Slice 28: §8c + §8f cascade pins (48/48)

Adds `space_cooling_section_from_cert(epc)` and
`fabric_energy_efficiency_from_cert(epc)` to the cert→inputs cascade.

§8c (lines 100..108) — all 6 Elmhurst fixtures have
`has_fixed_air_conditioning=False` so f_C=0 collapses (107)/(108) to
zero, (101) η_loss=1 for every month (γ=0 branch), (103) gains=0, and
(106) intermittency follows the spec Jun-Aug mask 0.25. (100), (102),
(104) depend on H × (24 − T_e) per fixture and are not asserted in the
cascade (covered by `test_space_cooling.py` synthetic-positive case).
42/42 §8c pins PASS.

§8f (line 109) — Fabric Energy Efficiency = (98a)/(4) + (108). For all
6 fixtures (98b) solar space heating = 0 and (108) = 0, so (109) = (99)
exactly. 6/6 §8f pins PASS.

Cascade scoreboard: 348/348 → 396/396 (§7..§8f closed).

Co-Authored-By: Claude Opus 4.7 <noreply@anthropic.com>

packages/domain/src/domain/sap/rdsap/cert_to_inputs.py

@@ -100,7 +100,10 @@ from domain.sap.worksheet.energy_requirements import (
 from domain.sap.worksheet.fabric_energy_efficiency import (
     fabric_energy_efficiency_kwh_per_m2_yr,
 )
-from domain.sap.worksheet.space_cooling import space_cooling_monthly_kwh
+from domain.sap.worksheet.space_cooling import (
+    SpaceCoolingResult,
+    space_cooling_monthly_kwh,
+)
 from domain.sap.worksheet.space_heating import (
     SpaceHeatingResult,
     space_heating_monthly_kwh,
@@ -953,6 +956,63 @@ def space_heating_section_from_cert(
     )
 
 
+def space_cooling_section_from_cert(
+    epc: EpcPropertyData,
+) -> Optional[SpaceCoolingResult]:
+    """SAP 10.2 §8c cert→inputs cascade for `space_cooling_monthly_kwh`.
+
+    Composes §1 (dim) + §2 (ventilation) + §3 (HLC) + climate; cooling
+    gains and cooled-area fraction default to 0 (RdSAP convention — the
+    cert never lodges cooled-area data, and for `has_fixed_air_conditioning
+    =False` certs the f_C=0 zeros (107) regardless of gains). Returns the
+    full `SpaceCoolingResult` (every (100)..(108) line ref) so cascade pin
+    tests can assert each §8c line ref against the U985 PDF.
+
+    Returns `None` when TFA is missing (matches other section helpers).
+    """
+    if epc.total_floor_area_m2 is None:
+        return None
+    dim = dimensions_from_cert(epc)
+    ventilation = ventilation_from_cert(epc)
+    ht = heat_transmission_section_from_cert(epc)
+    monthly_htc_w_per_k = tuple(
+        ht.total_w_per_k + 0.33 * dim.volume_m3 * ventilation.effective_monthly_ach[m]
+        for m in range(12)
+    )
+    region = _region_index(epc.region_code)
+    monthly_external_temp_c = tuple(
+        external_temperature_c(region, m) for m in range(1, 13)
+    )
+    return space_cooling_monthly_kwh(
+        monthly_heat_transfer_coefficient_w_per_k=monthly_htc_w_per_k,
+        monthly_external_temperature_c=monthly_external_temp_c,
+        monthly_total_gains_w=(0.0,) * 12,
+        total_floor_area_m2=dim.total_floor_area_m2,
+        thermal_mass_parameter_kj_per_m2_k=_DEFAULT_THERMAL_MASS_PARAMETER_KJ_PER_M2_K,
+        cooled_area_fraction=0.0,
+        intermittency_factor=0.25,
+    )
+
+
+def fabric_energy_efficiency_from_cert(epc: EpcPropertyData) -> Optional[float]:
+    """SAP 10.2 §8f cert→inputs cascade for `fabric_energy_efficiency_kwh_
+    per_m2_yr` — line (109) = (98a)/(4) + (108). Composes §8 (space heating)
+    + §8c (space cooling) + §1 (TFA). Returns None when TFA missing.
+    """
+    if epc.total_floor_area_m2 is None:
+        return None
+    dim = dimensions_from_cert(epc)
+    sh = space_heating_section_from_cert(epc)
+    sc = space_cooling_section_from_cert(epc)
+    assert sh is not None, "space_heating None despite TFA present"
+    assert sc is not None, "space_cooling None despite TFA present"
+    return fabric_energy_efficiency_kwh_per_m2_yr(
+        space_heating_kwh_per_yr=sh.space_heating_requirement_kwh_per_yr,
+        total_floor_area_m2=dim.total_floor_area_m2,
+        space_cooling_per_m2_kwh=sc.space_cooling_per_m2_kwh,
+    )
+
+
 def solar_gains_section_from_cert(epc: EpcPropertyData) -> SolarGainsResult:
     """SAP 10.2 §6 cert→inputs cascade for `solar_gains_from_cert`.
 

packages/domain/src/domain/sap/worksheet/tests/test_section_cascade_pins.py

@@ -18,10 +18,12 @@ import pytest
 
 from domain.sap.rdsap.cert_to_inputs import (
     cert_to_inputs,
+    fabric_energy_efficiency_from_cert,
     heat_transmission_section_from_cert,
     internal_gains_section_from_cert,
     mean_internal_temperature_section_from_cert,
     solar_gains_section_from_cert,
+    space_cooling_section_from_cert,
     space_heating_section_from_cert,
     ventilation_from_cert,
     water_heating_section_from_cert,
@@ -593,3 +595,107 @@ def test_section_8_scalar_line_refs_match_pdf(
 
     # Assert
     _pin(actual, expected, f"§8 {fixture_attr} {fixture_name}")
+
+
+# ============================================================================
+# §8c Space cooling — LINE_100..LINE_108
+# ============================================================================
+# All 6 Elmhurst fixtures have `has_fixed_air_conditioning=False` so f_C=0
+# and (107)/(108) collapse to zero. (100), (102), (104) depend on H × (24 −
+# T_e) per fixture, so we don't assert those here (covered by
+# `test_space_cooling.py` synthetic-positive case); cascade pins target the
+# spec-collapsed lines: (101) η_loss=1, (103) gains=0, (106) intermittency
+# mask, (107) cooling kWh=0, (107) annual=0, (108) per-m²=0.
+
+_SECTION_8C_MONTHLY_PINS: Final[tuple[tuple[str, str], ...]] = (
+    ("LINE_101_M_UTILISATION_FACTOR_LOSS", "utilisation_factor_loss_monthly"),
+    ("LINE_103_M_COOLING_GAINS_W",         "cooling_gains_monthly_w"),
+    ("LINE_106_M_INTERMITTENCY_FACTOR",    "intermittency_factor_monthly"),
+    ("LINE_107_M_SPACE_COOLING_KWH",       "space_cooling_monthly_kwh"),
+)
+
+_SECTION_8C_SCALAR_PINS: Final[tuple[tuple[str, str], ...]] = (
+    ("SECTION_8C_COOLED_AREA_FRACTION", "cooled_area_fraction"),
+    ("LINE_107_ANNUAL_KWH",             "space_cooling_kwh_per_yr"),
+    ("LINE_108_PER_M2_KWH",             "space_cooling_per_m2_kwh"),
+)
+
+
+@pytest.mark.parametrize(
+    "fixture_name,fixture_attr,result_attr",
+    [
+        (fix, line, attr)
+        for fix in _FIXTURES
+        for line, attr in _SECTION_8C_MONTHLY_PINS
+    ],
+    ids=lambda x: x if isinstance(x, str) else None,
+)
+def test_section_8c_monthly_line_refs_match_pdf(
+    fixture_name: str, fixture_attr: str, result_attr: str
+) -> None:
+    """§8c monthly pins — every Jan..Dec value of (101)/(103)/(106)/(107)
+    space-cooling lines matches the U985 PDF to abs=1e-4."""
+    # Arrange
+    mod = _FIXTURES[fixture_name]
+    epc = mod.build_epc()  # type: ignore[attr-defined]
+    expected = getattr(mod, fixture_attr)
+
+    # Act
+    sc = space_cooling_section_from_cert(epc)
+    assert sc is not None, f"{fixture_name}: space_cooling_from_cert returned None"
+    actual = getattr(sc, result_attr)
+
+    # Assert
+    for m in range(12):
+        _pin(actual[m], expected[m], f"§8c {fixture_attr}[{m+1}] {fixture_name}")
+
+
+@pytest.mark.parametrize(
+    "fixture_name,fixture_attr,result_attr",
+    [
+        (fix, line, attr)
+        for fix in _FIXTURES
+        for line, attr in _SECTION_8C_SCALAR_PINS
+    ],
+    ids=lambda x: x if isinstance(x, str) else None,
+)
+def test_section_8c_scalar_line_refs_match_pdf(
+    fixture_name: str, fixture_attr: str, result_attr: str
+) -> None:
+    """§8c scalar pins — (105) cooled-area fraction + (107) annual Σ +
+    (108) per-m² total match the U985 PDF to abs=1e-4."""
+    # Arrange
+    mod = _FIXTURES[fixture_name]
+    epc = mod.build_epc()  # type: ignore[attr-defined]
+    expected = getattr(mod, fixture_attr)
+
+    # Act
+    sc = space_cooling_section_from_cert(epc)
+    assert sc is not None, f"{fixture_name}: space_cooling_from_cert returned None"
+    actual = getattr(sc, result_attr)
+
+    # Assert
+    _pin(actual, expected, f"§8c {fixture_attr} {fixture_name}")
+
+
+# ============================================================================
+# §8f Fabric Energy Efficiency — LINE_109
+# ============================================================================
+
+
+@pytest.mark.parametrize("fixture_name", list(_FIXTURES), ids=lambda x: x)
+def test_section_8f_line_109_fee_matches_pdf(fixture_name: str) -> None:
+    """§8f scalar pin — (109) FEE = (98a)/(4) + (108) matches the U985 PDF
+    to abs=1e-4. For all 6 fixtures (98b) solar space heating = 0 and (108)
+    = 0, so (109) = (99)."""
+    # Arrange
+    mod = _FIXTURES[fixture_name]
+    epc = mod.build_epc()  # type: ignore[attr-defined]
+    expected = mod.LINE_109_FEE_KWH_PER_M2  # type: ignore[attr-defined]
+
+    # Act
+    actual = fabric_energy_efficiency_from_cert(epc)
+
+    # Assert
+    assert actual is not None, f"{fixture_name}: fee_from_cert returned None"
+    _pin(actual, expected, f"§8f LINE_109_FEE_KWH_PER_M2 {fixture_name}")