+**Property:** ground-floor FLAT, 2017 build, mains-gas combi, TFA 49.0 m²
+
+**Known divergences (flag, don't tune) — same full-SAP→RdSAP pattern as uprn_10093116543:**
+- **Walls/floor measured U:** cert lodges measured U (wall 0.184, floor 0.12); engine uses them, Elmhurst RdSAP forces band-L defaults (~0.28 / ~0.23). Expected residual.
+- **Boiler:** cert PCDB 17644 (88.5%); Elmhurst PCDB search disabled → generic BGW combi 84%.
+- **Age band:** engine 'M', build year 2017 → enter Elmhurst band **L (2012–2022)**.
+
+## Property Description
+| Elmhurst field | Value | Notes |
+|---|---|---|
+| Property Type | **Flat** | dwelling_type "Ground-floor flat" — SWITCH from House (prior cert) |
+| Built form | (flat — N/A) | — |
+| Age band | **L (2012–2022)** | construction_year 2017 |
+| Habitable rooms | 2 | habitable_rooms_count 2 |
+| Storeys | 1 | single-storey flat |
+
+## Flats
+| Elmhurst field | Value | Notes |
+|---|---|---|
+| Position of flat | Ground Floor | ground-floor flat |
+| Floor level | 0 | ground = storey 0 |
+| Corridor | **None** (all-exposed) | the "to corridor" wall is keyed as a semi-exposed wall element instead — see Walls. Avoids the sheltered-alt-wall validation trap. |
+
+## Dimensions
+| Elmhurst field | Value | Notes |
+|---|---|---|
+| Lowest-floor area | 49.03 m² | floor dim[0] |
+| Room height | 2.60 m | room_height_m |
+| Heat-loss perimeter | 28.45 m | heat_loss_perimeter_m |
+| Party-wall length | 4.34 m | party_wall_length_m |
+
+## Walls
+| Elmhurst field | Value | Notes |
+|---|---|---|
+| Main wall | Cavity / As Built | wall_construction 4; cert lodges measured U 0.184 (Elmhurst RdSAP default ~0.28) |
+| Wall area (external) | 56.6 m² | Wall 1 "External" |
+| "To corridor" wall | semi-exposed, 17.37 m², U 0.15 | Wall 3 (type 3). Heat loss to unheated corridor — key as an alternative/sheltered wall if Elmhurst allows; else note divergence. |
+| Party wall | Present, **U Unable to determine** | Wall 2 (type 4) area 11.28; party_walls_w_per_k 2.82 |
+
+## Roofs
+| Elmhurst field | Value | Notes |
+|---|---|---|
+| Roof type | **A Another dwelling above** | ground-floor flat → roof_w_per_k = 0 |
+
+## Floors
+| Elmhurst field | Value | Notes |
+|---|---|---|
+| Location | Ground floor | floor_type 2 |
+| Type / insulation | Solid / As built | cert lodges measured U 0.12 (Elmhurst RdSAP ~0.23) |
+
+## Openings
+| Elmhurst field | Value | Notes |
+|---|---|---|
+| Windows (combined) | ~24.9 m², East, Double post-2022 | 7 synth windows; U 1.4 / g 0.72 / frame 0.7 |
+| Doors | 1 insulated, U 1.6 | door_count 1 |
+
+## Ventilation & Lighting
+| Elmhurst field | Value | Notes |
+|---|---|---|
+| Ventilation | Natural + 2 intermittent extract fans | extract_fans_count 2 |
+| Air Pressure Test | Blower Door, **3.45** (+ cert number) | air_permeability_ap50 3.45 |
+| Sheltered sides | 2 | sheltered_sides 2 |
+| Lighting | 100% low-energy | 10 bulbs, all low-energy |
+
+## Space Heating
+| Elmhurst field | Value | Notes |
+|---|---|---|
+| Main heating | Mains gas condensing **combi** (generic BGW 84% substitute) | fuel 1, emitter radiators, control 2110, fan-assisted balanced flue, PCDB 17644 (88.5% — can't enter) |
+| Secondary | None | — |
+
+## Water Heating
+| Elmhurst field | Value | Notes |
+|---|---|---|
+| Water heating | From main (combi), gas | code 901; no cylinder |
+| Solar / WWHRS / FGHRS | None | — |
+
+## Fields to clear in Elmhurst (do NOT map)
+| Elmhurst field | Set to | Why absent |
+|---|---|---|
+| Property Description · extensions / room-in-roof | blank | none |
+| Dimensions · 1st-floor row | clear | single-storey flat (was 2-storey house) |
+| Conservatory | none / uncheck | not lodged (CLEAR — prior-cert leftover risk) |
+| Space Heating · Main Heating 2 / Secondary | none | single main system |
+| Water Heating · cylinder | none | combi |
+| New Tech · PV / Wind / Hydro | none | none lodged |

backend/epc_api/json_samples/real_life_examples/SAP-Schema-17.1/uprn_10093116529/epc.json

@@ -0,0 +1,390 @@
+{
+  "uprn": 10093116529,
+  "roofs": [
+    {
+      "description": "(other premises above)",
+      "energy_efficiency_rating": 0,
+      "environmental_efficiency_rating": 0
+    }
+  ],
+  "walls": [
+    {
+      "description": "Average thermal transmittance 0.17 W/m\u00b2K",
+      "energy_efficiency_rating": 5,
+      "environmental_efficiency_rating": 5
+    }
+  ],
+  "floors": [
+    {
+      "description": "Average thermal transmittance 0.12 W/m\u00b2K",
+      "energy_efficiency_rating": 5,
+      "environmental_efficiency_rating": 5
+    }
+  ],
+  "status": "entered",
+  "tenure": "ND",
+  "windows": {
+    "description": "High performance glazing",
+    "energy_efficiency_rating": 5,
+    "environmental_efficiency_rating": 5
+  },
+  "lighting": {
+    "description": "Low energy lighting in all fixed outlets",
+    "energy_efficiency_rating": 5,
+    "environmental_efficiency_rating": 5
+  },
+  "postcode": "PO10 8BG",
+  "data_type": 2,
+  "hot_water": {
+    "description": "From main system, flue gas heat recovery",
+    "energy_efficiency_rating": 5,
+    "environmental_efficiency_rating": 5
+  },
+  "post_town": "EMSWORTH",
+  "built_form": 2,
+  "created_at": "2018-06-04 10:56:20",
+  "living_area": 21.77,
+  "orientation": 0,
+  "region_code": 16,
+  "report_type": 3,
+  "sap_heating": {
+    "thermal_store": 1,
+    "water_fuel_type": 1,
+    "water_heating_code": 901,
+    "main_heating_details": [
+      {
+        "has_fghrs": "true",
+        "main_fuel_type": 1,
+        "heat_emitter_type": 1,
+        "fghrs_index_number": 60031,
+        "emitter_temperature": 1,
+        "is_flue_fan_present": "true",
+        "main_heating_number": 1,
+        "main_heating_control": 2110,
+        "is_interlocked_system": "true",
+        "main_heating_category": 2,
+        "main_heating_fraction": 1,
+        "main_heating_flue_type": 2,
+        "central_heating_pump_age": 2,
+        "main_heating_data_source": 1,
+        "main_heating_index_number": 17644,
+        "has_separate_delayed_start": "true",
+        "load_or_weather_compensation": 0,
+        "is_central_heating_pump_in_heated_space": "true"
+      }
+    ],
+    "has_hot_water_cylinder": "false",
+    "has_fixed_air_conditioning": "false",
+    "secondary_heating_category": 1
+  },
+  "sap_version": 9.92,
+  "schema_type": "SAP-Schema-17.1",
+  "uprn_source": "Energy Assessor",
+  "country_code": "ENG",
+  "main_heating": [
+    {
+      "description": "Boiler and radiators, mains gas",
+      "energy_efficiency_rating": 4,
+      "environmental_efficiency_rating": 4
+    }
+  ],
+  "air_tightness": {
+    "description": "Air permeability 3.5 m\u00b3/h.m\u00b2 (as tested)",
+    "energy_efficiency_rating": 4,
+    "environmental_efficiency_rating": 4
+  },
+  "dwelling_type": "Ground-floor flat",
+  "language_code": 1,
+  "property_type": 2,
+  "address_line_1": "6, Woodfield Park Road",
+  "assessment_date": "2018-06-01",
+  "assessment_type": "SAP",
+  "completion_date": "2018-06-04",
+  "inspection_date": "2018-06-01",
+  "sap_ventilation": {
+    "psv_count": 0,
+    "pressure_test": 1,
+    "air_permeability": 3.45,
+    "open_flues_count": 0,
+    "ventilation_type": 1,
+    "extract_fans_count": 2,
+    "open_fireplaces_count": 0,
+    "sheltered_sides_count": 2,
+    "flueless_gas_fires_count": 0
+  },
+  "design_water_use": 1,
+  "sap_data_version": 9.92,
+  "sap_flat_details": {
+    "level": 1
+  },
+  "total_floor_area": 49,
+  "transaction_type": 6,
+  "conservatory_type": 1,
+  "registration_date": "2018-06-04",
+  "sap_energy_source": {
+    "electricity_tariff": 1,
+    "wind_turbines_count": 0,
+    "wind_turbine_terrain_type": 2,
+    "fixed_lighting_outlets_count": 10,
+    "low_energy_fixed_lighting_outlets_count": 10,
+    "low_energy_fixed_lighting_outlets_percentage": 100
+  },
+  "sap_opening_types": [
+    {
+      "name": 1,
+      "type": 4,
+      "u_value": 1.4,
+      "data_source": 2,
+      "description": "Window",
+      "frame_factor": 0.7,
+      "glazing_type": 4,
+      "solar_transmittance": 0.72
+    },
+    {
+      "name": 8,
+      "type": 1,
+      "u_value": 1.6,
+      "data_source": 2,
+      "description": "Front Door",
+      "glazing_type": 1
+    }
+  ],
+  "secondary_heating": {
+    "description": "None",
+    "energy_efficiency_rating": 0,
+    "environmental_efficiency_rating": 0
+  },
+  "sap_building_parts": [
+    {
+      "sap_walls": [
+        {
+          "name": "Wall 1",
+          "u_value": 0.184,
+          "wall_type": 2,
+          "description": "External",
+          "total_wall_area": 56.6,
+          "is_curtain_walling": "false"
+        },
+        {
+          "name": "Wall 3",
+          "u_value": 0.15,
+          "wall_type": 3,
+          "description": "To corridor",
+          "total_wall_area": 17.37,
+          "is_curtain_walling": "false"
+        },
+        {
+          "name": "Wall 2",
+          "u_value": 0,
+          "wall_type": 4,
+          "description": "To flat",
+          "total_wall_area": 11.28
+        }
+      ],
+      "identifier": "Main Dwelling",
+      "overshading": 2,
+      "sap_openings": [
+        {
+          "name": 1,
+          "type": 1,
+          "width": 0.72,
+          "height": 2.5,
+          "location": "Wall 1",
+          "orientation": 3
+        },
+        {
+          "name": 2,
+          "type": 1,
+          "width": 1.6,
+          "height": 2.5,
+          "location": "Wall 1",
+          "orientation": 3
+        },
+        {
+          "name": 3,
+          "type": 1,
+          "width": 1,
+          "height": 2.5,
+          "location": "Wall 1",
+          "orientation": 7
+        },
+        {
+          "name": 4,
+          "type": 1,
+          "width": 2.5,
+          "height": 2.5,
+          "location": "Wall 1",
+          "orientation": 7
+        },
+        {
+          "name": 5,
+          "type": 1,
+          "width": 1.15,
+          "height": 2.5,
+          "location": "Wall 1",
+          "orientation": 1
+        },
+        {
+          "name": 6,
+          "type": 1,
+          "width": 1.5,
+          "height": 2.5,
+          "location": "Wall 1",
+          "orientation": 1
+        },
+        {
+          "name": 7,
+          "type": 1,
+          "width": 1.5,
+          "height": 2.5,
+          "location": "Wall 1",
+          "orientation": 1
+        },
+        {
+          "name": 8,
+          "type": 8,
+          "width": 1,
+          "height": 2.1,
+          "location": "Wall 3",
+          "orientation": 0
+        }
+      ],
+      "construction_year": 2017,
+      "sap_thermal_bridges": {
+        "thermal_bridges": [
+          {
+            "length": 10.97,
+            "psi_value": 0.3,
+            "psi_value_source": 2,
+            "thermal_bridge_type": "E2"
+          },
+          {
+            "length": 9.97,
+            "psi_value": 0.04,
+            "psi_value_source": 2,
+            "thermal_bridge_type": "E3"
+          },
+          {
+            "length": 39.2,
+            "psi_value": 0.05,
+            "psi_value_source": 2,
+            "thermal_bridge_type": "E4"
+          },
+          {
+            "length": 21.96,
+            "psi_value": 0.16,
+            "psi_value_source": 2,
+            "thermal_bridge_type": "E5"
+          },
+          {
+            "length": 21.96,
+            "psi_value": 0.07,
+            "psi_value_source": 2,
+            "thermal_bridge_type": "E7"
+          },
+          {
+            "length": 10.4,
+            "psi_value": 0.09,
+            "psi_value_source": 2,
+            "thermal_bridge_type": "E16"
+          },
+          {
+            "length": 2.6,
+            "psi_value": -0.09,
+            "psi_value_source": 2,
+            "thermal_bridge_type": "E17"
+          },
+          {
+            "length": 2.4,
+            "psi_value": 0.06,
+            "psi_value_source": 2,
+            "thermal_bridge_type": "E18"
+          },
+          {
+            "length": 6.68,
+            "psi_value": 0.16,
+            "psi_value_source": 4,
+            "thermal_bridge_type": "P1"
+          },
+          {
+            "length": 6.68,
+            "psi_value": 0,
+            "psi_value_source": 4,
+            "thermal_bridge_type": "P3"
+          }
+        ],
+        "thermal_bridge_code": 5
+      },
+      "building_part_number": 1,
+      "sap_floor_dimensions": [
+        {
+          "storey": 0,
+          "u_value": 0.12,
+          "floor_type": 2,
+          "description": "Floor 1",
+          "storey_height": 2.6,
+          "heat_loss_area": 49.03,
+          "total_floor_area": 49.03
+        }
+      ],
+      "thermal_mass_parameter": 100
+    }
+  ],
+  "heating_cost_current": {
+    "value": 185,
+    "currency": "GBP"
+  },
+  "co2_emissions_current": 0.9,
+  "energy_rating_average": 60,
+  "energy_rating_current": 81,
+  "lighting_cost_current": {
+    "value": 37,
+    "currency": "GBP"
+  },
+  "main_heating_controls": [
+    {
+      "description": "Time and temperature zone control",
+      "energy_efficiency_rating": 5,
+      "environmental_efficiency_rating": 5
+    }
+  ],
+  "has_hot_water_cylinder": "false",
+  "heating_cost_potential": {
+    "value": 185,
+    "currency": "GBP"
+  },
+  "hot_water_cost_current": {
+    "value": 58,
+    "currency": "GBP"
+  },
+  "co2_emissions_potential": 0.9,
+  "energy_rating_potential": 81,
+  "lighting_cost_potential": {
+    "value": 37,
+    "currency": "GBP"
+  },
+  "schema_version_original": "LIG-17.0",
+  "hot_water_cost_potential": {
+    "value": 58,
+    "currency": "GBP"
+  },
+  "is_in_smoke_control_area": "unknown",
+  "renewable_heat_incentive": {
+    "rhi_new_dwelling": {
+      "space_heating": 1927,
+      "water_heating": 1458
+    }
+  },
+  "seller_commission_report": "Y",
+  "energy_consumption_current": 108,
+  "has_fixed_air_conditioning": "false",
+  "multiple_glazed_percentage": 100,
+  "calculation_software_version": 6.2,
+  "energy_consumption_potential": 108,
+  "environmental_impact_current": 85,
+  "current_energy_efficiency_band": "B",
+  "environmental_impact_potential": 85,
+  "has_heated_separate_conservatory": "false",
+  "potential_energy_efficiency_band": "B",
+  "co2_emissions_current_per_floor_area": 19
+}

datatypes/epc/domain/mapper.py

@@ -1,3 +1,4 @@
+import copy
 import re
 from dataclasses import replace
 from datetime import date
@@ -2552,6 +2553,19 @@ class EpcPropertyDataMapper:
             return EpcPropertyDataMapper.from_sap_schema_17_1(
                 from_dict(SapSchema17_1, data)
             )
+        if schema == "SAP-Schema-16.2":
+            # SAP-Schema-16.2 is structurally an RdSAP-17.1 cert (reduced fields,
+            # glazed_area band, construction-code building parts) under a different
+            # name + a handful of renamed/omitted fields — normalise it onto the
+            # RdSAP-17.1 shape and reuse that tested mapper. See
+            # `_normalize_sap_schema_16_2`.
+            from datatypes.epc.schema.rdsap_schema_17_1 import RdSapSchema17_1
+
+            return _clear_basement_flag_when_system_built(
+                EpcPropertyDataMapper.from_rdsap_schema_17_1(
+                    from_dict(RdSapSchema17_1, _normalize_sap_schema_16_2(data))
+                )
+            )
 
         raise ValueError(f"Unsupported EPC schema: {schema!r}")
 
@@ -3008,6 +3022,81 @@ def _default_missing_post_town(data: Dict[str, Any]) -> Dict[str, Any]:
     return {**data, "post_town": ""}
 
 
+def _normalize_sap_schema_16_2(data: Dict[str, Any]) -> Dict[str, Any]:
+    """Rewrite a `SAP-Schema-16.2` API doc onto the `RdSAP-Schema-17.1` shape so
+    it can reuse the tested `from_rdsap_schema_17_1` mapper.
+
+    Despite the "SAP-Schema" name, 16.2 is structurally an RdSAP cert (reduced
+    fields: a `glazed_area` *band* not measured openings, construction-code
+    building parts, `main_gas`/`meter_type` energy source, a PCDB boiler index).
+    It differs from RdSAP-17.1 only by a handful of field names plus three
+    fields it omits:
+      * top-level   `windows` (list) → `window` (first element);
+                    `schema_version` → `schema_version_original`
+      * sap_heating `wwhrs` → `instantaneous_wwhrs` (identical shape);
+                    `immersion_heating_type` defaulted (16.2 omits it — gas cert)
+      * main_heating_details[] `boiler_index_number` → `main_heating_index_number`
+                    (preserves PCDB efficiency); `emitter_temperature` defaulted
+      * sap_floor_dimensions[] `party_wall_length` defaulted to 0 (16.2 does not
+                    lodge it — note: party-wall heat loss is then unmodelled)
+      * sap_energy_source `main_gas` → `mains_gas`
+
+    Mirrors `_normalize_shower_outlets` — mutates a deep copy, never the
+    caller's dict. Defaults use setdefault so a 16.2 cert that *does* carry the
+    RdSAP-17.1 name is left untouched.
+    """
+    d: Dict[str, Any] = copy.deepcopy(data)
+
+    def _dicts(value: Any) -> List[Dict[str, Any]]:
+        """The dict elements of `value` when it is a list, else []."""
+        if not isinstance(value, list):
+            return []
+        items: List[Any] = cast(List[Any], value)
+        return [cast(Dict[str, Any], x) for x in items if isinstance(x, dict)]
+
+    windows: Any = d.get("windows")
+    if isinstance(windows, list) and windows:
+        window_list: List[Any] = cast(List[Any], windows)
+        d.setdefault("window", window_list[0])
+    d.setdefault("schema_version_original", d.get("schema_version", ""))
+
+    # 16.2 lodges glazing in BOTH `multiple_glazing_type` (frequently the "ND"
+    # not-defined sentinel) AND the windows[].description. When the numeric field
+    # is undefined, honour an explicit "Single glazed" description so it is not
+    # defaulted to double — RdSAP-21 code 5 = single glazing (cascade single
+    # slot, U≈4.8). Otherwise keep the ND→double-modal default the cascade uses.
+    glazing_type: Any = d.get("multiple_glazing_type")
+    if not isinstance(glazing_type, int):
+        window: Any = d.get("window")
+        description = ""
+        if isinstance(window, dict):
+            description = str(cast(Dict[str, Any], window).get("description") or "").lower()
+        if "single" in description:
+            d["multiple_glazing_type"] = 5
+
+    sap_heating: Any = d.get("sap_heating")
+    if isinstance(sap_heating, dict):
+        heating: Dict[str, Any] = cast(Dict[str, Any], sap_heating)
+        if "wwhrs" in heating:
+            heating.setdefault("instantaneous_wwhrs", heating["wwhrs"])
+        heating.setdefault("immersion_heating_type", None)
+        for mh in _dicts(heating.get("main_heating_details")):
+            if "boiler_index_number" in mh:
+                mh.setdefault("main_heating_index_number", mh["boiler_index_number"])
+            mh.setdefault("emitter_temperature", None)
+
+    for bp in _dicts(d.get("sap_building_parts")):
+        for fd in _dicts(bp.get("sap_floor_dimensions")):
+            fd.setdefault("party_wall_length", 0)
+
+    energy_source: Any = d.get("sap_energy_source")
+    if isinstance(energy_source, dict):
+        source: Dict[str, Any] = cast(Dict[str, Any], energy_source)
+        if "main_gas" in source:
+            source.setdefault("mains_gas", source["main_gas"])
+    return d
+
+
 def _count_shower_outlets_by_type(
     schema_shower_outlets: Any,
     target_type: int,

datatypes/epc/domain/tests/test_from_sap_schema.py

@@ -376,3 +376,54 @@ class TestFromSapSchema17_1Perimeter:
         schema = from_dict(SapSchema17_1, data)
         with pytest.raises(UnmappedApiCode):
             EpcPropertyDataMapper.from_sap_schema_17_1(schema)
+
+
+class TestFromSapSchema16_2:
+    """SAP-Schema-16.2 — structurally an RdSAP-17.1 cert under a different name
+    + a few renamed/omitted fields. `from_api_response` normalises it onto the
+    RdSAP-17.1 shape (`_normalize_sap_schema_16_2`) and reuses that mapper.
+    Regression for uprn_100020933699 (cert 9548-…-0950, End-terrace house)."""
+
+    def test_16_2_dispatches_and_maps_via_rdsap_17_1(self) -> None:
+        # Arrange / Act — the raw 16.2 doc must dispatch (no "Unsupported
+        # schema") and map all the renamed seams: windows→window,
+        # main_gas→mains_gas, boiler_index_number→main_heating_index_number,
+        # wwhrs→instantaneous_wwhrs.
+        epc = EpcPropertyDataMapper.from_api_response(load("sap_16_2.json"))
+
+        # Assert — identity + the seams that would silently drop on a bad rename.
+        assert isinstance(epc, EpcPropertyData)
+        assert epc.uprn == 100020933699
+        assert epc.total_floor_area_m2 == 62.0
+        assert epc.dwelling_type == "End-terrace house"
+        mh = epc.sap_heating.main_heating_details[0]
+        assert mh.main_fuel_type == 26  # mains gas
+        # boiler_index_number must survive as the PCDB index (efficiency source).
+        assert mh.main_heating_index_number == 10321
+
+    def test_16_2_produces_a_sap_score(self) -> None:
+        # The mapped cert must run end-to-end through the SAP-10 engine.
+        from domain.sap10_calculator.calculator import Sap10Calculator
+
+        epc = EpcPropertyDataMapper.from_api_response(load("sap_16_2.json"))
+        result = Sap10Calculator().calculate(epc)
+        # Lodged 70; engine produces 71 (Elmhurst validation still pending).
+        assert result.sap_score == 71
+
+    def test_16_2_single_glazed_description_honoured_over_nd(self) -> None:
+        # 16.2 lodges multiple_glazing_type "ND" but a "Single glazed" windows
+        # description; the normaliser must route to single glazing (cascade slot
+        # 1, U≈4.8) not the ND→double default — else single-glazed older certs
+        # over-rate. Regression for uprn_100020933699.
+        epc = EpcPropertyDataMapper.from_api_response(load("sap_16_2.json"))
+        assert epc.sap_windows, "expected synthesised windows"
+        assert epc.sap_windows[0].glazing_type == 1  # cascade single-glazing slot
+
+    def test_16_2_normalizer_does_not_mutate_caller_dict(self) -> None:
+        # Mirror _normalize_shower_outlets' contract: the caller's dict is
+        # untouched (deep copy), so a re-dispatch sees the original shape.
+        data = load("sap_16_2.json")
+        before_keys = set(data.keys())
+        EpcPropertyDataMapper.from_api_response(data)
+        assert "window" not in data  # the rename landed only on the copy
+        assert set(data.keys()) == before_keys

datatypes/epc/schema/tests/fixtures/sap_16_2.json

@@ -0,0 +1,310 @@
+{
+  "uprn": 100020933699,
+  "roofs": [
+    {
+      "description": "Pitched, 100 mm loft insulation",
+      "energy_efficiency_rating": 3,
+      "environmental_efficiency_rating": 3
+    }
+  ],
+  "walls": [
+    {
+      "description": "Cavity wall, filled cavity",
+      "energy_efficiency_rating": 4,
+      "environmental_efficiency_rating": 4
+    }
+  ],
+  "floors": [
+    {
+      "description": "Solid, no insulation (assumed)",
+      "energy_efficiency_rating": 0,
+      "environmental_efficiency_rating": 0
+    }
+  ],
+  "status": "entered",
+  "tenure": 2,
+  "windows": [
+    {
+      "description": "Single glazed",
+      "energy_efficiency_rating": 1,
+      "environmental_efficiency_rating": 1
+    }
+  ],
+  "lighting": {
+    "description": "Low energy lighting in 22% of fixed outlets",
+    "energy_efficiency_rating": 2,
+    "environmental_efficiency_rating": 2
+  },
+  "postcode": "SE18 2PE",
+  "hot_water": {
+    "description": "From main system",
+    "energy_efficiency_rating": 4,
+    "environmental_efficiency_rating": 4
+  },
+  "post_town": "LONDON",
+  "built_form": 3,
+  "created_at": "2013-01-14 15:52:33.000000",
+  "door_count": 2,
+  "glazed_area": 1,
+  "region_code": 17,
+  "report_type": 2,
+  "sap_heating": {
+    "wwhrs": {
+      "rooms_with_bath_and_or_shower": 1,
+      "rooms_with_mixer_shower_no_bath": 0,
+      "rooms_with_bath_and_mixer_shower": 0
+    },
+    "cylinder_size": 2,
+    "water_heating_code": 901,
+    "water_heating_fuel": 26,
+    "cylinder_thermostat": "Y",
+    "main_heating_details": [
+      {
+        "has_fghrs": "N",
+        "main_fuel_type": 26,
+        "boiler_flue_type": 2,
+        "fan_flue_present": "Y",
+        "heat_emitter_type": 1,
+        "boiler_index_number": 10321,
+        "main_heating_number": 1,
+        "main_heating_control": 2106,
+        "main_heating_category": 2,
+        "main_heating_fraction": 1,
+        "main_heating_data_source": 1
+      }
+    ],
+    "cylinder_insulation_type": 1,
+    "has_fixed_air_conditioning": "false",
+    "cylinder_insulation_thickness": 25
+  },
+  "sap_version": 9.91,
+  "schema_type": "SAP-Schema-16.2",
+  "uprn_source": "Energy Assessor",
+  "country_code": "EAW",
+  "main_heating": [
+    {
+      "description": "Boiler and radiators, mains gas",
+      "energy_efficiency_rating": 4,
+      "environmental_efficiency_rating": 4
+    }
+  ],
+  "dwelling_type": "End-terrace house",
+  "language_code": 1,
+  "property_type": 0,
+  "address_line_1": "1, Acland Close",
+  "schema_version": "LIG-16.1",
+  "assessment_type": "RdSAP",
+  "completion_date": "2013-01-14",
+  "inspection_date": "2013-01-14",
+  "extensions_count": 0,
+  "measurement_type": 1,
+  "total_floor_area": 62,
+  "transaction_type": 8,
+  "conservatory_type": 1,
+  "heated_room_count": 4,
+  "registration_date": "2013-01-14",
+  "restricted_access": 0,
+  "sap_energy_source": {
+    "main_gas": "Y",
+    "meter_type": 2,
+    "photovoltaic_supply": {
+      "percent_roof_area": 0
+    },
+    "wind_turbines_count": 0,
+    "wind_turbines_terrain_type": 2
+  },
+  "secondary_heating": {
+    "description": "None",
+    "energy_efficiency_rating": 0,
+    "environmental_efficiency_rating": 0
+  },
+  "sap_building_parts": [
+    {
+      "identifier": "Main Dwelling",
+      "wall_dry_lined": "N",
+      "wall_thickness": 280,
+      "floor_heat_loss": 7,
+      "roof_construction": 4,
+      "wall_construction": 4,
+      "building_part_number": 1,
+      "sap_floor_dimensions": [
+        {
+          "floor": 0,
+          "room_height": 2.4,
+          "floor_insulation": 1,
+          "total_floor_area": 31.06,
+          "floor_construction": 1,
+          "heat_loss_perimeter": 15.8
+        },
+        {
+          "floor": 1,
+          "room_height": 2.4,
+          "total_floor_area": 31.06,
+          "heat_loss_perimeter": 15.8
+        }
+      ],
+      "wall_insulation_type": 2,
+      "construction_age_band": "G",
+      "wall_thickness_measured": "Y",
+      "roof_insulation_location": 2,
+      "roof_insulation_thickness": "100mm"
+    }
+  ],
+  "low_energy_lighting": 22,
+  "solar_water_heating": "N",
+  "bedf_revision_number": 333,
+  "habitable_room_count": 4,
+  "heating_cost_current": {
+    "value": 370,
+    "currency": "GBP"
+  },
+  "insulated_door_count": 0,
+  "co2_emissions_current": 2.2,
+  "energy_rating_average": 60,
+  "energy_rating_current": 70,
+  "lighting_cost_current": {
+    "value": 66,
+    "currency": "GBP"
+  },
+  "main_heating_controls": [
+    {
+      "description": "Programmer, room thermostat and TRVs",
+      "energy_efficiency_rating": 4,
+      "environmental_efficiency_rating": 4
+    }
+  ],
+  "multiple_glazing_type": "ND",
+  "open_fireplaces_count": 0,
+  "has_hot_water_cylinder": "true",
+  "heating_cost_potential": {
+    "value": 296,
+    "currency": "GBP"
+  },
+  "hot_water_cost_current": {
+    "value": 106,
+    "currency": "GBP"
+  },
+  "mechanical_ventilation": 0,
+  "percent_draughtproofed": 100,
+  "suggested_improvements": [
+    {
+      "sequence": 1,
+      "typical_saving": {
+        "value": 27,
+        "currency": "GBP"
+      },
+      "indicative_cost": "\u00a3800 - \u00a31,200",
+      "improvement_type": "W",
+      "improvement_details": {
+        "improvement_number": 47
+      },
+      "improvement_category": 5,
+      "energy_performance_rating": 71,
+      "environmental_impact_rating": 73
+    },
+    {
+      "sequence": 2,
+      "typical_saving": {
+        "value": 26,
+        "currency": "GBP"
+      },
+      "indicative_cost": "\u00a335",
+      "improvement_type": "E",
+      "improvement_details": {
+        "improvement_number": 35
+      },
+      "improvement_category": 5,
+      "energy_performance_rating": 72,
+      "environmental_impact_rating": 74
+    },
+    {
+      "sequence": 3,
+      "typical_saving": {
+        "value": 33,
+        "currency": "GBP"
+      },
+      "indicative_cost": "\u00a34,000 - \u00a36,000",
+      "improvement_type": "N",
+      "improvement_details": {
+        "improvement_number": 19
+      },
+      "improvement_category": 5,
+      "energy_performance_rating": 74,
+      "environmental_impact_rating": 76
+    },
+    {
+      "sequence": 4,
+      "typical_saving": {
+        "value": 52,
+        "currency": "GBP"
+      },
+      "indicative_cost": "\u00a33,300 - \u00a36,500",
+      "improvement_type": "O",
+      "improvement_details": {
+        "improvement_number": 8
+      },
+      "improvement_category": 5,
+      "energy_performance_rating": 77,
+      "environmental_impact_rating": 80
+    },
+    {
+      "sequence": 5,
+      "typical_saving": {
+        "value": 236,
+        "currency": "GBP"
+      },
+      "indicative_cost": "\u00a39,000 - \u00a314,000",
+      "improvement_type": "U",
+      "improvement_details": {
+        "improvement_number": 34
+      },
+      "improvement_category": 5,
+      "energy_performance_rating": 89,
+      "environmental_impact_rating": 92
+    },
+    {
+      "sequence": 6,
+      "typical_saving": {
+        "value": 19,
+        "currency": "GBP"
+      },
+      "indicative_cost": "\u00a31,500 - \u00a34,000",
+      "improvement_type": "V",
+      "improvement_details": {
+        "improvement_number": 44
+      },
+      "improvement_category": 5,
+      "energy_performance_rating": 90,
+      "environmental_impact_rating": 92
+    }
+  ],
+  "co2_emissions_potential": 0.5,
+  "energy_rating_potential": 90,
+  "lighting_cost_potential": {
+    "value": 37,
+    "currency": "GBP"
+  },
+  "hot_water_cost_potential": {
+    "value": 72,
+    "currency": "GBP"
+  },
+  "renewable_heat_incentive": {
+    "water_heating": 2577,
+    "impact_of_loft_insulation": -309,
+    "space_heating_existing_dwelling": 5864
+  },
+  "seller_commission_report": "Y",
+  "energy_consumption_current": 189,
+  "has_fixed_air_conditioning": "false",
+  "multiple_glazed_proportion": 0,
+  "calculation_software_version": 8.0,
+  "energy_consumption_potential": 36,
+  "environmental_impact_current": 71,
+  "fixed_lighting_outlets_count": 9,
+  "current_energy_efficiency_band": "C",
+  "environmental_impact_potential": 92,
+  "has_heated_separate_conservatory": "false",
+  "potential_energy_efficiency_band": "B",
+  "co2_emissions_current_per_floor_area": 36,
+  "low_energy_fixed_lighting_outlets_count": 2
+}

domain/sap10_calculator/worksheet/heat_transmission.py

@@ -231,6 +231,20 @@ def _is_flat_or_maisonette(property_type: Optional[str]) -> bool:
     return property_type in _PROPERTY_TYPES_FLAT_OR_MAISONETTE
 
 
+def _is_flat_or_maisonette_dwelling(dwelling_type: Optional[str]) -> bool:
+    """Fallback flat/maisonette detection from `epc.dwelling_type` for certs
+    where `property_type` is absent. Full-SAP / SAP-Schema certs carry the
+    flatness only in dwelling_type (e.g. "Ground-floor flat", "Mid-floor
+    maisonette"), so without this the RdSAP 10 Table 15 footnote * party-wall
+    U=0 default never fires for them and they wrongly take the 0.25 house
+    default. Houses/bungalows ("Detached house", "Mid-Terrace house") don't
+    contain these tokens, so they stay on the house default."""
+    if dwelling_type is None:
+        return False
+    dt = dwelling_type.lower()
+    return "flat" in dt or "maisonette" in dt
+
+
 @dataclass(frozen=True)
 class HeatTransmission:
     """SAP 10.2 §3 conduction HLC broken down per element type, summed
@@ -1029,7 +1043,10 @@ def heat_transmission_from_cert(
         # branch (they're houses for party-wall purposes per the spec).
         upw = u_party_wall(
             party_wall_construction=party_construction,
-            is_flat=_is_flat_or_maisonette(epc.property_type),
+            is_flat=(
+                _is_flat_or_maisonette(epc.property_type)
+                or _is_flat_or_maisonette_dwelling(epc.dwelling_type)
+            ),
         )
         # Per-bp `y` for backwards compat: when the bp's own age band
         # differs from the dwelling's primary, the cascade applies the

tests/domain/sap10_calculator/test_real_cert_sap_accuracy.py

@@ -129,6 +129,62 @@ _EXPECTATIONS: Final[tuple[RealCertExpectation, ...]] = (
         cert_num="8000-8495-2839-2607-9683",
         sap_score=82,
     ),
+    # UPRN 10093116543 → cert 8358-7436-5620-6889-0906. SAP-Schema-17.1 — a
+    # FULL-SAP cert (2017 mains-gas COMBI semi, Emsworth), forced through the
+    # RdSAP SAP-10 engine. Lodged 82; engine produces 81. Built in Elmhurst
+    # RdSAP10 on the lodged inputs (evidence saved: elmhurst_summary.pdf /
+    # elmhurst_worksheet.pdf): Elmhurst worksheet SAP 77. The +4 (81 vs 77) is
+    # the inherent full-SAP-lodged-value vs RdSAP-default methodology gap — the
+    # engine faithfully uses the cert's MEASURED full-SAP data that Elmhurst
+    # RdSAP structurally cannot:
+    #   • Ground floor: cert lodges measured U=0.11 (raw floor u_value 0.11,
+    #     "Average thermal transmittance 0.11 W/m²K"); engine uses 0.11, Elmhurst
+    #     RdSAP solid-floor default = 0.23 (~1.5 SAP). Elmhurst's U-value-known
+    #     override can't be set via the entry tool.
+    #   • Boiler: cert lodges PCDB index 17644 (88.5%); engine uses 88.5%,
+    #     Elmhurst's PCDB/SEDBUK boiler search is disabled in this UI state so the
+    #     only automatable combi is the generic SAP Table 4b "BGW condensing
+    #     combi" = 84% (~1 SAP). The 89% cascade option is a *regular* boiler
+    #     (needs a cylinder) — not valid for this combi/no-cylinder dwelling.
+    #   • Remainder: roof band-L 0.16 vs engine band-M 0.15, infiltration /
+    #     sheltered-sides 1-vs-2 (~0.5).
+    # Calculator confirmed faithful on the prior sibling cert (engine on
+    # Elmhurst's own parsed inputs ≈ worksheet). A leftover conservatory from the
+    # reused assessment was cleared during the build (worksheet 73→77). PINNED TO
+    # THE OBSERVED 81, not lodged 82 — mapping deliberately untuned; the Elmhurst
+    # delta is the documented full-SAP→RdSAP residual, NOT a mapper bug.
+    RealCertExpectation(
+        schema="SAP-Schema-17.1",
+        sample="uprn_10093116543",
+        cert_num="8358-7436-5620-6889-0906",
+        sap_score=81,
+    ),
+    # UPRN 10093116529 → cert 8178-7436-5600-9809-0906. SAP-Schema-17.1 — a
+    # FULL-SAP cert (2017 mains-gas combi GROUND-FLOOR FLAT, Emsworth, TFA 49 m²),
+    # forced through the RdSAP SAP-10 engine. Lodged 81; engine produces 81. Built
+    # in Elmhurst RdSAP10 on the lodged inputs (evidence saved: elmhurst_summary.pdf
+    # / elmhurst_worksheet.pdf): Elmhurst worksheet SAP 78. Calculator confirmed
+    # faithful — fed Elmhurst's own U-values the engine reproduces its HTC to ~0.6
+    # W/K (93.4 vs ~94). The +3 (81 vs 78) is the full-SAP→RdSAP methodology gap:
+    # cert lodges measured U (wall 0.184, floor 0.12), engine uses them, Elmhurst
+    # RdSAP forces band-L defaults; plus the generic 84% combi vs the cert's PCDB
+    # 17644 (88.5%). The "to corridor" wall (17.37 m², U 0.15) is already inside the
+    # heat-loss perimeter (28.45 m × 2.6 = 73.97 m² external), so Elmhurst derives
+    # it as part of the main cavity wall.
+    #   This cert surfaced + drove the FLAT PARTY-WALL FIX (heat_transmission.py
+    #   `_is_flat_or_maisonette_dwelling`): full-SAP flats carry their flatness in
+    #   `dwelling_type` not `property_type`, so the party-wall default was wrongly
+    #   the 0.25 house value instead of the RdSAP Table 15 footnote-* flat 0.0. The
+    #   cert lodges party `u_value: 0` and Elmhurst's worksheet uses 0.0; the fix
+    #   lifts this flat 80→81 (and matches the lodged/Elmhurst party wall).
+    # PINNED TO THE OBSERVED 81, not lodged 81-coincidence — mapping untuned; the
+    # Elmhurst delta is the documented full-SAP residual, not a bug.
+    RealCertExpectation(
+        schema="SAP-Schema-17.1",
+        sample="uprn_10093116529",
+        cert_num="8178-7436-5600-9809-0906",
+        sap_score=81,
+    ),
     # UPRN 10002468137 → cert 0215-2818-7357-9703-2145. RdSAP-Schema-17.1,
     # all-electric high-heat-retention storage heaters on Economy 7, solid-
     # brick uninsulated end-terrace. Validated against Elmhurst RdSAP10 on

tests/domain/sap10_calculator/worksheet/test_heat_transmission.py

@@ -1150,6 +1150,46 @@ def test_ground_floor_flat_exposure_keeps_floor_drops_roof() -> None:
     assert ground.roof_w_per_k == 0.0
 
 
+def test_full_sap_flat_party_wall_uses_flat_zero_default_via_dwelling_type() -> None:
+    # Arrange — a full-SAP / SAP-Schema cert carries its flatness in
+    # `dwelling_type` ("Ground-floor flat"), NOT `property_type` (which is
+    # None). The party-wall default must still fire the RdSAP 10 Table 15
+    # footnote * flat value U=0.0 (party wall between two heated dwellings is
+    # not a heat-loss element), not the 0.25 house default. Regression for
+    # uprn_10093116529: without the dwelling_type fallback the engine charged
+    # 2.82 W/K of phantom party-wall loss (cert lodged party u_value 0;
+    # Elmhurst's worksheet uses 0.0). `party_wall_construction=None` =
+    # "unknown" → the is_flat-dependent default branch.
+    def _build(dwelling_type: str) -> HeatTransmission:
+        main = make_building_part(
+            identifier="Main Dwelling",
+            construction_age_band="L",
+            wall_construction=4, wall_insulation_type=4,
+            party_wall_construction=None, roof_construction=4,
+            floor_dimensions=[
+                make_floor_dimension(
+                    total_floor_area_m2=49.0, room_height_m=2.6,
+                    party_wall_length_m=5.0, heat_loss_perimeter_m=28.0, floor=0,
+                ),
+            ],
+        )
+        epc = make_minimal_sap10_epc(
+            total_floor_area_m2=49.0, country_code="ENG",
+            dwelling_type=dwelling_type, property_type=None,
+            sap_building_parts=[main],
+        )
+        return heat_transmission_from_cert(epc)
+
+    # Act
+    flat = _build("Ground-floor flat")
+    house = _build("Mid-terrace house")
+
+    # Assert — flat party wall is a non-heat-loss element (U=0); the same
+    # geometry as a house takes the 0.25 unknown-house default (> 0).
+    assert flat.party_walls_w_per_k == 0.0
+    assert house.party_walls_w_per_k > 0.0
+
+
 def test_floor_over_another_dwelling_below_zeroes_floor_despite_exposed_flag() -> None:
     # Arrange — a "Ground-floor flat" lodged with floor_heat_loss=6
     # ("another dwelling below") sits over a heated dwelling (e.g. a