SAP 10.2 §4 line 7690 (full spec PDF p.136) defines the cylinder storage
loss cascade for any cert with a hot water cylinder lodged:
(54) = V × L × VF × TF (Table 2 absence-of-declared-loss branch)
(55) = (54) (no manufacturer's declared loss)
(56)m = (55) × n_m (per spec, n_m = days in month)
where
L = Table 2 (PDF p.158) Note 1 formula for the lodged insulation type
(factory-insulated cylinders: 0.005 + 0.55/(t+4.0); loose jacket:
0.005 + 1.76/(t+12.8))
VF = Table 2a (PDF p.158) Note 2 closed form (120/V)^(1/3)
TF = Table 2b (PDF p.159) base 0.60 for indirect / electric-immersion
cylinders, × 1.3 if no thermostat, × 0.9 if DHW separately timed
Prior, `water_heating_from_cert` hard-coded `solar_storage_monthly_kwh
= zero12` and `_water_heating_worksheet_and_gains` had no path to
populate it. The new `cylinder_storage_loss_monthly_kwh` helper in
`worksheet/water_heating.py` exposes Tables 2 / 2a / 2b as small typed
functions plus a composite; the cert-side orchestrator in
`rdsap/cert_to_inputs.py::_cylinder_storage_loss_override` resolves
the lodged cylinder fields and injects the override.
Code → litres mapping ground-truthed against worksheet (47) line refs
in /sap worksheets/Additional data with api/<cert>/dr87-*.pdf for the
7-cert ASHP cohort: code 3 → 160 L (Medium, 6 certs) and code 4 →
210 L (Large, cert 9418). Codes 2 / 5 / 6 (Normal / Inaccessible /
Exact) absent from the cohort and not yet mapped.
Cylinder insulation type code → "factory_insulated" mapping
(_CYLINDER_INSULATION_TYPE_FACTORY = 1) ground-truthed against all 7
ASHP cohort worksheets ("Foam" lodgement → SAP 10.2 Table 2 Note 2
"factory-insulated cylinder where the insulation is applied in the
course of manufacture irrespective of the insulation material used").
RdSAP §3 default table (PDF p.57) — "Hot water separately timed:
Post-1998 boiler: Yes" — applied to heat-pump main heating systems
(cat 4) per the cohort worksheet evidence.
Cert 0380 (Mitsubishi ASHP, 160 L factory 50 mm, thermostat + separately
timed) lands the spec formula at worksheet (56) Jan = 36.9530 kWh/month
(test pinned at 1e-4); HW kWh/yr 242.21 → 431.38, recovering ~189 kWh/yr
of cylinder loss the cascade was previously dropping.
Cohort regression: cert 0390-2954 (oil boiler + 160 L cylinder) tightens
PE residual -28.6783 → -27.5026 kWh/m² and CO2 residual -2.7640 →
-2.6570 t/yr — both move closer to the lodged values (improvement).
Re-pinned with a slice-102b note.
Closed boiler chain tests (001479, 0330, 9501) unaffected: those certs
lodge has_hot_water_cylinder=false so the override stays None and the
existing zero-storage-loss default fires.
Cert 0330 (mid-terrace boiler, Summary_000897.pdf) Summary path was at
Δ +0.4667 SAP vs worksheet 61.5993 because Ext1's flat roof fell through
`_ROOF_BY_AGE` (Table 18 column (1), pitched-roof "between joists"
defaults) to 0.40 W/m²K for age D — the spec value is 2.30 W/m²K from
column (3) "Flat roof" (RdSAP 10 spec page 45).
RdSAP 10 §5.11 Table 18 column (3) verbatim:
Age A,B,C,D → 2.30; E → 1.50; F → 0.68; G → 0.40; H,I → 0.35;
J,K → 0.25; L → 0.18; M → 0.15.
Footnote (a): "If the roof insulation is 'none' use U = 2.3 (all roof
types, except for thatched roofs)" — confirms the col-3 entries for
old ages are the uninsulated row, applied because cert 0330's Ext1
lodges "Flat" construction with no measured insulation thickness.
Changes:
- `_FLAT_ROOF_BY_AGE` added in rdsap_uvalues.py
- `u_roof` gains `is_flat_roof: bool = False` parameter
- `heat_transmission_from_cert` detects flat roofs from
`part.roof_construction_type` ("flat" substring) and routes through
the new column.
Effect on baseline:
- cert 0330 Summary chain test: RED Δ+0.4667 → GREEN at 1e-4 (worksheet
total fabric heat loss 237.7549 W/K matches cascade to 4 d.p.)
- cert 001479 Layer 4 chain test: unchanged (Main pitched, no flat
components)
- cohort certs 000477/000516: unchanged (no flat roofs)
- golden cert 0300-2747-7640-2526-2135: SAP residual +1 → 0 (improved),
Ext1 is genuinely flat; pe/co2 residuals re-pinned. The dwelling has
the same Main-pitched + Ext1-flat shape as cert 0330; same fix.
Co-Authored-By: Claude Opus 4.7 <noreply@anthropic.com>
Locality of reference — SAP-specific docs, specs, and runtime data
now live alongside the calculator that consumes them, mirroring the
prior packages→domain layout moves.
Move targets:
- Narrative MDs → domain/sap10_calculator/docs/
NEXT_AGENT_PROMPT.md, HANDOVER_NEXT.md, SAP_CALCULATOR.md
- Spec PDFs → domain/sap10_calculator/docs/specs/
RdSAP 10 Specification 10-06-2025.pdf
PCDF_Spec_Rev-06b_12_May_2021.pdf
sap-10-2-full-specification-2025-03-14.pdf
sap-10-3-full-specification-2026-01-13.pdf
- PCDB runtime data → domain/sap10_calculator/tables/pcdb/data/
pcdb10.dat (8.3MB) + 7× pcdb_table_*.jsonl (18MB total)
Path code rewrites (load-bearing):
- tables/pcdb/__init__.py: replaced parents[4]/'docs'/'sap-spec' with
Path(__file__).resolve().parent/'data' for Table 105 JSONL loading.
- tables/pcdb/postcode_weather.py: same rebase for the pcdb10.dat path
read by _postcode_climate_table().
- tables/pcdb/etl.py __main__: same rebase for the manual ETL invocation
(source + output_dir both now point inside the package).
- tests/test_pcdb_etl.py: _PCDB_DAT_PATH now derives from
parents[1]/'tables'/'pcdb'/'data' (was parents[3]/'docs'/'sap-spec').
Citation rewrites:
- 12 .py docstrings and 4 .md docs (ADRs + READMEs + narrative docs)
had `docs/sap-spec/<file>` strings rewritten to their new locations.
- Two cases where the catch-all sed misfired (an ADR-0009 line about a
PCDB extract; the pcdb __init__.py docstring about ETL output) were
hand-corrected to point at tables/pcdb/data/ rather than docs/specs/.
docs/sap-spec/ is now empty (will be removed in a follow-up sweep or
left as a vestigial empty dir for future repurposing). ADRs 0009 and
0010 remain at docs/adr/ — they're part of the chronological
cross-cutting decision log, not calculator-specific narrative.
Verified:
- Calculator's 1e-4 production gate
(test_api_001479_full_chain_sap_matches_worksheet_pdf_exactly) GREEN.
- Wider sweep (domain/sap10_calculator/ + domain/sap10_ml/): 1654
passed / 20 failed — exact pre-move baseline. All 20 failures
pre-existing (10 hand-built skeleton + 4 cohort chain + 6 cohort
diff).
- Pyright net-zero on the 4 touched runtime/test files (0 errors)
and unchanged on heat_transmission.py (13) / cert_to_inputs.py (35) /
mapper.py (33).
Co-Authored-By: Claude Opus 4.7 <noreply@anthropic.com>
Sibling migration to the sap10_calculator move — `domain.ml` now lives
at the root-level layout (`domain/sap10_ml/`) matching the pattern
already used by `domain.addresses`, `domain.tasks`, `domain.postcode`,
and `domain.sap10_calculator`.
Changes:
- `git mv packages/domain/src/domain/ml → domain/sap10_ml` (19 files;
history preserved).
- Subpackage rename: `domain.ml` → `domain.sap10_ml`. 32 references
rewritten across .py and .md files: 11 internal + 21 external
(datatypes/epc/domain/mapper.py, 14 files in domain/sap10_calculator,
2 backend tests, 2 ADRs, 1 README, 1 design doc).
- Path-string updates: `pytest.ini` testpath
`packages/domain/src/domain/ml/tests` → `domain/sap10_ml/tests` so
ML tests stay in the default auto-discovered sweep. `CONTEXT.md`
also updated.
`packages/domain/src/domain/` is now empty — the workspace `domain/`
tree has been fully migrated. Together with the `domain/__init__.py`
deletions from the sap10_calculator commit (29ac35cc), `domain` is
now a single root-level namespace package with subpackages
{addresses, sap10_calculator, sap10_ml, tasks} + the standalone
`postcode.py` module.
Verified:
- Focused sweep (backend mapper-chain + sap10_calculator worksheet
e2e + golden fixtures): 99 passed / 19 failed — identical baseline.
- Wider sweep (all sap10_calculator + sap10_ml): 1654 passed / 20
failed (same pre-existing failures).
- domain/sap10_ml/tests: 210/210 PASSED at new path.
- Pyright net-zero: heat_transmission.py 13, cert_to_inputs.py 35,
mapper.py 33, rdsap_uvalues.py 1 (all unchanged from baseline).
Note: `packages/domain/pyproject.toml` still declares
`packages = ["src/domain"]` for the hatchling wheel — that target
directory is now empty and the wheel build is effectively a no-op.
Retiring the workspace package or repointing the wheel is a follow-up.
Co-Authored-By: Claude Opus 4.7 <noreply@anthropic.com>
