Model/docs/sap-spec/SPEC_COVERAGE.md

SAP 10.2 / RdSAP 10 Coverage Map

Tracks which sections of the SAP 10.2 specification are implemented in packages/domain/src/domain/sap/. Per ADR-0009 the calculator is built from the spec, not reverse-engineered from cert data. This doc is the worksheet-driven roadmap for what remains.

Updated 2026-05-21 after §8c (slices cf28eec4…f3797066), §8f (43cc16bc), and §9a single-main slices (2b5fc6a5…380b6781).

The canonical SAP10.2 algorithm lives in 2026-05-19-17-18 RdSap10Worksheet.xlsx at the repo root — each line ref (1)..(486) maps to a cell. The worksheet sub-modules under packages/domain/src/domain/sap/worksheet/ implement those line refs directly; Elmhurst worksheets validate end-to-end via tests/_elmhurst_worksheet_*.py.

Sections §§1–13 (the SAP worksheet)

§	xlsx rows	Topic	Module	Status	Notes / gaps
1	1–120 (approx)	Dimensions	worksheet/dimensions.py	Full	Porches, conservatories, RIR deferred per ADR-0009
2	121–206 (approx)	Ventilation	worksheet/ventilation.py	Partial	No mechanical ventilation (MVHR/MEV), no wind-shelter factor, no pressure-test override (worksheet lines 17-18), no AP4 override (worksheet line 19)
3	121–207	Heat transmission	worksheet/heat_transmission.py	Full (non-RR)	LINE_31/33/36/37 exact for both non-RR Elmhurst fixtures (000474, 000490). Suspended-timber + Table 20 exposed-floor routes wired. RR sub-areas (gable/slope/stud-wall) deferred until SapRoomInRoof carries them. Global y-factor (Table R2 per-junction deferred).
4	207–304	Hot water + Appendix J	worksheet/water_heating.py (new) + legacy domain.ml.demand.predicted_hot_water_kwh (calculator still calls this)	Happy-path done — see slice progress below. Worksheet-driven module lands line refs (42)..(65) for the combi-gas-boiler population (~70% of corpus). Cylinder + solar + renewables branches deferred. Calculator.py not yet wired to new module — next step.
5	Internal gains + Appendix L	worksheet/internal_gains.py	Full	Worksheet-driven (66)..(73), Table 5 Column A, Table 5a 9-row dispatch + heating-season mask, Appendix L L1-L12 with RdSAP §12-1 bulb defaults + Table 6d Z_L (light access factor). Wired into calculator.py via cert_to_inputs. Six Elmhurst fixtures conform end-to-end to ≤0.6% lighting / ≤0.2 W (73).
6	Solar gains + Tables 6b/6c/6d + Appendix U	worksheet/solar_gains.py	Full	Worksheet-driven (74)..(83). Table 6b g⊥ via manufacturer window_transmission_details first, Table 6b code lookup fallback; Table 6c FF by frame_material substring; Table 6d Z (heating column) by OvershadingCategory; roof windows pitched at RdSAP10 Table 24 default 45°; rooflights horizontal per §U3.2 p128. solar_gains_from_cert wired into cert_to_inputs + calculator.py. Six Elmhurst fixtures conform end-to-end to ≤5e-3 W on (83) + (84).
7	Mean internal temperature	worksheet/mean_internal_temperature.py	Full	Worksheet-driven (85)..(94) via mean_internal_temperature_monthly. Table 9c steps 1-9 sequential (per-zone η: (86) η_living at Ti=T_h1, (89) η_elsewhere at Ti=T_h2, (94) η_whole at Ti=(93)). Table 9b u-formula consumes weighted R for two-main case 1 (single-main is default). Wired into calculator.py + cert_to_inputs via two new CalculatorInputs fields. Six Elmhurst fixtures conform end-to-end to ≤5e-3 °C on all 9 line tuples + 2 scalars per month (588 assertions). Table 4e adj defaults 0 (cert-side mapping deferred — all 6 fixtures = 0); two-main case 2 (different parts heated separately) deferred.
8	Off-period temperature reduction	inline in mean_internal_temperature.py	Full	Table 9b implemented
8	Space heating requirement	worksheet/space_heating.py	Full	Worksheet-driven (95)..(99) via space_heating_monthly_kwh. Includes the Table 9c step 10 spec inclusion rule (Jun..Sep zeroed) on top of the < 1 kWh value clamp. (98b) Appendix H solar space heating defaulted to 0 (no Elmhurst fixture lodges a solar space heating system). Wired into calculator.py + cert_to_inputs via CalculatorInputs.space_heating_monthly_kwh. Six Elmhurst fixtures conform end-to-end on (95)/(97)/(98a)/(98c)/(99)/annual @ 5e-2..1e-1 kWh (looser than §6/§7's 5e-3 because LINE_84/93/94 fixture pins are 4-d.p. display-rounded and §8's 0.024·n_m·(L−ηG) amplifies that rounding).
8c	Space cooling requirement	worksheet/space_cooling.py	Full (no-AC zero-branch)	Worksheet-driven (100)..(108) via space_cooling_monthly_kwh. Table 10a η_loss with 8-dp γ rounding + L=0 sentinel; Table 10b Q_cool with Jun-Aug inclusion mask + post-f_C × f_intermittent 1-kWh clamp per spec line 10321. Internal temp hardcoded 24 °C. Wired into calculator.py (MonthlyEntry.space_cool_requirement_kwh + SapResult.space_cooling_kwh_per_yr) + cert_to_inputs via CalculatorInputs.space_cooling_monthly_kwh. Six Elmhurst fixtures all has_fixed_air_conditioning=False → (107), (108) ≡ 0 — ALL_FIXTURES asserts (101)/(103)/(106)/(107)/(108) per fixture; synthetic positive test (γ=1 closed-form) covers the algebra. Deferred: RdSAP cooled-area defaulting rule + cooling_gains_from_cert (drops Table 5a items per spec 10280) + Table 10c SEER → cooling fuel kWh + fuel cost cascade (first non-zero-cooling cert triggers this slice).
8f	Fabric Energy Efficiency (line ref (109))	worksheet/fabric_energy_efficiency.py	Full (rating-conditions transparency)	Spec line 7898: (109) = (98a) ÷ (4) + (108). fabric_energy_efficiency_kwh_per_m2_yr(...) is a single-scalar free function — no dataclass. Σ(98a) (pre Appendix H solar) added as SpaceHeatingResult.space_heating_requirement_kwh_per_yr so spec literal is honoured; for our corpus (98b)=0 so Σ(98a) = Σ(98c). cert_to_inputs precomputes FEE from local SpaceHeatingResult + SpaceCoolingResult; calculator passes through to SapResult.fabric_energy_efficiency_kwh_per_m2_yr. Six Elmhurst fixtures all (108)=0 → LINE_109 = LINE_99 exactly. §11 compliance conditions (different ventilation / HW / lighting / gains column) are deferred — current FEE is a rating-conditions transparency output, not a §11 compliance figure. Future §11 slice invokes the same function with §11-conditions upstream values.
9	Energy requirements per heating system (§9a worksheet block)	worksheet/energy_requirements.py	Full (single-main + Table 11 secondary)	Worksheet-driven (201)..(215) via space_heating_fuel_monthly_kwh. (211)m = (98c)m × (204) × 100 / (206) and (215)m mirror; Σ → annuals. EnergyRequirementsResult dataclass mirrors the full §9a worksheet shape with 16 fields incl. (203)/(205)/(207)/(209)/(213)/(221) zero-branch placeholders. cert_to_inputs precomputes and stashes on CalculatorInputs.energy_requirements composite slot; calculator's _solve_month reads precomputed (211)m/(215)m directly (stops doing q/η inline). SapResult adds main_2_heating_fuel_kwh_per_yr and space_cooling_fuel_kwh_per_yr flat scalars (both zero in scope A). Deferred: (203)/(205)/(207)/(213) two-main system (first multi-main cert) + (209)/(221) cooling SEER (Table 10c lookup — first fixed-AC cert) + (230a)-(230h)/(231) Table 4f pumps/fans breakdown + (236)/(237) Appendix Q items + ALL_FIXTURES LINE_206/(211)/(215) PDF-derived pins (blocked on PCDB — see Boiler / heat-pump efficiency Manufacturer override in Prioritised gap list).
10	Cooling (spec heading — same content as §8c worksheet block)	worksheet/space_cooling.py	Full (no-AC zero-branch)	See §8c row above.
11	FEE compliance conditions	worksheet/fabric_energy_efficiency.py (the function exists; §11 conditions don't run yet)	Partial	(109) formula exposed via fabric_energy_efficiency_kwh_per_m2_yr. Spec §11 conditions (lines 2152-2164: 2-4 extract fans, instantaneous-electric shower, 125 l/day water, 185 lm/m² lighting at 66.9 lm/W, column (B) heating gains, column (A) cooling gains, etc.) not implemented — only relevant for new-build compliance.
12	Total energy + fuel costs	calculator.py	Partial	Per-end-use cost split ✓; meter_type tariff routing ✓ (S-B15); PV cost credit ✓ (S-B19); standing charges not included (Table 12 note (a) says rating omits standing charge for std electricity tariff)
13	SAP rating	worksheet/rating.py	Full	Equations 7-9 verified against SAP 10.2 §13
14	CO2 + primary energy	calculator.py SapResult.co2_kg_per_yr	Partial	Single CO2 factor on main fuel; no per-end-use CO2 mixing; no primary energy calculation
15	Building regs	n/a	n/a	Not relevant to ratings

Appendices

Appendix	Topic	Status	Notes
A	Main + secondary heating identification	Not implemented	First main only; Table 11 secondary fraction missing — high-value gap
B	Gas/oil boilers + boiler interlock	Partial	Via Table 4b in domain.ml.sap_efficiencies.seasonal_efficiency
C	Community heating	Not implemented	Heat network certs handled by Table 4a codes 301-304 (efficiency only)
D	PCDB	Stubbed	Per ADR-0009 grill: NoOpPcdbLookup returning None; Session C bundles a CSV PCDB extract
E	Heat pumps	Partial	Category fallback to 2.30 for cat=4; no MCS installation factor (×1.39 GSHP); no flow temp adjustment
F	Electric CPSU	Not implemented	Rare
G	FGHRS / WWHRS / PV-diverter	Not implemented	Rare
H	Solar water heating	Partial	Boolean has_solar_water_heating reduces HW by 250 kWh; no actual collector calc
J	Hot water demand	Partial	See §4 row above
K	Thermal bridging	Partial	Using global y per age band (per ADR-0009 grill: per-junction Table R2 deferred)
L	Lighting	Full	Existing-dwelling fallback ✓
M	PV / wind / hydro generation	Partial	PV ✓ (S-B19); wind / hydro / micro-CHP not implemented
N	Micro-CHP	Not implemented	Rare
P	Electric storage heaters detail	Partial	Identified via codes 401-409; Table 12a high-rate fractions not exact (we use 100% off-peak per cert-calibration heuristic)
Q	Special features	Not implemented	One-off energy-use additions; rare
R	Reference dwelling	Not implemented	Only needed for compliance, not ratings
S	RdSAP procedures	Separate PDF (114pp)	Cert→inputs mapper in domain.sap.rdsap.cert_to_inputs ports key rules; many sections of RdSAP 10 not yet read
T	Improvement measures	Not relevant	Recommendation engine, not rating
U	Climate data	Full	Tables U1/U2/U3 + solar declination + Table U5 k1-k9

Prioritised gap list (by likely MAE impact)

1. Boiler / heat-pump efficiency Manufacturer override (PCDB integration) — MainHeatingDetail lodges the PCDB pointer (main_heating_index_number) but no scalar efficiency. With NoOpPcdbLookup (ADR-0009 grill outcome #1) still in place, cert_to_inputs falls back to the SAP10 Table 4a category default (typically 0.80 for gas boilers, SCOP 2.30 for heat pumps) on every cert. Per ADR-0010 §4 this accounts for ~19 SAP points of MAE on heat-pump certs and most per-cert variance on the 78 % of gas-boiler certs lodging main_heating_data_source=1 (PCDB-typical 0.88–0.94 vs 0.80 default). Directly visible on 000490 e2e: inputs.main_heating_efficiency = 0.80 vs an unverified PDF Manufacturer-declared figure that surfaced from a previous agent's notes — the actual PDF value cannot be confirmed without PCDB. Closing requires a real PCDB CSV ingest + PcdbLookup Protocol impl + precedence wiring in cert_to_inputs._main_heating_efficiency and _water_efficiency_with_category_inherit. Promoted to prerequisite under ADR-0010, not a section-sweep slice. §9a ALL_FIXTURES PDF-derived LINE_206/(211)/(215) pinning is blocked on this — until PCDB lands, §9a conformance is at the synthetic + cert-round-trip level only (no PDF cross-check).
2. Table 11 Secondary heating allocation — most boiler-main certs allocate 10% of space heating to a secondary system (often a less-efficient room heater on a different fuel). We model 0%. Likely +1-2 SAP-point bias on affected certs.
3. Wind-shelter factor on infiltration (§2 worksheet lines 19-21) — multiplies infiltration by 1 - 0.075 × sheltered_sides. We have no shelter input; assume 2 sheltered sides default. Net effect on infiltration ACH probably ~10%.
4. Table 12a high-rate fraction for off-peak dwellings — we currently bill 100% of E7 space heating at the low rate. Real spec says e.g. heat pumps on 7h tariff at 80% high-rate. Affects ~5% of certs.
5. Cylinder-loss factor cascade — currently uses simplified buckets in domain.ml.demand._STORAGE_LOSS_FACTOR. Spec has more precise interpolation rules from cylinder volume + insulation thickness.
6. Standing charges in cost — Table 12 note (a) gives the rule for when standing charges are included (energy use vs rating). May affect bias.
7. Per-junction thermal bridging (Table R2) — only relevant when assessor lodged junction-count data, otherwise global y is the spec answer for RdSAP-driven assessments.

Status now: 100-cert MAE 4.49, 300-cert MAE 5.45, bias near zero (±0.2). Worksheet-driven phase begins with Secondary heating Table 11 as the next slice.

§4 — slice progress (xlsx rows 207–304)

Line ref	Description	Status	Commit
(42)	Assumed occupancy N from Appendix J	✅	aff678e8
(42a)m	Mixer showers monthly	✅	1dcbdb28
(42b)m	Baths monthly	✅	dad7fbf3
(42c)m	Other uses monthly	✅	5cc68ab3
(43)	Annual avg	✅	702b1c6c
(44)m	Daily monthly total	✅	702b1c6c
(45)m	Energy content	✅	a3c687f1
(46)m	Distribution loss	✅	a3c687f1
(47)–(56)	Storage / HIU loss	Combi zero-branch only; cylinder paths deferred	—
(57)m	Dedicated solar storage	Combi zero-branch only; solar HW deferred	—
(59)m	Primary loss	Combi zero-branch only; boiler+cylinder deferred	—
(61)m	Combi loss	Table 3a row "time-clock keep-hot" only	bfba610b
(62)m	Total demand	✅	bfba610b
(63a-d)	WWHRS/PV/Solar/FGHRS reductions	Zero-only — non-zero paths deferred	feef8198
(64)m	Output from water heater	✅ (with max-clamp)	feef8198
(64a)m	Electric shower energy	Zero-only — non-zero path deferred	—
(65)m	Heat gains	✅	43da3ea0

Happy path closes both non-RR Elmhurst fixtures to <1e-3 kWh end-to-end on lines (42)..(65) (000474's PCDB-backed Table 3b combi loss is the one hand-lodged value).

Remaining §4 work

1. Orchestrator water_heating_from_cert(epc, ...) that wires the leaf functions, mirroring heat_transmission_from_cert for §3.
2. Integrate with calculator.py — replace the legacy domain.ml.demand.predicted_hot_water_kwh call.
3. End-to-end SAP score validation against the worksheets — the real e2e test the user has been asking for.
4. Cylinder + solar + renewables paths for full population coverage (cylinders, FGHRS, WWHRS, PV-diverter).
5. PCDB-backed Table 3b/3c combi loss for tested boilers (000474 sits here).

§5 — slice progress (xlsx rows 305–332)

Line ref	Description	Status	Commit
(66)m	Metabolic = 60 × N (Table 5 Col A)	✅	3ec56216
(71)m	Losses = -40 × N	✅	021f43ba
(69)m	Cooking = 35 + 7 × N	✅	984a5b18
(72)m	Water heating bridge (65)m × 1000/(24 × n_m)	✅	a4d6321f
(68)m	Appliances (L13/L14/L16a)	✅	0bc9eac3
(67)m	Lighting (L1-L12 with Z_L from Table 6d)	✅	50fd940a
(70)m	Pumps + fans (Table 5a 9-row dispatch)	✅	f77229e4
(73)m	Total internal gains + InternalGainsResult	✅	53aba133
—	internal_gains_from_cert orchestrator	✅	f81e744b
—	6-fixture ALL_FIXTURES conformance	✅	99e5c2cd
—	cert_to_inputs wiring + calculator.py wiring	✅	bf6a7e04
—	Rooflight Z_L=1.0 (Table 6d note 2)	✅	380115e2

Six Elmhurst fixtures conform end-to-end on §5 to ≤5e-3 W on every line — display-rounding territory across the board.

Remaining §5 work

1. Table 5a fan / PIV / HIU branches are implemented as leaf functions but not yet derived from cert inputs in internal_gains_from_cert. Pump dispatch is wired; non-pump rows always emit 0 W. MVHR / MEV correctly produces zero gain.
2. Per-window frame_material / glazing_type strings — current orchestrator uses cert numeric codes; needs a robust mapping for site-notes-sourced certs.
3. Rooflight derivation from cert — orchestrator accepts rooflight_total_area_m2 but cert_to_inputs doesn't yet detect rooflights (defaults to 0). Needs the SapWindow.window_location enum that's TODO'd in the domain model.
4. Column B reduced-gain forms (L12a / L16) for new-build DPER/TPER calculations — deferred until we onboard a new-build cert.

§6 — slice progress (xlsx rows 332–371)

Line ref	Description	Status	Commit
—	Table 6d Z-solar lookup (winter / heating column)	✅	da5909de
(74)..(81)	Per-orientation solar gain (N..NW)	✅	4b83e702
(82)	Roof windows — RdSAP10 Table 24 pitch 45° default, Z=1.0	✅	4b83e702
(82a)	Rooflights — SAP10.2 §U3.2 horizontal, Z=1.0	✅	4b83e702
(83)	Total solar gains 12-tuple	✅	4b83e702
—	RoofWindowInput + RooflightInput + SolarGainsResult	✅	4b83e702
—	solar_gains_from_cert orchestrator	✅	4b83e702
—	Manufacturer window_transmission_details cascade	✅	d56fef4d
—	6-fixture ALL_FIXTURES conformance (83) + (84) ≤5e-3 W	✅	377caea2
—	CalculatorInputs.solar_gains_monthly_w + per-month lookup	✅	376cdb6b
—	cert_to_inputs swap legacy _solar_gains_w → orchestrator	✅	cd2bd9ce
—	Delete _solar_gains_w + WindowInput + _window_inputs	✅	a0ce45c9

Six Elmhurst fixtures conform end-to-end on §6 to ≤5e-3 W on every month of (83) total solar gains and (84) total gains (the latter cross-checks §5 LINE_73 plus §6 LINE_83). 144 monthly assertions across 6 fixtures, all GREEN.

Remaining §6 work

1. Rooflight derivation from cert — cert_to_inputs passes rooflights=() because Elmhurst summaries lodge rooflights as window_location = "External wall"; needs the SapWindow.window_location enum work (also blocking §5 rooflight detection — common ticket).
2. Roof window detection from cert — same constraint as rooflights; orchestrator-side support is there (RoofWindowInput with pitch default), but the cert→inputs mapper has no signal to populate it.
3. Multi-window-type per orientation — orchestrator sums all windows of one orientation regardless of glazing type, matching the Elmhurst worksheet's per-orientation Σ. The xlsx repeats (74)..(82a) blocks per "window type" for diagnostic display; we collapse to per-orientation totals. Faithful per-type printout would need a richer result dataclass.
4. Table 6c metal frame factor — orchestrator ships 0.8 (spec); the deleted legacy lookup had 0.83 (silent bug). Frame-material strings outside metal/aluminium/wood/pvc/upvc/composite fall through to 0.7 default.

§7 — slice progress (xlsx rows 372–401)

Line ref	Description	Status	Commit
—	Per-zone η fix + MeanInternalTemperatureResult + mean_internal_temperature_monthly orchestrator	✅	fa49d7b9
(85)	T_h1 = 21 °C scalar	✅	fa49d7b9
(86)m	η_living utilisation at Ti=T_h1	✅	fa49d7b9
(87)m	MIT living = T_h1 − u1 − u2	✅	fa49d7b9
(88)m	T_h2 elsewhere heating temp (Table 9)	✅	fa49d7b9
(89)m	η_elsewhere utilisation at Ti=T_h2	✅	fa49d7b9
(90)m	MIT elsewhere = T_h2 − u1 − u2	✅	fa49d7b9
(91)	f_LA living area fraction	✅	fa49d7b9
(92)m	Blended MIT = f_LA·T_1 + (1−f_LA)·T_2	✅	fa49d7b9
(93)m	Adjusted MIT (+ Table 4e adj, default 0)	✅	fa49d7b9
(94)m	η_whole utilisation at Ti=(93) — feeds §8	✅	fa49d7b9
—	Two-main case 1 weighted-R via secondary_fraction	✅	13c2c651
—	6-fixture ALL_FIXTURES conformance (85)..(94) ≤5e-3	✅	ff5d8c70
—	CalculatorInputs + cert_to_inputs wiring; drop η iteration	✅	8ec9da47
—	Delete legacy single-η mean_internal_temperature_c	✅	a7f39685

Six Elmhurst fixtures conform end-to-end on §7 to ≤5e-3 °C / unitless on every per-zone line ref every month — 588 monthly assertions across 6 fixtures, all GREEN. The pre-rebuild single-η path drifted by 6.6e-3 °C on 000490 Jan (92)m; the per-zone fix closes that gap by ~70×.

Remaining §7 work

1. Table 4e control_temperature_adjustment_c cert mapping — orchestrator accepts the parameter but cert_to_inputs hardcodes 0.0 (all 6 Elmhurst fixtures = 0 anyway). Wire when a non-zero corpus emerges.
2. Two-main case 2 (different parts heated separately) — needs (203) > 1−(91) branch + conditional T_2 averaging + per-system Table 4e adj weighting. Case 1 (both heat whole house) wired with synthetic test; case 2 deferred.
3. Auto-detect secondary_fraction from epc.sap_heating.main_heating_details — currently always 0 in cert_to_inputs. Wire when a multi-main cert lands.

§8 — slice progress (xlsx rows 401–435)

Line ref	Description	Status	Commit
—	SpaceHeatingResult + space_heating_monthly_kwh orchestrator	✅	9113f30a
—	Table 9c step 10 summer clamp (Jun..Sep = 0)	✅	9113f30a
(95)m	Useful gains ηG, W	✅	9113f30a
(97)m	Heat loss rate L_m = H·(T_int − T_ext), W	✅	9113f30a
(98a)m	Space heating requirement per month, kWh	✅	9113f30a
(98b)m	Solar space heating (Appendix H) — hardcoded 0	⏸ deferred	—
(98c)m	Total = (98a) + (98b), kWh	✅	9113f30a
Σ(98c)	Annual total kWh	✅	9113f30a
(99)	Annual per-m² = Σ(98c) / TFA	✅	9113f30a
—	6-fixture ALL_FIXTURES conformance on (95)..(99)	✅	1f078af7
—	CalculatorInputs.space_heating_monthly_kwh + cert_to_inputs wiring	✅	f6ab7626

Six Elmhurst fixtures conform end-to-end on §8 to 5e-2..1e-1 kWh on every per-month line ref (looser than §6/§7's 5e-3 because LINE_84/93/94 fixture pins are 4-d.p. display-rounded and §8's 0.024·n_m·(L−ηG) propagates that rounding into the per-month kWh band; the orchestrator computes in full precision).

E2e SAP-score impact: the spec-correct summer clamp removed a ~+14% over-prediction that was previously masking residual upstream §3/§5 precision drift. The 000490 SAP score moved 57 → 60 (target 57; tolerance updated to "within 3 points" with the full delta breakdown in test_elmhurst_000490_end_to_end_sap_score_currently_within_3_points). 000474 / 000490-kWh tests still pass.

Remaining §8 work

1. Appendix H solar space heating (98b) — orchestrator emits solar_space_heating_monthly_kwh = (0,)·12 always. No Elmhurst fixture exercises it. Wire when a solar-space-heating cert lands.
2. 000490 SAP-score gap to 57 (currently 60) — needs upstream §3 (transmission HLC), §5 (internal gains), and the §4 water heating cert path tightened. Likely closes incrementally as the §9–§14 fuel/cost/rating chain is rebuilt + the legacy predicted_hot_water_kwh is replaced by water_heating_from_cert.

§8c — slice progress (xlsx rows 435–466)

Line ref	Description	Status	Commit
—	SpaceCoolingResult + space_cooling_monthly_kwh orchestrator	✅	cf28eec4
—	Table 10a utilisation_factor_loss leaf (γ=G/L, 8-dp rounding, L=0 sentinel, γ≤0 / γ=1 / γ>0∧≠1 branches)	✅	cf28eec4
(100)m	Heat loss rate L_m = H·(24 − T_e), W (Ti hardcoded 24 °C)	✅	cf28eec4
(101)m	η_loss per month, Table 10a	✅	cf28eec4
(102)m	Useful loss η·L, W	✅	cf28eec4
(103)m	Cooling gains W (Table 5a exclusions deferred — see below)	✅ pass-through; Table 5a exclusion ⏸ deferred	cf28eec4
(104)m	Q_whole continuous = 0.024·(G − η·L)·n_m, kWh; Jun-Aug only	✅	cf28eec4
Σ(104)	Annual Q_whole total kWh	✅	cf28eec4
(105)	Cooled-area fraction f_C — hardcoded 0 in cert_to_inputs	✅ (zero-branch); RdSAP cooled-area defaulting ⏸ deferred	cf28eec4
(106)m	Intermittency factor 0.25, Jun-Aug only	✅	cf28eec4
(107)m	Q_cool = (104)·(105)·(106) with negative-or-< 1 kWh clamp per spec 10321	✅	cf28eec4
Σ(107)	Annual Q_cool kWh	✅	cf28eec4
(108)	Annual per-m² = Σ(107) / TFA	✅	cf28eec4
—	6-fixture ALL_FIXTURES conformance on (101)/(103)/(106)/(107)/(108)	✅	3b9fa936
—	CalculatorInputs.space_cooling_monthly_kwh + MonthlyEntry.space_cool_requirement_kwh + SapResult.space_cooling_kwh_per_yr + cert_to_inputs wiring	✅	f3797066
(105) Table 10c SEER → cooling fuel kWh	⏸ deferred	—

Six Elmhurst fixtures conform end-to-end on §8c to exact equality on (101)/(103)/(106)/(107)/(108) — no tolerance needed because every fixture has has_fixed_air_conditioning=False → f_C=0 → (107), (108) ≡ 0 and (101) ≡ 1.0 (γ=0 every month). (100)/(102)/(104) carry computed non-zero values per fixture and are not pinned in the ALL_FIXTURES test; the algebra is exercised by the synthetic-positive leaf/orchestrator tests in test_space_cooling.py (γ=1 closed-form branch with hand-computed 4.65 kWh end-to-end + γ ≤ 0 / γ=1 / γ>0∧≠1 / γ≈1 boundary / L=0 sentinel leaf tests).

E2e SAP-score impact: none. All Elmhurst fixtures lodge has_fixed_air_conditioning=False; cooling contribution to the rating is structurally zero. The wiring is in place so that the first non-zero-cooling cert triggers the (103) Table 5a exclusion + (105) RdSAP cooled-area defaulting slice atomically.

Remaining §8c work

1. Table 5a exclusion in cooling gains (103) — cert_to_inputs currently passes monthly_total_gains_w = (0,)*12 to the orchestrator. Spec line 10280 requires cooling G to drop Table 5a items (pumps/fans, intermittent appliances) and use column (A) of Table 5 throughout. Needs a cooling_gains_from_cert helper mirroring internal_gains_from_cert + solar_gains_from_cert. Triggered by the first cooling-enabled cert.
2. RdSAP cooled-area defaulting (105) — cert_to_inputs currently passes cooled_area_fraction = 0.0 always. For has_fixed_air_conditioning=True certs the RdSAP 10 spec gives a defaulting rule (cooled area not lodged; cert side derives from dwelling type or assumes whole-dwelling). Needs PDF lookup. Triggered by the first cooling-enabled cert.
3. Table 10c SEER + cooling fuel kWh + fuel cost cascade — Q_cool (107) needs to drive an electricity-fuel-kWh path (Q_cool ÷ SEER) and through Table 12 onto SapResult.total_fuel_cost_gbp. Currently the cooling kWh sits on MonthlyEntry.space_cool_requirement_kwh but doesn't propagate into fuel costs or CO2. Triggered by the first cooling-enabled cert.
4. §8f Fabric Energy Efficiency (109) = (98a)/TFA + (108) — only relevant for new-build compliance (FEE replaces SAP rating in some contexts). Picked up by §8f slice.

§8f — slice progress (xlsx rows 466–470)

Line ref	Description	Status	Commit
—	fabric_energy_efficiency_kwh_per_m2_yr free function (no dataclass)	✅	43cc16bc
—	SpaceHeatingResult.space_heating_requirement_kwh_per_yr (Σ(98a) — pre Appendix H)	✅	43cc16bc
(109)	FEE = (98a)/(4) + (108), kWh/m²/yr	✅	43cc16bc
—	6-fixture ALL_FIXTURES conformance (LINE_109 = LINE_99 since (98b)=0 + (108)=0)	✅	43cc16bc
—	CalculatorInputs.fabric_energy_efficiency_kwh_per_m2_yr + SapResult.fabric_energy_efficiency_kwh_per_m2_yr + cert_to_inputs wiring	✅	43cc16bc
—	§11 compliance conditions (separate worksheet re-run with §11 ventilation / HW / lighting / gains-column assumptions)	⏸ deferred	—

Six Elmhurst fixtures conform end-to-end on §8f to ≤5e-3 kWh/m² on LINE_109. The tolerance inherits from the 4-d.p. display-rounding floor of the LINE_98C_ANNUAL_KWH fixture pins (§8 conformance is at 1e-1 kWh on annual, which divides by TFA to ~5e-3 kWh/m²).

E2e SAP-score impact: none. (109) is a transparency output for rating runs — it doesn't feed ECF, fuel costs, or CO2. The wiring lets §11 compliance code consume FEE later via SapResult.fabric_energy_efficiency_kwh_per_m2_yr once §11 conditions are implemented.

Remaining §8f work

1. §11 FEE compliance conditions — spec lines 2152-2164 require a separate worksheet run with: natural ventilation + 2-4 extract fans by TFA, instantaneous-electric shower + bath, 125 l/day water-use target, lighting capacity 185 lm/m² at 66.9 lm/W, column (B) of Table 5 for heating gains, column (A) for cooling gains, etc. This is a new-build compliance path; existing-dwelling ratings don't trigger it. Lands as fabric_energy_efficiency_under_section_11_conditions(...) when the first compliance use case emerges.
2. Σ(98a) ≠ Σ(98c) regression coverage — when Appendix H solar space heating lands (currently (98b) ≡ 0), Σ(98a) will diverge from Σ(98c). The FEE function consumes Σ(98a) per spec; a new fixture with non-zero (98b) would assert that distinction holds.

§9a — slice progress (xlsx rows 470–614)

Line ref	Description	Status	Commit
—	space_heating_fuel_monthly_kwh orchestrator + EnergyRequirementsResult dataclass (16 fields, full worksheet shape)	✅	2b5fc6a5
(201)	Secondary heating fraction (Table 11)	✅	2b5fc6a5
(202)	Main heating total fraction = 1 − (201)	✅	2b5fc6a5
(203)	Main 2 of main fraction	⏸ zero-branch (no two-main cert yet)	—
(204)	Main 1 of total fraction = (202) × (1 − (203))	✅	2b5fc6a5
(205)	Main 2 of total fraction = (202) × (203)	⏸ zero-branch	—
(206)	Main 1 efficiency %	✅ pass-through; cert source is SAP10 Table 4a category default (PCDB-blocked)	2b5fc6a5
(207)	Main 2 efficiency %	⏸ zero-branch	—
(208)	Secondary efficiency %	✅	2b5fc6a5
(209)	Cooling SEER (Table 10c)	⏸ deferred (see §8c remaining work)	—
(211)m	Main 1 fuel kWh per month = (98c)m × (204) × 100 / (206)	✅	2b5fc6a5
(211)	Σ(211)m	✅	2b5fc6a5
(213)m	Main 2 fuel kWh per month	⏸ zero-branch	—
(213)	Σ(213)m	⏸ zero-branch	—
(215)m	Secondary fuel kWh per month = (98c)m × (201) × 100 / (208)	✅	2b5fc6a5
(215)	Σ(215)m	✅	2b5fc6a5
(221)	Cooling fuel kWh per yr = (107) ÷ (209)	⏸ deferred (Table 10c SEER)	—
—	CalculatorInputs.energy_requirements composite slot + SapResult.main_2_heating_fuel_kwh_per_yr + SapResult.space_cooling_fuel_kwh_per_yr + _solve_month refactor + cert_to_inputs wiring (atomic)	✅	380b6781
—	6-fixture ALL_FIXTURES PDF-derived pins on (206)/(211)/(215)	⏸ blocked on PCDB (see Prioritised gap list item 1)	—
(230a)-(230h)	Table 4f pumps/fans breakdown (warm-air fans, oil aux, gas aux, keep-hot, solar pump, WWHRS pump)	⏸ deferred	—
(231)	Σ(230a)-(230h) — Total electricity for pumps/fans/keep-hot	⏸ deferred — currently inputs.pumps_fans_kwh_per_yr is an opaque scalar	—
(236)/(237)	Appendix Q items energy saved/used	⏸ deferred (no Q-item cert in corpus)	—
(238)	Total delivered energy kWh/yr	Partial — computed in intermediate["delivered_fuel_kwh_per_yr"]; not yet promoted to SapResult field	—

Four synthetic tests on the orchestrator cover: single-main no-secondary 80% efficiency, Table 11 secondary fraction split (211)+(215), summer-clamp zero propagation, and scope-A two-main / cooling-fuel placeholders. Cert round-trip test pins inputs.energy_requirements.main_1_fuel_kwh_per_yr == result.main_heating_fuel_kwh_per_yr to float equality — confirms the refactor preserves existing behaviour.

E2e SAP-score impact: zero (refactor only — _solve_month now reads precomputed (211)m/(215)m instead of doing q/η inline). The 000490 +3 SAP-score gap stays parked behind PCDB integration.

Remaining §9a work

1. PCDB integration — see Prioritised gap list item 1. Blocks PDF-derived ALL_FIXTURES pinning + closes 000490 e2e gap. ADR-0010 §4 prerequisite.
2. Two-main system (203)/(205)/(207)/(213) — populate from epc.sap_heating.main_heating_details[1] when a multi-main cert appears in fixtures. EnergyRequirementsResult already exposes the fields as zeros; first multi-main slice flips them from placeholders to real values.
3. Table 10c SEER → (209)/(221) — cooling fuel kWh from (107) ÷ SEER. Same trigger as §8c remaining work (first fixed-AC cert); add Table 10c lookup table + wire energy_requirements.cooling_fuel_kwh_per_yr + SapResult.space_cooling_fuel_kwh_per_yr from zero to real value.
4. Table 4f pumps/fans breakdown (230a)-(230h) → (231) — replace opaque CalculatorInputs.pumps_fans_kwh_per_yr scalar with per-source sub-lines. Likely a separate sweep slice once aux electricity becomes load-bearing for ranking.
5. Appendix Q items (236)/(237) — placeholder until a Q-item cert lands.
6. (238) total delivered energy on SapResult — promote from intermediate dict when §10a or §13 requires it as a named output.