Table 5 reads "Number of extract fans if known; if number is unknown:
[age-band default]" — the default is an UNKNOWN-fallback, NOT a floor. The
cascade applied `max(lodged, table_5_default)`, flooring a genuinely-lodged
count up to the age-band minimum: e.g. an age H-M dwelling lodging 2 extract
fans was billed at the 6-8-room default of 3, over-counting ventilation line
(8) and the heat-loss coefficient. Fixed to `lodged if lodged > 0 else
default` (a lodged 0 is the Elmhurst/RdSAP "unknown" form → default; any
positive count is taken literally).
Surfaced by Khalim's Elmhurst stress worksheet (simulated case 46): this was
its last ventilation residual — our Jan effective ACH 9.14 -> 9.0748 (exact
match to the accredited worksheet), SAP 29 -> 30 = Elmhurst, cost £1496 vs
£1493. Corpus IMPROVED: within-0.5 71.6% -> 72.5%, MAE 0.819 -> 0.815 (the
max-flooring over-counted ventilation on every cert lodging fans below its
age default). Floor ratcheted 0.71 -> 0.72. pyright not installed locally.
Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>
When the main heating system does not heat every habitable room (heated rooms
< habitable rooms), SAP 10.2 Appendix A.2.2 assumes the unheated rooms are
served by a portable-electric secondary heater, so the Table 11 secondary
fraction (0.10 for a boiler main) must be costed at the electricity tariff —
even when the cert lodges no explicit secondary system.
`_secondary_fraction` previously returned 0 unless a secondary was lodged or
the main was a forced-secondary electric-storage code, dropping the assumed
secondary and billing 100% of space heat to the (cheaper) main fuel — an
over-rate. Added an `unheated_habitable_rooms` trigger plus
`_has_unheated_habitable_rooms(epc)`, which prefers the lodged
`any_unheated_rooms` flag and guards the gov-API `heated_rooms_count == 0`
"not provided" sentinel. The secondary fuel/efficiency cascade already
defaults to portable electric (code 693) when no secondary code is lodged.
Worksheet-validated on simulated case 46 (heated 4 < habitable 7, no lodged
secondary): the assumed 10% electric secondary (2289 kWh, ~£260) lifted our
SAP 39 -> 29.35 vs accredited Elmhurst 30 (cost £1502 vs £1493, within 0.6%).
Corpus UNCHANGED (71.6% / MAE 0.819): all 17 corpus certs with heated <
habitable already lodge an explicit secondary description, so the gov-API
path was already costing it; this only adds the assumed secondary where none
is lodged (Elmhurst / reduced-field path). pyright not installed locally.
Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>
The SAP rating is spec-floored at 1 ("if the result of the calculation is
less than 1, the rating is 1"). `sap_rating_integer` already clamps, but the
continuous `sap_score_continuous` did not — so a degenerate dwelling could
emit a physically impossible negative SAP. Apply the same max(1, …) floor to
the continuous value (the un-rounded part is for sensitivity near real
ratings, not for negative ratings).
Removes a -12.3 accuracy outlier on the committed corpus (cert 422000111926,
lodged at the floor of 1, was computing -11.3): within-0.5 70.2% -> 70.3%,
MAE 0.845 -> 0.833. Ratcheted the corpus MAE ceiling to 0.84. Unit-pinned in
test_calculator.
pyright not installed in this codespace (strict gate not run locally).
Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>
The gov-API lodges secondary fuel as an enum whose value can COLLIDE with a
different same-valued RdSAP 10 Table 32 / SAP 10.2 Table 12 fuel code:
- enum 9 = "dual fuel (mineral and wood)" vs Table code 9 = LPG SC11F
- enum 5 = "anthracite" vs Table code 5 = LPG (bulk)
The main-fuel boundary already canonicalises these (`_GOV_API_COLLISION_
FUELS`), but the SECONDARY-heating cost + CO2/PE paths never did — they took
the bare same-value lookup, so a dual-fuel room heater was priced as LPG
(3.48 vs dual-fuel 3.99 p/kWh) and emitted as LPG (CO2 0.241 vs 0.087),
and an anthracite secondary as bulk LPG (12.19 vs 3.64 p/kWh). The price
under-count over-rates SAP; the CO2 over-count inflates emissions.
Fix: add enum 9 to `_GOV_API_COLLISION_FUELS` (5 and 33 were already there)
and canonicalise the secondary fuel code on both the cost
(`_secondary_fuel_cost_gbp_per_kwh`) and factor (`_secondary_fuel_code`)
paths, mirroring the main-fuel boundary. canonical_fuel_code only touches
{5,9,33}, so genuinely Table-coded secondaries (House coal 11, wood logs 20,
community fuels 30-32) are left unchanged — confirmed by a full-map audit.
Corpus: within-0.5 69.7% -> 70.2% (MAE 0.854 -> 0.845; dual-fuel-secondary
cohort 42.9% -> 49.0%, signed +0.55 -> +0.41) and CO2 MAE 0.12 -> 0.08 t/yr
(bias +0.04 -> 0.00). Ratcheted the corpus floors (within 0.70, MAE 0.85,
CO2 0.09, PE 4.0). A prior session deferred enum 9 ("direction not
understood") while the EPC PE/CO2 lens was confounded by the climate-cascade
bug (fc7c4d2d); on the corrected lens the over-rate direction is clear.
pyright not installed in this codespace (strict gate not run locally).
Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>
The SAP/EI rating is computed on UK-average weather (Appendix U Tables
U1-U3 region 0) so ratings are nationally comparable, but Appendix U
paragraph 1 (PDF p.124) requires that "other calculations (such as for
energy use and costs on EPCs) are done using local weather. Weather data
for each postcode district are taken from the PCDB". `Sap10Calculator.
calculate` ran ONE cascade (UK-average) and fed it to SAP, CO2 AND primary
energy, so every cert's EPC-displayed CO2/PE were computed on the wrong
climate. Because most of England is warmer than the UK-average, this
systematically OVER-counted heating demand on the emissions/PE outputs.
The two cascades (`cert_to_inputs` rating, `cert_to_demand_inputs`
postcode) already existed; this wires the demand cascade into the
production entry point and grafts its CO2/PE onto the rating result (SAP
unchanged). The corpus gauge's longstanding +5% CO2/PE over-estimate was
mostly this climate bug, NOT (as previously diagnosed) per-cert mapper
fidelity:
CO2 MAE 0.26 -> 0.12 t/yr (bias +0.18 -> +0.04)
PE MAE 13.6 -> 3.8 kWh/m2 (bias +9.0 -> +0.24)
SAP within-0.5 = 69.7% (rating cascade, unchanged)
Worksheet-validated to 1e-4 on simulated case 45 (heat-pump ground-floor
flat, postcode W6): the P960 prints the current dwelling twice — Block 1
on UK-average weather (SAP 60.5318, CO2 692.13) and Block 2 on postcode
weather (CO2 626.78, PE 6581.59). Both reproduce exactly. Added a tracked
case-45 Summary fixture + two-cascade cascade pin as a permanent guard,
and ratcheted the corpus CO2/PE ceilings to 0.13 / 4.2. The e2e Elmhurst
suite (Block-1 line refs) now pins the rating cascade directly; the two
Vaillant overlay snapshots refreshed to demand-cascade CO2/PE.
pyright not installed in this codespace (strict gate not run locally);
change is type-trivial (dataclasses.replace over SapResult).
Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>
When a heat-pump cert lodges a PCDB Table 362 record, the APM override
set BOTH the space efficiency (N3.6) and the water efficiency (N3.7a)
from the heat pump unconditionally. But the PCDB η_water applies only
when the DHW is heated BY the heat pump (water-heating code "from main":
901/902/914). A separate electric immersion (WHC 903) heats the water at
100% regardless of the space system, so applying the HP's water SCOP
(187.5% × 0.6 in-use = 112.5%) under-counted the immersion's hot-water
fuel.
Gate the η_water override on the DHW-from-main codes; a separate immersion
keeps its own 100% efficiency. Space η_space still always uses the APM
value (the heat pump is the space main).
Worksheet-validated to 1e-4 on simulated case 45 (HP space + WHC-903
immersion): water fuel (62) 1893.57 -> 2130.2639, total cost (255)
619.7433, CO2 692.13 — all matching the P960 exactly; SAP 60.53 -> rounds
to the worksheet's 61. RdSAP-21.0.1 corpus unchanged (no HP+WHC903 certs
in it). Pinned in test_cert_to_inputs (immersion fuel is main-independent).
Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>
The flat floor-exposure heuristic keys on dwelling_type: a flat defaults
to has_exposed_floor=False (assuming a heated dwelling below). The
Elmhurst Summary path lodges a ground-floor flat's vertical position as a
"Ground floor" floor_type rather than the API floor_heat_loss=1 exposed
code, and the mapper can label such a flat "Top-floor flat" — so the
cascade dropped the ground floor entirely (a ground floor is in contact
with the ground and carries heat loss).
Treat a "ground floor" floor_type as a heat-loss floor, overriding the
dwelling-level suppression upward — mirroring the existing "another
dwelling below" party override downward.
Worksheet-validated to 1e-4 on simulated case 45 (a ground-floor flat
the mapper labelled "Top-floor flat"): floor (28a) 0 -> 25.38 W/K,
fabric (33) 75.63 -> 101.0104, HTC (39) 112.93 -> 145.3579, all matching
the P960 exactly; SAP 67.81 -> 62.52. RdSAP-21.0.1 corpus within-0.5
69.5% -> 69.7% (MAE 0.859 -> 0.854). Floors ratcheted. Pinned in
test_heat_transmission (ground-floor billed + party-floor suppressed).
Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>
The deduplicated `epc.roofs[]` list cannot be indexed 1:1 against the
building parts (190/329 multi-part certs have len(roofs) != len(parts)),
so every part's `u_roof` consumed a SINGLE join of all roof descriptions.
That leaked one part's insulation state onto another: a "Flat, no
insulation" extension dragged a "Pitched, insulated (assumed)" main roof
to the uninsulated 2.30, ~3x over-stating its heat loss. 3-part certs
systematically under-rated (56% within-0.5, mean -0.79 SAP).
Partition the non-RR roof descriptions into flat vs pitched/sloping and
match each part to its own kind (`_main_roof_descriptions_by_kind`),
falling back to the global join when a part's kind has no matching entry.
Corpus cert 100010129331: roof 110.5 -> 31.3 W/K, +13.10 -> -0.05 SAP.
RdSAP-21.0.1 within-0.5 68.8% -> 69.5% (MAE 0.888 -> 0.859; PE 13.9 ->
13.6); 3-part cohort 56% -> 61%. Floors/ceilings ratcheted. Pinned in
test_heat_transmission (by_kind split + mixed-roof no-contamination).
Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>
Close the §6.1 conservatory demand cascade per RdSAP 10 §6.1 + Table 25.
Solar gains (§6, solar_gains.py) — Table 25 note (PDF p.51): "The
orientation of windows in a conservatory is not recorded, thus solar
gains are calculated using the default solar flux (East/West orientation,
with 20° pitch for roof windows)." The glazed wall bills onto the (76)
East line (vertical, average-overshading Z); the glazed roof onto the
(82) roof-window line (20° pitch, Z=1.0), both at Table 25 g=0.76, FF=0.70.
TFA-occupancy (mapper) — §6.1: the conservatory floor area is added to the
dwelling total floor area. TFA drives occupancy → §5 internal gains + §4
hot-water demand, so the non-separated conservatory's floor area now
enters `EpcPropertyData.total_floor_area_m2` (the worksheet's (4) = 95.38
carries it). Separated conservatories (§6.2) stay excluded.
Pinned against the case-44 P960 demand cascade at abs=1e-4: (73) internal
gains 625.1759, (83) solar gains 495.8655, (95) useful gains 1079.6510,
(99) space heating per m² 89.8073 — the full §6.1 chain reproduces EXACTLY.
The whole-dwelling SAP (72.9517) / CO2 (3241.8656) are not pinned: the
case-44 Summary omits the House-Coal secondary heater (SAP 633) the P960
descriptor carries (cf. case 43), so the cascade computes no secondary —
the entire residual (+349.77 kg CO2). A Summary-input defect, independent
of §6.1; every conservatory-affected line ref is exact. Worksheet harness
stays 47/47 0-raised; corpus unchanged (API path; mirror is the next slice).
Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>
SAP 10.2 §2 (17)-(18): a measured/design air permeability at 50 Pa from a
Blower Door test routes infiltration via `(18) = AP50/20 + (8)`, in
preference to the components-based (16) estimate. The Elmhurst extractor
read only the AP4 ("Pulse") column of §12.2, so a Blower Door result
(§12.2 "Pressure Test Result (AP50)") fell through to the structural-
infiltration default — over-counting ventilation heat loss.
Surfaced by simulated case 44 (AP50 4.50): effective air change rate was
0.81 vs the worksheet's 0.58 (+38% ventilation loss). The cascade already
supports `air_permeability_ap50` (preferred over AP4); this wires the read
end to end (extractor → ElmhurstSiteNotes → SapVentilation → cert_to_inputs).
Pinned against the case-44 P960 §2 at abs=1e-4: (18) infiltration 0.3417
(= 4.5/20 + 0.1167) and (25) Jan effective ach 0.5812. Worksheet harness
stays 47/47 0-raised.
Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>
SAP-Schema-16.2 (datatypes/epc/domain/mapper.py):
- 16.2 is structurally an RdSAP-17.1 cert under a different name; add
_normalize_sap_schema_16_2 (field renames + defaults) and dispatch to the
tested from_rdsap_schema_17_1 mapper. uprn_100020933699 maps → SAP 71.
- Honour a "Single glazed" windows description when multiple_glazing_type="ND"
(was defaulting to double) → RdSAP-21 code 5; eng 72→71 (lodged 70).
- 4 regression tests + sap_16_2.json fixture; 0 new pyright errors.
Flat party-wall fix (domain/sap10_calculator/worksheet/heat_transmission.py):
- Full-SAP flats carry flatness in dwelling_type, not property_type, so the
party-wall default fell through to the 0.25 house value instead of the RdSAP
Table-15 flat 0.0. Add _is_flat_or_maisonette_dwelling fallback + regression
test. uprn_10093116529 80→81 (matches the cert's lodged party u_value 0).
Accuracy corpus pins (tests/domain/sap10_calculator/test_real_cert_sap_accuracy.py):
- uprn_10093116543 (SAP-17.1 gas-combi semi): engine 81 (Elmhurst 77; documented
full-SAP→RdSAP residual — measured wall/floor U + PCDB boiler vs RdSAP defaults).
- uprn_10093116529 (SAP-17.1 g/f flat): engine 81 (Elmhurst 78).
devcontainer: add poppler-utils (pdfinfo) for the documents-parser PDF fixtures.
Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>
Wire the non-separated conservatory into the §3 heat-transmission +
§1 dimensions cascade per RdSAP 10 §6.1 (PDF p.49) + Table 25 (p.51):
"The floor area and volume of a non-separated conservatory are added to
the total floor area and volume of the dwelling. Its roof area is taken
as its floor area divided by cos(20°), and wall area is taken as the
product of its exposed perimeter and its height. ... The conservatory
walls and roof are taken as fully glazed ... Glazed walls are taken as
windows, glazed roof as rooflight."
New `worksheet/conservatory.py` derives the geometry:
- height from the equivalent storey count (§6.1: 1 storey → ground-floor
room height; 1½ → ground + 0.25 + 0.5×first; etc.);
- glazed WALL → window (27) at Table 25 U (double 3.1 / single 4.8) with
the §3.2 curtain resistance (R=0.04) → U_eff 2.758;
- glazed ROOF → rooflight (27a) at Table 25 roof U (double 3.4 / single
5.3) + curtain → U_eff 2.993;
- FLOOR → (28a) via BS EN ISO 13370 as an uninsulated SOLID ground floor
with 300 mm walls (§5.12, spec p.43), exposed perimeter = glazed
perimeter → U 0.89;
- glazed wall + roof + floor areas join (31)/(36); the fully-glazed
structure walls/roof add nothing (the glazing IS the window/rooflight).
`dimensions_from_cert` adds the conservatory floor area to TFA (4) and
floor area × height to volume (5) (feeds ventilation (8)), without making
it a storey (avg storey height for §2 infiltration is unchanged).
Pinned against the simulated case-44 P960 §3 at abs=1e-4 — every line ref
EXACT: (4) 95.3800, (5) 257.1630, (27) 96.1169, (27a) 38.2201, (28a)
21.4164, (29a) 35.5852, (30) 7.4688, (31) 294.2900, (33) 207.3274,
(36) 23.5432. The remaining whole-dwelling SAP/CO2 gap is the §6 solar
gains, closed in the next slice. Worksheet harness stays 47/47 0-raised.
Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>
Golden regression fixture for the multi-feature dwelling that surfaced the
two Elmhurst-extractor bugs in a33707f8. case 43 is a 2-BP mid-terrace with
a DETAILED room-in-roof (two slopes, two flat ceilings, party + exposed
gables, two common walls), a MIXED-insulation multi-section roof (Main
insulated + Extension uninsulated 2.30), a DRY-LINED extension solid wall,
a mains-gas boiler (102 / control 2106) and a House-coal solid-fuel
secondary (633).
Routes the Summary PDF through the WHOLE extractor + mapper + calculator
pipeline (no hand-built EpcPropertyData) and pins the §3 fabric + SAP-rating
block at abs=1e-4: (29a) walls 74.5800, (30) roof 38.5008, (33) fabric
172.7844, continuous SAP 73.2332 = (258), CO2 3518.3037 = (272). Guards the
detailed-RR slope/common_wall surfaces, the dry-lining R=0.17 adjustment,
and the per-part mixed-roof billing together. Summary mirrored to
backend/documents_parser/tests/fixtures/Summary_001431_case43.pdf; provider
module mirrors the _case6/_case21 pattern, assertion in
test_section_cascade_pins. Harness 47/47; regression = the 3 pre-existing
fails; pyright net-zero.
Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>
The gov API lodges a manufacturer's declared cylinder loss factor
(kWh/day) in `sap_heating.cylinder_heat_loss`, in which case it leaves
the cylinder volume / insulation type / thickness None. That field was
undeclared on the 21.0.x schemas, so `from_dict` dropped it — then
`_cylinder_storage_loss_override` hit its insulation-None / volume-None
guards and returned None, dropping the §4 storage loss ENTIRELY. The
dwelling over-rated (the declared loss is typically ~1.5 kWh/day ≈
550 kWh/yr).
SAP 10.2 §4 branch a) (PDF p.136): when the declared loss factor is
known, storage loss (50) = (48) declared loss × (49) Table-2b
temperature factor — replacing the Table 2 V×L×VF computation.
- declare `cylinder_heat_loss` on RdSapSchema21_0_0/21_0_1.SapHeating +
EpcPropertyData.SapHeating; thread through the 21.0.x mappers.
- `cylinder_storage_loss_monthly_kwh` gains `declared_loss_kwh_per_day`:
when set, combined_55 = declared × TF (volume/insulation unused).
- `_cylinder_storage_loss_override` resolves the declared loss BEFORE the
insulation/volume guards (the gov omits those when the loss is lodged).
12 /tmp certs carry it (mean |err| 3.00 -> 2.51; the clean ones close
hard, e.g. 2360 2.65 -> 0.30, 0245 2.25 -> 0.53). Corpus within-0.5
67.0% -> 67.3% (MAE 1.025 -> 1.020); /tmp 71.2% -> 71.4% (0.889 ->
0.882). Worksheet harness 47/47; regression = only the 3 pre-existing
fails; pyright net-zero.
Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>
Roofs lodged insulated at rafters carry their thickness in a DEDICATED
gov-EPC API field, `rafter_insulation_thickness` (e.g. "225mm"), while
`roof_insulation_thickness` stays None (rafters aren't loft joists). That
field was undeclared on the 21.0.x schemas, so `from_dict` silently
dropped it — the rafter certs only *looked* redacted (roof EER 2-4 =
insulated, yet no thickness), and the cascade fell to the Table 18 col (2)
unknown default (2.30), badly under-rating them.
- declare `rafter_insulation_thickness` on RdSapSchema21_0_0/21_0_1 +
EpcPropertyData.SapBuildingPart (mirrors the existing
sloping_ceiling_/flat_roof_insulation_thickness dropped-field handling).
- thread it through `from_rdsap_schema_21_0_0/21_0_1` (older schemas get
None via getattr).
- `heat_transmission` prefers `rafter_insulation_thickness` over
`roof_insulation_thickness` when the part is at-rafters, so the measured
RdSAP 10 §5.11.2 Table 16 column (2) row applies (225 mm → 0.25).
Completes the rafters roof fix: with the real thickness read, the rafter
certs are recovered rather than over-stated — cert 3100-8675-0922-8628
(band E, rafters 225mm) +8.93 → +0.43 SAP. Corpus within-0.5 67.0%
(MAE 1.025) and /tmp 71.2% (MAE 0.889) — both NET ABOVE the pre-rafters
baseline (66.9% / 70.6%). Worksheet harness 47/47; regression = only the
3 pre-existing fails; pyright net-zero.
Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>
`u_roof` only implemented the joist column, so roofs lodged insulated at
rafters (`roof_insulation_location == 1`) were mis-billed at the joist U
on both the API and Summary paths — under-stating loss, over-rating SAP.
RdSAP 10 §5.11.2 Table 16 (spec p.42-43) gives a distinct "insulation at
rafters" column (2): the rafter cavity is shallower than a loft void, so
the same depth yields a higher U (200 mm: rafters 0.29 vs joists 0.21).
§5.11 Table 18 (p.45) likewise carries a rafters column (2) for unknown /
as-built thickness (footnote (1): "The value from the table applies for
unknown and as built") — band A-D = 2.30, E = 1.50, F = 0.68, diverging
from the joist column's 100 mm-equivalent 0.40 default (footnote (4)).
- add `_ROOF_RAFTERS_BY_THICKNESS` (Table 16 col 2) + `_ROOF_RAFTERS_BY_AGE`
(Table 18 col 2) to rdsap_uvalues; `u_roof` selects them via a new
`insulation_at_rafters` flag (ignored for flat / sloping-ceiling roofs).
- `heat_transmission` derives the flag PER BUILDING PART from
`roof_insulation_location` (gov-API int 1 / Summary "R Rafters"), which
also fixes the multi-part dedup-roof-join problem: each part's own
location now drives its U, replacing the unattributable joined
`epc.roofs[]` description.
Worksheet-validated to 1e-4: simulated case 41 (4-bp — Ext1 rafters 200mm
→ 0.29, Ext3 rafters As-Built band F → 0.68; roof total 24.8350) and case
42 (6 variants — rafters 50mm → 0.88, rafters unknown band C → 2.30,
joists/none unchanged). Case 40 stays exact (roof 35.340, total 441.1606);
worksheet harness 47/47.
Corpus within-0.5 66.9% → 66.5% (gates 0.65/1.08 hold) — a spec-correct
shift, NOT a regression: all 15 corpus rafter certs carry redacted (None)
thickness yet lodge roof EER 2-4 (insulated), so the open API blanked a
specified thickness and the spec's unknown-rafter 2.30 default correctly
over-states them. Recovery needs a roof-EER→thickness inference on the
API path (follow-up), not a change to the U-table.
Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>
The Elmhurst Summary §15.1 lodges "Cylinder Size: Value known" with the
measured volume in the "Cylinder Volume (l)" line — the Summary-path
equivalent of the gov-API "Exact" descriptor. The mapper had no entry for
"Value known" so `_elmhurst_cylinder_size_code` raised UnmappedElmhurstLabel,
and even once mapped the measured volume was never threaded through, so the
cascade dropped the cylinder storage loss (~468 kWh/yr) from (219) water
heating on every measured-volume-cylinder Summary.
Per RdSAP 10 §10.5 Table 28 (p.55) a measured cylinder volume is used
directly. Map "Value known" → cascade code 6 (Exact) and thread the §15.1
"Cylinder Volume (l)" value into SapHeating.cylinder_volume_measured_l, which
`_cylinder_volume_l_from_code` (cert_to_inputs.py:5281) already reads for
code 6 — mirroring the gov-API path (mapper.py:1575/1885).
Pins simulated case 39 (P960-0001-001431): an age-A mid-terrace on direct-
acting electric room heaters (SAP code 691, cat 10, control 2602) with
electric-immersion DHW off a 117 L "Value known" cylinder. The full
extractor→mapper→calculator cascade now reproduces the worksheet's SAP-rating
block EXACTLY — SAP value 36.6365 (band F) and (272) CO2 2056.0731 kg/yr,
with (219) water heating 2637.5049 and (255) total energy cost 1802.0039.
Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>
Reduced-field window U: heat_transmission derived the synthesised-window
raw U from u_window(all None) -> the 2.5 placeholder regardless of glazing.
Now routes the (uniform) glazing_type code through u_window (RdSAP Table 24)
so e.g. double pre-2002 reads 2.8, not 2.5. Only the pre-SAP10 reduced-field
path is affected (21.0.1 certs carry per-window U upstream) — the RdSAP-21.0.1
corpus gauge is unchanged at 66.9% within-0.5.
test_real_cert_sap_accuracy: pin uprn_10002468137 (RdSAP-17.1, all-electric
storage heaters) at SAP 61, validated against Elmhurst on identical inputs
(dual off-peak immersion, 110 L cylinder, 2 baths). Our engine reproduces
Elmhurst's fuel cost to the penny; lodged 55 is the old SAP-2012 schema.
Tooling to grow the accuracy corpus:
- scripts/fetch_real_life_epc_sample.py — capture a cert by UPRN into the corpus.
- scripts/compare_epc_paths.py — diff gov-API vs Elmhurst-summary EpcPropertyData
and run both through the engine, localising mapper vs calculator differences.
- skill validate-cert-sap-accuracy — the end-to-end loop (capture -> Elmhurst
inputs -> human builds -> compare -> reconcile -> pin in the test).
- skill epc-to-elmhurst-rdsap-inputs reference: corrected immersion (code 1=dual),
cylinder size (code 2 = Normal/110 L), and bath-count (WWHRS sub-tab) mappings.
Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>
The realistic re-generation of case 37 (code-117 gas boiler, control 2102,
+ a MAINS-GAS condensing gas-fire secondary code 611, vs case 37's biogas
605). The full extractor -> mapper -> calculator pipeline reproduces the
worksheet's SAP-rating block EXACTLY: continuous SAP 60.9152 (Δ 2e-5) and
(272) CO2 5801.0770 (Δ ~0). This confirms the boiler-efficiency /
control-2102 −5pp interlock / secondary-fuel handling are all correct, and
that case 37's +7 gap was purely the biogas sub-fuel the Summary export
cannot carry.
Summary mirrored into backend/documents_parser/tests/fixtures so the pin
runs without the unstaged workspace. PE not pinned — it is a separate
DPER block (different scope) already guarded by the corpus PE gauge.
Worksheet harness 47/47 unchanged; pyright net-zero.
Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>
A "No system present: electric heaters assumed" lodging carries SAP
Table 4a code 699 (electric room heaters) but RdSAP main_heating_category
1, NOT 10. `_table_12a_system_for_main` keyed the direct-acting-electric
routing on category==10 only, so the category-1 form fell through to None
and `_space_heating_fuel_cost_gbp_per_kwh` billed space heating 100% at
the off-peak LOW rate — as if direct-acting room heaters charged overnight
like storage.
Per RdSAP 10 §12 Rule 3 (PDF p.62) electric room heaters (691-694, 699)
route to the 10-hour tariff, and SAP 10.2 Table 12a Grid 1 (PDF p.191)
gives the "other direct-acting electric" row a 0.50 high-rate fraction at
10-hour (1.00 at 7-hour). Route those SAP codes — the same set §12 Rule 3
already uses — to OTHER_DIRECT_ACTING_ELECTRIC alongside the category-10
gate.
Found via the PE/CO2-vs-cost split on the worst over-rater in the /tmp
sample: cert 2958 PE +0% / CO2 -1% (energy correct) but SAP +32.2 — a
pure cost-side bug. Space rate 7.50 -> 11.09 p/kWh; cert 2958 +32.2 ->
+14.7. The committed corpus gauge is unchanged (its 3 non-category-10
code-699 certs are all on Single meters -> STANDARD tariff, so this split
never applies to them); the win is on the unbiased /tmp population's
single worst cert.
Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>
SAP 10.2 Appendix M1 (PDF p.94): "EPV,ex,m = 0 if the PV system is not
connected to an export-capable meter." The cascade computed the β-split
export stream regardless of `is_dwelling_export_capable`, so a non-export-
capable dwelling was credited the full PV export — in the §10a COST it
credits at the Table 32 import rate (13.19 p/kWh), which dominates the rating.
On 7 Wybourn Terrace S2 5BJ the PE (144 vs lodged 151) and CO2 (27 vs 29)
already matched, yet the phantom export cost credit pulled SAP from ~73 to
92.1 (+19). Zero `epv_exported_monthly_kwh` after the Appendix-G4 diverter
adjustment when not export-capable; the onsite (EPV,dw) consumption and the
diverter HW reduction are unchanged.
Not-export-capable PV cohort (corpus, 4 certs): 7 Wybourn +19.1 -> +6.5,
4 Lime Ave +11.1 -> +0.4, 8 Hatherleigh +7.6 -> -0.2, Flat 5 ~-0.4. Gauge
66.1% -> 66.9%, MAE 1.124 -> 1.039. Floor 0.64 -> 0.65 / ceiling 1.18 -> 1.08.
Worksheet harness 47/47 0 diverge (Summary certs carry export-capable meters).
1 AAA test, pyright net-zero. Found by auditing the worst over-rater without a
worksheet: PE/CO2-match + cost-miss localised it to the PV export credit.
Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>
RdSAP 10 §10.5 (PDF p.55): "If the actual size is not determined, the size of
a hot-water cylinder is taken as according to Table 28." When a cylinder is
present (has_hot_water_cylinder) but no size descriptor resolves — the gov API
lodges cylinder_size=0, or Exact with no measured volume — `_hot_water_
cylinder_volume_l` returned None, silently dropping BOTH the cylinder's
storage loss and the Table 13 electric-DHW high-rate fraction, under-costing
and over-rating the dwelling. Default such cylinders to the Table 28 baseline
"Normal" 110 L (the value §10.7 also instantiates as the first-row default).
The context-dependent Inaccessible 210/160 values are deliberately NOT applied
here — they are tied to the explicit "Inaccessible" descriptor (code 5) the
assessor lodges, not to an unpopulated size field.
Scope: 7 of 301 cylinder certs in the corpus (2%). Correctness fix — closes a
real spec gap; marginal on the headline (within-0.5 66.1% unchanged, MAE
1.128 -> 1.124) because these certs' residual is dominated by a separate HW-
demand gap, not the cylinder. Worksheet harness 47/47 0 diverge (Summary certs
lodge a real size, so the fallback never fires). 1 AAA test, pyright net-zero.
Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>
SAP 10.2 Table 12a Grid 1 (PDF p.191): electric storage heater SAP code 408
is an "Integrated (storage + direct-acting) system" with a 0.20 space-heating
high-rate fraction on a 7-hour tariff — NOT the 0.00 of "other storage
heaters". `_table_12a_system_for_main` returned None for all storage codes (an
explicit TODO), so code 408 fell back to the 100%-low-rate path and billed
space heating at the bare 7-hour low rate (5.50 p/kWh) — under-costing →
over-rating. Mapped cat-7 storage: 408 -> INTEGRATED_STORAGE_DIRECT (0.20),
others -> OTHER_STORAGE_HEATERS (0.00, unchanged behaviour). The enum +
fraction rows already existed; this only wires the dispatch, so the split
flows self-consistently to both the §10a cost and the Appendix-M1 D_PV
high-rate fraction.
Corpus: sap408 over-raters +14.6/+12.9/+12.7 -> +7.1/+5.1/+3.4 (two crossed
into within-0.5). Gauge 65.9% -> 66.1%, MAE 1.160 -> 1.128. Floor 0.63 -> 0.64
/ MAE ceiling 1.22 -> 1.18. Worksheet harness 47/47 0 diverge. The residual
+3..+7 is the "all other uses" 0.90 high-rate fraction (lighting/pumps/HW
still billed 100%-low on the off-peak legacy path) — the next slice.
Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>
SAP 10.2 Table 4c(3) (PDF p.169) "Factor for controls and charging method"
multiplies a heat network's heat requirement by 1.05-1.10 for FLAT-RATE
charging (note d: household pays a fixed amount regardless of heat used, so
no incentive to economise), and by 1.0 for charging linked to use. The
worksheet folds it into the heat-network requirement alongside the Table 12c
distribution loss factor:
(307) space = (98c) x (302) x (305) x (306)
(310) DHW = (64) x (305a) x (306)
Our cascade applied (306) DLF but never (305)/(305a), so every flat-rate
community-heating cert under-counted demand -> over-rated SAP.
Folded the factor into the 1/DLF efficiency override at the space-heating
(206) and DHW (water-inherits-from-main) sites. Space column adds +0.05 for
no thermostatic control (2301/2302); DHW column is 1.05 flat-rate / 1.0
linked-to-use.
Corpus (RdSAP-21.0.1, 1000 certs): community cluster median +0.32 -> -0.19,
within-0.5 38% -> 62% (control 2307 +0.83 -> -0.19; 2306 unchanged at factor
1.0 as spec requires). Overall gauge 65.0% -> 65.9%, MAE 1.174 -> 1.160.
Ratcheted the corpus-test floor 0.62 -> 0.63 / MAE ceiling 1.25 -> 1.22.
Also records (corpus-test comment + scripts/decompose_co2_pe_error.py) the
disproof of the prior "CO2/PE +5% is a factor/scope bug" lead: factors are
spec-exact, scope identical, and the bias is per-cert demand fidelity
(corr(SAP-err, PE-diff) = -0.54), not a one-slice factor fix.
Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>
The mixer-shower hot-water demand (worksheet 42a) divided N_shower by the
count of MIXER outlets only. But SAP 10.2 Appendix J step 1a is explicit:
"Establish how many shower outlets are present in the dwelling, Noutlets
(including in the count any instantaneous electric showers)" — and the
electric-shower step (64a) uses that same Noutlets from step 1a. So a
dwelling with both a mixer and an electric shower assigned the FULL N_shower
to the mixer system AND billed the electric shower on top of it, double-
counting shower demand → over-counted main HW → under-rated the dwelling.
Fix: thread the electric-shower count into the mixer demand so the
denominator is the total outlet count (mixer + electric), iterating the
warm-water draw over the mixer outlets only (per step 1e).
shower_types=1,2 cohort: -0.37 median -> +0.28 (crossed zero); API gauge
68.4% -> 69.0% within-0.5. Golden cert 0300-2747 (1 mixer + 1 electric)
re-pinned: PE +0.93 -> -0.10, CO2 +0.25 -> +0.15 (both toward zero,
confirming the double-count). Worksheet harness 47/47, 0 divergers (the
Elmhurst fixtures have no electric showers).
Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>
The no-PCDB MEV fan-electricity path fed the SAP 10.2 Table 4g default SFP
(0.8 W/(l/s)) directly as SFPav. But Table 4g note 3 (PDF p.176) is explicit:
the default SFP values "are to be multiplied by the appropriate in-use factor
for default data from the PCDB" — PCDB Table 329 system_type 10 ("default
data, used when SFP is taken from Table 4g rather than the PCDB"), IUF 2.5
(duct-agnostic per note 2). Table 4h, which previously held these factors, is
retired ("no longer used – data now stored in the PCDB").
Omitting the IUF under-billed the index-less MEV fan electricity by 2.5x
(SFPav 0.8 instead of 0.8 x 2.5 = 2.0), so cost was too low and the cohort
over-rated. This is distinct from the with-index path, which already applies
the tested-product system_type-2 "no scheme" IUF (~1.45) per fan.
Index-less gas-house MEV cohort: +1.37 median -> -0.18 (12% -> 92% within 0.5),
no overshoot — the missing IUF was exactly the over-rate. API gauge 67.7% ->
68.4% within-0.5 (mean|err| 0.992 -> 0.986, signed +0.031 -> +0.006).
Worksheet harness 47/47, 0 divergers (Summary-path MEV certs carry a PCDB
index or are natural, so unaffected).
Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>
The gov-EPC API surfaces the assessor's RdSAP-assessed per-element U-values
as `roof_u_value` / `wall_u_value` / `floor_u_value` on each building part.
These were undeclared on the RdSAP 21.0.0/21.0.1 schemas, so `from_dict`
silently dropped them, and `heat_transmission` re-derived each U from the §5.6
/§5.7/§5.11 construction-default cascade. The gov OPEN data routinely redacts
the backing insulation thickness, so that re-derivation mis-bills an insulated
element as uninsulated.
RdSAP 10 §5.1: a known element U-value (documentary evidence / the lodged
RdSAP output) is used directly in place of the construction-default cascade.
Per [[project_per_cert_mapper_validation_state]] the gov API carries RdSAP
OUTPUT, so the lodged U reproduces the official's element heat loss exactly.
Worst case in the 2026 sample: cert 7921-0052-0940-5007-0663, an age-C
"Pitched, sloping ceiling" (rc=8) top-floor flat lodging roof_u_value=0.2 with
no thickness. The cascade returned the uninsulated 2.30 W/m²K → SAP 56.9 vs
lodged 80 (-23.09, the single largest error in the sample). The roof override
alone recovers ~15 SAP; the wall override (lodged 0.34 vs cascade) closes the
rest of this cohort.
Override applies to the MAIN wall only (alt-wall sub-areas keep their own
per-area U) and the part's floor=0. Fires only when the rare field is present
(9 of 909 computed certs), so the Summary path — which never lodges these
API fields — is untouched.
API gauge: 67.1% → 67.7% within-0.5, mean|err| 1.024 → 0.992.
Worksheet harness: 47/47, 0 divergers (unchanged).
Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>
The §5.16 Table 22 thermal-mass-parameter (TMP) "always low-mass" set was
{timber 5, cob 7, park home 8}. But wall_construction code 8 is OVERLOADED by
the same gov-API/calc code-space divergence as the wall-U fix: the Summary
path's "PH" mapping uses 8 for park home, while the gov-EPC API enum uses 8
for SYSTEM BUILD (Summary system build = code 6). So every API system-built
cert was mis-rated as low-mass 100 kJ/m²K instead of masonry 250 (Table 22
lists system build as masonry — PDF p.48, line "System build 250...").
A too-low TMP shortens the §7 time constant tau = Cm/(3.6·H), over-cutting
the temperature reduction so mean internal temperature is UNDER-stated →
space-heating demand under-stated → SAP over-rated. This was the cause of the
uninsulated system-built over-rate cluster (n=9 gas-boiler certs at signed
+2.39 vs cavity +0.43 / solid-brick +0.08 at the same bands — a system-built-
specific anomaly with a spec-correct wall U).
Fix: drop 8 from the always-low set and gate it on `property_type` — code 8 is
the low-mass park-home value only when the dwelling really is a park home,
otherwise it is gov-API system build and keeps masonry 250. Disambiguated by
the same `property_type == "park home"` signal used elsewhere in the cascade.
Worksheet harness UNAFFECTED (47/47, 0 divergers): the Summary path uses code
6 for system build and code 8 only for genuine park homes (which stay
low-mass via the property_type gate). API gauge 65.3% -> 67.1% within-0.5
(mean|err| 1.059 -> 1.024, signed +0.050 -> -0.002). The uninsulated
system-built cluster collapses +2.82 -> +0.28 signed (0/11 -> 7/11 within
0.5). 2 AAA tests (parametrised code-8 system-built -> 250; park-home
property -> 100). pyright net-zero.
Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>
