_u_brick_thin_wall_age_a_to_e's `<= 280` check put an uninsulated solid-
brick wall of exactly 280mm in the "200 to 280mm -> 1.7" row; RdSAP 10
§5.7 Table 13 (spec PDF p.41) shares 280 as an unlabelled edge between
that row and "280 to 420mm -> 1.4", so the table text alone doesn't say
which row owns it.
Found by building cert 100031768368 (280mm exactly, band C) in Elmhurst
and comparing every worksheet line to the calculator: volume/ACH/floor/
doors matched exactly, but the wall didn't (1.70 vs Elmhurst's 1.40)
despite an identical input crosswalk. Initially reverted a first attempt
at this fix when it appeared to regress an already-pinned cert
(217091901, band A, also nominally 280mm, previously "confirmed" at
U=1.70) — but that cert's build script never actually set a wall
thickness field, so its shared Elmhurst assessment had silently
inherited a stale 260mm from an earlier build. Fixed that build script
and rebuilt with the correct 280mm entry: Elmhurst's worksheet now also
gives U=1.40, matching 100031768368 and confirming the fix rather than
contradicting it.
Both certs move to (near-)exact lodged matches: 100031768368 59.12 ->
61.21 (lodged 61, within 0.5); 217091901 60.82 -> 61.59 (lodged 62,
exact). Corpus gauge 77.8% -> 78.6% within-0.5, MAE 0.636 -> 0.627 (14
corpus certs lodge exactly 280mm solid brick). TDD'd, 46 pins + full
suite green (2310 passed).
Co-Authored-By: Claude Fable 5 <noreply@anthropic.com>
Per the PR #1439 handoff: swept every cert now sitting at |Δ| in [1.0, 2.0)
(58 certs) using the cost-vs-demand signature bucketer (why_diverge.py's
logic) plus field_bias.py's full-corpus subgroup scan (re-run clean after
the two engine fixes above — no |meanΔ|>=0.5 systematic subgroup with
coherent median).
Breakdown: 17 room-in-roof (already spec-mandated/worksheet-validated per
PRs #1440/#1441), 7 electric cost/tariff variants (spec-faithful vs lodged,
consistent with the diagnosed electric cluster), 4 non-electric cost
residuals (spec-faithful), ~26 non-electric fabric/demand certs. Manually
inspected geometry (floor areas/perimeters/heights, wall/roof codes,
window/door counts) for the 4 largest fabric/demand outliers in the band
(100031768368, 100070450818, 100110097281, 100051051866) — no data-entry
anomaly comparable to the earlier 12109191 decimal-floor-area bug. This
confirms the handoff's "our calc faithful, lodged differs" pattern holds
across the band; no engine bug survived the pass. Notes appended per-cert
in worklist.md (`<-`, preserved by build_worklist.py reruns).
Co-Authored-By: Claude Fable 5 <noreply@anthropic.com>
Audits identity pass-through fields (dims, counts, thicknesses) raw cert vs
EpcPropertyData across all 1000 certs. All apparent mismatches are legitimate
mapper behavior the first-pass audit didn't model: window_wall_type=4 windows
correctly split to sap_roof_windows (not dropped); empty placeholder building
parts correctly discarded; 'measured' insulation-thickness sentinel resolved to
the wall_insulation_thickness_measured value. Remaining per-BP diffs were an
index-misalignment artifact (raw BP[i] vs epc BP[i] after empty BP0 dropped).
Conclusion: mapper is faithful; divergences are Playwright-entry or calc-side.
Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>
Field-level bias scan (scripts/corpus_1000/field_bias.py) flagged solid-brick +
internal-insulation certs (wall_con+ins=(3,3)) systematically under-rating
(median -0.40, n=18). Root cause: _insulation_bucket routed insulation that is
KNOWN PRESENT but with a thin lodged thickness (5-24mm, below the smallest
tabulated 50mm column) to bucket 0 (uninsulated, U 1.7) - WORSE than the
present-but-unknown case, which the RdSAP Table 6 footnote correctly routes to
the 50mm row. A known 10mm shouldn't read as higher-U than not knowing at all.
Now present insulation never falls to bucket 0; thin/unknown thickness both
round up to the 50mm row. Only genuinely absent insulation maps to 0.
Corpus cert 5117280 (10mm internal, no wall thickness -> bucket path): Δ -4.44
-> +1.08. Corpus MAE 0.641 -> 0.637, PE MAE 3.0 -> 2.9. Gauge 77.7% holds; 44
RealCert pins + 342 fabric tests green. TDD: 2 new unit tests.
Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>
Added scripts/corpus_1000/demand_cohort.py (isolates fabric/demand-driven
divergences from cost noise). Investigation conclusion: the demand-side tail is
one-offs, not a cluster. 12109191 (+13.1) is a LODGED decimal error (365.67 m²
floor, 10x its ground floor). 217060420 (-4.4) is spec-faithful (36.6 m2 lodged
glazing at spec U). The only >=3 structural clusters among diverging certs are
electric flats (already diagnosed spec-faithful). No generic fabric bug remains;
gauge 77.7% is near its structural ceiling. Marked 12109191 unbuildable in ledger.
Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>
Electric-tariff cluster investigation. The 112-cert electric-main cohort is
mixed-sign within every category/meter - no systematic tariff bias. Root cause
of the biggest non-xfail divergences (10012334488 +13.2, 10091578598 +7.81):
SAP code 195 = 'Electric water storage boiler' (Table 4a p.170), which SAP 10.2
§12 Rule 2 correctly bills mostly at the 7-hour off-peak rate. Both are pure
cost gaps (PE/CO2 match lodged -> demand right); the lodged software over-billed
the storage boilers at peak rate. The engine is SPEC-FAITHFUL - matching lodged
would tune against §12/Table-4a. Pinned to the spec-faithful engine values.
Adds scripts/corpus_1000/elec_cohort.py (electric-main cohort analyzer).
Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>
A FLAT roof lodges its insulation thickness in the DEDICATED gov-EPC API
`flat_roof_insulation_thickness` field (e.g. "75mm"), leaving
`roof_insulation_thickness` None (that field is for pitched-loft joists).
`heat_transmission_from_cert` read only the latter, so a measured
flat-roof thickness was ignored and the roof billed at the uninsulated
age-band flat default (age E = 1.5) instead of its Table-16 insulated U.
Fixed by preferring `flat_roof_insulation_thickness` when the part is a
flat roof — the exact mirror of the existing rafter-thickness branch.
An "AB"/"NI" (as-built/unknown) value parses to None and keeps the
age-band default, unchanged; only measured thicknesses move.
PER-CERT ELMHURST VALIDATION (cert 47084930, top-floor flat, flat roof
75 mm): built on the lodged inputs in accredited Elmhurst RdSAP10-Online
(evidence saved: elmhurst_summary.pdf / elmhurst_worksheet.pdf). The
worksheet bills "insulated flat roof" at U 0.5 (floor 0.70 + wall 0.25
also matching the engine). The fix takes the engine roof 96.4 -> 32.1 W/K
(= 64.26 x 0.5, Elmhurst-exact), PE +47 -> +0.2, SAP 69.51 -> 74.34 =
lodged 74.
Gauge: within 77.3% -> 77.7%, SAP MAE 0.648 -> 0.641, CO2 0.074 -> 0.072,
PE 3.1 -> 2.97. Unit-pinned in test_heat_transmission
(flat_roof_insulation_thickness -> U 0.5); RealCertExpectation 47084930
= 74 (Elmhurst-validated). Also adds the build script build_47084930.py.
Co-Authored-By: Claude Fable 5 <noreply@anthropic.com>
A hot-water cylinder lodging gov-API `cylinder_size=0` ("size not
determined", with has_hot_water_cylinder=true) resolved to a None volume
in `_cylinder_storage_loss_override` (which reads `_cylinder_volume_l_
from_code`, returning None for code 0). The subsequent `if volume_l is
None: return None` then DROPPED the cylinder's Table-2 storage loss
entirely — under-costing the DHW and over-rating the dwelling. Meanwhile
the Table-13 high-rate-fraction path already used `_hot_water_cylinder_
volume_l` (which defaults size 0 to 110 L), so the two DHW paths
disagreed on the same cylinder.
RdSAP 10 §10.5 Table 28 ("if the actual size is not determined, the size
is taken as according to Table 28") makes an unsized present cylinder the
110 L "Normal" baseline, which STILL incurs the storage loss. Fixed by
defaulting the storage-loss volume to 110 L for the explicit size-0 case.
Gated on the EXPLICIT 0 (not None): a full-SAP cert whose RdSAP
cylinder_size is simply unlodged (None, e.g. pinned 10091568921) keeps
its own cylinder handling rather than a forced 110 L RdSAP default.
7 corpus certs lodge cylinder_size=0 + has_cylinder=true. Gauge: within
77.0% -> 77.3%, SAP MAE ~flat (0.648), CO2 0.074 -> 0.073, PE 3.2 -> 3.05
(the previously-dropped storage loss now correctly counted in the demand
cascade). Unit-pinned in test_cert_to_inputs (storage loss non-None for
size 0); RealCertExpectation 200004017091 = 71.
Co-Authored-By: Claude Fable 5 <noreply@anthropic.com>
A SOLID-BRICK or STONE wall lodging External/Internal insulation
(wall_insulation_type 1/3) but no measured insulation thickness (gov-API
"NI" -> None) was billed at its UNINSULATED §5.6/Table-6 U-value: the §5.8
added-insulation R-value adjustment gates on `insulation_thickness_mm > 0`,
so an unknown thickness fell straight through to the raw solid-wall U
(~1.4-1.7). This over-counted wall heat loss and under-rated the dwelling.
RdSAP 10 §5.4 (PDF p.32): "the U-value with additional insulation is based
on the thickness of insulation of mineral wool type (assume 100 mm if
thickness is unknown)". Apply that 100 mm default so the §5.8 Table-14
R-value fires. Scoped to solid brick / stone (the only constructions with
a §5.8 R-value path in u_wall) so cavity (composite path) and timber /
system-built walls are untouched.
Localised by deep-diving corpus cert 200004296092 (end-terrace, solid
brick 360 mm "with external insulation", NI): walls 101.7 W/K (U~1.40,
HLP 3.46 = absurd for an insulated wall) -> ~0.29; PE +59.6 -> ~0; engine
64.35 (Δ -6.65) -> 71.74 = lodged 71. ~8 solid-brick/stone corpus certs
carry this NI-thickness-with-insulation shape.
Gauge: within-0.5 held at 77.0%, SAP MAE 0.658 -> 0.647, CO2 0.074 ->
0.073, PE 3.2 -> 3.1 (floor ratcheted). Unit-pinned in test_rdsap_uvalues
(brick 360 mm external NI -> 0.29) + RealCertExpectation 200004296092 = 72.
Co-Authored-By: Claude Fable 5 <noreply@anthropic.com>
An instantaneous point-of-use electric water heater (WHC 907/909, no
cylinder) on an off-peak tariff was billed 100% at the off-peak LOW rate
by the generic electric-off-peak else-branch. But SAP 10.2 §12 (PDF line
2680) computes the off-peak on-peak HW proportion via Table 13, "dependent
on the total floor area and the CYLINDER size" — it presumes a stored-water
cylinder charged overnight. An instantaneous heater has NO cylinder, heats
on demand, and cannot shift to the off-peak window, so 100% of its
consumption bills at the HIGH rate (Table 12a WH high-rate fraction 1.0).
Both the SAP-cost rate (`_hot_water_fuel_cost_gbp_per_kwh`) and the
ADR-0014 / CO2-PE fraction (`_hot_water_high_rate_fraction`) fixed
consistently (low-rate scalar -> 7-hour high rate; fraction 0.0 -> 1.0).
Localised by deep-diving corpus cert 74061136 (HHR-storage mid-floor flat,
WHC 909): PE matched lodged (+1.6, roof+floor zero-loss) while SAP over-rated
+7.72 — the cost-only signature. Its DHW was ours £59 vs lodged £344 (5.8x);
the tariff was the whole gap. Fix: +7.72 -> -1.25 (residual is separate small
fabric). 7 corpus certs carry electric-instantaneous DHW on off-peak; the 3
outside 0.5 all move sharply inward (MAE the win, not within-0.5 crossings).
RdSAP 10 §12 tariff routing confirmed spec-correct (Unknown meter + storage
409 -> off-peak 7-hour, Rule 2) — the bug was the DHW rate, not the tariff.
Unit-pinned in test_cert_to_inputs; RealCertExpectation 74061136 = 72.
Co-Authored-By: Claude Fable 5 <noreply@anthropic.com>
The gov-API `secondary_fuel_type` enums 5 (anthracite) / 9 (dual fuel) /
33 (coal) collide in VALUE with same-valued RdSAP-10 Table-32 codes for
OTHER fuels (5=bulk LPG, 9=LPG SC11F, 33=elec 10h-low). The main-fuel
boundary and the CO2/display `_secondary_fuel_cost_gbp_per_kwh` already
canonicalise these via `canonical_fuel_code`, but the SAP-DRIVING
`_fuel_cost` cascade had a SEPARATE inline secondary rate that passed the
raw enum straight to the price lookup — so the two paths diverged and the
cost path silently mis-priced.
Anthracite (enum 5) was billed at the bulk-LPG code-5 rate 12.19 p/kWh
instead of 3.64 — a 3x over-cost on the secondary that under-rated every
solid-fuel-secondary dwelling. Worst: corpus cert 100050355518 (semi,
2 extensions, anthracite room-heater secondary) lodged 36 / engine 20.8
-> 35.5. Its CO2/PE already matched lodged (the demand cascade was right)
— a pure cost-side gap, which is what localised it.
Fix: canonicalise `secondary_fuel` before the Table-32 lookup in
`_fuel_cost`, mirroring the main-fuel boundary. 55 corpus certs carry a
colliding secondary.
Gauge: within-0.5 75.5% -> 77.0%, SAP MAE 0.708 -> 0.668 (floors
ratcheted). The prior enum-9 test only guarded the display helper; new
test_fuel_cost_secondary_colliding_fuel_priced_at_canonical_rate pins the
_fuel_cost cost path directly. RealCertExpectation pinned for
100050355518 (36 = lodged).
Co-Authored-By: Claude Fable 5 <noreply@anthropic.com>
RdSAP 10 §5.11.4: a pitched roof lodging thickness "NI" with description
"...insulated (assumed)" was billed at the §5.11.4 observed-retrofit
50 mm row (U 0.68) while the SAME description lodged with "ND" fell
through to the Table 18 age-band default (0.40 for bands A-G). The
ND-vs-NI sentinel is lodging-software noise; "(assumed)" means the
insulation PRESENCE is an age-band assumption, not an observed
retrofit, so Table 18's "thickness cannot be determined" clause
governs both forms. The bare "insulated" description (observed
retrofit, no qualifier) keeps the 50 mm row.
Evidence: the 27-cert loc4+NI corpus cohort was systematically
under-rated (~-1 SAP; zero positive movers among "(assumed)" certs),
vs the 102-cert loc4+ND cohort already on Table 18 at ~0 bias.
Gauge: within-0.5 74.2% -> 75.5%, SAP MAE 0.721 -> 0.708, CO2 MAE
0.09 -> 0.074, PE MAE 3.5 -> 3.2 (floors ratcheted). Unit-pinned in
test_rdsap_uvalues (assumed -> Table 18; bare-insulated -> 0.68
regression guard); integration pin in test_heat_transmission updated;
RealCertExpectation pinned for 10094975827 (66 = lodged, was -1.87).
Ledger: C002 103001004 deferred pending Elmhurst arbitration
(single-immersion off-peak pricing + declared cylinder loss vs
Table-2); C006 quadruplet marked ⚠ (LIG-21.0 software honours lodged
0 extract fans literally vs the Elmhurst-validated 0=unknown->default
convention, worksheet case 46).
Co-Authored-By: Claude Fable 5 <noreply@anthropic.com>
Setup for the RdSAP-21.0.1 corpus gauge campaign (74.2% within-0.5,
SAP MAE 0.721 at HEAD, 1000/1000 computed):
- scripts/corpus_1000/build_worklist.py — runs all 1000 corpus certs
through the gauge's own path (from_api_response -> Sap10Calculator),
ranks |engine - lodged| descending, clusters by dwelling signature,
and (re)writes scripts/corpus_1000/worklist.md preserving per-cert
statuses and notes. 258 certs outside 0.5 in 249 clusters.
- C001 (worst cert, Δ +23.9): uprn 4510053280, ground-floor flat 47 m²
on ASHP PCDB 100053 (Mitsubishi Ecodan 5 kW, PSR table 0.2-2.0).
Dwelling PSR 2.031 -> SAP 10.2 N2 footnotes 44/45 heat-pump extension
(reciprocal interpolation toward 100% at 2x largest PSR) = 305%
space efficiency, which accredited Elmhurst also applies (golden
case 56, record 100061). The LODGED software instead treated the
out-of-range record as invalid and billed 100% direct electric +
standard schedule (reproduces lodged CO2 to 1%). Lodged-software
methodology gap, worklist ⚠, engine untouched; observed engine 75
pinned in test_real_cert_sap_accuracy.
Gauge floors unchanged (no engine change).
Co-Authored-By: Claude Fable 5 <noreply@anthropic.com>
