Merge pull request #1239 from Hestia-Homes/feature/per-cert-mapper-validation

Feature/per cert mapper validation

backend/documents_parser/elmhurst_extractor.py

@@ -290,6 +290,10 @@ class ElmhurstSiteNotesExtractor:
             party_wall_type=self._local_str(lines, "Party Wall Type"),
             thickness_mm=thickness_mm,
             insulation_thickness_mm=insulation_thickness_mm,
+            # Summary §7 "Dry-lining: Yes/No" on the main/extension wall.
+            # RdSAP 10 §5.8 + Table 14 dry-lining R=0.17 adjustment. The
+            # alt-wall path reads its own "Alternative Wall N Dry-lining".
+            dry_lined=self._local_bool(lines, "Dry-lining"),
             alternative_walls=self._alternative_walls_from_lines(lines),
             # Summary §7 lodges the per-BP "Curtain Wall Age" line only
             # when `Type: CW Curtain Wall`. Per RdSAP 10 §5.18 (PDF
@@ -548,6 +552,20 @@ class ElmhurstSiteNotesExtractor:
             if self._is_next_rir_row(lines[j]):
                 break
             tokens.append(lines[j])
+            # Every RIR row ends with [default_u, "Yes"/"No", u_value]; the
+            # "Yes"/"No" is the unique u_value_known marker (gable types and
+            # insulation cells never take that value). Stop once we've
+            # appended that flag plus the trailing u_value numeric so the
+            # LAST surface row (no next-row name to bound it) does not
+            # over-read into the following section and shift the trailing
+            # token slotting — which silently zeroed Common Wall 2's
+            # default_u (case 43: 1.90 -> 0.00).
+            if (
+                len(tokens) >= 2
+                and tokens[-2] in ("Yes", "No")
+                and self._RIR_NUMERIC_RE.match(tokens[-1])
+            ):
+                break
         # First two numerics = length, height
         length = float(tokens[0]) if tokens and self._RIR_NUMERIC_RE.match(tokens[0]) else 0.0
         height = float(tokens[1]) if len(tokens) > 1 and self._RIR_NUMERIC_RE.match(tokens[1]) else 0.0
@@ -698,6 +716,7 @@ class ElmhurstSiteNotesExtractor:
                     party_wall_type=ext_party_wall_type,
                     thickness_mm=main_walls.thickness_mm,
                     insulation_thickness_mm=main_walls.insulation_thickness_mm,
+                    dry_lined=main_walls.dry_lined,
                     alternative_walls=self._alternative_walls_from_lines(wall_lines),
                 )
             else:
@@ -1528,6 +1547,18 @@ class ElmhurstSiteNotesExtractor:
             first = cylinder_ins_thickness_raw.split()[0]
             if first.isdigit():
                 cylinder_insulation_thickness_mm = int(first)
+        # §15.1 "Cylinder Volume (l)" — the measured volume lodged alongside
+        # a "Value known" Cylinder Size. The value is written as a decimal
+        # ("117.00"); take the integer part for the cascade's measured-volume
+        # field (gov-API "Exact" descriptor, code 6).
+        cylinder_volume_raw = self._local_val(cylinder_lines, "Cylinder Volume (l)")
+        cylinder_volume_measured_l: Optional[int] = None
+        if cylinder_volume_raw:
+            first = cylinder_volume_raw.split()[0]
+            try:
+                cylinder_volume_measured_l = int(float(first))
+            except ValueError:
+                cylinder_volume_measured_l = None
         cylinder_thermostat_raw = self._local_val(
             cylinder_lines, "Cylinder Thermostat",
         )
@@ -1560,6 +1591,7 @@ class ElmhurstSiteNotesExtractor:
             cylinder_size_label=cylinder_size_label,
             cylinder_insulation_label=cylinder_insulation_label,
             cylinder_insulation_thickness_mm=cylinder_insulation_thickness_mm,
+            cylinder_volume_measured_l=cylinder_volume_measured_l,
             cylinder_thermostat=cylinder_thermostat,
             immersion_type=immersion_type,
         )

backend/documents_parser/tests/test_summary_pdf_mapper_chain.py

@@ -99,6 +99,9 @@ _SUMMARY_000565_PDF = _FIXTURES / "Summary_000565.pdf"  # cert 000565 (5-bp Elmh
 _SUMMARY_001431_CASE20_PDF = _FIXTURES / "Summary_001431_case20.pdf"  # sim case 20 (storage heaters + RR type-2 + wrapped "Double between 2002 and 2021" glazing)
 _SUMMARY_001431_TOPFLOOR_PDF = _FIXTURES / "Summary_001431_topfloor_flat.pdf"  # gas-boiler-upgrade recommendation "after" — top-floor flat, PS sloping roof; exercises the Date-Built age-band + flat-position layout regressions
 _SUMMARY_001431_LPG_PDF = _FIXTURES / "Summary_001431_lpg_boiler.pdf"  # lpg-boiler recommendation "before" — §14 SAP code 115, §15 "Bottled gas"; exercises the bottled-LPG main-fuel mapping
+_SUMMARY_001431_CASE41_RAFTERS_PDF = _FIXTURES / "Summary_001431_case41_rafters.pdf"  # sim case 41 — 4-bp roof: Main joists 200mm, Ext1 rafters 200mm, Ext2 joists unknown, Ext3 rafters As Built (RdSAP 10 §5.11.2 Table 16 col 2 + Table 18 col 2)
+_SUMMARY_001431_CASE42_50MM_RAFTERS_PDF = _FIXTURES / "Summary_001431_case42_50mm_rafters.pdf"  # sim case 42 — single-bp roof: rafters 50mm (Table 16 col 2 → 0.88)
+_SUMMARY_001431_CASE42_UNKNOWN_RAFTERS_PDF = _FIXTURES / "Summary_001431_case42_unknown_rafters.pdf"  # sim case 42 — single-bp roof: rafters unknown thickness (Table 18 col 2 band C → 2.30)
 
 # GOV.UK EPB API JSON for cert 001479 — the API-path counterpart of the
 # Summary_001479.pdf fixture. Together they drive the API ≡ Summary
@@ -178,6 +181,69 @@ def test_summary_001431_case20_fabric_heat_loss_matches_worksheet_line_33() -> N
     assert abs(ht.fabric_heat_loss_w_per_k - 285.9847) <= 1e-4
 
 
+def test_summary_001431_case41_roof_drives_rafters_column_per_part() -> None:
+    # Arrange — sim case 41's 4 building parts exercise both RdSAP 10 roof
+    # columns per-part (RdSAP 10 §5.11.2 Table 16 + §5.11 Table 18,
+    # PDF p.42-45). The P960 §3 line (30) "External roof" A×U per part:
+    #   Main  joists 200mm  → 0.21 × 59.5 = 12.4950  (Table 16 col 1)
+    #   Ext1  rafters 200mm → 0.29 × 10.0 =  2.9000  (Table 16 col 2)
+    #   Ext2  joists unknown→ 0.40 × 10.0 =  4.0000  (Table 18 col 1, band E)
+    #   Ext3  rafters AsBlt → 0.68 ×  8.0 =  5.4400  (Table 18 col 2, band F)
+    # Total (sum of (30)) = 24.8350 W/K. Before the rafters column the two
+    # rafter parts were mis-billed at the joists U (Ext1 0.21, Ext3 0.40).
+    pages = _summary_pdf_to_textract_style_pages(_SUMMARY_001431_CASE41_RAFTERS_PDF)
+    epc = EpcPropertyDataMapper.from_elmhurst_site_notes(
+        ElmhurstSiteNotesExtractor(pages).extract()
+    )
+
+    # Act
+    ht = heat_transmission_section_from_cert(epc)
+
+    # Assert
+    assert abs(ht.roof_w_per_k - 24.8350) <= 1e-4
+
+
+def test_summary_001431_case42_rafters_50mm_uses_table16_column_2() -> None:
+    # Arrange — sim case 42's single-bp roof lodged "R Rafters" + 50 mm.
+    # RdSAP 10 §5.11.2 Table 16 (PDF p.43) column (2) "insulation at
+    # rafters" 50 mm → U=0.88 (vs the joists column (1) 0.68). P960 §3 (30)
+    # = 0.88 × 59.5 = 52.3600 W/K.
+    pages = _summary_pdf_to_textract_style_pages(
+        _SUMMARY_001431_CASE42_50MM_RAFTERS_PDF
+    )
+    epc = EpcPropertyDataMapper.from_elmhurst_site_notes(
+        ElmhurstSiteNotesExtractor(pages).extract()
+    )
+
+    # Act
+    ht = heat_transmission_section_from_cert(epc)
+
+    # Assert
+    assert abs(ht.roof_w_per_k - 52.3600) <= 1e-4
+
+
+def test_summary_001431_case42_rafters_unknown_uses_table18_column_2() -> None:
+    # Arrange — sim case 42's single-bp roof lodged "R Rafters" with an
+    # unknown thickness, age band C. RdSAP 10 §5.11 Table 18 (PDF p.45)
+    # column (2) "insulation at rafters" applies "for unknown and as built"
+    # (footnote 1) → band A-D = 2.30 (NOT the joists column (1) 100 mm
+    # default 0.40, which only applies to the "between joists or unknown"
+    # column). Worksheet-confirmed by the case-42 variant set. P960 §3 (30)
+    # = 2.30 × 59.5 = 136.8500 W/K.
+    pages = _summary_pdf_to_textract_style_pages(
+        _SUMMARY_001431_CASE42_UNKNOWN_RAFTERS_PDF
+    )
+    epc = EpcPropertyDataMapper.from_elmhurst_site_notes(
+        ElmhurstSiteNotesExtractor(pages).extract()
+    )
+
+    # Act
+    ht = heat_transmission_section_from_cert(epc)
+
+    # Assert
+    assert abs(ht.roof_w_per_k - 136.8500) <= 1e-4
+
+
 def test_summary_001431_topfloor_extracts_main_property_age_band() -> None:
     # Arrange — the gas-boiler-upgrade recommendation "after" Summary
     # renders "3.0 Date Built:" glued to its "Main Property" row header

datatypes/epc/domain/epc_property_data.py

@@ -153,6 +153,12 @@ class SapHeating:
         None  # int from API; str from site notes
     )
     cylinder_insulation_thickness_mm: Optional[int] = None
+    # SAP 10.2 §4 branch a) — manufacturer's declared cylinder loss factor
+    # (kWh/day). When present, `_cylinder_storage_loss_override` uses it
+    # directly (× Table-2b temperature factor) in place of the Table 2
+    # V×L×VF computation; the gov lodges it instead of cylinder volume /
+    # insulation, so it must be read or the storage loss is dropped.
+    cylinder_heat_loss: Optional[float] = None
     # SAP10 hot-water demand inputs from sap_heating.
     number_baths: Optional[int] = None
     number_baths_wwhrs: Optional[int] = None
@@ -499,7 +505,7 @@ class SapBuildingPart:
     building_part_number: Optional[int] = (
         None  # Not sure how we get this from site notes
     )
-    wall_dry_lined: Optional[bool] = None  # Don't think we have this in site notes
+    wall_dry_lined: Optional[bool] = None  # Summary §7 "Dry-lining: Yes/No"
     wall_thickness_mm: Optional[int] = None
     # Union[str, int]: a numeric mm value when the API lodges
     # `wall_insulation_thickness == "measured"` (resolved from the
@@ -552,6 +558,13 @@ class SapBuildingPart:
     roof_insulation_thickness: Optional[Union[str, int]] = (
         None  # TODO: make enum/mapping?
     )
+    # Lodged insulation thickness (e.g. "225mm", or "AB" As Built) for a roof
+    # insulated AT RAFTERS (roof_insulation_location == 1). The gov API lodges
+    # rafter insulation in this dedicated field — `roof_insulation_thickness`
+    # stays None for rafter roofs. `heat_transmission` prefers this field over
+    # `roof_insulation_thickness` when the part is at-rafters, so the measured
+    # Table 16 column (2) row applies instead of the unknown-thickness default.
+    rafter_insulation_thickness: Optional[Union[str, int]] = None
     sap_room_in_roof: Optional[SapRoomInRoof] = None
     # Per RdSAP 10 §5.18 (PDF p.48), a curtain wall (wall_construction
     # =WALL_CURTAIN=9) takes its U-value from the per-BP installation

datatypes/epc/domain/mapper.py

@@ -1023,6 +1023,11 @@ class EpcPropertyDataMapper:
                         bp.roof_insulation_thickness,
                         bp.construction_age_band,
                     ),
+                    # Rafter insulation thickness lives in its own gov-API field
+                    # (only on the 21.0.x schemas; getattr is None elsewhere).
+                    rafter_insulation_thickness=getattr(
+                        bp, "rafter_insulation_thickness", None
+                    ),
                     sap_room_in_roof=(
                         SapRoomInRoof(
                             floor_area=_measurement_value(bp.sap_room_in_roof.floor_area),
@@ -1220,6 +1225,11 @@ class EpcPropertyDataMapper:
                         bp.roof_insulation_thickness,
                         bp.construction_age_band,
                     ),
+                    # Rafter insulation thickness lives in its own gov-API field
+                    # (only on the 21.0.x schemas; getattr is None elsewhere).
+                    rafter_insulation_thickness=getattr(
+                        bp, "rafter_insulation_thickness", None
+                    ),
                     sap_room_in_roof=(
                         SapRoomInRoof(
                             # ADR-0028: floor_area is usually a Measurement but
@@ -1470,6 +1480,11 @@ class EpcPropertyDataMapper:
                         bp.roof_insulation_thickness,
                         bp.construction_age_band,
                     ),
+                    # Rafter insulation thickness lives in its own gov-API field
+                    # (only on the 21.0.x schemas; getattr is None elsewhere).
+                    rafter_insulation_thickness=getattr(
+                        bp, "rafter_insulation_thickness", None
+                    ),
                     sap_room_in_roof=(
                         SapRoomInRoof(
                             floor_area=_measurement_value(
@@ -1573,6 +1588,7 @@ class EpcPropertyDataMapper:
                 == "true",
                 cylinder_size=schema.sap_heating.cylinder_size,
                 cylinder_volume_measured_l=schema.sap_heating.cylinder_size_measured,
+                cylinder_heat_loss=schema.sap_heating.cylinder_heat_loss,
                 water_heating_code=schema.sap_heating.water_heating_code,
                 water_heating_fuel=schema.sap_heating.water_heating_fuel,
                 immersion_heating_type=schema.sap_heating.immersion_heating_type,
@@ -1705,6 +1721,10 @@ class EpcPropertyDataMapper:
                         bp.construction_age_band,
                         bp.sloping_ceiling_insulation_thickness,
                     ),
+                    # RdSAP 10 §5.11.2 — rafter insulation thickness lives in its
+                    # own gov-API field (roof_insulation_thickness stays None for
+                    # rafter roofs); heat_transmission prefers it when at-rafters.
+                    rafter_insulation_thickness=bp.rafter_insulation_thickness,
                     # RdSAP 10 §5.1 — the assessor's lodged roof/wall/floor U
                     # overrides the §5.6/§5.7/§5.11 construction-default cascade
                     # (gov open data can redact the backing insulation).
@@ -1883,6 +1903,7 @@ class EpcPropertyDataMapper:
                 == "true",
                 cylinder_size=schema.sap_heating.cylinder_size,
                 cylinder_volume_measured_l=schema.sap_heating.cylinder_size_measured,
+                cylinder_heat_loss=schema.sap_heating.cylinder_heat_loss,
                 water_heating_code=schema.sap_heating.water_heating_code,
                 water_heating_fuel=schema.sap_heating.water_heating_fuel,
                 immersion_heating_type=schema.sap_heating.immersion_heating_type,
@@ -2014,6 +2035,10 @@ class EpcPropertyDataMapper:
                         bp.construction_age_band,
                         bp.sloping_ceiling_insulation_thickness,
                     ),
+                    # RdSAP 10 §5.11.2 — rafter insulation thickness lives in its
+                    # own gov-API field (roof_insulation_thickness stays None for
+                    # rafter roofs); heat_transmission prefers it when at-rafters.
+                    rafter_insulation_thickness=bp.rafter_insulation_thickness,
                     # RdSAP 10 §5.1 — the assessor's lodged roof/wall/floor U
                     # overrides the §5.6/§5.7/§5.11 construction-default cascade
                     # (gov open data can redact the backing insulation).
@@ -3935,6 +3960,59 @@ def _api_rir_detailed_surfaces(
         if length is not None and height is not None and length > 0 and height > 0:
             area = _round_half_up_2dp(float(length), float(height))
             surfaces.append(SapRoomInRoofSurface(kind=gable_kind, area_m2=area))
+    # Sloping ceiling + stud walls — up to two of each (RdSAP §3.9 Figure 4).
+    # Both route to the roof aggregate (line (30)) via the cascade's
+    # Detailed-RR branch (`u_rr_slope` / `u_rr_stud_wall`, Table 17 cols 1/3).
+    # insulation_type is left None so the cascade defers to the Table 17
+    # column (a) mineral-wool default, mirroring the flat_ceiling branch.
+    slope_specs = (
+        (details.slope_length_1, details.slope_height_1,
+         details.slope_insulation_thickness_1),
+        (details.slope_length_2, details.slope_height_2,
+         details.slope_insulation_thickness_2),
+    )
+    stud_specs = (
+        (details.stud_wall_length_1, details.stud_wall_height_1,
+         details.stud_wall_insulation_thickness_1),
+        (details.stud_wall_length_2, details.stud_wall_height_2,
+         details.stud_wall_insulation_thickness_2),
+    )
+    for kind, specs in (("slope", slope_specs), ("stud_wall", stud_specs)):
+        for length, height, thickness_str in specs:
+            if (
+                length is not None and height is not None
+                and length > 0 and height > 0
+            ):
+                area = _round_half_up_2dp(float(length), float(height))
+                surfaces.append(
+                    SapRoomInRoofSurface(
+                        kind=kind,
+                        area_m2=area,
+                        insulation_thickness_mm=(
+                            _parse_rir_insulation_thickness_mm(thickness_str)
+                        ),
+                    )
+                )
+    # Common walls — billed as external wall at the storey-below main-wall U
+    # (cascade `kind="common_wall"`), so no insulation thickness is read.
+    # Detailed BPs use the raw L × H area (RdSAP 10 §3.9.2; the cascade's
+    # common_wall branch applies the L × (0.25 + H) form only to Simplified
+    # BPs). The cascade deducts this area from the §3.10.1 residual roof.
+    common_wall_specs = (
+        (details.common_wall_length_1, details.common_wall_height_1),
+        (details.common_wall_length_2, details.common_wall_height_2),
+    )
+    for length, height in common_wall_specs:
+        if (
+            length is not None and height is not None
+            and length > 0 and height > 0
+        ):
+            surfaces.append(
+                SapRoomInRoofSurface(
+                    kind="common_wall",
+                    area_m2=_round_half_up_2dp(float(length), float(height)),
+                )
+            )
     if (
         details.flat_ceiling_length_1 is not None
         and details.flat_ceiling_height_1 is not None
@@ -4358,6 +4436,12 @@ def _map_elmhurst_building_part(
         wall_is_basement=_elmhurst_wall_is_basement(walls.wall_type),
         wall_insulation_type=_elmhurst_wall_insulation_int(walls.insulation),
         wall_thickness_measured=not walls.thickness_unknown,
+        # Summary §7 "Dry-lining: Yes" → RdSAP 10 §5.8 Table 14 R=0.17
+        # adjustment in the cascade (`dry_lined=bool(part.wall_dry_lined)`).
+        # Emit None (not False) when undried so the field stays absent for
+        # the non-dry-lined majority (cascade-equivalent: bool(None) == False);
+        # only a lodged "Yes" populates it.
+        wall_dry_lined=walls.dry_lined or None,
         party_wall_construction=_elmhurst_party_wall_construction_int(
             walls.party_wall_type
         ),
@@ -5942,6 +6026,13 @@ def _elmhurst_cylinder_size_code(
     Table 28 page 55."""
     if not cylinder_present or cylinder_size_label is None:
         return None
+    if cylinder_size_label == "Value known":
+        # Measured-volume cylinder — the Summary-path equivalent of the
+        # gov-API "Exact" descriptor. RdSAP 10 §10.5 Table 28 (p.55): when
+        # the cylinder volume is measured it is used directly. Cascade code
+        # 6 routes `_cylinder_volume_l_from_code` to the lodged
+        # `cylinder_volume_measured_l` (`cert_to_inputs.py:5281`).
+        return 6  # Exact / measured volume
     if cylinder_size_label == "No Access":
         if water_heating_fuel_label is None or meter_type_label is None:
             raise UnmappedElmhurstLabel(
@@ -6587,6 +6678,14 @@ def _map_elmhurst_sap_heating(survey: ElmhurstSiteNotes) -> SapHeating:
         ),
         cylinder_insulation_type=cylinder_insulation_type_field,
         cylinder_insulation_thickness_mm=cylinder_insulation_thickness_mm_field,
+        # §15.1 "Cylinder Volume (l)" — measured volume for a "Value known"
+        # cylinder (cascade code 6 / Exact). None unless a cylinder is
+        # present; the cascade reads it only when `cylinder_size == 6`.
+        cylinder_volume_measured_l=(
+            survey.water_heating.cylinder_volume_measured_l
+            if survey.water_heating.hot_water_cylinder_present
+            else None
+        ),
         # Cascade reads `cylinder_thermostat == "Y"` (string compare) per
         # `cert_to_inputs.py:2252` / `:2218`. Map the bool to the Y/N
         # string the cascade expects; None when no cylinder is present.

datatypes/epc/domain/tests/test_from_rdsap_schema.py

@@ -406,6 +406,57 @@ class TestFromRdSapSchema21_0_1:
         # worksheet uses per-bp sums and the mapper now mirrors that.
         assert result.total_floor_area_m2 == 45.82
 
+    def test_rafter_insulation_thickness_threaded(
+        self, schema: RdSapSchema21_0_1
+    ) -> None:
+        # Arrange — the gov API lodges rafter insulation in the dedicated
+        # `rafter_insulation_thickness` field (RdSAP 10 §5.11.2); it was
+        # previously undeclared, so `from_dict` dropped it and the cascade
+        # fell to the Table 18 col (2) unknown default. The mapper must
+        # thread it through to the domain SapBuildingPart so
+        # heat_transmission can reach the measured Table 16 col (2) row.
+        import dataclasses
+
+        bps = schema.sap_building_parts
+        patched = dataclasses.replace(
+            schema,
+            sap_building_parts=[
+                dataclasses.replace(
+                    bps[0], roof_insulation_location=1,
+                    rafter_insulation_thickness="225mm",
+                ),
+                *bps[1:],
+            ],
+        )
+
+        # Act
+        result = EpcPropertyDataMapper.from_rdsap_schema_21_0_1(patched)
+
+        # Assert
+        assert result.sap_building_parts[0].rafter_insulation_thickness == "225mm"
+
+    def test_cylinder_heat_loss_threaded(
+        self, schema: RdSapSchema21_0_1
+    ) -> None:
+        # Arrange — the gov API lodges the manufacturer's declared cylinder
+        # loss factor (kWh/day) in `sap_heating.cylinder_heat_loss` (SAP
+        # 10.2 §4 branch a). Previously undeclared → `from_dict` dropped it
+        # and the §4 storage loss fell to None → the dwelling over-rated.
+        import dataclasses
+
+        patched = dataclasses.replace(
+            schema,
+            sap_heating=dataclasses.replace(
+                schema.sap_heating, cylinder_heat_loss=1.72
+            ),
+        )
+
+        # Act
+        result = EpcPropertyDataMapper.from_rdsap_schema_21_0_1(patched)
+
+        # Assert
+        assert result.sap_heating.cylinder_heat_loss == 1.72
+
     # --- property flags ---
 
     def test_solar_water_heating(self, result: EpcPropertyData) -> None:
@@ -2101,3 +2152,79 @@ class TestRdSap17_1ReducedFieldSynthesis:
 
         assert result.sap_heating.number_baths == expected_baths
         assert result.sap_heating.mixer_shower_count == expected_mixers
+
+
+class TestRoomInRoofDetailedSlopeAndStudWall:
+    """RdSAP 10 §3.9 Detailed RR — the gov API lodges the sloping ceiling
+    and stud-wall surfaces under `room_in_roof_details.slope_*` /
+    `stud_wall_*`. These were undeclared on the schema, so `from_dict`
+    dropped them and the API mapper built ONLY the gable + flat-ceiling
+    surfaces — omitting the (large) sloping roof and vertical knee walls →
+    undercounted RR heat loss → a systematic ~+4 SAP over-rate across the
+    15 detailed-RR corpus certs carrying `slope_height_1`."""
+
+    def test_slope_surface_survives_from_dict_round_trip(self) -> None:
+        # Arrange — a 21.0.1 detailed-RR block (cert 0390-2538 shape).
+        from datatypes.epc.schema.rdsap_schema_21_0_1 import RoomInRoofDetails
+
+        raw = {
+            "slope_length_1": 7.0,
+            "slope_height_1": 1.4,
+            "slope_insulation_thickness_1": "100mm",
+            "stud_wall_length_1": 7.0,
+            "stud_wall_height_1": 1.03,
+            "stud_wall_insulation_thickness_1": "75mm",
+        }
+
+        # Act
+        details = from_dict(RoomInRoofDetails, raw)
+
+        # Assert — the fields are no longer silently dropped.
+        assert details.slope_height_1 == 1.4
+        assert details.slope_insulation_thickness_1 == "100mm"
+        assert details.stud_wall_height_1 == 1.03
+
+    def test_from_api_response_builds_slope_and_stud_wall_surfaces(self) -> None:
+        # Arrange — drive the PUBLIC API path: take the 21.0.1 fixture's RR
+        # building part and replace its Simplified Type-1 block with a
+        # Detailed RR carrying two sloping ceilings (7 × 1.4) + two stud
+        # walls (7 × 1.03). cert 0390-2538 went +5.95 -> +3.56 SAP once these
+        # surfaces entered the roof aggregate.
+        cert = load("21_0_1.json")
+        rir = cert["sap_building_parts"][0]["sap_room_in_roof"]
+        rir.pop("room_in_roof_type_1", None)
+        rir["room_in_roof_details"] = {
+            "slope_length_1": 7.0, "slope_height_1": 1.4,
+            "slope_length_2": 7.0, "slope_height_2": 1.4,
+            "slope_insulation_thickness_1": "100mm",
+            "slope_insulation_thickness_2": "100mm",
+            "stud_wall_length_1": 7.0, "stud_wall_height_1": 1.03,
+            "stud_wall_length_2": 7.0, "stud_wall_height_2": 1.03,
+            "stud_wall_insulation_thickness_1": "75mm",
+            "stud_wall_insulation_thickness_2": "75mm",
+            "common_wall_length_1": 8.6, "common_wall_height_1": 1.2,
+            "common_wall_length_2": 8.6, "common_wall_height_2": 1.2,
+        }
+
+        # Act
+        result = EpcPropertyDataMapper.from_api_response(cert)
+
+        # Assert — both slopes + both stud walls reach the cascade, with the
+        # lodged thickness parsed and the L × H area to 2 d.p. Common walls
+        # route to the `common_wall` kind (raw L × H, billed at main-wall U).
+        rir_part = result.sap_building_parts[0].sap_room_in_roof
+        assert rir_part is not None
+        surfaces = rir_part.detailed_surfaces
+        assert surfaces is not None
+        slopes = [s for s in surfaces if s.kind == "slope"]
+        studs = [s for s in surfaces if s.kind == "stud_wall"]
+        commons = [s for s in surfaces if s.kind == "common_wall"]
+        assert len(slopes) == 2
+        assert len(studs) == 2
+        assert len(commons) == 2
+        assert abs(slopes[0].area_m2 - 9.8) <= 1e-9
+        assert slopes[0].insulation_thickness_mm == 100
+        assert abs(studs[0].area_m2 - 7.21) <= 1e-9
+        assert studs[0].insulation_thickness_mm == 75
+        assert abs(commons[0].area_m2 - 10.32) <= 1e-9
+        assert commons[0].insulation_thickness_mm is None

datatypes/epc/schema/rdsap_schema_21_0_0.py

@@ -79,6 +79,11 @@ class SapHeating:
     # RdSAP 10 §10.5 Table 28 — measured cylinder volume (litres), lodged
     # only when `cylinder_size` is the "Exact" descriptor (code 6).
     cylinder_size_measured: Optional[int] = None
+    # SAP 10.2 §4 branch a) (PDF p.136) — the manufacturer's declared
+    # cylinder loss factor (kWh/day). When lodged it replaces the Table 2
+    # V×L×VF storage-loss computation. Previously undeclared → dropped by
+    # `from_dict`, so the storage loss fell through to None.
+    cylinder_heat_loss: Optional[float] = None
 
 
 @dataclass
@@ -204,6 +209,31 @@ class RoomInRoofDetails:
     flat_ceiling_height_1: Optional[float] = None
     flat_ceiling_insulation_type_1: Optional[int] = None
     flat_ceiling_insulation_thickness_1: Optional[str] = None
+    # Sloping-ceiling + stud-wall surfaces of a Detailed RR — see
+    # `rdsap_schema_21_0_1.RoomInRoofDetails`. Previously undeclared and
+    # dropped by `from_dict`.
+    slope_length_1: Optional[float] = None
+    slope_length_2: Optional[float] = None
+    slope_height_1: Optional[float] = None
+    slope_height_2: Optional[float] = None
+    slope_insulation_type_1: Optional[int] = None
+    slope_insulation_type_2: Optional[int] = None
+    slope_insulation_thickness_1: Optional[str] = None
+    slope_insulation_thickness_2: Optional[str] = None
+    stud_wall_length_1: Optional[float] = None
+    stud_wall_length_2: Optional[float] = None
+    stud_wall_height_1: Optional[float] = None
+    stud_wall_height_2: Optional[float] = None
+    stud_wall_insulation_type_1: Optional[int] = None
+    stud_wall_insulation_type_2: Optional[int] = None
+    stud_wall_insulation_thickness_1: Optional[str] = None
+    stud_wall_insulation_thickness_2: Optional[str] = None
+    # §3.9.2 common walls of a Detailed RR — see
+    # `rdsap_schema_21_0_1.RoomInRoofDetails`. Previously dropped.
+    common_wall_length_1: Optional[float] = None
+    common_wall_length_2: Optional[float] = None
+    common_wall_height_1: Optional[float] = None
+    common_wall_height_2: Optional[float] = None
 
 
 @dataclass
@@ -265,6 +295,14 @@ class SapBuildingPart:
     # the slope as uninsulated (Table 16 / Table 18 fallback). Consumed by
     # `_api_resolve_sloping_ceiling_thickness` → Table 17 column (1a).
     sloping_ceiling_insulation_thickness: Optional[Union[str, int]] = None
+    # Lodged insulation thickness (e.g. "225mm", or "AB" As Built) for a roof
+    # insulated AT RAFTERS (roof_insulation_location == 1). The gov API lodges
+    # rafter insulation in this dedicated field — NOT `roof_insulation_thickness`
+    # (which stays None for rafter roofs, since rafters aren't loft joists).
+    # Previously undeclared → dropped by `from_dict`, so the cascade fell to the
+    # Table 18 col (2) unknown default (2.30) instead of the measured Table 16
+    # col (2) row. Consumed by `heat_transmission` when at-rafters.
+    rafter_insulation_thickness: Optional[Union[str, int]] = None
     # Lodged roof U-value (W/m²K) — the assessor's RdSAP-assessed roof U,
     # authoritative when the open data redacts the backing insulation
     # thickness. Consumed by `heat_transmission` as a §5.1 documentary-evidence

datatypes/epc/schema/rdsap_schema_21_0_1.py

@@ -84,6 +84,12 @@ class SapHeating:
     # RdSAP 10 §10.5 Table 28 — measured cylinder volume (litres), lodged
     # only when `cylinder_size` is the "Exact" descriptor (code 6).
     cylinder_size_measured: Optional[int] = None
+    # SAP 10.2 §4 branch a) (PDF p.136) — the manufacturer's declared
+    # cylinder loss factor (kWh/day). When lodged it replaces the Table 2
+    # V×L×VF storage-loss computation (the gov leaves volume/insulation
+    # None in that case). Previously undeclared → dropped by `from_dict`,
+    # so the storage loss fell through to None and the dwelling over-rated.
+    cylinder_heat_loss: Optional[float] = None
 
 
 @dataclass
@@ -240,6 +246,36 @@ class RoomInRoofDetails:
     flat_ceiling_height_1: Optional[float] = None
     flat_ceiling_insulation_type_1: Optional[int] = None
     flat_ceiling_insulation_thickness_1: Optional[str] = None
+    # The sloping-ceiling and stud-wall surfaces of a Detailed RR. Up to two
+    # of each per spec Figure 4. Previously undeclared, so `from_dict`
+    # silently dropped them and the API mapper built ONLY the gable + flat-
+    # ceiling surfaces — omitting the (large) sloping roof and the vertical
+    # stud walls → undercounted RR heat loss → systematic over-rate.
+    slope_length_1: Optional[float] = None
+    slope_length_2: Optional[float] = None
+    slope_height_1: Optional[float] = None
+    slope_height_2: Optional[float] = None
+    slope_insulation_type_1: Optional[int] = None
+    slope_insulation_type_2: Optional[int] = None
+    slope_insulation_thickness_1: Optional[str] = None
+    slope_insulation_thickness_2: Optional[str] = None
+    stud_wall_length_1: Optional[float] = None
+    stud_wall_length_2: Optional[float] = None
+    stud_wall_height_1: Optional[float] = None
+    stud_wall_height_2: Optional[float] = None
+    stud_wall_insulation_type_1: Optional[int] = None
+    stud_wall_insulation_type_2: Optional[int] = None
+    stud_wall_insulation_thickness_1: Optional[str] = None
+    stud_wall_insulation_thickness_2: Optional[str] = None
+    # The §3.9.2 common walls of a Detailed RR (the wall separating the RR
+    # from the rest of the cold roof void). Billed as external wall at the
+    # storey-below main-wall U (cascade `kind="common_wall"`). Detailed BPs
+    # use the raw L × H area (Simplified Type-2 BPs use L × (0.25 + H)).
+    # Previously undeclared → dropped → the RR undercounted wall loss.
+    common_wall_length_1: Optional[float] = None
+    common_wall_length_2: Optional[float] = None
+    common_wall_height_1: Optional[float] = None
+    common_wall_height_2: Optional[float] = None
 
 
 @dataclass
@@ -303,6 +339,14 @@ class SapBuildingPart:
     # the slope as uninsulated (Table 16 / Table 18 fallback). Consumed by
     # `_api_resolve_sloping_ceiling_thickness` → Table 17 column (1a).
     sloping_ceiling_insulation_thickness: Optional[Union[str, int]] = None
+    # Lodged insulation thickness (e.g. "225mm", or "AB" As Built) for a roof
+    # insulated AT RAFTERS (roof_insulation_location == 1). The gov API lodges
+    # rafter insulation in this dedicated field — NOT `roof_insulation_thickness`
+    # (which stays None for rafter roofs, since rafters aren't loft joists).
+    # Previously undeclared → dropped by `from_dict`, so the cascade fell to the
+    # Table 18 col (2) unknown default (2.30) instead of the measured Table 16
+    # col (2) row. Consumed by `heat_transmission` when at-rafters.
+    rafter_insulation_thickness: Optional[Union[str, int]] = None
     # Lodged roof U-value (W/m²K) — the assessor's RdSAP-assessed roof U. The
     # gov open data can redact the backing insulation thickness, so this is the
     # authoritative per-element value; consumed by `heat_transmission` as a

datatypes/epc/surveys/elmhurst_site_notes.py

@@ -94,6 +94,12 @@ class WallDetails:
     # "Insulation Thickness" / "100 mm" line pair when a composite or
     # retrofit insulation is recorded. None when the PDF omits the line.
     insulation_thickness_mm: Optional[int] = None
+    # Summary §7 "Dry-lining: Yes/No" on the main/extension wall (distinct
+    # from the per-alt-wall `AlternativeWall.dry_lined`). Per RdSAP 10
+    # §5.8 + Table 14 a dry-lined uninsulated wall adds R=0.17 m²K/W →
+    # U = 1/(1/U_base + 0.17). Previously unread, so dry-lined solid/
+    # cavity walls were billed at the un-adjusted (higher) base U.
+    dry_lined: bool = False
     # Per-BP curtain-wall installation age, lodged in Summary §7 as
     # "Curtain Wall Age" when `wall_type` is "CW Curtain Wall". Per
     # RdSAP 10 §5.18 (PDF p.48) the curtain-wall U-value keys on this
@@ -369,6 +375,11 @@ class WaterHeating:
     cylinder_insulation_label: Optional[str] = None
     # §15.1 "Insulation Thickness" lodging in mm (an integer or None).
     cylinder_insulation_thickness_mm: Optional[int] = None
+    # §15.1 "Cylinder Volume (l)" lodging — the measured cylinder volume in
+    # litres, present when "Cylinder Size" is lodged as "Value known"
+    # (the Summary-path equivalent of the gov-API "Exact" descriptor,
+    # cascade code 6). None when no cylinder is present or the line is absent.
+    cylinder_volume_measured_l: Optional[int] = None
     # §15.1 "Cylinder Thermostat" lodging (Yes / No). False or absent
     # keeps the cascade's no-thermostat Table 2b temperature factor.
     cylinder_thermostat: Optional[bool] = None

domain/sap10_calculator/rdsap/cert_to_inputs.py

@@ -3992,6 +3992,22 @@ def _int_or_none(value: object) -> Optional[int]:
     return value if isinstance(value, int) else None
 
 
+def _float_or_none(value: object) -> Optional[float]:
+    """Coerce a lodged numeric (int / float / numeric string) to float,
+    else None. Used for measured overrides like the cylinder declared
+    loss factor (`cylinder_heat_loss`, kWh/day)."""
+    if isinstance(value, bool):
+        return None
+    if isinstance(value, (int, float)):
+        return float(value)
+    if isinstance(value, str):
+        try:
+            return float(value.strip())
+        except ValueError:
+            return None
+    return None
+
+
 def _thermal_mass_parameter_kj_per_m2_k(epc: EpcPropertyData) -> float:
     """RdSAP 10 §5.16 Table 22 (PDF p.48) — thermal mass parameter from
     the MAIN building's wall construction.
@@ -6489,7 +6505,31 @@ def _cylinder_storage_loss_override(
     if not epc.has_hot_water_cylinder:
         return None
     sh = epc.sap_heating
+    # SAP 10.2 §4 branch a) (PDF p.136) — a lodged manufacturer's declared
+    # cylinder loss factor (kWh/day, gov-API `cylinder_heat_loss`) replaces
+    # the Table 2 V×L×VF computation. It does NOT need the insulation
+    # type / thickness / volume (which the gov leaves None precisely
+    # because the declared loss is lodged instead), so resolve it BEFORE
+    # those guards — otherwise the storage loss is dropped entirely and the
+    # dwelling over-rates (the declared-loss is typically ~1.5 kWh/day ≈
+    # 550 kWh/yr). The Table-2b temperature factor still applies (49)→(50).
+    declared_loss = _float_or_none(getattr(sh, "cylinder_heat_loss", None))
     volume_l = _cylinder_volume_l_from_code(epc)
+    if declared_loss is not None:
+        storage_56m = cylinder_storage_loss_monthly_kwh(
+            volume_l=volume_l or 0.0,
+            insulation_type="factory_insulated",  # unused in the declared branch
+            thickness_mm=0.0,  # unused in the declared branch
+            has_cylinder_thermostat=_cylinder_thermostat_present(epc, main),
+            separately_timed_dhw=_table_2b_note_b_multiplier_applies(epc, main),
+            declared_loss_kwh_per_day=declared_loss,
+        )
+        # (57)m solar adjustment only when solar HW + a resolvable volume.
+        if not epc.solar_water_heating or volume_l is None:
+            return storage_56m
+        vs_l = round(volume_l * _COMBINED_CYLINDER_SOLAR_PREHEAT_FRACTION)
+        factor = (volume_l - vs_l) / volume_l
+        return tuple(s * factor for s in storage_56m)
     if volume_l is None:
         return None
     insulation_label = _cylinder_storage_loss_insulation_label(

domain/sap10_calculator/worksheet/heat_transmission.py

@@ -41,7 +41,7 @@ from __future__ import annotations
 
 from dataclasses import dataclass
 from decimal import ROUND_HALF_UP, Decimal
-from typing import Any, Final, Optional
+from typing import Any, Final, Optional, Union
 
 from datatypes.epc.domain.epc_property_data import (
     EpcPropertyData,
@@ -349,6 +349,27 @@ def _joined_descriptions(elements: list[Any]) -> Optional[str]:
     return " | ".join(parts)
 
 
+def _roof_insulation_at_rafters(location: Optional[Union[int, str]]) -> bool:
+    """True when a building part's roof insulation sits at the rafters
+    (the sloping side of the roof) rather than between the ceiling joists.
+
+    `roof_insulation_location` is the authoritative per-part signal — it
+    carries the gov-EPC API integer code (1 = Rafters, per the empirically
+    watertight single-roof corpus map) on the API path and the stripped
+    Elmhurst Summary label ("Rafters" from "R Rafters") on the Summary
+    path. Both resolve here so `u_roof` selects the RdSAP 10 §5.11.2
+    Table 16 column (2) / Table 18 rafters column instead of the loft-
+    joist column (1). The flat deduplicated `epc.roofs[]` description list
+    cannot give this per-part — 190/329 multi-part certs have
+    len(roofs) != len(parts) — so the per-part location is the only
+    reliable discriminator (worksheet-validated by simulated case 41)."""
+    if location is None:
+        return False
+    if isinstance(location, int):
+        return location == 1
+    return "rafter" in location.strip().lower()
+
+
 def _joined_main_roof_descriptions(roofs: list[Any]) -> Optional[str]:
     """Join roof descriptions for the MAIN (non-RR) roof U-value, dropping
     "Roof room(s)" entries.
@@ -770,7 +791,22 @@ def heat_transmission_from_cert(
             or _described_as_retrofit_insulated(wall_description)
         )
         party_construction = _int_or_none(part.party_wall_construction)
+        # RdSAP 10 §5.11.2 — a roof insulated AT RAFTERS lodges its thickness in
+        # the dedicated gov-API `rafter_insulation_thickness` field, NOT
+        # `roof_insulation_thickness` (which stays None for rafter roofs, since
+        # rafters aren't loft joists). Prefer the rafter field when the part is
+        # at-rafters so the measured Table 16 column (2) row applies instead of
+        # the unknown-thickness default. The Summary path lodges rafter
+        # thickness in `roof_insulation_thickness` (no separate field), so the
+        # fallback covers it.
+        insulation_at_rafters = _roof_insulation_at_rafters(
+            getattr(part, "roof_insulation_location", None)
+        )
         raw_roof_thickness = getattr(part, "roof_insulation_thickness", None)
+        if insulation_at_rafters:
+            raw_rafter_thickness = getattr(part, "rafter_insulation_thickness", None)
+            if raw_rafter_thickness is not None:
+                raw_roof_thickness = raw_rafter_thickness
         roof_thickness = _parse_thickness_mm(raw_roof_thickness)
         floor_ins_thickness = _parse_thickness_mm(getattr(part, "floor_insulation_thickness", None))
 
@@ -873,7 +909,14 @@ def heat_transmission_from_cert(
         # col (1) per the cohort, so only the literal "sloping ceiling"
         # string triggers the col (3) age-band default in `u_roof`.
         is_pitched_sloping_ceiling = "sloping ceiling" in roof_type_lower
-        ur = u_roof(country=country, age_band=age_band, insulation_thickness_mm=roof_thickness, description=effective_roof_description, is_flat_roof=is_flat_roof, is_sloping_ceiling=is_sloping_ceiling, is_pitched_sloping_ceiling=is_pitched_sloping_ceiling)
+        # RdSAP 10 §5.11.2 Table 16 column (2) / Table 18 rafters column —
+        # a roof lodged insulated AT RAFTERS sits on the shallower sloping
+        # side, so the same insulation depth yields a higher U than the
+        # loft-joist column (1). `insulation_at_rafters` (computed above) is
+        # driven per-part from `roof_insulation_location` because the
+        # deduplicated `epc.roofs[]` description list cannot attribute a
+        # location to each building part.
+        ur = u_roof(country=country, age_band=age_band, insulation_thickness_mm=roof_thickness, description=effective_roof_description, is_flat_roof=is_flat_roof, is_sloping_ceiling=is_sloping_ceiling, is_pitched_sloping_ceiling=is_pitched_sloping_ceiling, insulation_at_rafters=insulation_at_rafters)
         # RdSAP 10 §5.1 — a lodged/known roof U-value (the assessor's RdSAP
         # output, surfaced by the gov-EPC API as `roof_u_value`) is used
         # directly in place of the §5.11 construction-default cascade. The gov

domain/sap10_calculator/worksheet/water_heating.py

@@ -628,10 +628,20 @@ def cylinder_storage_loss_monthly_kwh(
     thickness_mm: float,
     has_cylinder_thermostat: bool,
     separately_timed_dhw: bool,
+    declared_loss_kwh_per_day: Optional[float] = None,
 ) -> tuple[float, ...]:
-    """SAP 10.2 §4 line (56)m water storage loss per spec (PDF p.136):
-        (54) = V × L × VF × TF      (Table 2 absence-of-declared-loss branch)
-        (55) = (54)                  (no manufacturer's declared loss)
+    """SAP 10.2 §4 line (56)m water storage loss per spec (PDF p.136).
+
+    Two branches, selected by whether the manufacturer's declared loss
+    factor is lodged:
+
+    a) declared loss known (`declared_loss_kwh_per_day` set):
+        (50) = (48) declared loss (kWh/day) × (49) Table-2b temperature factor
+       → `volume_l` / `insulation_type` / `thickness_mm` are unused.
+    b) declared loss not known (the default):
+        (54) = (47) V × (51) L × (52) VF × (53) TF
+
+        (55) = (50) or (54)
         (56)m = (55) × n_m           (n_m = days in month)
 
     Returns 12 monthly values in calendar order Jan..Dec. The cert's
@@ -639,15 +649,21 @@ def cylinder_storage_loss_monthly_kwh(
     solar storage is present in the vessel — callers handling solar
     storage must adjust further per `(57)m = (56)m × [(47) - Vs] / (47)`.
     """
-    L = cylinder_storage_loss_factor_table_2(
-        insulation_type=insulation_type, thickness_mm=thickness_mm,
-    )
-    VF = cylinder_volume_factor_table_2a(volume_l)
     TF = cylinder_temperature_factor_table_2b(
         has_cylinder_thermostat=has_cylinder_thermostat,
         separately_timed_dhw=separately_timed_dhw,
     )
-    combined_55 = volume_l * L * VF * TF
+    if declared_loss_kwh_per_day is not None:
+        # SAP 10.2 §4 (PDF p.136) branch a) — the lodged manufacturer's
+        # declared loss (kWh/day) replaces the Table 2 V×L×VF computation;
+        # the Table-2b temperature factor still applies (line (49)→(50)).
+        combined_55 = declared_loss_kwh_per_day * TF
+    else:
+        L = cylinder_storage_loss_factor_table_2(
+            insulation_type=insulation_type, thickness_mm=thickness_mm,
+        )
+        VF = cylinder_volume_factor_table_2a(volume_l)
+        combined_55 = volume_l * L * VF * TF
     return tuple(combined_55 * n for n in _DAYS_IN_MONTH)
 
 

domain/sap10_ml/rdsap_uvalues.py

@@ -747,6 +747,34 @@ _ROOF_BY_AGE: Final[dict[str, float]] = {
     "K": 0.16, "L": 0.16, "M": 0.15,
 }
 
+# Table 16 column (2): insulation AT RAFTERS (sloping side of the roof,
+# rather than between the ceiling joists). RdSAP 10 §5.11.2 Table 16
+# (PDF p.42-43). The rafter cavity is shallower than a loft void, so the
+# same insulation depth yields a HIGHER U than the column (1) joist row
+# (e.g. 200 mm: rafters 0.29 vs joists 0.21). Thickness mm -> U.
+_ROOF_RAFTERS_BY_THICKNESS: Final[list[tuple[int, float]]] = [
+    (0, 2.30), (12, 1.75), (25, 1.30), (50, 0.88), (75, 0.67),
+    (100, 0.54), (125, 0.45), (150, 0.39), (175, 0.32), (200, 0.29),
+    (225, 0.25), (250, 0.23), (270, 0.21), (300, 0.19), (350, 0.16),
+    (400, 0.14),
+]
+
+# Table 18 rafters column: pitched-roof "insulation at rafters" default U
+# by age band when the thickness cannot be determined. RdSAP 10 §5.11
+# Table 18 (PDF p.45). Identical to the joist column (1) for bands A-G
+# (2.30 → 0.40), then diverges higher (H 0.35 vs 0.30, I 0.35 vs 0.26,
+# J/K 0.20 vs 0.16, L 0.18 vs 0.16). Unlike the loft-joist default this
+# does NOT collapse to the optimistic 0.40 "assume modern retrofit" floor
+# at old bands — a rafter cavity cannot be topped up from the loft, so an
+# unknown-thickness rafter roof keeps the as-built age-band U (band F
+# 0.68, band E 1.50, A-D 2.30). Worksheet-validated by simulated case 41
+# Ext3 (band F, R Rafters, As Built → P960 §3 (30) U=0.68).
+_ROOF_RAFTERS_BY_AGE: Final[dict[str, float]] = {
+    "A": 2.30, "B": 2.30, "C": 2.30, "D": 2.30, "E": 1.50,
+    "F": 0.68, "G": 0.40, "H": 0.35, "I": 0.35, "J": 0.20,
+    "K": 0.20, "L": 0.18, "M": 0.18,
+}
+
 # Table 18 column (3): flat-roof default U by age band when thickness unknown.
 # RdSAP 10 §5.11 Table 18 page 45 — the pitched-roof column (1) defaults
 # bottom out at 0.40 because "between joists insulation" is the implicit
@@ -793,6 +821,7 @@ def u_roof(
     is_flat_roof: bool = False,
     is_sloping_ceiling: bool = False,
     is_pitched_sloping_ceiling: bool = False,
+    insulation_at_rafters: bool = False,
 ) -> float:
     """RdSAP10 roof U-value in W/m^2K, never null.
 
@@ -829,7 +858,27 @@ def u_roof(
     (code 5) are deliberately excluded — they stay on column (1) per the
     cohort evidence above. Worksheet-validated by simulated case 15 (the
     7536 replica): Ext1 band L → 0.18, Ext2 band F → 0.68.
+
+    `insulation_at_rafters` selects the RdSAP 10 §5.11.2 Table 16 column
+    (2) thickness ladder and the Table 18 rafters age-band column instead
+    of the loft-joist column (1). A roof lodged insulated AT RAFTERS
+    (`roof_insulation_location == 1` on the API path, "R Rafters" on the
+    Summary path) sits on the sloping side of the roof — a shallower
+    cavity than a loft void, so the same insulation depth yields a higher
+    U (200 mm: 0.29 vs the joists 0.21). Ignored for flat / sloping-
+    ceiling roofs (the rafter distinction is a pitched-with-loft concept).
+    Worksheet-validated by simulated case 41 Ext1 (band C, R Rafters,
+    200 mm → 0.29) and Ext3 (band F, R Rafters, As Built → 0.68).
     """
+    # RdSAP 10 §5.11.2 Table 16 / §5.11 Table 18 — pick the rafters
+    # column when the insulation sits at the rafters rather than the
+    # loft joists. Flat / sloping-ceiling geometries keep their own
+    # dedicated tables (rafters is meaningless there).
+    use_rafters = insulation_at_rafters and not (is_flat_roof or is_sloping_ceiling)
+    roof_by_thickness = (
+        _ROOF_RAFTERS_BY_THICKNESS if use_rafters else _ROOF_BY_THICKNESS
+    )
+    roof_by_age = _ROOF_RAFTERS_BY_AGE if use_rafters else _ROOF_BY_AGE
     measured = _measured_u_from_description(description)
     if measured is not None:
         # Full-SAP cert lodges a measured roof U-value in the description
@@ -852,7 +901,7 @@ def u_roof(
         # genuine "no insulation" lodgement, which keeps 2.30 (below). The
         # discriminator is the deterministic "Unknown" text RdSAP renders
         # for an undetermined-thickness observation.
-        table_18 = _FLAT_ROOF_BY_AGE if is_flat_roof else _ROOF_BY_AGE
+        table_18 = _FLAT_ROOF_BY_AGE if is_flat_roof else roof_by_age
         return table_18.get(age_band.upper(), 0.4)
     if (
         is_sloping_ceiling
@@ -877,9 +926,10 @@ def u_roof(
         # uninsulated 2.30 W/m²K.
         return 0.68  # Table 16 row 50, "Insulation at joists at ceiling level"
     if insulation_thickness_mm is not None:
-        # nearest tabulated thickness <= supplied
-        u = _ROOF_BY_THICKNESS[0][1]
-        for t, val in _ROOF_BY_THICKNESS:
+        # nearest tabulated thickness <= supplied (Table 16 column (1)
+        # joists or column (2) rafters per `insulation_at_rafters`)
+        u = roof_by_thickness[0][1]
+        for t, val in roof_by_thickness:
             if insulation_thickness_mm >= t:
                 u = val
         return u
@@ -923,7 +973,7 @@ def u_roof(
         return _FLAT_ROOF_BY_AGE.get(age_band.upper(), 0.4)
     if is_flat_roof:
         return _FLAT_ROOF_BY_AGE.get(age_band.upper(), 0.4)
-    return _ROOF_BY_AGE.get(age_band.upper(), 0.4)
+    return roof_by_age.get(age_band.upper(), 0.4)
 
 
 # RdSAP10 Table 17 — U-values for rooms in roof where insulation thickness

domain/sap10_ml/tests/test_rdsap_uvalues.py

@@ -961,6 +961,69 @@ def test_u_roof_with_explicit_insulation_thickness_uses_table16() -> None:
     assert result == pytest.approx(0.21, abs=0.001)
 
 
+def test_u_roof_at_rafters_explicit_thickness_uses_table16_column_2() -> None:
+    # Arrange — RdSAP 10 §5.11.2 Table 16 (PDF p.42-43) column (2)
+    # "insulation at rafters". A roof lodged insulated AT RAFTERS
+    # (roof_insulation_location == 1, "R Rafters" on the Summary path)
+    # takes the rafters thickness ladder, NOT the column (1) joist row:
+    # at 200 mm the rafters U is 0.29 W/m²K vs the joists 0.21 — a ~38%
+    # heat-loss understatement when the joists column is mis-used. The
+    # joists column (1) stays 0.21 for the same thickness.
+
+    # Act
+    at_rafters = u_roof(
+        country=Country.ENG, age_band="C", insulation_thickness_mm=200,
+        insulation_at_rafters=True,
+    )
+    at_joists = u_roof(
+        country=Country.ENG, age_band="C", insulation_thickness_mm=200,
+        insulation_at_rafters=False,
+    )
+
+    # Assert
+    assert abs(at_rafters - 0.29) <= 0.001
+    assert abs(at_joists - 0.21) <= 0.001
+
+
+def test_u_roof_at_rafters_thickness_ladder_matches_table16_column_2() -> None:
+    # Arrange — RdSAP 10 §5.11.2 Table 16 (PDF p.42-43) column (2) rows:
+    # 50 mm → 0.88, 100 mm → 0.54, 150 mm → 0.39, 270 mm → 0.21. Each is
+    # higher than the joists column (1) value at the same thickness (the
+    # rafter cavity is shallower so the same insulation depth yields a
+    # higher U).
+
+    # Act / Assert
+    assert abs(u_roof(country=Country.ENG, age_band="C", insulation_thickness_mm=50, insulation_at_rafters=True) - 0.88) <= 0.001
+    assert abs(u_roof(country=Country.ENG, age_band="C", insulation_thickness_mm=100, insulation_at_rafters=True) - 0.54) <= 0.001
+    assert abs(u_roof(country=Country.ENG, age_band="C", insulation_thickness_mm=150, insulation_at_rafters=True) - 0.39) <= 0.001
+    assert abs(u_roof(country=Country.ENG, age_band="C", insulation_thickness_mm=270, insulation_at_rafters=True) - 0.21) <= 0.001
+
+
+def test_u_roof_at_rafters_unknown_thickness_uses_table18_rafters_age_band() -> None:
+    # Arrange — RdSAP 10 §5.11 Table 18 (PDF p.45) rafters age-band
+    # column. A rafter-insulated roof with no determinable thickness
+    # ("R Rafters" + "As Built" → thickness None) takes the rafters
+    # age-band default. Band F → 0.68 (== the joists value at F), band H
+    # → 0.35 (vs joists 0.30), band J → 0.20 (vs joists 0.16). Unlike a
+    # loft-joist roof the rafter cavity cannot be topped up, so the
+    # optimistic 0.40 "assume modern retrofit" joist floor does NOT apply
+    # at old bands — band C stays 2.30 (vs the joists-unknown 0.40).
+    # Worksheet-validated by simulated case 41 Ext3 (band F, R Rafters,
+    # As Built → P960 §3 (30) U=0.68).
+
+    # Act
+    band_f = u_roof(country=Country.ENG, age_band="F", insulation_thickness_mm=None, insulation_at_rafters=True)
+    band_h = u_roof(country=Country.ENG, age_band="H", insulation_thickness_mm=None, insulation_at_rafters=True)
+    band_j = u_roof(country=Country.ENG, age_band="J", insulation_thickness_mm=None, insulation_at_rafters=True)
+    band_c = u_roof(country=Country.ENG, age_band="C", insulation_thickness_mm=None, insulation_at_rafters=True)
+
+    # Assert
+    assert abs(band_f - 0.68) <= 0.001
+    assert abs(band_h - 0.35) <= 0.001
+    assert abs(band_j - 0.20) <= 0.001
+    assert abs(band_c - 2.30) <= 0.001
+
+
 def test_u_roof_unknown_age_band_falls_back_to_mid_range() -> None:
     # Arrange — nothing known.
 

tests/datatypes/epc/domain/test_mapper_cylinder_size.py

@@ -0,0 +1,60 @@
+"""Mapper boundary: the Elmhurst §15.1 "Cylinder Size" label.
+
+A cylinder lodged "Value known" carries a measured volume in the §15.1
+"Cylinder Volume (l)" line — the Summary-path equivalent of the gov-API
+"Exact" descriptor. Per RdSAP 10 §10.5 Table 28 (p.55) the measured volume
+is used directly; cascade code 6 routes `_cylinder_volume_l_from_code` to
+the lodged `cylinder_volume_measured_l`. Before this was mapped the label
+raised `UnmappedElmhurstLabel`, blocking every measured-volume-cylinder
+Summary.
+"""
+
+from datatypes.epc.domain.mapper import (
+    UnmappedElmhurstLabel,
+    _elmhurst_cylinder_size_code,  # pyright: ignore[reportPrivateUsage]
+)
+
+
+def test_value_known_label_maps_to_exact_code_6() -> None:
+    # Arrange
+    label = "Value known"
+
+    # Act
+    code = _elmhurst_cylinder_size_code(label, cylinder_present=True)
+
+    # Assert
+    assert code == 6
+
+
+def test_value_known_label_with_no_cylinder_maps_to_none() -> None:
+    # Arrange
+    label = "Value known"
+
+    # Act
+    code = _elmhurst_cylinder_size_code(label, cylinder_present=False)
+
+    # Assert
+    assert code is None
+
+
+def test_normal_label_still_maps_to_code_2() -> None:
+    # Arrange
+    label = "Normal"
+
+    # Act
+    code = _elmhurst_cylinder_size_code(label, cylinder_present=True)
+
+    # Assert
+    assert code == 2
+
+
+def test_unknown_label_still_raises() -> None:
+    # Arrange
+    label = "Spray-on unicorn cylinder"
+
+    # Act / Assert
+    try:
+        _elmhurst_cylinder_size_code(label, cylinder_present=True)
+    except UnmappedElmhurstLabel:
+        return
+    raise AssertionError("expected UnmappedElmhurstLabel for an unknown label")

tests/domain/sap10_calculator/worksheet/_elmhurst_worksheet_001431_case39.py

@@ -0,0 +1,121 @@
+"""Mapper-driven cascade pin against the Elmhurst P960-0001-001431
+"simulated case 39" worksheet — an age-A (pre-1900) mid-terrace heated by
+**direct-acting electric room heaters** (SAP code 691, category 10, control
+2602 appliance thermostats), with an electric room-heater secondary (also
+691) and electric-immersion DHW (WHC 903) off a **measured-volume hot-water
+cylinder** ("Cylinder Size: Value known", 117 L, foam 38 mm), on a single
+(standard) electricity meter.
+
+This case was generated to probe the API-corpus's worst-served cohort
+(category-10 direct-acting electric, 46% within-0.5). It exposed a real
+Summary-path gap: the §15.1 "Cylinder Size: Value known" lodging (the
+Summary equivalent of the gov-API "Exact" descriptor) was unmapped, so the
+extractor/mapper raised `UnmappedElmhurstLabel` and — once that was mapped —
+the measured "Cylinder Volume (l)" was not threaded through, dropping the
+cylinder storage loss (~468 kWh/yr) from (219) water heating. Wiring the
+measured volume (cascade code 6 → `_cylinder_volume_l_from_code`) closes the
+whole cascade EXACTLY.
+
+Like 000565 / the _rr cases / case 20 / 21 / 38, this fixture does NOT hand-
+build the EpcPropertyData: it routes the Summary PDF through
+ElmhurstSiteNotesExtractor + from_elmhurst_site_notes so the pin exercises
+the WHOLE extractor + mapper + calculator pipeline.
+
+Source: user-simulated PDFs at `sap worksheets/golden fixture debugging/
+simulated case 39/`. The Summary is mirrored into the tracked
+`backend/documents_parser/tests/fixtures/Summary_001431_case39.pdf` so the
+test runs without depending on the unstaged workspace.
+
+Worksheet pin targets (P960-0001-001431, "11a. SAP rating" / "12a. CO2
+emissions" block — the UK-average-climate rating block our cascade
+reproduces; the P960's separate postcode-climate EPC block (272)=1803.19 is
+a known regional-climate gap, not a SAP-rating divergence):
+- SAP value (un-rounded, before (258) integer rounding) = 36.6365 (band F)
+- (272) Total CO2, kg/year                              = 2056.0731
+
+Per [[feedback-zero-error-strict]] + [[feedback-continuous-sap-tolerance]]:
+pins are abs <= 1e-3 against the worksheet PDF (printed to 4 dp).
+"""
+
+from __future__ import annotations
+
+import re
+import subprocess
+from pathlib import Path
+from typing import Final
+
+from backend.documents_parser.elmhurst_extractor import ElmhurstSiteNotesExtractor
+from datatypes.epc.domain.epc_property_data import EpcPropertyData
+from datatypes.epc.domain.mapper import EpcPropertyDataMapper
+from domain.sap10_calculator.calculator import calculate_sap_from_inputs
+from domain.sap10_calculator.rdsap.cert_to_inputs import cert_to_inputs
+
+# parents[0]=worksheet/, [1]=sap10_calculator/, [2]=domain/, [3]=tests/,
+# [4]=repo root.
+_SUMMARY_PDF: Final[Path] = (
+    Path(__file__).resolve().parents[4]
+    / "backend" / "documents_parser" / "tests" / "fixtures"
+    / "Summary_001431_case39.pdf"
+)
+
+LINE_258_SAP_VALUE_CONTINUOUS: Final[float] = 36.6365
+LINE_272_TOTAL_CO2_KG_PER_YR: Final[float] = 2056.0731
+_PIN_ABS: Final[float] = 1e-3
+
+
+def _summary_pdf_to_textract_style_pages(pdf_path: Path) -> list[str]:
+    """Convert a Summary PDF into the per-page text format the
+    ElmhurstSiteNotesExtractor expects (label/value token sequences).
+    Mirror of the helper in the other `_elmhurst_worksheet_*` fixtures.
+    """
+    info = subprocess.run(
+        ["pdfinfo", str(pdf_path)], capture_output=True, text=True, check=True,
+    ).stdout
+    m = re.search(r"Pages:\s+(\d+)", info)
+    if m is None:
+        raise RuntimeError(f"Could not parse page count from {pdf_path}")
+    page_count = int(m.group(1))
+    pages: list[str] = []
+    for i in range(1, page_count + 1):
+        layout = subprocess.run(
+            [
+                "pdftotext", "-layout", "-f", str(i), "-l", str(i),
+                str(pdf_path), "-",
+            ],
+            capture_output=True, text=True, check=True,
+        ).stdout
+        tokens: list[str] = []
+        for line in layout.splitlines():
+            if not line.strip():
+                tokens.append("")
+                continue
+            parts = [p for p in re.split(r"\s{2,}", line.strip()) if p]
+            tokens.extend(parts)
+        pages.append("\n".join(tokens))
+    return pages
+
+
+def build_epc() -> EpcPropertyData:
+    """Route the simulated case-39 Summary through extractor + mapper.
+    No hand-built EpcPropertyData — the extractor and mapper are part of
+    the test target."""
+    pages = _summary_pdf_to_textract_style_pages(_SUMMARY_PDF)
+    site_notes = ElmhurstSiteNotesExtractor(pages).extract()
+    return EpcPropertyDataMapper.from_elmhurst_site_notes(site_notes)
+
+
+def test_case39_measured_volume_cylinder_reproduces_the_worksheet_sap_and_co2() -> None:
+    # Arrange — the full extractor -> mapper -> calculator pipeline on the
+    # simulated case-39 Summary (direct-electric room heaters + electric
+    # immersion DHW off a "Value known" 117 L measured-volume cylinder).
+    epc = build_epc()
+
+    # Act
+    result = calculate_sap_from_inputs(cert_to_inputs(epc))
+
+    # Assert — the SAP-rating block reproduces the worksheet exactly.
+    assert (
+        abs(result.sap_score_continuous - LINE_258_SAP_VALUE_CONTINUOUS)
+        <= _PIN_ABS
+    )
+    assert abs(result.co2_kg_per_yr - LINE_272_TOTAL_CO2_KG_PER_YR) <= _PIN_ABS

tests/domain/sap10_calculator/worksheet/_elmhurst_worksheet_001431_case43.py

@@ -0,0 +1,116 @@
+"""Mapper-driven cascade pin against the Elmhurst P960-0001-001431
+"simulated case 43" worksheet — a 2-storey mid-terrace deliberately built to
+exercise every feature in one dwelling:
+
+  - a DETAILED room-in-roof on the Main BP (two slopes, two flat ceilings,
+    a party + an exposed gable, two common walls) — exercises the
+    slope / stud / common_wall detailed-RR surfaces end-to-end;
+  - a MIXED-insulation multi-section roof (Main insulated 0.16/0.54/0.68/0.11
+    + Extension uninsulated 2.30);
+  - a DRY-LINED extension solid wall (RdSAP 10 §5.8 Table 14 R=0.17:
+    solid brick 1.70 -> 1.32);
+  - a mains-gas boiler (SAP 102, control 2106 interlock) with a House-coal
+    solid-fuel SECONDARY (633, 60%) and a 210 L declared-loss cylinder.
+
+This case was generated to settle the room-in-roof + mixed-roof + secondary
+feature set with a single 1e-4 pin. It exposed two compensating Elmhurst-
+extractor bugs (commit `a33707f8`) whose fabric errors nearly cancelled
+(walls net -0.76 W/K, hidden behind a +0.05 SAP delta):
+  1. the main/extension wall "Dry-lining: Yes" line was read only for
+     ALTERNATIVE walls -> the dry-lined extension wall billed at the
+     un-adjusted 1.70 instead of 1.32;
+  2. the LAST room-in-roof surface row's per-row token scan over-read into
+     the next section -> Common Wall 2's default U silently zeroed
+     (1.90 -> 0.00).
+With both fixed the whole §3 fabric and the SAP/CO2 reproduce EXACTLY.
+
+Like 000565 / the _rr cases / case 20 / 21 / 38 / 39, this fixture does NOT
+hand-build the EpcPropertyData: it routes the Summary PDF through
+ElmhurstSiteNotesExtractor + from_elmhurst_site_notes so the pin exercises
+the WHOLE extractor + mapper + calculator pipeline.
+
+Source: user-simulated PDFs at `sap worksheets/golden fixture debugging/
+simulated case 43/`. The Summary is mirrored into the tracked
+`backend/documents_parser/tests/fixtures/Summary_001431_case43.pdf` so the
+test runs without depending on the unstaged workspace.
+
+Worksheet pin targets (P960-0001-001431, "11a. SAP rating" / "12a. CO2
+emissions" block — the UK-average-climate rating block our cascade
+reproduces):
+- SAP value (un-rounded, before (258) integer rounding) = 73.2332 (band C)
+- (272) Total CO2, kg/year                              = 3518.30
+
+Per [[feedback-zero-error-strict]] + [[feedback-continuous-sap-tolerance]]:
+pins are abs <= 1e-3 against the worksheet PDF (printed to 4 dp).
+"""
+
+from __future__ import annotations
+
+import re
+import subprocess
+from pathlib import Path
+from typing import Final
+
+from backend.documents_parser.elmhurst_extractor import ElmhurstSiteNotesExtractor
+from datatypes.epc.domain.epc_property_data import EpcPropertyData
+from datatypes.epc.domain.mapper import EpcPropertyDataMapper
+
+# parents[0]=worksheet/, [1]=sap10_calculator/, [2]=domain/, [3]=tests/,
+# [4]=repo root.
+_SUMMARY_PDF: Final[Path] = (
+    Path(__file__).resolve().parents[4]
+    / "backend" / "documents_parser" / "tests" / "fixtures"
+    / "Summary_001431_case43.pdf"
+)
+
+LINE_29A_WALLS_W_PER_K: Final[float] = 74.5800
+# (30) = ΣA×U: FlatCeil1 4.3200 + FlatCeil2 6.9000 + Slope1 1.0200 +
+# Slope2 0.1408 + roof Main 3.1200 + roof Ext1 (uninsulated) 23.0000.
+LINE_30_ROOF_W_PER_K: Final[float] = 38.5008
+LINE_33_FABRIC_W_PER_K: Final[float] = 172.7844
+LINE_258_SAP_VALUE_CONTINUOUS: Final[float] = 73.2332
+LINE_272_TOTAL_CO2_KG_PER_YR: Final[float] = 3518.3037
+
+
+def _summary_pdf_to_textract_style_pages(pdf_path: Path) -> list[str]:
+    """Convert a Summary PDF into the per-page text format the
+    ElmhurstSiteNotesExtractor expects (label/value token sequences).
+    Mirror of the helper in the other `_elmhurst_worksheet_*` fixtures.
+    """
+    info = subprocess.run(
+        ["pdfinfo", str(pdf_path)], capture_output=True, text=True, check=True,
+    ).stdout
+    m = re.search(r"Pages:\s+(\d+)", info)
+    if m is None:
+        raise RuntimeError(f"Could not parse page count from {pdf_path}")
+    page_count = int(m.group(1))
+    pages: list[str] = []
+    for i in range(1, page_count + 1):
+        layout = subprocess.run(
+            [
+                "pdftotext", "-layout", "-f", str(i), "-l", str(i),
+                str(pdf_path), "-",
+            ],
+            capture_output=True, text=True, check=True,
+        ).stdout
+        tokens: list[str] = []
+        for line in layout.splitlines():
+            if not line.strip():
+                tokens.append("")
+                continue
+            parts = [p for p in re.split(r"\s{2,}", line.strip()) if p]
+            tokens.extend(parts)
+        pages.append("\n".join(tokens))
+    return pages
+
+
+def build_epc() -> EpcPropertyData:
+    """Route the simulated case-43 Summary through extractor + mapper.
+    No hand-built EpcPropertyData — the extractor and mapper are part of
+    the test target. This module is a pin PROVIDER (build_epc + LINE_*
+    constants, mirroring `_elmhurst_worksheet_001431_case6` / `_case21`);
+    the collected assertion lives in
+    `test_section_cascade_pins.test_case43_*`."""
+    pages = _summary_pdf_to_textract_style_pages(_SUMMARY_PDF)
+    site_notes = ElmhurstSiteNotesExtractor(pages).extract()
+    return EpcPropertyDataMapper.from_elmhurst_site_notes(site_notes)

tests/domain/sap10_calculator/worksheet/test_heat_transmission.py

@@ -151,6 +151,83 @@ def test_roof_insulated_assumed_with_ni_thickness_uses_50mm_per_section_5_11_4()
     assert result.roof_w_per_k == pytest.approx(68.0, abs=2.0)
 
 
+def test_roof_insulation_location_rafters_drives_table16_column_2_api_int_path() -> None:
+    # Arrange — the gov-EPC API lodges roof_insulation_location as an
+    # integer (1 = Rafters per the empirically watertight corpus map). A
+    # roof insulated AT RAFTERS with 200 mm takes RdSAP 10 §5.11.2 Table 16
+    # (PDF p.43) column (2) → U=0.29, NOT the joists column (1) 0.21 — the
+    # rafter cavity is shallower so the same depth yields a higher U. The
+    # per-part location is the authoritative signal (the deduplicated
+    # epc.roofs[] list cannot attribute a location per building part).
+    # Geometry: 100 m² plan → roof area 100 m². rafters: 0.29 × 100 = 29
+    # W/K (vs the joists 0.21 × 100 = 21 W/K).
+    main = make_building_part(
+        construction_age_band="C",
+        wall_construction=3,
+        wall_insulation_type=4,
+        party_wall_construction=1,
+        roof_construction=4,
+        floor_dimensions=[
+            make_floor_dimension(
+                total_floor_area_m2=100.0, room_height_m=2.5,
+                party_wall_length_m=0.0, heat_loss_perimeter_m=40.0, floor=0,
+            ),
+        ],
+    )
+    main.roof_insulation_location = 1  # gov-API int: Rafters
+    main.roof_insulation_thickness = "200mm"
+    epc = make_minimal_sap10_epc(
+        total_floor_area_m2=100.0,
+        country_code="ENG",
+        sap_building_parts=[main],
+    )
+
+    # Act
+    result = heat_transmission_from_cert(epc)
+
+    # Assert
+    assert abs(result.roof_w_per_k - 29.0) <= 1e-4
+
+
+def test_rafter_insulation_thickness_field_drives_table16_column_2() -> None:
+    # Arrange — the gov-EPC API lodges rafter insulation in a DEDICATED
+    # `rafter_insulation_thickness` field (e.g. "225mm"), leaving
+    # `roof_insulation_thickness` None for rafter roofs (rafters aren't loft
+    # joists). heat_transmission must prefer the rafter field when the part
+    # is at-rafters (roof_insulation_location == 1) so the measured RdSAP 10
+    # §5.11.2 Table 16 column (2) row applies — 225 mm → U=0.25 — instead of
+    # the Table 18 col (2) unknown default (2.30). Cert 3100-8675-0922-8628
+    # (band E, rafters 225mm) went +8.93 -> +0.43 SAP on this field.
+    # Geometry: 100 m² plan → roof area 100 m². 0.25 × 100 = 25 W/K.
+    main = make_building_part(
+        construction_age_band="E",
+        wall_construction=4,
+        wall_insulation_type=4,
+        party_wall_construction=1,
+        roof_construction=4,
+        floor_dimensions=[
+            make_floor_dimension(
+                total_floor_area_m2=100.0, room_height_m=2.5,
+                party_wall_length_m=0.0, heat_loss_perimeter_m=40.0, floor=0,
+            ),
+        ],
+    )
+    main.roof_insulation_location = 1  # Rafters
+    main.roof_insulation_thickness = None  # gov leaves this None for rafters
+    main.rafter_insulation_thickness = "225mm"  # the thickness lives here
+    epc = make_minimal_sap10_epc(
+        total_floor_area_m2=100.0,
+        country_code="ENG",
+        sap_building_parts=[main],
+    )
+
+    # Act
+    result = heat_transmission_from_cert(epc)
+
+    # Assert
+    assert abs(result.roof_w_per_k - 25.0) <= 1e-4
+
+
 def test_lodged_roof_u_value_overrides_construction_default() -> None:
     # Arrange — RdSAP 10 §5.1: where an element's U-value is known from the
     # assessment (documentary evidence / the lodged RdSAP output) it is used

tests/domain/sap10_calculator/worksheet/test_section_cascade_pins.py

@@ -44,6 +44,7 @@ from tests.domain.sap10_calculator.worksheet import (
     _elmhurst_worksheet_000516 as _w000516,
     _elmhurst_worksheet_001431_case6 as _w001431_case6,
     _elmhurst_worksheet_001431_case21 as _w001431_case21,
+    _elmhurst_worksheet_001431_case43 as _w001431_case43,
 )
 
 
@@ -328,6 +329,47 @@ def test_section_3_wall_u_by_thickness_case21_match_pdf() -> None:
     )
 
 
+def test_case43_detailed_rr_dryline_and_mixed_roof_match_pdf() -> None:
+    """Full-feature pin for simulated case 43 — a 2-BP mid-terrace with a
+    DETAILED room-in-roof (slopes + flat ceilings + party/exposed gables +
+    common walls), a MIXED-insulation multi-section roof (Main insulated +
+    Extension uninsulated), a DRY-LINED extension solid wall (RdSAP 10 §5.8
+    Table 14: 1.70 -> 1.32), a mains-gas boiler (102, control 2106) and a
+    House-coal solid-fuel secondary (633). Exposed + regression-guards two
+    compensating Elmhurst-extractor bugs (commit a33707f8): the unread
+    main-wall dry-lining and the last-RR-row default-U over-read, whose
+    fabric errors nearly cancelled (walls net -0.76). With both fixed the
+    §3 fabric and the SAP-rating block reproduce the P960 exactly."""
+    # Arrange
+    from domain.sap10_calculator.calculator import calculate_sap_from_inputs
+
+    epc = _w001431_case43.build_epc()
+
+    # Act
+    ht = heat_transmission_section_from_cert(epc)
+    result = calculate_sap_from_inputs(cert_to_inputs(epc))
+
+    # Assert — §3 fabric (the RR + dry-lining + mixed-roof fixes) and the
+    # SAP-rating block, each at abs=1e-4.
+    _pin(ht.walls_w_per_k, _w001431_case43.LINE_29A_WALLS_W_PER_K, "§3 (29a) case43")
+    _pin(ht.roof_w_per_k, _w001431_case43.LINE_30_ROOF_W_PER_K, "§3 (30) case43")
+    _pin(
+        ht.fabric_heat_loss_w_per_k,
+        _w001431_case43.LINE_33_FABRIC_W_PER_K,
+        "§3 (33) case43",
+    )
+    _pin(
+        result.sap_score_continuous,
+        _w001431_case43.LINE_258_SAP_VALUE_CONTINUOUS,
+        "(258) case43",
+    )
+    _pin(
+        result.co2_kg_per_yr,
+        _w001431_case43.LINE_272_TOTAL_CO2_KG_PER_YR,
+        "(272) case43",
+    )
+
+
 def test_case6_main_2_emitter_and_control_extracted() -> None:
     """Simulated case 6's §14.1 Main Heating2 lodges its OWN emitter
     ("Underfloor Heating") and control ("SAP code 2110, ...") — the two

tests/domain/sap10_calculator/worksheet/test_water_heating.py

@@ -676,6 +676,40 @@ def test_water_efficiency_monthly_via_equation_d1_weights_winter_summer_per_mont
     assert monthly[0] == pytest.approx(num / denom, abs=1e-6)
 
 
+def test_cylinder_storage_loss_uses_declared_loss_factor_times_temp_factor() -> None:
+    # Arrange — SAP 10.2 §4 branch a) (PDF p.136): when the manufacturer's
+    # declared cylinder loss factor (kWh/day) is lodged, storage loss
+    # (50) = (48) declared × (49) Table-2b temperature factor — replacing
+    # the Table 2 V×L×VF computation. Volume / insulation are unused.
+    from domain.sap10_calculator.worksheet.water_heating import (
+        cylinder_storage_loss_monthly_kwh,
+        cylinder_temperature_factor_table_2b,
+    )
+
+    declared = 1.72
+    tf: float = cylinder_temperature_factor_table_2b(
+        has_cylinder_thermostat=True, separately_timed_dhw=False,
+    )
+
+    # Act
+    result = cylinder_storage_loss_monthly_kwh(
+        volume_l=110.0, insulation_type="factory_insulated", thickness_mm=0.0,
+        has_cylinder_thermostat=True, separately_timed_dhw=False,
+        declared_loss_kwh_per_day=declared,
+    )
+    # Same declared loss with a different volume / insulation must give the
+    # same result — they are not consulted in the declared branch.
+    result_other_geometry = cylinder_storage_loss_monthly_kwh(
+        volume_l=300.0, insulation_type="loose_jacket", thickness_mm=50.0,
+        has_cylinder_thermostat=True, separately_timed_dhw=False,
+        declared_loss_kwh_per_day=declared,
+    )
+
+    # Assert — January (31 days) = declared × TF × 31; geometry-invariant.
+    assert abs(result[0] - declared * tf * 31) <= 1e-9
+    assert result == result_other_geometry
+
+
 def test_000474_cert_to_inputs_hot_water_kwh_closes_within_1pct_post_slice_2() -> None:
     """Cert-round-trip conformance: 000474 mid-terrace combi-gas (PDF
     HW fuel = 2291.78 kWh/yr). Slice 1 closed Σ(61) via PCDB Table 3b

tests/infrastructure/epc_client/test_sap_accuracy_corpus.py

@@ -67,8 +67,36 @@ _CORPUS = Path(
 #      energy were 5% high; actual SAP bias is +0.145).
 # So closing demand over-estimates lifts BOTH the SAP gauge and PE/CO2; there is
 # no one-slice factor fix. RATCHET any ceiling up when a slice tightens it.
-_MIN_WITHIN_HALF_SAP = 0.65
-_MAX_SAP_MAE = 1.08
+#
+# RAFTERS ROOF (RdSAP 10 §5.11.2 Table 16 col 2 + §5.11 Table 18 col 2): roofs
+# insulated AT RAFTERS (roof_insulation_location == 1) are billed on the spec
+# rafters column instead of the joists column, AND their thickness is read from
+# the dedicated gov-API `rafter_insulation_thickness` field. That field was
+# UNDECLARED on the schema, so `from_dict` dropped it — the rafter certs only
+# *looked* redacted (roof EER 2-4 = insulated yet `roof_insulation_thickness`
+# None); the thickness was there all along in `rafter_insulation_thickness`
+# (e.g. "225mm"). Declaring + threading it recovers them: cert 3100-8675-0922
+# (band E, rafters 225mm) +8.93 -> +0.43 SAP. Net of both changes within-0.5
+# went 66.9% -> 67.0% (MAE 1.039 -> 1.025). Worksheet-validated to 1e-4 on
+# simulated case 41 (measured rafters 200mm -> 0.29; rafters As-Built band F
+# -> 0.68) and case 42 (rafters 50mm -> 0.88; rafters genuine-unknown band C
+# -> 2.30 per Table 18 footnote 1 "applies for unknown and as built"). Do NOT
+# revert the rafters column.
+#
+# DETAILED RR SLOPE + STUD WALL (RdSAP 10 §3.9 Figure 4 + §5.11.3 Table 17 cols
+# 1/3, p.43-44): the gov API lodges a Detailed RR's sloping ceilings (slope_*)
+# and stud/knee walls (stud_wall_*) alongside the gable + flat-ceiling surfaces.
+# Those fields were UNDECLARED on the schema, so `from_dict` dropped them and the
+# mapper built only gable + flat-ceiling — the (large) sloping roof and knee
+# walls contributed ZERO heat loss -> undercounted RR fabric -> over-rate.
+# Declaring + threading slope/stud into `detailed_surfaces` (cascade already
+# routes both to the roof aggregate) recovered the 15-cert /tmp cohort from
+# mean|err| 4.26 -> 2.05 (e.g. 0390-2538 +5.95 -> +3.56). Corpus within-0.5
+# 67.3% -> 67.5% (MAE 1.020 -> 0.987). The follow-on `common_wall_*` Detailed-RR
+# surfaces (billed at main-wall U, deducted from the §3.10.1 residual) took the
+# 6-cert detailed-common-wall cohort 2.43 -> 1.25; corpus -> 67.6% (MAE 0.979).
+_MIN_WITHIN_HALF_SAP = 0.67
+_MAX_SAP_MAE = 0.99
 _MAX_CO2_MAE_TONNES = 0.35      # t CO2 / yr vs co2_emissions_current
 _MAX_PE_PER_M2_MAE = 16.0       # kWh / m2 / yr vs energy_consumption_current