fix(u-value): RdSAP10 ignores gov-API wall insulation conductivity → §5.8 default λ

The gov EPC API field wall_insulation_thermal_conductivity is OUTPUT
metadata in the openly-published EPC, not an input to the RdSAP10 tool
(Elmhurst) that produced it — its wall entry is Type + Insulation +
thickness only, with no conductivity field. So the RdSAP10 reduced-data
method always uses the SAP 10.2 §5.8 (p.41) default λ=0.04 W/m·K,
whatever code the register lodged.

`_resolve_wall_insulation_lambda_w_per_mk` previously mapped only code 1
(→0.04) and RAISED on others, blocking cert 2090-6909-8060-5201-6401
(code 3 on an internally-insulated 360mm solid-brick wall) with
calc_raise:ValueError. Now it returns the §5.8 default for any code.

Validated: 2090 computes to SAP 73.97 vs lodged 74 (err -0.03); λ of
0.04 / 0.03 / 0.025 all round to 74, and Elmhurst exposes no conductivity
input, so 0.04 is the spec-faithful RdSAP10 value. Eval computed
905→906; mean|err| 1.708→1.706. Regression green (only the 2 pre-existing
stone-wall U failures); pyright net-zero (69=69).

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

domain/sap10_ml/rdsap_uvalues.py

@@ -177,42 +177,27 @@ WALL_INSULATION_CAVITY_PLUS_INTERNAL: Final[int] = 7
 # (cavity + external/internal insulation).
 _WALL_INSULATION_LAMBDA_W_PER_MK: Final[float] = 0.04
 
-# RdSAP 10 §5.8 (page 41) — when documentary evidence lodges the insulation
-# thermal conductivity, the R-value calc uses it instead of the 0.04 default.
-# The spec offers three λ: 0.04 (mineral wool / EPS, the default), 0.03 (XPS),
-# 0.025 (PUR / PIR / phenolic). The GOV.UK API surfaces a coded value
-# (`wall_insulation_thermal_conductivity`); code 1 = the default 0.04 (the
-# only code observed — cert 2130 Ext1, whose documentary-evidence path does
-# not fire as no wall thickness is lodged, so the value is captured but
-# unused there). Other codes raise until a worksheet-backed fixture confirms
-# their λ — the same incremental-coverage discipline as the glazing-type map.
-_WALL_INSULATION_CONDUCTIVITY_CODE_TO_LAMBDA: Final[dict[int, float]] = {
-    1: 0.04,
-}
-
-
 def _resolve_wall_insulation_lambda_w_per_mk(
     conductivity: "str | int | None",
 ) -> float:
-    """Resolve the insulation λ (W/m·K) for the §5.8 documentary-evidence
-    R-value calc. Absent / "Unknown" → the 0.04 default; a mapped integer
-    code → its λ; an unmapped integer code raises so the enum is confirmed
-    against a worksheet rather than silently mis-factored."""
-    if conductivity is None:
-        return _WALL_INSULATION_LAMBDA_W_PER_MK
-    if isinstance(conductivity, str):
-        text = conductivity.strip()
-        if not text or text.lower() == "unknown" or not text.isdigit():
-            return _WALL_INSULATION_LAMBDA_W_PER_MK
-        conductivity = int(text)
-    lam = _WALL_INSULATION_CONDUCTIVITY_CODE_TO_LAMBDA.get(conductivity)
-    if lam is None:
-        raise ValueError(
-            "unmapped wall_insulation_thermal_conductivity code "
-            f"{conductivity!r}; add its RdSAP 10 §5.8 λ "
-            "(0.04 / 0.03 / 0.025 W/m·K) once a worksheet confirms it"
-        )
-    return lam
+    """Insulation λ (W/m·K) for the §5.8 documentary-evidence R-value calc.
+
+    The RdSAP10 reduced-data method does NOT consume the gov-API
+    `wall_insulation_thermal_conductivity` field: the Elmhurst RdSAP10
+    tool exposes no conductivity input (a wall is Type + Insulation +
+    thickness only), so SAP 10.2 §5.8 (p.41) default λ=0.04 W/m·K
+    (mineral wool / EPS) always applies, whatever code the register
+    lodged. The argument is retained for call-site compatibility but
+    every value resolves to the default.
+
+    SAP 10.2 §5.8 also lists 0.03 (XPS) / 0.025 (PUR/PIR/phenolic) for
+    *full* SAP documentary evidence, but those are not selectable in the
+    RdSAP10 path we model. Verified: cert 2090-6909-8060-5201-6401 lodges
+    code 3 on an internally-insulated solid-brick wall and reproduces its
+    lodged SAP 74 at λ=0.04 (continuous 73.97; 0.04/0.03/0.025 all round
+    to 74). Pre-this the helper mapped only code 1 and raised on others,
+    blocking the cert with `unmapped ... code 3`."""
+    return _WALL_INSULATION_LAMBDA_W_PER_MK
 
 # RdSAP10 §5.8 final note + Table 14 page 41: "For drylining including
 # laths and plaster use Rinsulation = 0.17 m²K/W." Applied additively to

domain/sap10_ml/tests/test_rdsap_uvalues.py

@@ -1954,15 +1954,26 @@ def test_resolve_wall_insulation_lambda_code_1_is_default_mineral_wool() -> None
     assert abs(lam_str - 0.04) <= 1e-9
 
 
-def test_resolve_wall_insulation_lambda_unmapped_code_raises() -> None:
-    # Arrange — an unmapped code must raise (incremental-coverage gate)
-    # rather than silently mis-factor the R-value.
-    import pytest as _pytest
-
+def test_resolve_wall_insulation_lambda_any_code_uses_default() -> None:
+    # Arrange — the RdSAP10 reduced-data method does NOT consume the
+    # gov-API `wall_insulation_thermal_conductivity` field: the Elmhurst
+    # RdSAP10 tool exposes no conductivity input (a wall is Type +
+    # Insulation + thickness only), so SAP 10.2 §5.8 (p.41) default
+    # λ=0.04 W/m·K always applies regardless of the lodged code. Cert
+    # 2090-6909-8060-5201-6401 lodges code 3 on an internally-insulated
+    # solid-brick wall and reproduces its lodged SAP 74 at λ=0.04
+    # (continuous 73.97; 0.04/0.03/0.025 all round to 74). Pre-this the
+    # helper mapped only code 1 and RAISED on 2/3, blocking the cert.
     from domain.sap10_ml.rdsap_uvalues import (
         _resolve_wall_insulation_lambda_w_per_mk,
     )
 
-    # Act / Assert
-    with _pytest.raises(ValueError):
-        _resolve_wall_insulation_lambda_w_per_mk(2)
+    # Act
+    lam_2 = _resolve_wall_insulation_lambda_w_per_mk(2)
+    lam_3 = _resolve_wall_insulation_lambda_w_per_mk(3)
+    lam_3_str = _resolve_wall_insulation_lambda_w_per_mk("3")
+
+    # Assert — every code resolves to the §5.8 default 0.04, never raises.
+    assert abs(lam_2 - 0.04) <= 1e-9
+    assert abs(lam_3 - 0.04) <= 1e-9
+    assert abs(lam_3_str - 0.04) <= 1e-9