Merge pull request #1436 from Hestia-Homes/fix/cylinder-uninsulated-storage-loss

Uninsulated / unknown-insulation cylinders no longer drop the SAP storage loss

domain/sap10_calculator/rdsap/cert_to_inputs.py

@@ -5879,6 +5879,10 @@ _CYLINDER_INSULATION_TYPE_FACTORY: Final[int] = 1
 # which SAP 10.2 Table 2 Note 1 gives a SEPARATE (higher) loss factor
 # L = 0.005 + 1.76 / (t + 12.8) vs the factory L = 0.005 + 0.55 / (t+4).
 _CYLINDER_INSULATION_TYPE_LOOSE_JACKET: Final[int] = 2
+# RdSAP 10 field 7-11 code 0 = NO insulation. SAP 10.2 Table 2 has no
+# separate uninsulated row — the loose-jacket formula at t = 0 IS the
+# uninsulated factor (L = 0.005 + 1.76 / 12.8 = 0.1425 kWh/L/day).
+_CYLINDER_INSULATION_TYPE_NONE: Final[int] = 0
 
 
 def _cylinder_storage_loss_insulation_label(
@@ -7106,9 +7110,38 @@ def _cylinder_storage_loss_override(
     insulation_label = _cylinder_storage_loss_insulation_label(
         sh.cylinder_insulation_type
     )
+    thickness_mm: Optional[float] = (
+        float(sh.cylinder_insulation_thickness_mm)
+        if sh.cylinder_insulation_thickness_mm is not None
+        else None
+    )
+    # SAP 10.2 Table 2: an uninsulated cylinder takes the loose-jacket
+    # formula at t = 0 — the WORST loss SAP knows, never the zero-loss
+    # combi default (which over-rates the dwelling). Two lodgement shapes
+    # describe it: the EPB API's insulation type 0, and the Elmhurst
+    # site-notes path's type None + explicit 0 mm ("No Insulation" maps to
+    # no material; the lodged thickness carries the signal — see
+    # `_ELMHURST_CYLINDER_NO_INSULATION_LABELS` in the mapper).
+    if _int_or_none(sh.cylinder_insulation_type) == _CYLINDER_INSULATION_TYPE_NONE:
+        insulation_label, thickness_mm = "loose_jacket", 0.0
+    if insulation_label is None and thickness_mm == 0.0:
+        insulation_label = "loose_jacket"
+    # RdSAP 10 Table 29 (PDF p.56) "Hot water cylinder insulation if not
+    # accessible": a lodged cylinder with NO insulation data at all takes
+    # the age-band default — the same row the §10.7 no-water-heating
+    # default uses. An ABSENT thickness means not accessible (Table 29);
+    # a lodged 0 mm means uninsulated (handled above). When the age band
+    # itself is unresolvable, fall through to the legacy None (zero loss)
+    # rather than raising mid-rebaseline.
+    if insulation_label is None and thickness_mm is None:
+        band = (_dwelling_age_band(epc) or "")[:1].upper()
+        table_29_default = _TABLE_29_DEFAULT_CYLINDER_INSULATION_BY_AGE.get(band)
+        if table_29_default is not None:
+            default_code, default_mm = table_29_default
+            insulation_label = _cylinder_storage_loss_insulation_label(default_code)
+            thickness_mm = float(default_mm)
     if insulation_label is None:
         return None
-    thickness_mm = sh.cylinder_insulation_thickness_mm
     if thickness_mm is None:
         return None
     storage_56m = cylinder_storage_loss_monthly_kwh(

tests/domain/sap10_calculator/rdsap/test_cert_to_inputs.py

@@ -6365,6 +6365,237 @@ def test_loose_jacket_cylinder_computes_storage_loss_via_table2_loose_jacket_bra
     assert got_jan_kwh > 36.9530  # loose jacket loses more than factory
 
 
+def test_uninsulated_cylinder_computes_storage_loss_via_table2_jacket_t0() -> None:
+    """SAP 10.2 Table 2 (PDF p.158): an UNINSULATED cylinder takes the
+    loose-jacket loss factor at t = 0 — L = 0.005 + 1.76 / 12.8 = 0.1425
+    kWh/L/day, the worst storage loss SAP knows. The EPB API lodges
+    cylinder_insulation_type=0 = no insulation (1 = factory, 2 = loose
+    jacket) with no thickness field. Before this fix
+    `_cylinder_storage_loss_override` returned None for type 0, so the
+    worksheet kept the zero-storage-loss combi default and the dwelling
+    OVER-RATED — the opposite of what "no insulation" means. Portfolio
+    814's audit (2026-07-03) found all 26 such properties over-rated
+    +1..+18 SAP vs lodged (avg +12.7 for type 0); same-lodged WD5 0DP
+    neighbours (pids 742215/742216, both lodged 54, identical building
+    parts) split effective 50 vs 69 because one lodged a 12 mm jacket and
+    the other lodged no insulation.
+    """
+    # Arrange — identical to the loose-jacket storage-loss test but
+    # cylinder_insulation_type=0 (none) and no lodged thickness.
+    from domain.sap10_calculator.worksheet.water_heating import (
+        cylinder_storage_loss_factor_table_2,
+        cylinder_temperature_factor_table_2b,
+        cylinder_volume_factor_table_2a,
+    )
+
+    hp_main = MainHeatingDetail(
+        has_fghrs=False,
+        main_fuel_type=29,
+        heat_emitter_type=1,
+        emitter_temperature=1,
+        main_heating_control=2206,
+        main_heating_category=4,
+        sap_main_heating_code=None,
+    )
+    epc = make_minimal_sap10_epc(
+        total_floor_area_m2=_TYPICAL_TFA_M2,
+        habitable_rooms_count=4,
+        country_code="ENG",
+        has_hot_water_cylinder=True,
+        sap_building_parts=[make_building_part()],
+        sap_heating=make_sap_heating(
+            main_heating_details=[hp_main],
+            water_heating_code=901,
+            cylinder_size=3,  # Medium → 160 L
+            cylinder_insulation_type=0,  # no insulation
+            cylinder_insulation_thickness_mm=None,
+            cylinder_thermostat="Y",
+        ),
+    )
+    # Expected (56)m Jan from the Table 2 loose-jacket branch at t=0 —
+    # the SAP uninsulated-cylinder factor (same V / VF / TF as the
+    # loose-jacket test; only the thickness differs).
+    loss_factor = cylinder_storage_loss_factor_table_2(
+        insulation_type="loose_jacket", thickness_mm=0.0
+    )
+    vol_factor = cylinder_volume_factor_table_2a(160.0)
+    temp_factor = cylinder_temperature_factor_table_2b(
+        has_cylinder_thermostat=True, separately_timed_dhw=True
+    )
+    expected_jan_kwh = 160.0 * loss_factor * vol_factor * temp_factor * 31
+
+    # Act
+    wh_result, _ = _water_heating_worksheet_and_gains(
+        epc=epc,
+        water_efficiency_pct=1.7,
+        is_instantaneous=False,
+        primary_age="D",
+        pcdb_record=None,
+    )
+
+    # Assert — non-None (was the zero-loss combi default) and equal to
+    # the loose-jacket branch at t=0; an uninsulated cylinder must lose
+    # MORE than the 50 mm loose-jacket case, never less.
+    assert wh_result is not None
+    got_jan_kwh = wh_result.solar_storage_monthly_kwh[0]
+    assert abs(got_jan_kwh - expected_jan_kwh) < 1e-4
+    jacket_50mm_jan_kwh = (
+        160.0
+        * cylinder_storage_loss_factor_table_2(
+            insulation_type="loose_jacket", thickness_mm=50.0
+        )
+        * vol_factor
+        * temp_factor
+        * 31
+    )
+    assert got_jan_kwh > jacket_50mm_jan_kwh
+
+
+def test_elmhurst_no_insulation_cylinder_thickness_zero_takes_uninsulated_loss() -> None:
+    """The Elmhurst site-notes mapper lodges a "No Insulation" cylinder as
+    `cylinder_insulation_type=None` + `cylinder_insulation_thickness_mm=0`
+    — per its own comment "the lodged §15.1 Insulation Thickness (0 mm)
+    carries the storage-loss signal the cascade's SAP 10.2 Table 2
+    dispatch needs" (`_ELMHURST_CYLINDER_NO_INSULATION_LABELS`,
+    datatypes/epc/domain/mapper.py). The cascade must honour that signal:
+    a lodged 0 mm with no insulation type is the uninsulated cylinder —
+    Table 2 loose-jacket branch at t = 0 — not the zero-loss combi
+    default it previously fell to (the type-None guard returned None
+    before the thickness was ever read).
+    """
+    # Arrange — same dwelling as the type-0 test; only the lodgement
+    # shape differs (type None + explicit 0 mm, the Elmhurst path).
+    from domain.sap10_calculator.worksheet.water_heating import (
+        cylinder_storage_loss_factor_table_2,
+        cylinder_temperature_factor_table_2b,
+        cylinder_volume_factor_table_2a,
+    )
+
+    hp_main = MainHeatingDetail(
+        has_fghrs=False,
+        main_fuel_type=29,
+        heat_emitter_type=1,
+        emitter_temperature=1,
+        main_heating_control=2206,
+        main_heating_category=4,
+        sap_main_heating_code=None,
+    )
+    epc = make_minimal_sap10_epc(
+        total_floor_area_m2=_TYPICAL_TFA_M2,
+        habitable_rooms_count=4,
+        country_code="ENG",
+        has_hot_water_cylinder=True,
+        sap_building_parts=[make_building_part()],
+        sap_heating=make_sap_heating(
+            main_heating_details=[hp_main],
+            water_heating_code=901,
+            cylinder_size=3,  # Medium → 160 L
+            cylinder_insulation_type=None,  # Elmhurst "No Insulation"
+            cylinder_insulation_thickness_mm=0,
+            cylinder_thermostat="Y",
+        ),
+    )
+    expected_jan_kwh = (
+        160.0
+        * cylinder_storage_loss_factor_table_2(
+            insulation_type="loose_jacket", thickness_mm=0.0
+        )
+        * cylinder_volume_factor_table_2a(160.0)
+        * cylinder_temperature_factor_table_2b(
+            has_cylinder_thermostat=True, separately_timed_dhw=True
+        )
+        * 31
+    )
+
+    # Act
+    wh_result, _ = _water_heating_worksheet_and_gains(
+        epc=epc,
+        water_efficiency_pct=1.7,
+        is_instantaneous=False,
+        primary_age="D",
+        pcdb_record=None,
+    )
+
+    # Assert — identical series to the gov-API type-0 lodgement: the two
+    # front-ends describe the same uninsulated cylinder.
+    assert wh_result is not None
+    got_jan_kwh = wh_result.solar_storage_monthly_kwh[0]
+    assert abs(got_jan_kwh - expected_jan_kwh) < 1e-4
+
+
+def test_cylinder_with_unknown_insulation_defaults_per_table_29_age_band() -> None:
+    """RdSAP 10 Table 29 (PDF p.56) "Hot water cylinder insulation if not
+    accessible": when a cylinder is lodged but its insulation is unknown
+    (type absent AND no thickness — ADR-0028 records ~308/1000 17.0 certs
+    omitting `cylinder_insulation_type`), the age-band default applies:
+    bands A-F → 12 mm loose jacket, G/H → 25 mm factory, I-M → 38 mm
+    factory. This is the same Table 29 row the §10.7 no-water-heating
+    default already uses. Previously the cascade returned None (zero
+    storage loss), silently treating an unknown cylinder as a combi.
+    Distinct from the uninsulated case: a lodged 0 mm means NO insulation
+    (t = 0), an absent thickness means NOT ACCESSIBLE (Table 29).
+    """
+    # Arrange — same dwelling, insulation fields both absent; the
+    # fixture's building part lodges construction_age_band "B" → the
+    # Table 29 A-F row (12 mm loose jacket).
+    from domain.sap10_calculator.worksheet.water_heating import (
+        cylinder_storage_loss_factor_table_2,
+        cylinder_temperature_factor_table_2b,
+        cylinder_volume_factor_table_2a,
+    )
+
+    hp_main = MainHeatingDetail(
+        has_fghrs=False,
+        main_fuel_type=29,
+        heat_emitter_type=1,
+        emitter_temperature=1,
+        main_heating_control=2206,
+        main_heating_category=4,
+        sap_main_heating_code=None,
+    )
+    epc = make_minimal_sap10_epc(
+        total_floor_area_m2=_TYPICAL_TFA_M2,
+        habitable_rooms_count=4,
+        country_code="ENG",
+        has_hot_water_cylinder=True,
+        sap_building_parts=[make_building_part()],  # age band B
+        sap_heating=make_sap_heating(
+            main_heating_details=[hp_main],
+            water_heating_code=901,
+            cylinder_size=3,  # Medium → 160 L
+            cylinder_insulation_type=None,  # not lodged
+            cylinder_insulation_thickness_mm=None,  # not lodged
+            cylinder_thermostat="Y",
+        ),
+    )
+    expected_jan_kwh = (
+        160.0
+        * cylinder_storage_loss_factor_table_2(
+            insulation_type="loose_jacket", thickness_mm=12.0
+        )
+        * cylinder_volume_factor_table_2a(160.0)
+        * cylinder_temperature_factor_table_2b(
+            has_cylinder_thermostat=True, separately_timed_dhw=True
+        )
+        * 31
+    )
+
+    # Act
+    wh_result, _ = _water_heating_worksheet_and_gains(
+        epc=epc,
+        water_efficiency_pct=1.7,
+        is_instantaneous=False,
+        primary_age="D",
+        pcdb_record=None,
+    )
+
+    # Assert — the Table 29 band-B default (12 mm loose jacket), not the
+    # zero-loss combi default and not the harsher uninsulated t=0.
+    assert wh_result is not None
+    got_jan_kwh = wh_result.solar_storage_monthly_kwh[0]
+    assert abs(got_jan_kwh - expected_jan_kwh) < 1e-4
+
+
 def test_no_water_heating_default_age_a_to_f_uses_12mm_loose_jacket_per_table_29() -> None:
     """RdSAP 10 §10.7 + Table 29 (PDF p.55-56): when no water heating
     system is lodged, the default cylinder takes the age-band insulation,