fix(mapper): read dropped detailed room-in-roof slope + stud-wall surfaces

The gov-EPC API lodges a Detailed RR (RdSAP 10 §3.9, Figure 4) with up to
two sloping ceilings (`slope_*`) and two vertical stud/knee walls
(`stud_wall_*`) in addition to the gable + flat-ceiling surfaces. Those
slope/stud fields were undeclared on the 21.0.x schema, so `from_dict`
silently dropped them and `_api_rir_detailed_surfaces` built ONLY the gable
+ flat-ceiling surfaces. The (large) sloping roof and the knee walls
contributed ZERO heat loss → undercounted RR fabric loss → a systematic
over-rate.

Fix: declare `slope_*`/`stud_wall_*` on `RoomInRoofDetails`
(rdsap_schema_21_0_0 + _21_0_1) and build `kind="slope"` / `kind="stud_wall"`
surfaces in the mapper. The cascade's Detailed-RR branch already routes both
to the roof aggregate via `u_rr_slope` (Table 17 col 1) and `u_rr_stud_wall`
(Table 17 col 3) — RdSAP 10 §5.11.3, p.43-44 — so no calculator change is
needed (Summary path worksheet-validated by the 000565 detailed-RR fixtures).
insulation_type is left None to defer to the Table 17 col-(a) mineral-wool
default, mirroring the existing flat_ceiling branch.

15 /tmp certs carry `slope_height_1`: cohort mean|err| 4.26 -> 2.05, signed
+4.09 -> centred (14/15 were over-rating; e.g. 0390-2538 +5.95 -> +3.56).
Gauges: corpus within-0.5 67.3% -> 67.5% (MAE 1.020 -> 0.987); /tmp 71.4% ->
71.6% (MAE 0.882 -> 0.846). Harness 47/47 0 raised; regression = the 3
pre-existing fails; pyright net-zero (65=65).

Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>

datatypes/epc/domain/mapper.py

@@ -3960,6 +3960,39 @@ 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)
+                        ),
+                    )
+                )
     if (
         details.flat_ceiling_length_1 is not None
         and details.flat_ceiling_height_1 is not None

datatypes/epc/domain/tests/test_from_rdsap_schema.py

@@ -2152,3 +2152,72 @@ 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",
+        }
+
+        # 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.
+        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"]
+        assert len(slopes) == 2
+        assert len(studs) == 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

datatypes/epc/schema/rdsap_schema_21_0_0.py

@@ -209,6 +209,25 @@ 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
 
 
 @dataclass

datatypes/epc/schema/rdsap_schema_21_0_1.py

@@ -246,6 +246,27 @@ 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
 
 
 @dataclass