Merge pull request #1396 from Hestia-Homes/community-heating-hhrsh

Don't recommend HHRSH or ASHP to properties with community heating

datatypes/epc/domain/field_mappings.py

@@ -1,3 +1,21 @@
+from typing import Optional
+
+from datatypes.epc.domain.epc_property_data import MainHeatingDetail
+
 PROPERTY_TYPE_LOOKUP = {0: "House", 1: "Bungalow", 2: "Flat", 3: "Maisonette"}
 ROOF_CONSTRUCTION_LOOKUP = {}
 ROOF_INSULATION_LOCATION_LOOKUP = {}
+
+HEAT_NETWORK_MAIN_CODES: frozenset[int] = frozenset({301, 302, 303, 304})
+HEAT_NETWORK_CATEGORY: int = 6
+
+
+def is_heat_network_main(main: Optional[MainHeatingDetail]) -> bool:
+    """True when the dwelling's main heating is connected to a shared heat
+    network — by SAP Table 4a code (301–304) or by main_heating_category 6."""
+    if main is None:
+        return False
+    code = main.sap_main_heating_code
+    if isinstance(code, int) and code in HEAT_NETWORK_MAIN_CODES:
+        return True
+    return main.main_heating_category == HEAT_NETWORK_CATEGORY

domain/modelling/generators/heating_recommendation.py

@@ -15,7 +15,7 @@ produced by scoring (ADR-0016).
 from typing import Optional
 
 from datatypes.epc.domain.epc_property_data import EpcPropertyData, MainHeatingDetail
-from datatypes.epc.domain.field_mappings import PROPERTY_TYPE_LOOKUP
+from datatypes.epc.domain.field_mappings import PROPERTY_TYPE_LOOKUP, is_heat_network_main
 from domain.geospatial.planning_restrictions import PlanningRestrictions
 from domain.modelling.products import (
     AshpCostInputs,
@@ -670,10 +670,14 @@ def _ashp_eligible(epc: EpcPropertyData, restrictions: PlanningRestrictions) ->
     installability — the Optimiser owns the economics (ADR-0024), so floor area,
     built form, fuel, and fabric are deliberately not gates. A conservation area
     does not exclude ASHP (offered with a planning caveat); a listed/heritage
-    protection (`blocks_internal`) does."""
+    protection (`blocks_internal`) does. Community heating (SAP Table 4a codes
+    301–304 or category 6) is excluded by topology: replacing a shared heat
+    network with an individual ASHP is never appropriate."""
     main: MainHeatingDetail = epc.sap_heating.main_heating_details[0]
     if main.main_heating_category == _HEAT_PUMP_CATEGORY:
         return False
+    if is_heat_network_main(main):
+        return False
     if restrictions.blocks_internal:
         return False
     return _is_house_or_bungalow(epc)
@@ -718,11 +722,14 @@ def _hhr_storage_eligible(epc: EpcPropertyData) -> bool:
     heat pump.  Eligibility keys on the heating *fuel* (main_fuel_type not in
     _GAS_FUEL_CODES), not the gas-connection flag — a dwelling on a gas street
     with electric or oil heating has gas_connection_available=True but still
-    qualifies."""
+    qualifies. Community heating (SAP Table 4a codes 301–304 or category 6) is
+    excluded by topology regardless of fuel: ripping out a shared heat network
+    to install storage heaters is never appropriate."""
     main: MainHeatingDetail = epc.sap_heating.main_heating_details[0]
     if main.sap_main_heating_code == _HHR_STORAGE_SAP_CODE:
         return False
     if main.main_heating_category == _HEAT_PUMP_CATEGORY:
         return False
-    non_gas_fuel: bool = main.main_fuel_type not in _GAS_FUEL_CODES
-    return non_gas_fuel
+    if is_heat_network_main(main):
+        return False
+    return main.main_fuel_type not in _GAS_FUEL_CODES

domain/sap10_calculator/rdsap/cert_to_inputs.py

@@ -62,6 +62,7 @@ from datatypes.epc.domain.epc_property_data import (
     SapVentilation,
     SapWindow,
 )
+from datatypes.epc.domain.field_mappings import is_heat_network_main
 
 from domain.sap10_ml.demand import predicted_hot_water_kwh
 from domain.sap10_ml.rdsap_uvalues import Country, u_floor
@@ -1076,15 +1077,6 @@ _HEAT_NETWORK_DLF_BY_AGE: Final[dict[str, float]] = {
 _HEAT_NETWORK_DLF_DEFAULT: Final[float] = 1.50
 
 
-# SAP 10.2 Table 4a codes for heat-network main heating systems:
-#   301 = boiler-driven community heating
-#   302 = boiler-driven community heating with CHP
-#   303 = community CHP only
-#   304 = electric heat-pump community heating
-_HEAT_NETWORK_MAIN_CODES: Final[frozenset[int]] = frozenset({301, 302, 303, 304})
-_HEAT_NETWORK_CATEGORY: Final[int] = 6
-
-
 # SAP 10.2 Table 4a (PDF p.164) heat-network heat-source efficiency by
 # SAP code. Verbatim:
 #   301 "Boilers (RdSAP)" → 80%
@@ -1116,17 +1108,6 @@ _HEAT_NETWORK_HEAT_SOURCE_EFFICIENCY: Final[dict[int, float]] = {
 _HEAT_NETWORK_STANDING_CHARGE_GBP: Final[float] = 120.0
 
 
-def _is_heat_network_main(main: Optional[MainHeatingDetail]) -> bool:
-    """True when the cert's main heating is a heat network — either by
-    SAP code (Table 4a 301-304) or by `main_heating_category` (6)."""
-    if main is None:
-        return False
-    code = main.sap_main_heating_code
-    if isinstance(code, int) and code in _HEAT_NETWORK_MAIN_CODES:
-        return True
-    return main.main_heating_category == _HEAT_NETWORK_CATEGORY
-
-
 def _heat_network_heat_source_efficiency_scaling(
     main: Optional[MainHeatingDetail],
 ) -> float:
@@ -1138,7 +1119,7 @@ def _heat_network_heat_source_efficiency_scaling(
     factor by 1/heat_source_eff. Returns 1.0 for code 302 (CHP+boilers
     — separate split-formula path) and non-heat-network mains.
     """
-    if not _is_heat_network_main(main):
+    if not is_heat_network_main(main):
         return 1.0
     code = main.sap_main_heating_code if main is not None else None
     if not isinstance(code, int):
@@ -1159,7 +1140,7 @@ def _is_heat_network_electric_main(main: Optional[MainHeatingDetail]) -> bool:
     scaling. Non-electric heat networks (gas/oil/coal boilers, codes
     51/53/54) have no monthly factor set and keep the annual Table 12
     value."""
-    if not _is_heat_network_main(main):
+    if not is_heat_network_main(main):
         return False
     return co2_monthly_factors_kg_per_kwh(_main_fuel_code(main)) is not None
 
@@ -1293,7 +1274,7 @@ def _heat_network_distribution_electricity(
     per the §C3.2 text — verified line-by-line against the community-
     heating corpus worksheets. We mirror the spec text (space + water).
     """
-    if not _is_heat_network_main(main) or efficiency <= 0.0:
+    if not is_heat_network_main(main) or efficiency <= 0.0:
         return None
     distribution_monthly_kwh = tuple(
         _HEAT_NETWORK_PUMPING_FRACTION_OF_HEAT * (sh + hw) / efficiency
@@ -1995,7 +1976,7 @@ def _is_community_heating_hw_from_main(epc: EpcPropertyData) -> bool:
     if epc.sap_heating.water_heating_code not in _WATER_INHERIT_FROM_MAIN_CODES:
         return False
     main = _water_heating_main(epc)
-    if not _is_heat_network_main(main):
+    if not is_heat_network_main(main):
         return False
     code = main.sap_main_heating_code if main is not None else None
     return isinstance(code, int) and (
@@ -2026,7 +2007,7 @@ def _heat_network_standing_charge_gbp(
     gas community) is not a Table-32 gas code, so `_is_gas_code` returned
     False and the standing came out £0 — cert 9390 lost the whole £120.
     """
-    if _is_heat_network_main(main):
+    if is_heat_network_main(main):
         return _HEAT_NETWORK_STANDING_CHARGE_GBP
     if _is_community_heating_hw_from_main(epc):
         return _HEAT_NETWORK_STANDING_CHARGE_GBP / 2.0
@@ -2062,7 +2043,7 @@ def _main_heating_detail_efficiency(
         eff = pcdb_main.winter_efficiency_pct / 100.0
     else:
         eff = seasonal_efficiency(main_code, main_category, main_fuel)
-    if _is_heat_network_main(main):
+    if is_heat_network_main(main):
         primary_age = _dwelling_age_band(epc)
         # Worksheet (307): heat required = demand × (305) × (306 DLF), so the
         # delivered-per-fuel efficiency carries 1 / ((305) charging factor ×
@@ -2307,7 +2288,7 @@ def _heat_network_community_fuel_code(
     42/43/44 (the same rows the backwards-compat enum codes 11/12/13 map
     to). Cert 8536 (biomass community, SAP code 301) closed -17.2 → -6.5.
 
-    Gating on `_is_heat_network_main` keeps the bare Table-32 code 30 the
+    Gating on `is_heat_network_main` keeps the bare Table-32 code 30 the
     cascade uses internally as grid electricity untouched on
     non-community certs (e.g. cert 2211 whose whc=999 default writes
     `water_heating_fuel=30`).
@@ -2317,7 +2298,7 @@ def _heat_network_community_fuel_code(
     gap loudly instead of silently mis-pricing it as grid electricity,
     per the strict-raise principle ([[reference-unmapped-sap-code]]).
     """
-    if fuel not in _API_COMMUNITY_COLLISION_FUELS or not _is_heat_network_main(main):
+    if fuel not in _API_COMMUNITY_COLLISION_FUELS or not is_heat_network_main(main):
         return None
     translated = API_FUEL_TO_TABLE_12.get(fuel)
     if translated is None:
@@ -2420,7 +2401,7 @@ def _heat_network_factor_fuel_code(
     (367) CO2 factor 0.2100, (467) PE factor 1.1300.
     """
     fuel = _main_fuel_code(main)
-    if fuel is None or not _is_heat_network_main(main):
+    if fuel is None or not is_heat_network_main(main):
         return fuel
     return _table_12_factor_fuel_code(fuel)
 
@@ -6009,7 +5990,7 @@ def _apply_heat_network_hiu_default_store(
     if epc.has_hot_water_cylinder:
         return epc
     dhw_main = _water_heating_main(epc)
-    if not _is_heat_network_main(dhw_main):
+    if not is_heat_network_main(dhw_main):
         return epc
     if dhw_main is not None and dhw_main.main_heating_index_number is not None:
         return epc
@@ -6183,7 +6164,7 @@ def _table_2b_note_b_multiplier_applies(
         return False
     if main is None:
         return False
-    if _is_heat_network_main(main):
+    if is_heat_network_main(main):
         return False
     return True
 
@@ -6544,7 +6525,7 @@ def _primary_loss_applies(
     # HIU/connection — Table 3 row 1 (heat generator connected to a
     # cylinder via primary pipework) applies.
     if (
-        _is_heat_network_main(main)
+        is_heat_network_main(main)
         and water_heating_code in _WATER_INHERIT_FROM_MAIN_CODES
     ):
         return True
@@ -6986,7 +6967,7 @@ def _primary_loss_override(
     # pre-2007 stock. See `_HEAT_NETWORK_PIPEWORK_INSULATION_FRACTION`.
     pipework_p = (
         _HEAT_NETWORK_PIPEWORK_INSULATION_FRACTION
-        if _is_heat_network_main(main)
+        if is_heat_network_main(main)
         else _pipework_insulation_fraction_table_3(primary_age)
     )
     base = primary_loss_monthly_kwh(
@@ -6998,7 +6979,7 @@ def _primary_loss_override(
         # row applies regardless of the thermostat / separate-timing
         # lodgement (and so is robust to the community-fuel-as-electric
         # collision that would otherwise route DHW to the h=5 row).
-        heat_network=_is_heat_network_main(main),
+        heat_network=is_heat_network_main(main),
     )
     # SAP 10.2 §12.4.4 (PDF p.36-37): for back-boiler combos summer DHW
     # comes from an electric immersion, not from the boiler — the boiler
@@ -7037,7 +7018,7 @@ def _cylinder_thermostat_present(
     if epc.sap_heating.cylinder_thermostat == "Y":
         return True
     dhw_main = _water_heating_main(epc)
-    if _is_heat_network_main(dhw_main):
+    if is_heat_network_main(dhw_main):
         return True
     if epc.sap_heating.water_heating_code == _WHC_ELECTRIC_IMMERSION:
         return True
@@ -7828,7 +7809,7 @@ def cert_to_inputs(
         ):
             water_eff = apm_water_eff
     if (
-        _is_heat_network_main(main)
+        is_heat_network_main(main)
         and epc.sap_heating.water_heating_code in _WATER_INHERIT_FROM_MAIN_CODES
     ):
         # HW from main on a heat-network cert: the DHW also incurs the

tests/domain/modelling/test_heating_recommendation.py

@@ -31,6 +31,14 @@ _API_ELECTRICITY = 29
 _OLD_STORAGE_SAP_CODE = 402
 
 
+def _hhr_measure_type_in(rec: Recommendation | None) -> bool:
+    if rec is None:
+        return False
+    return MeasureType.HIGH_HEAT_RETENTION_STORAGE_HEATERS in {
+        o.measure_type for o in rec.options
+    }
+
+
 def _electric_storage_baseline() -> EpcPropertyData:
     """A 000490 dwelling re-cast as an existing (non-HHR) electric storage
     system: electric main fuel, Table 4a code 402."""
@@ -160,6 +168,20 @@ def test_on_gas_street_electric_dwelling_yields_hhr_storage_bundle() -> None:
     assert "high_heat_retention_storage_heaters" in options
 
 
+def test_community_heated_dwelling_yields_no_hhr_storage_bundle() -> None:
+    # Arrange — community boiler network (SAP code 301, category 6) with
+    # electricity as the upstream heat source fuel (code 41): not gas, so the
+    # fuel gate alone would pass — the topology gate must block it.
+    epc = build_epc()
+    main = epc.sap_heating.main_heating_details[0]
+    main.sap_main_heating_code = 301
+    main.main_heating_category = 6
+    main.main_fuel_type = 41
+
+    # Act / Assert
+    assert _hhr_measure_type_in(recommend_heating(epc, _StubProducts())) is False
+
+
 def _gas_boiler_house() -> EpcPropertyData:
     """A 000490 mains-gas combi dwelling, explicitly a House — ASHP-eligible."""
     epc: EpcPropertyData = build_epc()
@@ -314,6 +336,22 @@ def test_existing_heat_pump_yields_no_ashp_bundle() -> None:
         }
 
 
+def test_community_heated_house_yields_no_ashp_bundle() -> None:
+    # Arrange — community boiler network (SAP code 301, category 6) on a house:
+    # topology alone must block ASHP regardless of fuel.
+    epc = build_epc()
+    main = epc.sap_heating.main_heating_details[0]
+    main.sap_main_heating_code = 301
+    main.main_heating_category = 6
+
+    # Act / Assert
+    recommendation: Recommendation | None = recommend_heating(epc, _StubProducts())
+    if recommendation is not None:
+        assert MeasureType.AIR_SOURCE_HEAT_PUMP not in {
+            o.measure_type for o in recommendation.options
+        }
+
+
 # --- Gas boiler upgrade (Heating/HW expansion) ----------------------------