S0380.214: as-built sloping-ceiling roof → Table 18 col (3)

A "Pitched, sloping ceiling" roof (roof_construction code 8) lodged with
"As Built" insulation (no measured thickness → None) was wrongly routed to
RdSAP 10 Table 18 column (1) "insulation between joists or unknown". A
sloping ceiling has no joist void, so per RdSAP 10 §5.11 roof-input item
5-5 ("Sloping ceiling insulation … unknown / as built → Table 18") and
Table 18 note (b) ("Applies also to roof with sloping ceiling") it takes
column (3) — band F = 0.68, band L = 0.18 (vs col 1 0.40 / 0.16).

Discriminator is the code-8 "sloping ceiling" string only: code-5 vaulted
ceilings stay on column (1) per the 33 cohort-2 "ND" vaulted certs
(S0380.211), and the "NI"/"ND" unknown case is untouched. New
`is_pitched_sloping_ceiling` flag threaded from heat_transmission to
`u_roof`; pre-1950 bands already reach the same col (3) value (2.30) via
the mapper's thickness=0 → Table 16 row-0 override, so the new branch
carries the post-1950 bands where col 1 ≠ col 3.

Worksheet-validated by simulated case 15 (the 7536 replica): our cascade
on its Summary matches the P960 worksheet exactly — roof HLC 29.17 W/K,
cont SAP 65.04 vs 65. Re-pins golden cert 7536: roof 26.77 → 29.17, cont
SAP 69.071 → 68.924, PE -7.0776 → -6.1952, CO2 -0.1875 → -0.1639 (SAP
integer 68, resid +1 unchanged — the remaining +0.92 is a diffuse demand
under-count needing a fully-faithful worksheet). Blast radius: 7536 only.

Suite: 2388 passed, 1 skipped (main); sap10_ml 233 passed + 2 pre-existing
stone-formula failures (out of scope). Zero new pyright errors.

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

domain/sap10_calculator/worksheet/heat_transmission.py

@@ -791,7 +791,13 @@ def heat_transmission_from_cert(
         is_sloping_ceiling = (
             "sloping ceiling" in roof_type_lower or "vaulted" 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)
+        # RdSAP 10 Table 18 col (3) routing for an AS-BUILT "Pitched,
+        # sloping ceiling" (code 8). Narrower than `is_sloping_ceiling`
+        # (which also covers code-5 vaulted): vaulted ceilings stay on
+        # 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)
         # Floor U-value routing (in priority order):
         #   1. Basement floor — Table 23 F-column override (whole floor=0).
         #   2. Exposed/semi-exposed upper floor — Table 20 lookup; no

domain/sap10_ml/rdsap_uvalues.py

@@ -721,6 +721,7 @@ def u_roof(
     description: Optional[str] = None,
     is_flat_roof: bool = False,
     is_sloping_ceiling: bool = False,
+    is_pitched_sloping_ceiling: bool = False,
 ) -> float:
     """RdSAP10 roof U-value in W/m^2K, never null.
 
@@ -745,6 +746,18 @@ def u_roof(
     default (band J = 0.16) — the same value a vaulted roof lodged "ND"
     (thickness None) already reaches by falling through. The 33 cohort-2
     "ND" vaulted certs (code 5, band D → 0.40 = col 1) are the evidence.
+
+    `is_pitched_sloping_ceiling` is the narrower code-8 ("Pitched, sloping
+    ceiling") signal for the AS-BUILT case (insulation lodged "As Built",
+    parsed to thickness None — distinct from the "NI"/"ND" unknown case
+    above). Per RdSAP 10 roof-input item 5-5 ("Sloping ceiling insulation
+    ... as built → Table 18") and Table 18 note (b) ("applies also to roof
+    with sloping ceiling"), an as-built sloping ceiling takes the column
+    (3) age-band default (band F = 0.68, band L = 0.18), NOT the column (1)
+    loft-joist default (band F = 0.40, band L = 0.16). Vaulted ceilings
+    (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.
     """
     measured = _measured_u_from_description(description)
     if measured is not None:
@@ -789,6 +802,15 @@ def u_roof(
             return _ROOF_BY_THICKNESS[1][1]  # 1.50 W/m^2K (12mm row)
     if age_band is None:
         return 0.4
+    if is_pitched_sloping_ceiling:
+        # RdSAP 10 §5.11 Table 18 page 45 column (3) + roof-input item 5-5:
+        # an as-built "Pitched, sloping ceiling" (code 8) with no measured
+        # thickness takes the column (3) age-band default, not the column
+        # (1) loft-joist default. Note (b): column (3) "applies also to
+        # roof with sloping ceiling". (Pre-1950 bands reach the same value
+        # via the mapper's thickness=0 → Table 16 row-0 2.30 override, so
+        # this branch carries the post-1950 bands where col 1 ≠ col 3.)
+        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)

domain/sap10_ml/tests/test_rdsap_uvalues.py

@@ -945,6 +945,66 @@ def test_u_roof_flat_age_band_l_returns_table18_col3_value() -> None:
     assert abs(result - 0.18) <= 1e-4
 
 
+def test_u_roof_pitched_sloping_ceiling_as_built_band_f_uses_col3() -> None:
+    # Arrange — RdSAP 10 §5.11 Table 18 page 45 + roof-input item 5-5
+    # ("Sloping ceiling insulation ... unknown / as built → Table 18").
+    # A "Pitched, sloping ceiling" roof (roof_construction code 8) with an
+    # "As Built" insulation lodgement (no measured thickness → None) takes
+    # the Table 18 column (3) age-band default, NOT the column (1)
+    # "insulation between joists" default. Note (b) on column (3) states it
+    # "applies also to roof with sloping ceiling". For age band F the
+    # column (3) value is 0.68 W/m²K (vs column (1) 0.40 — the loft-joist
+    # assumption that is wrong for a sloping ceiling with no joist void).
+    #
+    # Worksheet-validated: simulated case 15 (7536 replica) lodges Ext2 as
+    # band F "PS Pitched, sloping ceiling, As Built"; its P960 worksheet
+    # pins `External roof Ext2 … 0.68`, and the full-cascade roof HLC and
+    # SAP match Elmhurst exactly only with column (3).
+
+    # Act
+    result = u_roof(
+        country=Country.ENG, age_band="F", insulation_thickness_mm=None,
+        is_pitched_sloping_ceiling=True,
+    )
+
+    # Assert
+    assert abs(result - 0.68) <= 1e-4
+
+
+def test_u_roof_pitched_sloping_ceiling_as_built_band_l_uses_col3() -> None:
+    # Arrange — same rule at band L (2012-2022): Table 18 column (3) gives
+    # 0.18 W/m²K, where columns (2)/(3) coincide. Simulated case 15's Ext1
+    # (band L PS sloping ceiling, As Built) pins worksheet U=0.18 (vs the
+    # column (1) value 0.16 the cascade returned pre-fix).
+
+    # Act
+    result = u_roof(
+        country=Country.ENG, age_band="L", insulation_thickness_mm=None,
+        is_pitched_sloping_ceiling=True,
+    )
+
+    # Assert
+    assert abs(result - 0.18) <= 1e-4
+
+
+def test_u_roof_vaulted_nd_unknown_band_d_still_col1_not_col3() -> None:
+    # Arrange — regression guard for the discriminator: a code-5 "vaulted"
+    # roof lodged "ND" (thickness None) is the UNKNOWN-insulation case and
+    # must stay on Table 18 column (1) — band D = 0.40 — per the 33
+    # cohort-2 vaulted certs (S0380.211). The col (3) routing fires only
+    # for code-8 "Pitched, sloping ceiling" (is_pitched_sloping_ceiling),
+    # NOT for vaulted ceilings, so this defaults False here and resolves
+    # to column (1) 0.40, NOT column (3) 2.30.
+
+    # Act
+    result = u_roof(
+        country=Country.ENG, age_band="D", insulation_thickness_mm=None,
+    )
+
+    # Assert
+    assert abs(result - 0.40) <= 1e-4
+
+
 def test_u_roof_description_no_insulation_overrides_age_band_default() -> None:
     # Arrange — surveyor description on a Victorian roof says uninsulated;
     # Table 18 age-B default (0.40) is far too optimistic. Table 16 row 0mm

tests/domain/sap10_calculator/rdsap/test_golden_fixtures.py

@@ -370,8 +370,8 @@ _EXPECTATIONS: tuple[_GoldenExpectation, ...] = (
         cert_number="7536-3827-0600-0600-0276",
         actual_sap=68,
         expected_sap_resid=+1,
-        expected_pe_resid_kwh_per_m2=-7.0776,
-        expected_co2_resid_tonnes_per_yr=-0.1875,
+        expected_pe_resid_kwh_per_m2=-6.1952,
+        expected_co2_resid_tonnes_per_yr=-0.1639,
         notes=(
             "Detached + 2 extensions, TFA 152. Multi-age bps (Main=D, "
             "Ext1=L, Ext2=F). Slice 59 (per-bp window apportionment) and "
@@ -379,10 +379,23 @@ _EXPECTATIONS: tuple[_GoldenExpectation, ...] = (
             "age band, not per-bp) jointly tightened: SAP +4 → +3, PE "
             "-27.17 → -22.53, CO2 -0.72 → -0.60. Slice 97 added "
             "glazing_type=2 (Table 24 spec U=2.0): SAP 0 → +1, PE/CO2 "
-            "widened. The cert's actual lodged U for glazing_type=2 "
-            "appears higher than the spec's table default — multi-age "
-            "geometry probably surfaces a per-bp U-value the spec table "
-            "doesn't capture exactly."
+            "widened. Slice S0380.214 fixed the as-built sloping-ceiling "
+            "roof U: Ext1 (band L) and Ext2 (band F) lodge "
+            "roof_construction=8 'Pitched, sloping ceiling' + 'As Built', "
+            "which take RdSAP 10 Table 18 col (3) (L=0.18, F=0.68) not "
+            "col (1) (0.16/0.40) — per item 5-5 + note (b). Roof HLC "
+            "26.77 → 29.17 W/K; cont SAP 69.071 → 68.924, PE -7.0776 → "
+            "-6.1952, CO2 -0.1875 → -0.1639 (SAP integer still 68 vs "
+            "lodged → resid +1). Worksheet-validated by simulated case 15 "
+            "(the 7536 replica): our cascade on its Summary matches the "
+            "P960 worksheet exactly (roof 29.17, SAP 65.04 vs 65). The "
+            "glazing hypothesis from the prior handover was wrong — maxing "
+            "the glazing U past spec can't flip 69→68, and every per-bp "
+            "fabric U is spec-plausible. The residual +0.92 cont SAP is a "
+            "diffuse demand under-count (window split + Main suspended-"
+            "timber floor) not capturable from the API-only JSON; needs a "
+            "fully-faithful 7536 worksheet (in progress) to localise or "
+            "conclude it is 0240-like."
         ),
     ),
     _GoldenExpectation(