Code 3 = "(other premises below)" = above partially heated space (§3.12 →
U=0.7), confirmed 9/9 on single-BP certs (the diagnostic that dodged the
lossy-floors[] contamination). Records the 7536 re-pin and the lesson that
"irreducible residual" golden notes can mask a real mapper bug.
Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>
The API `floor_heat_loss` code is authoritative — confirmed by joining each
single-BP cert's code to its independent `floors[].description` (which the
gov register publishes alongside the code):
code 1 ↔ "To external air" (exposed, 9/9)
code 2 ↔ "To unheated space" (semi-exposed, 6/6)
code 3 ↔ "(other premises below)" (partially htd, 9/9)
code 6 ↔ "(another dwelling below)" (party, 176/176)
code 7 ↔ "Solid"/"Suspended …" (ground, all)
Code 3 was mis-mapped to "To unheated space" (semi-exposed) and, on
mid-/top-floor flats, had its floor area zeroed entirely by the
dwelling-level exposure heuristic. RdSAP 10 §3.12 (PDF p.25) classes a
flat's floor over non-domestic "other premises … heated, but at different
times" as "above a partially heated space" → the §5.14 (PDF p.47) constant
U=0.7 W/m²K — distinct from semi-exposed (Table 20) and party (no loss).
Fix: the mapper sets `is_above_partially_heated_space` on the floor=0
dimension for code 3 (string → "(other premises below)" for fidelity), and
the heat-transmission step lets that per-BP lodgement override the flat
suppression upward (mirroring the existing exposed / "another dwelling
below" overrides). The cascade already routes is_above_partial → U=0.7.
Re-pins golden cert 7536-3827: its Ext2 (bp3) lodges code 3, but the cert's
lossy `floors[]` summary dropped that description, so a prior agent guessed
"code 3 = ground" (U=1.12) and concluded the residual was an irreducible
"register-rounding" artifact. It was this bug: Ext2 floor U 1.12 → 0.70,
PE -6.1952 → -5.6414, CO2 -0.1639 → -0.1492 (both toward 0), SAP unchanged.
Eval: 909 computed, 45.1% → 45.3% within 0.5, mean|err| 1.702 → 1.659,
<1.0 59.5% → 60.2%. 13 code-3 certs improve (0380 +3.71 → -0.63, 0350
+7.82 → +0.83, 2610 +7.47 → -1.29); the few that overshoot were already
failing and carry independent fabric bugs (9763's walls = 8 W/K for 60 m²).
Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>
Record that profiler lead #1 (floor_codes=3) is not a clean single cause
(bimodal + confounded), that the paired worksheet certs confirm only
codes 1/6/7 (code 3 unmapped → needs a worksheet for 0380-2087), and that
immersion_type=2 / main_control=2107 / roof_codes=1 are scatter, not
dispatch bugs. The exposed-floor-on-flats fix (§3.12) shipped at b40e0f67.
Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>
A mid-/top-floor flat whose lowest floor is lodged as an exposed floor
(API floor_heat_loss=1) had its floor area zeroed by the dwelling-level
exposure heuristic, which keys only on the flat label and defaults
has_exposed_floor=False (assuming the floor sits over another *heated*
dwelling). RdSAP 10 §3.12 (PDF p.25) is explicit:
"Otherwise the floor area of the flat ... is:
- an exposed floor if there is an open space below"
i.e. a flat cantilevered over a passageway IS a heat-loss floor on
Table 20. The per-BP `is_exposed_floor` lodgement is authoritative and
now overrides the dwelling-level suppression upward, mirroring the
existing "another dwelling below" party override (which suppresses
downward). The code-1↔"E To external air" enum is confirmed by the
paired API+Summary worksheet certs (0350, 3800).
Eval: 45.1% → 45.3% within 0.5 (909 computed); cert 3836 +6.79 → +0.77,
5717 +1.31 → -0.07 and 0997 +0.76 → +0.05 cross into <0.5. Two
already-failing under-rated certs (7636, 2241) shift further — both are
dominated by independent cost-side over-counts the exposed floor merely
unmasks (7636 walls = 8.98 W/K for 33.87 m² is the real defect).
Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>
Joins each computed cert's signed error (eval _results.csv) with a rich
feature set extracted from its RAW API JSON (not the mapped
EpcPropertyData), then ranks (feature, value) buckets by error carried
and by |mean signed| bias. Surfaces systematic API-path handling gaps —
a field the mapper silently drops still shows as an error-correlated
bucket. Companion to eval_api_sap_accuracy.py / decompose_api_cost_error.py.
Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>
main_heating_category=9 (warm-air systems, NOT heat pump) had no entry
in _SECONDARY_HEATING_FRACTION_BY_CATEGORY, so a warm-air main with a
lodged secondary raised UnmappedSapCode in
_secondary_heating_fraction_for_category — the last calc_raise in the
API sample (cert 0380-2197-2590-2996-2715: warm air mains gas code 506 +
electric room-heater secondary).
SAP 10.2 Table 11 (p.188): a gas/oil warm-air unit falls under "All gas,
liquid and solid fuel systems" (0.10), and electric warm air under
"Other electric systems" (also 0.10) — so 0.10 regardless of fuel. The
warm-air efficiency (Table 4a code→eff: 506→0.70) and Table 4f fan
energy were already wired; this was the only missing dispatch entry.
0380 now computes: SAP 78.1 vs lodged 77 (+1.1; the residual is per-cert
fabric/PV, not the warm-air dispatch — a faithful 0380 worksheet isn't
available, sim case 28 diverges at SAP 57 / code 502 / condensing unit).
Eval: zero raises remain, computed 908→909; mean|err| 1.703→1.702.
Regression green (2448 pass incl. golden 6035 + cohort); pyright
net-zero (44=44).
Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>
API floor_heat_loss=8 is observed on EXTENSION building parts whose
floor sits over a heated space within the SAME dwelling (an upper-storey
extension over a heated room). RdSAP 10 §3 gives an internal floor
between heated storeys no floor heat loss — mechanically identical to a
code-6 party floor. `_api_floor_type_str` had no entry for 8, raising
UnmappedApiCode and blocking certs 0370-2254-6520-2426-5971 and
0997-1206-9806-0715-2904.
Map code 8 to the code-6 no-heat-loss string "(another dwelling below)"
(consumed by heat_transmission's party-floor suppression; != "Ground
floor" so the §5 (12) suspended-timber rule stays inert). Empirically
confirmed against both certs: the no-heat-loss treatment lands them
within 0.5 of lodged (0370-2254 68.92 vs 69; 0997-1206 40.68 vs 41),
whereas Ground-floor / unheated / external mappings miss 0997 by ~4 SAP.
Eval computed 906→908. Regression green (only the pre-existing
test_total_floor_area fails); pyright net-zero (38=38).
Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>
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>
SAP 10.2 Table 3 (PDF p.160) names "Direct-acting electric boiler"
verbatim in the primary-loss zero list (alongside electric immersion,
combi, CPSU, integral-vessel heat pump). RdSAP 10 §12 (p.62) classifies
SAP code 191 as the direct-acting electric boiler. Its cylinder is
immersion-heated with no primary pipework, so no primary circuit loss
applies — but `_primary_loss_applies` had no 191 branch, so a 191 main
(main_heating_category 2, "Boiler and radiators, electric") fell through
to the cat-{1,2} boiler branch and accrued ~1177 kWh/yr of phantom
primary loss on the electric-flat segment.
Validated against the cert-2474 worksheet: §4 (59) primary loss = 0,
(64) HW output 1760 (cylinder) + (64a) shower 581. Cert 2474 HW kWh
3585 → 2408; SAP 64.66 → 70.35 (the residual to the lodged 78 is an
Unknown-meter data-fidelity artifact — the register recorded meter_type=3
"Unknown" but the lodged rating used an 18-hour off-peak meter, per RdSAP
§12 / the example worksheets).
Eval mean|err| 1.720 → 1.708 (headline 45.0%, flat ±1 cert — the
electric-flat segment is dominated by the meter data-fidelity artifact).
Regression green (2448 pass incl. golden 6035 + ASHP cohort 1e-4);
pyright net-zero.
Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>
When DHW is heated by the main heat pump (WHC 901/902/914 = "from main
system") and the main carries a PCDB Table 362 record,
`_hot_water_fuel_cost_gbp_per_kwh` billed the electric HW at 100% off-peak
low rate (its long-standing TODO). SAP 10.2 Table 12a Grid 1 WH column
(PDF p.191) puts HP-DHW on the ASHP/GSHP-from-database row: 0.70
high-rate fraction at 7-hour and 10-hour → 0.70×14.68 + 0.30×7.50 =
12.526 p/kWh (10-hour), not 7.50 p. The low-rate collapse over-credited
the cat-4 HP-DHW cluster.
Fix: pass the cert WHC into the helper and, for HP-DHW (WHC ∈ {901,902,
914} + PCDB-HP main), bill at the ASHP_APP_N WH blended rate. Electric
IMMERSION (WHC 903) is a different Table 12a row (off-peak immersion 0.17
/ Table 13) and stays on the 100%-low-rate fallback until that slice
lands.
cat-4 cluster (20 certs): mean|err| 2.43→2.11, mean signed +0.06→-0.52
(now per-cert scatter, no systematic bias); cert 9472 +6.4→+3.2, 2789
+6.8→+4.0, 4135 +2.7→within 0.5. Headline mean|err| 1.727→1.720.
Regression green (2447 pass incl. golden 6035 + ASHP cohort at 1e-4);
pyright net-zero.
Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>
A heat pump that resolves via its PCDB Table 362 index alone (API path,
data_source=1, no Table-4a SAP code) had sap_main_heating_code=None, so
`_table_12a_system_for_main` fell through the 211-227/521-524 code-range
gate to None → the "100% off-peak low-rate" fallback. On a Dual meter
(RdSAP §12 Rule 3 routes heat pumps to the 10-hour tariff) this billed
space heating at 7.50 p/kWh instead of the SAP 10.2 Table 12a Grid 1
(PDF p.191) ASHP/GSHP-from-database row: 0.80 high-rate fraction →
0.80×14.68 + 0.20×7.50 = 13.244 p/kWh. The collapse over-credited the
whole cat-4 heat-pump cluster.
Fix: route any main with a PCDB heat-pump record to ASHP_APP_N regardless
of SAP code (a Table 362 record IS an Appendix-N heat pump by
definition). ASHP_APP_N and GSHP_APP_N share the 0.80 SH fraction at
7h/10h, so ASHP_APP_N is the canonical Appendix-N row for the SH split.
cat-4 cluster (20 certs): within-0.5 45%→50%, mean signed +1.43→+0.06,
mean|err| 3.81→2.43; cert 9472 +15.0→+6.4, 2789 +13.4→+6.8. Headline
45.0%→45.1%, mean|err| 1.757→1.727. Regression green (only the
pre-existing test_total_floor_area fails); pyright net-zero.
Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>
Electric storage heaters (and CPSU) charge overnight and cannot run
economically on a single rate, so their presence is physical evidence the
dwelling is on an off-peak tariff. RdSAP 10 §12 (PDF p.62) applied Rules
1-4 only for a Dual meter; an "Unknown" (code 3) meter returned STANDARD
without consulting the heating type, so a cat-7 storage main billed its
overnight charge at the standard 13.19 p/kWh instead of the 7-hour low
rate (5.50 p/kWh) — ~2.4x too high → large under-rate.
Two coupled fixes:
- `rdsap_tariff_for_cert`: for an Unknown meter, infer the off-peak tariff
from a Rule-1 CPSU (→10-hour) or Rule-2 storage (→7-hour) main; keep
STANDARD otherwise. Direct-acting/room heaters/heat pumps (Rule 3) are
NOT off-peak evidence (run on demand, exist on single-rate meters) so
they stay STANDARD — billing them 100% at the low rate over-credits.
- `_fuel_cost` now resolves its tariff via the §12-aware `_rdsap_tariff`
(not the raw `tariff_from_meter_type`), so the off-peak branch fires for
these storage certs and the legacy scalar fields bill the low rate.
Mirrors `_is_off_peak_meter`'s existing Unknown+electric heuristic (which
already routes HW/secondary off-peak), closing the main-space-heating gap.
Meter-3 electric cluster: mean |err| 11.18 → 6.52, within-1.0 3 → 5 (cert
7336 -26.1 → -0.16, 0380 -19.9 → +1.0). Eval headline 44.9% → 45.0%, mean
|err| 1.82 → 1.76, mean signed -0.08 → +0.02. A few storage certs overshoot
(other residuals the standard rate was masking).
Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>
The main pitched/flat roof U-value was derived from the JOINED text of
every roofs[] entry. A room-in-roof carries its own §3.9/§3.10 shell
area + U-value cascade (Table 17 / Table 18 col 4), so a multi-roof cert
lodged "Pitched, insulated (assumed) | Roof room(s), no insulation
(assumed)" leaked the RR's "no insulation" marker into the main roof's
u_roof → U=2.30 applied to the WHOLE main roof, ~3x over-stating its heat
loss. This is the 4700-family regular-roof-U leak.
`_joined_main_roof_descriptions` drops "Roof room(s)" entries before the
main-roof u_roof, falling back to the unfiltered join only for pure-RR
dwellings (every entry an RR) to preserve their prior behaviour. The RR
shell U is unaffected (computed separately) — golden 6035 stays green.
RR-leak cluster (18 certs, RR "no insulation" + a non-RR primary roof):
mean |err| 6.14 → 4.85, within-1.0 0 → 8, within-0.5 0 → 3. Eval headline
44.8% → 44.9%, mean |err| 1.851 → 1.824, mean signed -0.152 → -0.081. Two
certs overshoot (other residuals the leak was masking); the spec rule is
applied uniformly.
Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>
A roof lodged "Unknown loft insulation" carries roof_insulation_thickness
"NI" (Not Indicated → parsed to 0) or "ND" (None): the thickness is
UNDETERMINED, not zero. RdSAP 10 §5.11.4 (p.44) is deterministic here —
"U-values in Table 18 are used when thickness of insulation cannot be
determined" — so the roof takes the Table 18 age-band default (column (1)
pitched / column (3) flat), NOT the uninsulated 2.30 the Table 16 row-0
lookup returns for a parsed-0 thickness. The "Unknown" text is RdSAP's
rendering of the undetermined-thickness observation, distinct from a
genuine "no insulation" lodgement (which keeps 2.30).
u_roof gains an "unknown"-description branch ahead of the parsed-0 → 2.30
path, gated on undetermined thickness (None or 0). Top-floor flats with
"Pitched/Flat, Unknown ... insulation" were the worst electric-flat
under-raters: roof U=2.30 gave HLP ~3.7 on dwellings rated SAP 69-70.
Cluster (14 certs, roof desc contains "unknown", no "no insulation"):
mean |err| 7.79 → 1.82, within-0.5 1→4, within-1.0 1→6. Cert 9836
roof_w_per_k 58.2→10.1, SAP -27.8 → -3.5. Eval headline 44.4% → 44.8%,
mean |err| 1.944 → 1.851. Two certs overshoot (other residuals the wrong
roof-U was masking); the spec value is applied uniformly regardless.
Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>
A floor lodged API floor_heat_loss=6 ("another dwelling below") sits over
another heated dwelling, so it is a party floor with no heat loss (RdSAP
10 §3). The mapper mapped code 6 → None and the heat-transmission step
drove floor exposure solely from the dwelling-level `has_exposed_floor`
flag — which is keyed only on the dwelling_type label and defaults a
"Ground-floor flat" to an exposed floor. So a ground-floor flat above a
basement dwelling kept its full ground-floor heat-loss area.
Map code 6 → "(another dwelling below)" (still != "Ground floor", so the
§5 (12) suspended-timber rule stays inert) and have the cascade suppress
that BP's floor when its floor_type carries the signal, mirroring the
roof's existing "another dwelling above" per-BP party override.
Cert 2115-4121-4711-9361-3686 (ground-floor flat, floor_heat_loss=6):
floor_w_per_k 47.85 → 0; SAP -23.44 → -4.41. Cert 0350-…-6435 -12.38 →
-0.55; 0926-…-9024 -2.35 → -0.82. Eval mean |err| 1.982 → 1.944.
Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>
A Summary §14.0 Table 4b gas boiler (SAP code 101-119) lodges no §14.0
"Fuel Type" string in the newer Elmhurst export. The carrier was resolved
only from §15.0 "Water Heating Fuel Type" — fine when the same boiler
heats the water, but a gas boiler paired with a SEPARATE electric
immersion lodges §15.0 "Electricity", so `_elmhurst_gas_boiler_main_fuel`
returned None and the cascade strict-raised MissingMainFuelType.
Cert 001431 boiler-1/boiler-2 "before" variants are exactly this config:
§14.0 SAP code 102/104 (mains-gas boiler), §15.0 electric immersion
(code 909), §14.2 Meters "Main gas: Yes". The meter flag is the
authoritative carrier signal — a 101-119 boiler on mains gas burns mains
gas — so adopt it (SAP10 main_fuel 26 per _ELMHURST_MAIN_FUEL_TO_SAP10
"Mains gas") when §15.0 can't disambiguate. §15.0 gas/LPG still wins when
present (keeps LPG-vs-mains-gas precision); no mains-gas meter + non-gas
§15.0 still strict-raises rather than guessing.
Spec: SAP 10.2 Table 4b "Seasonal efficiency for gas and liquid fuel
boilers" (PDF p.168), rows 101-119. Both certs now resolve main_fuel=26
and compute (was: hard raise).
Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>
A "Pitched, sloping ceiling" (roof_construction == 8) lodges its
insulation in the dedicated `sloping_ceiling_insulation_thickness` field,
not `roof_insulation_thickness` (which stays None — the loft-joist field
is meaningless for a slope-following ceiling). The schema dataclasses
dropped that field, so `from_dict` discarded it and the cascade treated
the slope as uninsulated; worse, the pre-1950 None-fallback forced 0 mm
(U=2.30), over-stating roof heat loss ~74%.
Surface the field on SapBuildingPart (schemas 21.0.0 / 21.0.1) and prefer
it in `_api_resolve_sloping_ceiling_thickness` when it carries a NUMERIC
thickness: "100mm" now reaches Table 17 column (1a) "Insulated slope –
sloping ceiling, mineral wool/EPS" (RdSAP 10 §5.11.3 p.44 — 100 mm →
U=0.40) instead of 2.30. Categorical lodgements ("AB" As Built / "NI")
are not measured thicknesses, so they fall through to the existing
as-built rule (Table 18 col (3) via is_pitched_sloping_ceiling).
Cert 9884-3059-9202-7506 (code 8, age B, sloping 100 mm): SAP −5.54 → +0.06.
Cert 8036-2925-6600-0202: −4.94 → +1.55. No regressions in the roof-8
cohort (the "AB" certs are unchanged). Eval headline 43.8% → 44.3% within
0.5; golden fixtures incl. 6035 green.
Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>
Mirror of eval_api_sap_accuracy.py that decomposes each cert's SAP error
into per-component energy/cost deltas WITHOUT generating an Elmhurst
worksheet. Calibrates the consumer price from the certs we already get
right (gas £0.0809/kWh n=291, elec £0.2839/kWh n=326 over |SAP err|<0.4),
then for every cert compares our_component_kWh × price to the lodged
heating_cost_current / hot_water_cost_current / lighting_cost_current and
back-calculates a numeric energy target (lodged_cost / price).
Clusters errors by (component × direction). On the 905-cert sample this
reveals heat:high (we over-state heating energy → under-rate SAP) as the
dominant broken cluster: 332 certs, only 36.7% within 0.5. Output CSV at
<cache>/_cost_decomposition.csv.
Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>
A 440 mm (>420 mm) solid brick AS-BUILT wall computed U = 1.70 (the
220 mm bucket default) instead of the RdSAP-correct 1.10. The §5.7
Table 13 thickness path only fired for *insulated* brick (external/
internal + thickness > 0); the as-built case fell through to the
Table 6 cavity/solid age-band default.
Spec: RdSAP 10 Specification (9th June 2025), §5.7 "U-values for
uninsulated brick walls, age bands A to E", Table 13 (PDF p.40):
≤200 mm → 2.5, 200–280 mm → 1.7, 280–420 mm → 1.4, >420 mm → 1.1.
Table 6 footnote (b) on the "Solid brick as built" row (PDF p.40):
"Or from 5.7 if wall thickness is other than 200mm to 280mm" — the
thickness table supersedes the flat 1.7 default whenever a documentary
wall thickness is lodged (200–280 mm gives 1.7 either way). The §5.8 /
Table 14 dry-lining R is added on top only when the wall is dry-lined,
per the §5.7 closing sentence.
Validated against the user-generated Elmhurst worksheet "simulated
case 21" (replica of API cert 2818-3053-3203-2655-9204: mid-terrace,
age band B, solid brick as-built 440 mm, room-in-roof). New §3 cascade
pin `test_section_3_wall_u_by_thickness_case21_match_pdf` routes the
Summary through the real extractor + mapper and pins:
(31) 155.1000, (33) 175.6208, (36) 23.2650, (37) 198.8858 — all 1e-4.
External walls Main U → 1.1000; Sheltered RR gable → 1/(1/1.10+0.5) =
0.71 (was 0.92). Pinned on §3 only (case-6 precedent): its code-908
instantaneous multi-point gas water heater has a separate §4 (219) gap.
Cross-check: sim case 20 (220 mm) stays at 1.70 — unchanged.
API SAP accuracy (scripts/eval_api_sap_accuracy.py, 896 computed certs):
% |err| < 0.5 SAP vs lodged: 42.6% → 43.8%; mean |err| 2.045 → 2.010.
Regression: tests/domain/sap10_calculator/ (1861), backend/
documents_parser/tests/ (574), datatypes/epc/ + rdsap golden fixtures
all green (pre-existing test_total_floor_area excepted). pyright strict
net-zero. No solid-brick fixture pin shifted (200–280 mm unchanged).
Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>
The 2026 API sample raised UnmappedApiCode on `gable_wall_type` 2 (10 certs)
and 3 (4 certs) — the two RR gable variants beyond Party(0)/Exposed(1).
Sim case 21 (an Elmhurst replica of API cert 2818-3053-3203-2655-9204:
gable_wall_type_1=2, gable_wall_type_2=3) lodges them as "Sheltered" and
"Connected", confirming **2=Sheltered, 3=Connected**.
- Mapper: `_API_TYPE_1_GABLE_TYPE_TO_KIND` gains 2 → `gable_wall_sheltered`,
3 → `connected_wall` (U=0, area deducts — already handled).
- Calculator: new `gable_wall_sheltered` branch. The API path lodges no
per-gable U, so the cascade DERIVES it as RdSAP 10 Table 4 (p.22)
Sheltered = 1/(1/U_wall + 0.5) — back-solved + validated against case 21
(U_wall 1.10 → 0.71) and case 20 (1.70 → 0.92). A lodged U (Summary path)
still rides through as an override.
API sample: 14 raises clear → `computed` 882 → 896, `raise:ValueError` 16 → 2.
Summary path unchanged (Sheltered stays `gable_wall_external` + lodged U, so
cert 000487's hand-built fixture is untouched). 2861 pass (lone
test_total_floor_area pre-existing); pyright strict net-zero (32=32 / 12=12).
NOTE: the derived Sheltered U on cert 2818 lands at 0.92 not 0.71 because the
cascade computes its 440 mm solid-brick wall U as 1.70 (the 220 mm default) —
a SEPARATE wall-U-vs-thickness bug (next slice, validated by case 21's 1.10).
Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>
Locks sim case 20 (storage heaters + Detailed RR + loose-jacket cylinder)
as a golden vector: _elmhurst_worksheet_001431_case20.build_epc() routes the
Summary PDF through extractor → mapper → calculator, registered in
test_e2e_elmhurst_sap_score with all 11 SapResult headline pins at 1e-4.
10 pinned exact off slices 1-2 (window extractor, RR stud walls); this slice
closes the last one, co2_kg_per_yr (was 3797.62 vs (272) 3815.4060).
Root cause: on a dual-rate (E7) meter the CO2 path ignored the tariff's
high/low Table-12 electricity codes that the cost path already uses:
- Secondary (direct-acting portable heaters, on-peak) keyed the monthly
Table 12d cascade on standard code 30 (0.15405) instead of the E7 HIGH
code 32 → (263) 0.1616. SAP 10.2 Table 12a Grid 1 direct-acting electric
is 100% high-rate; mirrors the cost side billing it at 15.29 p/kWh.
- Main storage heaters fell through `_table_12a_system_for_main`=None to
the FLAT annual factor (0.136) rather than the dual-rate LOW code: per
the Table 12a design intent ("storage … 100% low rate") they charge
off-peak → E7 LOW code 31 → (261) 0.1357.
case-20 co2 now EXACT. 2433 calculator + 112 golden + documents_parser tests
pass — no dual-meter/storage cohort regression; pyright strict net-zero (32=32).
Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>
A Detailed room-in-roof lodges "Stud Wall" surfaces, but the cascade billed
every one through Table 17 from its insulation — over-counting fabric on
internal studs that carry no heat loss. sim case 20's two studs lodge §8.1
Default U-value 0.00 and the P960 worksheet omits them from BOTH fabric heat
loss (§3: (33)=285.9847) and total exposed area (31)=239.68; the cascade
computed ~0.52 each → (33) +4.16 W/K and continuous SAP 43.05 vs 43.6322.
Gate the drop on the lodged Default U-value: 0.00 → internal knee wall,
return None (no heat loss, no area); positive → a real exposed knee wall
(cert 000565 Ext2 Detailed: 0.31 / 0.10) that still falls through to the
Table-17 path. The earlier over-broad "drop all studs" zeroed 000565's
genuine studs — this keeps them.
Pins test_summary_001431_case20_fabric_heat_loss_matches_worksheet_line_33
((33)=285.9847 at 1e-4); case 20 continuous SAP now EXACT (43.6322). 2850
pass (the lone test_total_floor_area failure is pre-existing on base);
pyright strict net-zero (32=32).
Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>
Sim case 20's §11 lodges 5 windows but only 1 surfaced. The "W H Area"
cells tokenize inconsistently: a narrow Area column keeps all three on one
line ("1.80 2.10 3.78" — matches _WIDTH_HEIGHT_AREA_RE), but a wider Area
column triggers pdftotext's 2+-space split, dropping the Area onto its own
line ("5.79 2.00" then "11.58"). The 3-decimal data anchor never matched
those four rows, so they were lost — gutting §6 solar gains (5 windows →
1) and dropping continuous SAP 43.05 → 38.32 vs the worksheet's 43.6322.
Pre-merge a "W H" line + a following lone-decimal Area into the canonical
"W H Area" line, gated on Area ≈ W × H (the §11 Area is always the product)
so a frame factor / g-value / U-value below a dimension line is never
absorbed. One-line layouts (3 decimals) are untouched.
Pins via test_summary_001431_case20_extracts_all_five_section11_windows
(Summary_001431_case20.pdf mirrors sap worksheets/golden fixture debugging/
simulated case 20/). 573 documents_parser tests pass; pyright strict net-zero.
Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>
The first cut of elmhurst_input_sheet.py introspected the `schema`
dataclasses (rdsap_schema_*.py) but the mapper emits the `epc_property_data`
domain types, whose fields differ (wall_thickness_mm not wall_thickness;
total_floor_area_m2 not total_floor_area; frame_material not pvc_frame;
cylinder_insulation_thickness_mm; SapRoomInRoof has gable_*_length_m not
insulation/roof_room_connected). Worse, the getattr-with-None-default helper
printed None over real data, nearly sending a debug session chasing a
non-existent "dimensions dropped" mapper bug on cert 2100 (the dims map
fine; that cert's error is elsewhere). Switched to direct attribute access
so a future rename fails loudly, fixed every field name against the live
domain objects, and added roof_construction_type / floor_type for context.
Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>
Reconstructs the per-cert "Elmhurst SAP input sheet" generator that the
API-accuracy debugging loop relied on (the worked example survives at
'sap worksheets/golden fixture debugging/6035_elmhurst_input_sheet.md'); the
original was a throwaway and never committed. Companion to
eval_api_sap_accuracy.py: once that names a worst-offender cert, this dumps
the codes the mapper hands the calculator (from_api_response → EpcPropertyData)
in the 6035 layout — header, lodged element descriptions, building parts +
dimensions, windows, doors/heating/water/vent — plus the lodged reference
outputs and OUR continuous SAP next to the lodged value, to read side-by-side
with the Elmhurst Summary / P960 worksheet PDF.
Reads the fetch_2026_epc_sample.py cache (EPC_SAMPLE_CACHE, default
/tmp/epc_2026_sample). `--out-dir` writes <cert>_elmhurst_input_sheet.md.
Pyright strict clean.
Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>
Slice f68cea27 (re-homed here as 97f44b53) added a guard to
_is_elmhurst_roof_window — "a window lodged on a wall is vertical by
definition" — to keep 001431's two "Double pre 2002" External-wall units in
the vertical sap_windows list for the Modelling draught-proofing count. But
that guard fires on the §11 `location` string, which is an unreliable
lodging artifact: every one of cert 000516's six §11 rows reads "External
wall", and only the U-value separates the five vertical panes (U 2.8) from
the one genuine rooflight (U 3.1, area 1.18, lifted to 3.40 by the Table 24
lookup). Elmhurst's own worksheet routes that U 3.1 "External wall" unit
through (27a) Roof Windows — so location is NOT a vertical signal and the
U > 3.0 backstop (RdSAP 10 §3.7.1) is what matches the worksheet.
Removing the guard restores both 000516 pins
(test_summary_000516_full_chain_sap_matches_worksheet_pdf_exactly,
test_from_elmhurst_site_notes_matches_hand_built_000516) with no other
regression (2879 pass; the lone test_total_floor_area failure is
pre-existing on the branch base, unrelated to window classification).
The extractor half of 97f44b53 (capturing the standalone "BFRC data" §11
row) is retained — it is independent of this classifier and harmless here.
The 001431 Modelling draught-proofing count must instead include roof
windows (the draught_proofed-on-SapRoofWindow approach noted in the glazing
handover), which is feature/bill-derivation's front, not this branch.
Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>
RdSAP 10 §2 (Ventilation, "Walls" row): "Structural infiltration: 0.25
for steel or timber frame or 0.35 for masonry construction ... System
build: treated as masonry." `_is_timber_or_steel_frame` wrongly included
wall_construction code 6 (system build) alongside code 5 (timber frame),
handing system-build dwellings the 0.25 structural ACH instead of 0.35.
On the cat-10 room-heater fixture (ref 001431, walls SY System Build →
code 6) this under-stated the infiltration rate (18) by exactly 0.10
(0.45 vs worksheet 0.55), dropping the effective air change (25), the
ventilation heat loss (38)m = 0.33 × (25)m × (5), and the heat-transfer
coefficient (39) — so space-heating demand (98) came out 404 kWh low
((211) 11158.6 vs worksheet 11563.2). Restrict the 0.25 branch to code 5
only; code 6 (and everything else) is masonry at 0.35.
Pins the rating-block (38)m ventilation heat loss mean = 83.3613 W/K at
abs 1e-4 and asserts the classifier treats the system-build wall as
masonry. §4 suite green (2415 passed, 1 skipped); no existing fixture
relied on system-build → 0.25.
Residual after this slice: SAP +0.03 / cost -£0.95 — a small fabric (33)
gap (-0.15 W/K) plus lighting (232) +1.0 kWh remain as separate causes.
Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>
Water heating SAP code 909 (electric instantaneous) and 907 (single-point
gas) heat water at the point of use, serving one outlet with no
distribution pipework. Per SAP 10.2 §4 (p.23, l.1416): "'Single-point'
heaters, which are located at the point of use and serve only one outlet,
do not have distribution losses either." So worksheet (46)m = 0 and the
heat-required line collapses to SAP 10.2 worksheet l.7704
(62)m = 0.85 × (45)m + (46)m + (57)m + (59)m + (61)m
= 0.85 × (45)m (all loss terms zero for a no-cylinder system).
`distribution_loss_monthly_kwh` already supported the
`is_instantaneous_at_point_of_use` flag (and its docstring already named
codes 907/909), but `water_heating_from_cert` hard-coded it to False, so
the cascade applied (46)m = 0.15 × (45)m to single-point heaters. That
0.15 distribution loss exactly cancelled the 0.85 reduction, leaving
(62)m = (45)m. On the cat-10 room-heater fixture (ref 001431, code 909)
that over-stated the water fuel (219) as 2082.6250 instead of the
worksheet's 1770.2313, and inflated the (65)m heat gains (692.47 vs
worksheet 442.55) which in turn suppressed space-heating demand.
Thread the cert's existing instantaneous flag (`_INSTANTANEOUS_WATER_CODES`
= {907, 909}) through `_water_heating_worksheet_and_gains` into both the
demand-pass and final `water_heating_from_cert` calls.
Pins (219) water fuel = 1770.2313 at abs 1e-4 via the extractor → mapper →
rating cascade. §4 suite green (2414 passed, 1 skipped); no existing
fixture exercised the 907/909 path. The residual space-heating fuel gap
((211) 11158.59 vs worksheet 11563.17) this exposes is a separate cause —
next slice.
Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>
cert 001431's §11 lodges 17 windows but only 14 surfaced, via two distinct gaps:
1. Extractor (_extract_windows_from_layout): the one "Double glazing, known
data" row whose §11 Data-Source cell is "BFRC data" was rejected — it is
laid out as a standalone keyword line with the U-value on the next line
and lodges no Frame Type/Factor/Gap cells, so it never matched the joined
"<source> <U>" Manufacturer-line shape. Now anchored by a standalone
data-source form, with the RdSAP 10 §3.7 default frame factor (0.7) for
the absent frame cell.
2. Mapper (_is_elmhurst_roof_window): the two "Double pre 2002" rows
(U 3.1 / 3.4 > 3.0) were reclassified as roof windows by the U-value
backstop even though both are lodged on an "External wall". A window
lodged on a wall is vertical by definition; guard the U-value backstop so
it only fires when location/BP give no roof signal.
With both closed: 17 sap_windows, 0 misrouted to sap_roof_windows.
Re-homed onto the mapper-validation line from feature/bill-derivation
(orig f68cea27); the modelling-only regression test
(tests/domain/modelling/test_window_extraction_001431.py) stays on
bill-derivation. KNOWN: the mapper guard breaks cert 000516's
test_summary_pdf_mapper_chain pins (W6 U=3.10 routing) — must be resolved
before this PRs to main.
Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>
The fuel codes the calculator now puts on SapResult are its own codes — raw
gov-API enums or already-Table-32, depending on the source mapper (ADR-0015).
sap_code_to_fuel now runs the code through table_32.to_table_32_code
(promoted from private _to_table_32_code) — T32-first, then API-translate,
the SAME normalization the calculator's pricing/CO2 helpers use — before the
Table-32 -> Fuel dispatch, so the bill's carrier matches what the calculator
billed (incl. the API/T32 collision codes, e.g. 20 = wood-logs not heat-net).
Falls back to the raw code for billing fuels the price table omits (the 41-58
heat-network range), which resolve to HEAT_NETWORK -> UnpricedFuel — stricter
than, and intentionally divergent from, the calculator's lossy
default-to-mains-gas for an unpriced code (ADR-0014 §5).
Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>
ADR-0014 BillDerivation attributes each end-use (HEATING / HOT_WATER /
SECONDARY / APPLIANCES / COOKING) to a fuel carrier and credits PV
export. SapResult already carried the per-end-use kWh but not WHICH
fuel each end-use burns, nor the annual exported kWh — so a downstream
SapResult->EnergyBreakdown adapter could not pick the right tariff.
Surfaces five output-only fields, threaded exactly like the recently
merged appliances/cooking change (2f039aeb):
main_heating_fuel_code RdSAP10 Table 32 / SAP 10.2 Table 12 fuel
main_2_heating_fuel_code code column (the lodged fuel code, e.g.
secondary_heating_fuel_code mains gas 26). None when the corresponding
hot_water_fuel_code system is absent / fuel not resolvable.
pv_exported_kwh_per_yr SAP 10.2 Appendix M1 §3-4 annual export kWh
(0.0 when no PV).
cert_to_inputs.py populates the four fuel codes from the existing
resolvers the cost/CO2 cascade already uses — `_main_fuel_code`,
`_secondary_fuel_code`, `_water_heating_fuel_code` (not reinvented);
Main 2 is the second `main_heating_details` entry, guarded for length.
There is a single CalculatorInputs construction site (cert_to_demand_
inputs delegates to cert_to_inputs). `pv_exported_kwh_per_yr` already
existed on CalculatorInputs; SapResult collapses its Optional to 0.0.
HARD CONSTRAINT honoured — output-only, zero rating drift. These fields
do NOT feed ECF / total_fuel_cost_gbp / co2_kg_per_yr / primary_energy_*
/ sap_score / any monthly value. Every golden-fixture, Elmhurst e2e
SapResult pin, section cascade pin, and heating-corpus residual stays
byte-identical: calculator suite 1658 -> 1661 passed (+3 new tests),
4 skipped, 0 failed before and after. pyright net-zero (51 -> 51 in
domain/; no new errors in the touched test files).
New tests: a synthetic threading test (four fuel codes + PV export pass
unchanged through calculate_sap_from_inputs; None PV collapses to 0.0)
and a cert-level pin (mains-gas combi cert 000516 -> main fuel code 26,
no Main 2, secondary 30, HW 26). Synthetic CalculatorInputs / SapResult
fixtures updated for the new SapResult fields (defaults cover Inputs).
Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>
`test_epc_property_data_round_trips[RdSAP-Schema-21.0.1]` failed with
`sap_roof_windows: None != []` — a normalization mismatch, not lost data.
The 21.0.1 fixture has no roof windows, but the 21.0.1 API mapper emitted
an empty list `[]` while the domain field defaults to None
(`Optional[List[SapRoofWindow]] = None`), the 21.0.0 path yields None, and
the persistence reload yields None (roof windows aren't stored yet — doc
§2.4). Append `or None` so "no roof windows" has one canonical
representation across mapper paths and the round-trip.
No data-loss change: a cert WITH roof windows still produces the
populated list (test_golden_fixtures pins a 6-roof-window cert), and the
§2.4 roof-window persistence gap remains separately tracked. Full
sap10_calculator + documents_parser + epc-repository suites pass (2420);
pyright unchanged.
Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>
PR feedback (dancafc): the `_api_resolve_wall_insulation_thickness` tests
passed literals straight into the Act call. Bind them as named variables
in Arrange (`lodged_thickness`, `measured_value_mm`, `ni_lodgement`) and
have the asserts reference those names, so the Act line reads
declaratively and the inputs/expectations are stated once. Applied to all
three tests in the class. No behaviour change; tests pass.
Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>
PR feedback (dancafc): the simplified room-in-roof branch used cryptic
locals. Rename for clarity (behaviour-unchanged; the geom dict keys and
the builder-function locals are untouched):
rr_a_rr -> rr_roof_area (the worksheet's simplified A_RR)
rr_common -> rr_common_wall_area
rr_gable -> rr_gable_area
a_rr_final -> rr_residual_roof_area (leftover roof-going area after
deducting perimeter walls/gables
/rooflights — takes the roof U)
Names now mirror the `rr_*_area_m2` geom keys they read from and say
"area of what". Added a one-line note that `rr_roof_area` is the RdSAP 10
§3.10.1 A_RR. Pyright unchanged; 1087 heat-transmission/cascade-pin tests
pass.
Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>
PR feedback (dancafc): the SQLModel column was Optional[str], but the
domain `SapBuildingPart.wall_insulation_thickness` is Optional[Union[str,
int]] — `_api_resolve_wall_insulation_thickness` returns an int mm when the
API lodges `wall_insulation_thickness == "measured"` (SAP 10.2 §5.7 /
Table 8). The plain str column round-trips that int back as the string
"100", corrupting the Table 8 insulated-wall U-value lookup.
This column was missed in the round-trip-fidelity §1 JSONB sweep
(#1129) — its `Union[str, int]` sibling `roof_insulation_thickness` was
converted, but `wall_insulation_thickness` was not, and no 21.0.0/21.0.1
fixture lodges "measured" so the gap stayed latent. Convert to JSONB
(matching `roof_insulation_thickness` / `flat_roof_insulation_thickness`),
align the column type to Optional[Union[str, int]] (also removes a pyright
type-mismatch), record it in the migration doc §1, and add a round-trip
guard test asserting an int survives as an int (fails as '100' == 100 on
the old str column).
Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>
PR feedback (dancafc): `_parse_thickness_mm` handles a None input and
returns Optional[int], so its call-return locals — and the Optional[str]
raws they read from `_local_val` — read clearer when annotated. Annotates
`thickness_raw`/`ins_thickness_raw: Optional[str]` and
`thickness_mm`/`insulation_thickness_mm: Optional[int]` at all four call
sites (_wall_details_from_lines, _alternative_walls_from_lines,
_roof_details_from_lines, _floor_details_from_lines), plus the adjacent
`u_val_raw`/`default_u` Optional pair in _floor_details_from_lines for
consistency. Matches the project convention of typehinting call-return
locals. No behaviour change; pyright clean, 569 parser tests pass.
Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>
Captures the diagnosis so the next agent doesn't re-derive it: what's done
(S0380.235-237), what's confirmed correct (calculator U-adjustment, party
wall, glazing labels), the worksheet pin targets, and the two open causes —
crucially the 000516 trap (byte-identical Summary data classified as a roof
window there but a wall window here, so flipping the U>3 rule regresses
000516). Includes a rebuildable tracer recipe.
Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>
Completes the secondary-glazing family. S0380.235 mapped the unknown-data
(7) and normal-emissivity (11) secondary variants; the RdSAP-21.0.1
`glazed_type` enum also defines code 12 "secondary glazing, low
emissivity", whose Elmhurst §11 label "Secondary glazing - Low
emissivity" was unmapped and would strict-raise. Cascade code 12 carries
the same daylight/solar bucket as 7/11 (g_L=0.80, g⊥=0.76); the lodged
manufacturer U/g drive §3/§6. With this the double family (codes 1/2/3/
7/13 via their Elmhurst phrasings) and the secondary family (4/11/12) are
fully covered. Coverage test extended.
Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>
RdSAP 10 §3.3: "As Main Wall: Yes" makes an extension inherit the main
dwelling's external wall CONSTRUCTION only — the party wall type is
lodged separately per building part in the Summary §7 block and may
differ. `_extract_extensions` was copying `main_walls.party_wall_type`
into the inherited WallDetails, so every extension reused the main's
party wall U.
On the double_glazing fixture (Summary_001431) the Main lodges party
"CU Cavity masonry unfilled" (SAP10 wall_construction 4 → u_party_wall
0.5) but the 1st Extension lodges "U Unable to determine" (→ 0 → RdSAP
default 0.25). Pre-fix both building parts used 0.5, inflating worksheet
(32) party-wall heat loss by 6.56 W/K (Ext1 26.25 m² × 0.25). After the
fix worksheet (32) is exact: ours 32.573 vs worksheet 32.5725.
Now reads the extension's own "Party Wall Type" from its §7 chunk,
falling back to the main's only when the extension lodges none. Adds a
fixture + test asserting Main=4 / Ext=0 with distinct u_party_wall.
Suite 2413 pass; no cohort regression.
Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>
The double_glazing recommendation fixture (Summary_001431) exercises every
RdSAP-21 §11 glazing lodging in one cert; five labels were missing from
`_ELMHURST_GLAZING_LABEL_TO_SAP10` and strict-raised `UnmappedElmhurstLabel`:
"Secondary glazing" -> 7 (Table 6b "secondary glazing", g_L 0.80)
"Secondary glazing - Normal emissivity" -> 11 (RdSAP-21 secondary normal-E, g_L 0.80)
"Triple pre 2002" -> 10 (triple pre-2002, g_L 0.70)
"Triple with unknown install date" -> 6 (generic triple glazed, g_L 0.70)
"Single glazing, known data" -> 15 (single known-data, g_L 0.90)
The glazing code's only cascade effect is the §5 (66)..(67) daylight factor
g_L in `_G_LIGHT_BY_GLAZING_CODE` (single 0.90 / double+secondary 0.80 /
triple 0.70); the lodged manufacturer U-value and solar_transmittance drive
§3 / §6 directly (`_g_perpendicular` prefers the lodged value). Codes are the
semantically-exact RdSAP-21 rows within the correct g_L bucket, kept distinct
for the strict-raise audit trail. Adds a full-coverage test over all 13
distinct labels. Suite 2413 pass.
Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>
Records the three PV slices shipped (D_PV off-peak exclusion, weighted
dwelling import price, Appendix G4 diverter), the resulting case-19 state
(SAP 50.33→51.34, rounds to lodged 51), and the two remaining case-19
causes (winter Appendix-M EPV monthly shape; fabric (33) +1.0). Adds the
`2100-5421` worst-offender diagnosis (a 352 m² uninsulated solid-wall
dwelling on the as-built-insulated-assumed roof-U front, not a flats bug).
Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>
SAP 10.2 Appendix G4 (PDF p.72-73). A PV diverter routes surplus PV
generation (the would-be export EPV,m × (1 − βm)) to an immersion heater
in the hot-water cylinder. Per G4 step 4:
SPV,diverter,m = EPV,m × (1 − βm) × 0.8 × fPV,diverter,storageloss
(0.8 = cylinder heat-acceptance; fPV,diverter,storageloss = 0.9 for the
higher storage temperature), clamped to ≤ (62)m + (63a)m, and entered as
the negative worksheet (63b)m (step 5). The β factor is computed on the
PRE-diverter (219) per the §3a note (lines 5485-5486). Effects:
- (64)m = (62)m + (63b)m → less main-system water-heating fuel (219);
- export drops to EPV,ex,m = EPV,m(1 − βm) + (63b)m / 0.9 (§4 p.94
line 5501); the onsite dwelling portion EPV,m × βm is unchanged.
Inclusion (G4 step 1) requires ALL of: a PV system connected to the
dwelling; a cylinder larger than (43) average daily HW use; no solar
water heating; no battery — else the diverter is disregarded.
Three layers:
- extractor reads Summary §19 "Diverter present"; schema 21.0.0/21.0.1
SapEnergySource gains `pv_diverter` (API `sap_energy_source.pv_diverter`);
- `Renewables.pv_diverter_present` + domain `SapEnergySource.pv_diverter_present`,
set in both the Elmhurst and API mapper paths;
- `_pv_diverter_monthly_kwh` applies the G4 math after the β split;
`cert_to_inputs` recomputes (219) and the PV export.
On simulated case 19 (electric storage heaters, 7-hour, PV + diverter):
SAP continuous 50.33 → 51.34 (worksheet 51.2221; both round to the
lodged 51), cost (255) 1847.5 → 1812.3 (ws 1816.6), CO2 (272) 3331 →
3120 (ws 3126), with (233a) dwelling 1280.6 (ws 1280.4). The residual
+0.11 SAP is an upstream winter Appendix-M monthly-EPV-shape gap +
fabric (33) +1.0, tracked as the next case-19 cause. Suite: 2412 pass.
Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>
SAP 10.2 Appendix M1 §6 (PDF p.94, lines 5510-5513): "apply the normal
import electricity price to PV energy used within the dwelling and the
'electricity sold to grid, PV' price from Table 12 to the energy
exported. In the case of the former, use a weighted average of high and
low rates (Table 12a)."
`_pv_dwelling_import_price_gbp_per_kwh` was returning the bare off-peak
LOW rate (5.50 p/kWh on a 7-hour tariff) for the PV-used-in-dwelling
credit. PV self-consumption displaces the dwelling's "all other uses"
electricity (lighting / appliances / pumps), which on an off-peak tariff
bills at the Table 12a Grid 2 ALL_OTHER_USES weighted blend, not the low
rate. On simulated case 19 the worksheet (252)/(269) credits
PV-used-in-dwelling at 14.3110 p/kWh = 0.90 × 15.29 + 0.10 × 5.50; we
credited it at 5.50, under-crediting onsite PV by ~£0.088/kWh on every
off-peak PV cert.
Fix delegates to `_other_fuel_cost_gbp_per_kwh(tariff, prices)` (the same
ALL_OTHER_USES rate): STANDARD tariff still returns the flat Table 32
code 30 13.19 p/kWh (golden cohort unchanged — all 2412 tests pass);
off-peak returns the weighted high/low blend. Call sites now pass the
resolved `_rdsap_tariff(epc)`. The now-unused
`_off_peak_low_rate_gbp_per_kwh_via_meter_heuristic` (its only caller)
is removed.
Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>
SAP 10.2 Appendix M1 §3a (PDF p.93, lines 5470-5476): "E_space,m =
(211)m + (213)m + (215)m, where (211), (213) and/or (215) should be
included only where the fuel code applied to them in Section 10a of the
SAP worksheet is 30, 32, 34, 35 or 38 (i.e. electricity not at the
low-rate)."
The PV-eligible demand D_PV,m was adding 100% of the main space-heating
fuel (211)m whenever the main's Table-12 code was in the eligible set
(30, …), ignoring the off-peak high/low split that §10a already bills
via `_space_heating_fuel_cost_gbp_per_kwh`. Electric STORAGE heaters on
a 7-hour tariff are charged wholly at the low rate (Table 12a Grid 1 SH
fraction 0.00; worksheet (240) high-rate cost = 0), so none of (211)
may enter D_PV — but the cascade counted it all, inflating R_PV,m =
E_PV,m / D_PV,m and therefore the β onsite-PV split in the heating
months.
Fix mirrors the cost-side rate split: `_main_space_heating_high_rate_
fraction(main, tariff)` returns the high-rate portion (1.0 for
non-electric / STANDARD, the published Grid 1 SH fraction otherwise,
0.0 when the Grid 1 SH row is unwired → 100% low rate), and
`_pv_eligible_demand_monthly_kwh` scales the (211)m contribution by it.
Backward-compatible: STANDARD-tariff electric mains and the gas-main /
electric-secondary PV cohort are unchanged (fraction 1.0).
On simulated case 19 (electric storage heaters, 7-hour, PV) this takes
β_Jan 0.894 → 0.792, matching the worksheet 0.791, and the summer months
(no main heating) already pinned exactly.
Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>
