Three more pre-existing failures (present at 9ee38211, before this branch's
recent commits; same family as the orchestration multi-measure re-pin) —
golden-cert plan expectations that predate the ASHP generator (ADR-0025)
and the optimiser folding forced dependencies into candidate gain (ADR-0016):
- test_console: a multi-measure plan now leads with air_source_heat_pump,
not cavity_wall_insulation (which is dropped — its forced ventilation makes
the pair net-negative). Assert a measure actually in the package.
- test_report 0330: package is now {solid_floor_insulation, air_source_heat_
pump}; cavity_wall + forced mechanical_ventilation correctly excluded.
- test_report 0036: gain-maximising package is now {solid_floor_insulation,
low_energy_lighting}.
Same verified-correct optimiser evolution as 077e3a39 (cavity_wall +2.9 SAP
alone but its forced fabric→ventilation dep drags the pair net-negative).
Re-pin to the actual packages + their trigger fields; the forced wall→vent
edge stays covered by test_measure_dependency / test_optimiser.
Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>
The optimiser-package expectation was stale: it predated the optimiser
folding a triggered measure's forced dependency into its candidate gain
(ADR-0016). The run considers ALL measures (considered_measures defaults
to None — no restriction), so once the ASHP bundle became SAP-beneficial
(ADR-0025) the gain-maximising package shifted.
Verified the new package is CORRECT, not a regression: on the test EPC,
cavity-wall insulation earns +2.9 SAP alone but its forced fabric→
ventilation dependency (ADR-0016) drags the wall+ventilation pair to a
NET −1.8 SAP (−0.9 on top of the ASHP package), so the gain-maximising
Optimiser correctly excludes the wall and its forced ventilation. Update
the expected set to {air_source_heat_pump, suspended_floor_insulation,
low_energy_lighting, secondary_heating_removal} and drop the wall/vent-
specific assertions — the forced wall→ventilation edge is covered by
test_measure_dependency / test_optimiser; this integration test keeps its
end-to-end optimise→persist→telescope coverage on the chosen package.
Pre-existing failure (present before this branch's recent commits), outside
the handover regression gate.
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>
The HHR-storage HeatingOverlay (ADR-0024) added an off-peak electric
immersion cylinder but never set `immersion_heating_type`, so the overlaid
cert left it None. The calculator then could not resolve `immersion_single`
for the SAP 10.2 Table 13 HW high-rate split and billed hot water 100% at
the off-peak low rate — £127.41 vs the relodged after-cert's £169.39,
overstating the overlay's SAP by +1.26 (CO2/PE matched, isolating it to the
HW cost path).
Add `immersion_heating_type` to HeatingOverlay, route it through
`_fold_heating` (it lives on `sap_heating`), and set it to 1 (single
off-peak immersion) on the HHR overlay to match the relodged reference.
Closes both `test_hhr_storage_overlay_reproduces_the_relodged_after_*`
cascade pins (electric-storage and no-system befores share the after).
Pre-existing failure (present before this branch's recent commits), outside
the handover regression gate. Full modelling suite 220 pass, pyright net-
zero.
Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>
End-to-end API-path regression pin for the battery behaviour validated by
the user-simulated Elmhurst worksheet pair (cert 001431 "simulated case
35/36", 5 kWh, export-capable, mains-gas, standard tariff). The official
SAP rating ("10a. Fuel costs - using Table 12 prices") values PV used-in-
dwelling and PV exported identically at 13.19 p/kWh (export code 60 ==
import code 30, ADR-0010), so a battery only redistributes PV between two
equally-priced lines: worksheet PV credit (252) = -455.6458 and SAP (258)
= 88.0859 are IDENTICAL with/without the battery (ΔSAP = 0).
Two tests over the committed RdSAP-21.0.1 corpus:
- standard tariff (meter 2): toggling the battery holds continuous SAP
EXACTLY constant, while at least one cert's primary energy DOES respond
(proving the App-M1 §3c β-split is wired, not a dropped battery).
- off-peak tariff (meter != 2): the battery STRICTLY raises SAP, because
self-consumed PV displaces high-rate import (15.29) above the 13.19
export credit — confirming the standard-tariff neutrality is a price
coincidence, not a no-op.
Guards table_32 export price (code 60) and the battery β-split against
silent regression. Complements the unit-level β tests in
test_photovoltaic.py.
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>
Adds a committed integration test driving the full API path — raw gov-EPC
response → from_api_response → cert_to_inputs → calculate_sap_from_inputs —
across all 1000 certs in the in-repo RdSAP-21.0.1 corpus, and pins the
aggregate accuracy of our continuous SAP (plus CO2 and primary energy)
against each cert's lodged figures. Mirrors scripts/eval_api_sap_accuracy.py
but runs in CI off the committed corpus (~2s, no /tmp sample needed).
Scoped to RdSAP-21.0.1 — the SAP 10.2-era schema whose lodged rating uses the
same methodology we compute (a fair target). Pre-SAP10 schemas (17.x-20.0.0)
lodge SAP 2012 ratings and are out of scope (guarded for mapping only by
test_mapper_corpus.py).
Current: SAP within-0.5 = 65.0%, MAE = 1.174 (tight floor/ceiling — the
optimised gauge). CO2 MAE = 0.27 t/yr (bias +0.17) and PE MAE = 14.6
kWh/m2/yr (bias +8.9) are reported + loosely guarded: cost is well-calibrated
but CO2/PE both run ~+5-10% high (uniform across fuels — a systematic
CO2/PE-factor or scope gap, not yet investigated). Thresholds ratchet as
slices tighten each metric.
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>
Orchestrator runs recommend_secondary_heating_removal; report._triggers_for
explains it via the lodged secondary_heating_type; harness catalogue + ARA seed
price it. Re-pins the golden/integration plans it shifts: it is a cheap (\£250)
SAP lever, so on gas-main certs lodging an electric secondary (691) it displaces
the \£12k ASHP (0330, 0036) or joins the all-beneficial-measures package (000490,
where its marginal SAP is 0 under the category-4 ASHP but the heater is still
physically removed). Consistent with the optimiser's existing kitchen-sink
package behaviour.
Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>
Two cascade tests on the worksheet-pinned 001431 build_epc() (the user's
before/after Summary PDFs trip the documented 001431 window-extraction bug, so
the repo's sanctioned 001431 baseline is used instead):
- electric-storage main (code 402) + secondary 691: removal reproduces the
secondary-removed cert at delta 0 — RdSAP §A.2.2 re-forces a default secondary,
matching the user's F35→F35 example;
- gas combi main (code 104) + secondary 691: removal strictly raises SAP
(74.22→77.61) — the Table 11 fraction reallocates to the cheaper main.
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>
Flat per-dwelling decommission price (sample_catalogue \£250) + 0.25 contingency
(covers unknown heater count / hard-wired-vs-plugged / repaint extent). The JSON
repo joins the contingency from config, proven by the new repo test. No composite
Products machinery — a lodged secondary is one roughly-fixed job, not room-scaled.
Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>
recommend_secondary_heating_removal offers one standalone Option that clears the
lodged secondary system. Eligibility is purely physical (offer iff
sap_heating.secondary_heating_type is set) — no effectiveness gate, since a
lodged secondary is a fixed emitter per RdSAP (portables are ignored), and the
electric-storage §A.2.2 no-op is the Optimiser's call (ADR-0028 decisions 1-2).
Priced at a flat per-dwelling decommission cost, not room-scaled.
Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>
The first overlay surface that sets fields to *absent* rather than to a
target state: _fold_secondary_heating clears sap_heating.secondary_heating_type
+ secondary_fuel_type, so the calculator's Table 11 secondary-fraction split
(SAP 10.2 §9a) routes 100% of space heating to the main. On an electric-storage
main RdSAP §A.2.2 re-forces a default secondary, making removal a no-op there —
left to the Optimiser to de-select (ADR-0028 decisions 2-3).
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>
`_CYLINDER_SIZE_CODE_TO_LITRES` held only codes 2/3/4 (Normal/Medium/Large →
110/160/210 L); codes 5 (Inaccessible) and 6 (Exact) fell through to None,
so the Table-13 high-rate fraction AND the cylinder storage loss were skipped
for those certs (20 code-6 certs in the API sample).
Per RdSAP 10 Specification (10-06-2025) §10.5 Table 28 (PDF p.55):
- Code 6 "Exact": use the lodged measured volume. The gov API carries it in
`cylinder_size_measured` (e.g. 150 L) — now plumbed through the 21.0.0/21.0.1
schema → mapper → `SapHeating.cylinder_volume_measured_l`.
- Code 5 "Inaccessible": 210 L if off-peak electric dual immersion, 160 L from
a solid-fuel boiler, otherwise 110 L (n=0 in the current sample, but
spec-complete).
New `_cylinder_volume_l_from_code` centralises Table 28 resolution and replaces
the three raw-dict call sites (`_hot_water_cylinder_volume_l`, the cylinder
storage-loss path, and the PCDB performance check) so all three honour codes
5/6 identically. `_cylinder_inaccessible_volume_l` applies the code-5 context
rule via the existing immersion/off-peak-meter/solid-fuel-boiler detectors.
Worksheet harness UNAFFECTED (47/47, 0 divergers): the Summary path lodges
neither code 5/6 nor a measured volume. API gauge: within-0.5 64.4% -> 65.1%
(mean|err| 1.085 -> 1.075) — the 20 code-6 certs now size their cylinder from
the measured volume. 4 AAA tests (code 6 measured; code 5 solid-fuel/default/
off-peak-dual-immersion). pyright net-zero.
Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>
The main-wall `u_wall(...)` call dropped the `dry_lined` kwarg, so the RdSAP 10
§5.7/§5.8 (PDF p.40-41) Table 14 dry-lining adjustment — U_adj = 1/(1/U₀ +
0.17) for a dry-lined (incl. lath-and-plaster) uninsulated wall — was never
applied to any main wall, even when the cert lodged `wall_dry_lined=Y`. The
ALTERNATIVE-wall path already passes `dry_lined` (line 1367); this one-sided
omission billed every dry-lined main wall at the un-adjusted (too-high) U →
wall heat loss too high → SAP under-rated.
Per-cert: a solid-brick (construction 3) band-A 230 mm main wall computes
U₀=1.70; dry-lined it is 1/(1/1.70+0.17)=1.32 — we were 22% too high. Across
the API gov-EPC sample the dry-lined `wall_construction=3` (solid brick)
sub-cohort sat at 10% within-0.5 / signed -1.33.
Fix: pass `dry_lined=bool(part.wall_dry_lined)` to the main-wall `u_wall`
call, mirroring the alt-wall path. `part.wall_dry_lined` is already plumbed
(Optional[bool], None → False). The three dry-lining branches in `u_wall`
(stone §5.6, solid-brick-by-thickness §5.7, generic uninsulated bucket §5.8)
are all spec-correct and already worksheet-validated (the bucket-0 cavity
case against cert 7700 age-C → 1.20).
Worksheet harness UNAFFECTED (47/47, 0 divergers): the Elmhurst/Summary
extractor only captures dry-lining for ALTERNATIVE walls (Summary §7), never
the main wall, so `part.wall_dry_lined` stays None on that path — this is a
pure API-path improvement. API gauge: within-0.5 60.1% -> 64.4% (mean|err|
1.163 -> 1.085, signed -0.097 -> +0.049). Both affected buckets improved
with no overshoot: solid brick (wc=3) 50% -> 57% within-0.5; cavity (wc=4,
dry-lined via the §5.8 bucket-0 path) 68% -> 72%.
Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>
A flat accessed via an unheated corridor/stairwell assumes a draught lobby
is present, so SAP 10.2 §2 line (13) = 0.0 rather than the 0.05 no-lobby
infiltration penalty. Per RdSAP 10 Specification (10-06-2025, p.30, "Draught
lobby"): "add infiltration 0.05 if draught lobby is not present, or use 0.0
if present. ... Flat or maisonette: Assume draught lobby if entrance door is
facing corridor (heated or unheated) or stairwell."
Signal: a SHELTERED alternative wall (the RdSAP §5.9 wall-to-unheated-corridor
surface) is the evidence that the flat's entrance faces a corridor — the same
evidence the corridor door (Table 26 U=1.4) rides on. New helper
`_has_sheltered_corridor_wall` factors that check out of `_corridor_door_count`
and gates `_has_draught_lobby`. Houses and exposed-gable flats (no sheltered
alt wall) keep the lodged value / "assume no lobby if cannot be determined"
default, so the §2 cascade is unchanged for every non-corridor dwelling.
The cascade previously added the 0.05 penalty unconditionally, over-counting
(16)/(18)/(21) by 0.05 ACH. On simulated case 34 (cert 001431 storage flat)
this lifted effective air change (25)m from the worksheet's monthly 0.572-0.638
to 0.574-0.668, over-counting space-heating demand (98) by +46.3 kWh/yr
(+0.41%) -> SAP -0.18. Closing it lands (25)m exactly on the worksheet (avg
0.6024) and (98) at 11356.3 vs ws 11357.2:
case 34 SAP 35.1325 -> 35.3130 vs ws 35.3094 (Δ -0.1769 -> +0.0036)
Guard-rails held (both improved): worksheet harness 47/47, 0 divergers (the
other corridor flat, cert 2474, -0.32 -> -0.02); API gauge 60.0% -> 60.1%
within 0.5, mean|err| 1.167 -> 1.163.
Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>
A door opening to an unheated corridor/stairwell takes U=1.4 W/m²K (RdSAP 10
Table 26, p.51 — any age band) instead of the 3.0 external-door default, and
its area deducts from the SHELTERED wall, not the main wall (RdSAP §3.7,
p.18: "the door of a flat/maisonette to an unheated stairwell or corridor
... is deducted from the sheltered wall area"). The cascade previously
billed every door at the external U on the main wall.
Signal: a SHELTERED alternative wall (`is_sheltered`, the RdSAP §5.9
wall-to-unheated-corridor surface, already modelled) is the evidence that
the dwelling is accessed via an unheated corridor, so one lodged door opens
to it. `_corridor_door_count` returns 1 when a sheltered alt wall is present
and >=1 door is lodged, else 0 — so the door channel is unchanged for every
non-corridor dwelling (houses, exposed-gable flats). `heat_transmission_
from_cert` gains a `corridor_door_count` param (default 0): it splits the
door area into external (main wall, age-default U) + corridor (sheltered
alt wall, U=1.4), threading the corridor door's area into that wall's
opening deduction and billing it at 1.4.
Validated on TWO faithful worksheets: simulated case 34 (cert 001431
storage flat — doors 8.14 exact, fabric 207.47 ≈ ws 207.48) and the
long-standing worksheet-harness diverger cert 2474 (−0.87 → −0.32, the
"space-demand thread" was the dropped corridor door). The worksheet harness
is now 47/47 with ZERO divergers.
API SAP gauge: 57.6% → 60.0% within 0.5; mean|err| 1.185 → 1.167; signed
−0.165 → −0.115 — ~22 sheltered-corridor flats were a systematic gap.
Regression gate green (3 pre-existing fails unrelated); pyright net-zero.
Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>
Don't offer a like-for-like gas boiler swap to a dwelling whose existing gas
boiler is already at least as efficient as the new condensing boiler (SAP 10.2
Table 4b codes 102/104 = 84% winter) — it gains nothing, and the dwelling gets
the tune-up (cylinder + controls) instead. `_already_condensing` compares the
existing code's Table 4b winter efficiency to 84%; a non-Table-4b code (solid
fuel) has no comparable efficiency and is never treated as already-condensing.
The gate is GAS-ONLY: a non-gas boiler → gas is a fuel switch whose value (cost
/ carbon) is not captured by winter efficiency, so oil/LPG/coal → gas is never
suppressed on efficiency grounds (only gated on the mains-gas connection).
This correctly demotes the gas-with-cylinder example (cert lodges code 114
"Regular, condensing", 84% winter) to a tune-up case — confirming that 114→102
is ~0 boiler-efficiency gain in both our calc and Elmhurst (both Table 4b 84%);
Elmhurst's uplift there came from the cylinder + flue, not the boiler. The
boiler-with-cylinder overlay stays validated by the lpg pin (code 115, non-
condensing + cylinder) and by recasting the 114 fixtures' code to a pre-1998
non-condensing boiler (110) in the boiler tests — the overlay overwrites the
code to 102 regardless, so only eligibility changes, not the delta-0 result.
New tests: an already-condensing gas boiler yields no boiler upgrade (but a
tune-up); an oil condensing boiler is not gated (the fuel switch survives).
Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>
SAP 10.2 Table 12a (PDF p.191) is titled "High-rate fractions for systems
using 7-hour and 10-hour tariffs"; its "Immersion water heater" row lists
the tariff as "7-hour or 10-hour" only, routing to Table 13. An 18-hour or
24-hour tariff is OUTSIDE the table's scope — it provides at least 18
hours/day at the low rate, more than enough to heat any immersion cylinder
off-peak, so the high-rate fraction is 0 (all DHW billed at the low rate).
`electric_dhw_high_rate_fraction` previously mapped 18-/24-hour to the
10-hour equations (returning ~0.10 for a 110 L dual immersion) on an
over-literal reading of Table 13 Note 1 ("at least 10 hours"). The Elmhurst
dr87 worksheet for solid fuel 5 (cert 001431: 18-hour meter, 110 L dual
immersion, WHC 903) refutes that: HW (245) high-rate = 0.0 kWh, (246)
low-rate = 100%. Table 12a's title bounds the table to the two named
tariffs; 18-/24-hour fall outside it.
Resolves the Table-13 blocker on the immersion-extractor fix: once the
Summary extractor captures the dual immersion, the 18-hour solid-fuel
corpus certs stay at high_frac=0 (matching their worksheets) instead of
regressing to the 10-hour-column 0.10.
API SAP eval unchanged: 57.6% within 0.5, mean|err| 1.185, signed -0.165
(the cached sample has no 18-hour WHC-903 certs; one 24-hour cert shifts
sub-threshold). Regression gate green (3 pre-existing fails unrelated).
Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>
SAP 10.2 §9.4.9 (PDF p.32) verbatim: "A cylinder thermostat should be
assumed to be present when the domestic hot water is obtained from a heat
network, an immersion heater, a thermal store, a combi boiler or a CPSU."
RdSAP 10 Table 29 (p.56) points the no-access default at this rule.
The storage-loss Table 2b temperature factor previously read only the
lodged `cylinder_thermostat` ("Y") — so an unlodged thermostat always took
the ×1.3 absent-penalty, over-stating storage loss by 30%. New
`_cylinder_thermostat_present` assumes it present when DHW is from a heat
network, WHC 903 (immersion), or a direct-acting electric boiler (SAP code
191 — electric-resistance, immersion-equivalent).
Found via the worksheet-folder harness: cert 2474-3059-4202-4496-3200
(Summary path: WHC 901, main SAP 191, electric, no lodged cylinder stat)
diverged −1.86 from its dr87 worksheet. The worksheet lodges (53)
temperature factor 0.6000 (present) and "add cylinder thermostat (SAP
increase too small)" — already assumed present. Fix lands HW output (64)
2701.99 → 2323.88, EXACT to the worksheet; 2474 −1.86 → −0.87 (residual is
a separate space-demand fabric thread). No other worksheet in the 47-cert
harness moved.
API eval within-0.5 56.9% → 57.6%; mean|err| 1.197 → 1.185; signed
−0.202 → −0.165. Regression green (only pre-existing fails); goldens +
heating corpus unaffected.
Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>
SAP 10.2 Table 3 (PDF p.160) verbatim: "For heat networks apply the
formula above with p = 1.0 and h = 3 for all months." The primary
circulation hours for a heat-network main are fixed at h=3 winter and
summer, independent of the cylinder-thermostat / separate-timing
lodgement that selects the h=5/h=11 rows for boiler systems.
`primary_loss_monthly_kwh` / `primary_circuit_hours_per_day_table_3` gain
a `heat_network` flag (→ (3, 3)); `_primary_loss_override` passes
`_is_heat_network_main(main)`. p=1.0 was already pinned via
`_HEAT_NETWORK_PIPEWORK_INSULATION_FRACTION`; only the hours were wrong.
Before, cert 8536 routed through the h=5/3 row because its community
biomass DHW fuel (31) collides with electricity code 31, so
`_separately_timed_dhw` returned False. The Table 3 heat-network rule
overrides that path: 8536 primary loss (59) 335.81 → 273.90, EXACT to
the faithful case-32 worksheet (storage (56) 376.58 also matches 376.94).
API eval within-0.5 57.0% → 56.9% (one offsetting-error cert crosses
out; signed err −0.205 → −0.202). Applied spec-uniformly per the
determinism principle — the heat-network primary hours are unambiguous.
Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>
A heat-network main with DHW from the network and no lodged cylinder was
billed the Table 3a keep-hot 600 kWh/yr combi loss (cat 6 sat in
`_TABLE_3A_COMBI_LOSS_MAIN_HEATING_CATEGORIES`). A heat network is not a
combi boiler — SAP 10.2 §4 line 7702 says combi loss is 0 for non-combi
systems.
SAP 10.2 p.24 "Heat networks" (c): when neither a PCDB Heat Interface
Unit nor a lodged cylinder applies, "a measured loss of 1.72 kWh/day
should be used, corrected using Table 2b. This is equivalent to a
cylinder of 110 litres and a factory insulation thickness of 50 mm".
RdSAP 10 Table 29 (p.56): a cylinder thermostat is assumed present when
DHW is from a heat network (Table 2b temperature factor 0.60).
New `_apply_heat_network_hiu_default_store` rebinds the 110 L / 50 mm-
factory store (thermostat present) onto a heat-network DHW cert with no
cylinder and no PCDB index, mirroring `_apply_rdsap_no_water_heating_
system_default`. The injected store routes storage loss (56) ≈ 376.7
kWh/yr (= 1.72 × 0.60 × 365) + primary loss (59) through the existing
machinery and zeroes the combi (61) loss via the has_hot_water_cylinder
gate. Verified against the user's faithful case-32 worksheet: storage
(56) 376.58 vs worksheet 376.94.
Cert 8536 storage 0→376.6, combi 600→0. API eval within-0.5 56.8% →
57.0%; signed err −0.218 → −0.205. Reworked
`test_heat_network_main_with_hw_from_main_dlf_scales_hot_water_kwh` to
assert the DLF scaling directly (fuel ÷ §4 output = 1.41) since the old
two-cert baseline premise (both combi-600) no longer holds.
Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>
Replace the flat placeholder scalars (boiler £3000; tune-up £500/£900) with a
per-dwelling composite cost, mirroring the ASHP architecture (ADR-0025): a
`HeatingRates` table (data, `heating_rates.json`), typed `BoilerCostInputs` /
`TuneUpCostInputs`, pure `Products.boiler_bundle_cost` / `tune_up_cost`, and
modelling-layer interpreters that read the dwelling into those inputs.
The cost mirrors the Simulation Overlay component-for-component, sharing the
controls + cylinder pricing across both options:
- tune-up (standard) = standard controls + cylinder fixes
- tune-up (zone) = zone controls + cylinder fixes
- boiler upgrade = £3200 all-in + standard controls (only when the upgrade
fired a controls change) + cylinder fixes
Standard controls are priced INCREMENTALLY — only the parts missing to reach
SAP 2106 (programmer £120 / room thermostat £150 / TRV £35×radiators), read
from a Table 4e Group-1 feature map so a dwelling that already has a room
thermostat + TRVs is only charged the programmer. Zone controls are a full
smart kit (hub £205 + smart TRV £50×radiators) — the smart TRV is itself the
room sensor, so there is no separate per-room sensor line. Cylinder fixes:
jacket £50 (when under-insulated) + thermostat £150 (when absent). The boiler
is a like-for-like wet swap (no radiators/flue/pipework — eligibility already
requires an existing wet boiler), so those dead-code extras are not modelled.
Figures are research-validated 2025/26 UK installed costs (legacy Costs.py
lineage); fully-loaded totals with one contingency on top (Model B, not the
legacy VAT/preliminaries engine). Contingency: boiler 0.26; tune-ups 0.10
(was a 0.15 placeholder). ADR-0027 records the design; CONTEXT.md's Heating
Eligibility entry updated to cover the partial boiler/tune-up family + composed
cost. Products cost pins (delta<=1e-9) + interpreter tests + generator
composite-cost assertions.
Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>
The GOV.UK API lodges a junk empty leading building part (all fields
None) ahead of the real Main Dwelling on some certs. Four sites in
cert_to_inputs.py read `sap_building_parts[0].construction_age_band` →
got None → silently dropped the dwelling age band. New `_dwelling_age_band`
helper takes the first part that lodges a band (a no-op for normal certs
where [0] is the Main part).
Closes two age-band-keyed defects on the 5 affected certs:
- SAP 10.2 Table 12c (p.193): the heat-network Distribution Loss Factor
defaulted to the K-or-newer 1.50 instead of the dwelling's true band
(cert 8536-0929-6500-0815-7206 is age A → 1.20), inflating distribution
loss by 30%.
- RdSAP 10 §4.1 Table 5 (p.28): the empty band ("") fell through the
age-band branches to the H–M habitable-rooms branch, defaulting in
phantom extract fans. The true band A correctly yields 0 fans
(bands A–E → 0).
Cert 8536: 31.76 → 41.12 vs lodged 39 (was −7.24, now +2.12). API eval
mean|err| 1.197 → 1.192, signed −0.229 → −0.218; headline within-0.5
holds at 56.8% (8536 lands at +2.1, a documented overshoot vs the
faithful case-31 worksheet — separate slice).
Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>
