§8c slice 3: CalculatorInputs + MonthlyEntry + SapResult + cert_to_inputs wiring (atomic)

Full §8 mirror per Q9 grilling: CalculatorInputs.space_cooling_monthly_kwh (default (0,)*12), MonthlyEntry.space_cool_requirement_kwh, SapResult.space_cooling_kwh_per_yr. _solve_month indexes into the cooling tuple and calculate_sap_from_inputs sums the per-month entries.

cert_to_inputs calls space_cooling_monthly_kwh with f_C=0 and cooling_gains=(0,)*12 — RdSAP convention since the cert never lodges cooled-area data and every `has_fixed_air_conditioning=False` cert collapses (107) to zero. The first cooling-enabled fixture needs a cooling_gains_from_cert helper + RdSAP cooled-area defaulting rule (deferred — SPEC_COVERAGE §8c row).

Round-trip test pins inputs.space_cooling_monthly_kwh = (0,)*12, result.space_cooling_kwh_per_yr = 0.0, and every MonthlyEntry.space_cool_requirement_kwh = 0.0 for a typical SAP10 minimal cert.

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

packages/domain/src/domain/sap/calculator.py

@@ -129,6 +129,12 @@ class CalculatorInputs:
     secondary_heating_fraction: float = 0.0
     secondary_heating_efficiency: float = 1.0
     secondary_heating_fuel_cost_gbp_per_kwh: float = 0.0
+    # SAP10.2 (107)m — space cooling requirement kWh per month from §8c
+    # orchestrator `space_cooling_monthly_kwh`. Includes spec Jun-Aug
+    # inclusion mask + 1-kWh clamp. Default (0,)*12 for backwards
+    # compatibility — every cert without `has_fixed_air_conditioning`
+    # collapses cooling to zero.
+    space_cooling_monthly_kwh: tuple[float, ...] = (0.0,) * 12
 
 
 @dataclass(frozen=True)
@@ -145,6 +151,7 @@ class MonthlyEntry:
     space_heat_requirement_kwh: float
     main_heating_fuel_kwh: float
     secondary_heating_fuel_kwh: float = 0.0
+    space_cool_requirement_kwh: float = 0.0
 
 
 @dataclass(frozen=True)
@@ -159,6 +166,7 @@ class SapResult:
     total_fuel_cost_gbp: float
     co2_kg_per_yr: float
     space_heating_kwh_per_yr: float
+    space_cooling_kwh_per_yr: float
     main_heating_fuel_kwh_per_yr: float
     secondary_heating_fuel_kwh_per_yr: float
     hot_water_kwh_per_yr: float
@@ -210,6 +218,10 @@ def _solve_month(
         else 0.0
     )
 
+    # SAP 10.2 §8c — (107)m precomputed upstream by `space_cooling_monthly_kwh`
+    # (includes Jun-Aug inclusion mask + post-f_C × f_intermittent clamp).
+    q_cool = inputs.space_cooling_monthly_kwh[month - 1]
+
     return MonthlyEntry(
         month=month,
         external_temp_c=t_ext,
@@ -221,6 +233,7 @@ def _solve_month(
         space_heat_requirement_kwh=q_heat,
         main_heating_fuel_kwh=fuel_main,
         secondary_heating_fuel_kwh=fuel_secondary,
+        space_cool_requirement_kwh=q_cool,
     )
 
 
@@ -262,6 +275,7 @@ def calculate_sap_from_inputs(inputs: CalculatorInputs) -> SapResult:
     )
 
     space_heating_kwh = sum(e.space_heat_requirement_kwh for e in monthly)
+    space_cooling_kwh = sum(e.space_cool_requirement_kwh for e in monthly)
     main_fuel_kwh = sum(e.main_heating_fuel_kwh for e in monthly)
     secondary_fuel_kwh = sum(e.secondary_heating_fuel_kwh for e in monthly)
     delivered_fuel_kwh = (
@@ -377,6 +391,7 @@ def calculate_sap_from_inputs(inputs: CalculatorInputs) -> SapResult:
         total_fuel_cost_gbp=total_cost,
         co2_kg_per_yr=co2,
         space_heating_kwh_per_yr=space_heating_kwh,
+        space_cooling_kwh_per_yr=space_cooling_kwh,
         main_heating_fuel_kwh_per_yr=main_fuel_kwh,
         secondary_heating_fuel_kwh_per_yr=secondary_fuel_kwh,
         hot_water_kwh_per_yr=inputs.hot_water_kwh_per_yr,

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

@@ -72,6 +72,7 @@ from domain.sap.worksheet.mean_internal_temperature import (
     mean_internal_temperature_monthly,
 )
 from domain.sap.worksheet.solar_gains import solar_gains_from_cert
+from domain.sap.worksheet.space_cooling import space_cooling_monthly_kwh
 from domain.sap.worksheet.space_heating import space_heating_monthly_kwh
 from domain.sap.worksheet.ventilation import (
     MechanicalVentilationKind,
@@ -928,18 +929,35 @@ def cert_to_inputs(
     # SAP10.2 §8 — compose (98c)m via the orchestrator. Reuses the per-month
     # HTC + total-gains tuples already computed for §7 and adds T_int + η
     # from the MIT result. Includes the Table 9c step 10 summer clamp.
+    monthly_external_temp_c = tuple(
+        external_temperature_c(_region_index(epc.region_code), m)
+        for m in range(1, 13)
+    )
     space_heating_result = space_heating_monthly_kwh(
         monthly_heat_transfer_coefficient_w_per_k=monthly_htc_w_per_k,
         monthly_internal_temperature_c=mit_result.adjusted_mean_internal_temp_monthly,
-        monthly_external_temperature_c=tuple(
-            external_temperature_c(_region_index(epc.region_code), m)
-            for m in range(1, 13)
-        ),
+        monthly_external_temperature_c=monthly_external_temp_c,
         monthly_utilisation_factor=mit_result.utilisation_factor_whole_monthly,
         monthly_total_gains_w=monthly_total_gains_w,
         total_floor_area_m2=dim.total_floor_area_m2,
     )
 
+    # SAP10.2 §8c — compose (107)m via the orchestrator. RdSAP convention:
+    # `cooled_area_fraction = 0` always (the cert never lodges cooled-area
+    # data) and `cooling_gains = (0,)*12` until a real cooling-gains-from-
+    # cert helper lands. Both decisions deferred per SPEC_COVERAGE §8c row;
+    # for `has_fixed_air_conditioning=False` certs the f_C=0 zeros (107)
+    # regardless of gains so the stub is harmless.
+    space_cooling_result = 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,
+    )
+
     return CalculatorInputs(
         dimensions=dim,
         heat_transmission=ht,
@@ -962,6 +980,9 @@ def cert_to_inputs(
         # SAP10.2 (98c)m — total space heating kWh/month from §8 orchestrator
         # above (includes the spec Jun..Sep summer clamp).
         space_heating_monthly_kwh=space_heating_result.total_space_heating_monthly_kwh,
+        # SAP10.2 (107)m — space cooling kWh/month from §8c orchestrator
+        # above (includes Jun-Aug inclusion mask + 1-kWh clamp).
+        space_cooling_monthly_kwh=space_cooling_result.space_cooling_monthly_kwh,
         region=_region_index(epc.region_code),
         control_type=control_type_value,
         responsiveness=responsiveness_value,

packages/domain/src/domain/sap/rdsap/tests/test_cert_to_inputs.py

@@ -292,6 +292,27 @@ def test_minimal_cert_round_trips_through_calculator_and_returns_sap_result() ->
     assert result.total_fuel_cost_gbp > 0
 
 
+def test_no_ac_cert_round_trips_to_zero_space_cooling_on_sap_result() -> None:
+    """RdSAP cert without a fixed air-conditioning system (the dominant
+    case) must wire through cert_to_inputs → calculator with the §8c
+    orchestrator producing all-zero cooling. SapResult.space_cooling_kwh_
+    per_yr == 0.0 and every MonthlyEntry.space_cool_requirement_kwh == 0.0.
+    """
+    # Arrange — has_fixed_air_conditioning is False by default on the
+    # SAP10 minimal heating fixture (mirrors every Elmhurst fixture).
+    epc = _typical_semi_detached_epc()
+    assert epc.sap_heating.has_fixed_air_conditioning is False
+
+    # Act
+    inputs = cert_to_inputs(epc)
+    result = Sap10Calculator().calculate(epc)
+
+    # Assert
+    assert inputs.space_cooling_monthly_kwh == (0.0,) * 12
+    assert result.space_cooling_kwh_per_yr == 0.0
+    assert all(entry.space_cool_requirement_kwh == 0.0 for entry in result.monthly)
+
+
 def test_calculator_always_uses_uk_average_weather_for_rating() -> None:
     # Arrange — SAP 10.2 Appendix U explicitly states: "Calculations for
     # ratings (SAP rating and environmental impact rating) are done with