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RdSAP 10 §3.10.1 (PDF p.24) "Default U-values of the roof rooms":
> "The residual area (area of roof less the floor area of room(s)-in-
> roof) has a U-value from Table 16 : Roof U-values when loft
> insulation thickness is known according to its insulation thickness
> if at least half the area concerned is accessible, otherwise it is
> the default for the age band of the original property or extension."
Plus RdSAP 10 §3.9.1 step (d-e) (PDF p.21-22) — the Simplified A_RR
formula `12.5 × √(A_RR_floor / 1.5)` is the empirical estimator for
the total RR exposed shell; residual = A_RR − Σ lodged walls. The
worksheet applies this same formula to Detailed mode when the lodged
surface set has no roof-going entries (cert 000565 BP[0]:
12.5 × √(45/1.5) − (9.8 + 14.7) = 43.96 ≈ ws 43.97).
Pre-slice the cascade computed residual area ONLY in the Simplified
RR branch (via `_part_geometry`'s `rr_simplified_a_rr_m2` − rr_common
− rr_gable subtractions). The Detailed-RR branch in
`heat_transmission` iterated `rir.detailed_surfaces` and missed the
residual entirely. Cert 000565 routes all 5 BPs through Detailed mode
(the Elmhurst mapper translates Summary "Simplified" lodgements to
`SapRoomInRoofSurface` records when per-surface L×H is present), so
cascade total_external_element_area_m2 was 779.27 m² vs worksheet
(31) = 857.64 m² (Δ −78.37 m² → thermal_bridging cascade −11.76 W/K
under).
Slice span (1 file):
- `heat_transmission.py`: Detailed-RR branch adds residual area via
the §3.9.1 A_RR formula minus wall-going lodgements (gable_wall,
gable_wall_external, common_wall). Residual area contributes to
`rr_detailed_area` (→ part_external_area → (31) → thermal_bridging
multiplier) and to `roof` at `u_rr_default_all_elements`.
- Discriminator: residual fires only when no roof-going surface kinds
(slope, flat_ceiling, stud_wall) are lodged — true Detailed-mode
lodgements (cohort fixture 000516) lodge the entire roof shell
explicitly and have no residual.
Cert 000565 movement (HEAD `78c57c0d` → this slice):
- thermal_bridging_w_per_k: 116.89 → 129.35 ✓ vs ws 128.65 (Δ +0.70)
- total_external_area_m2: 779.27 → 862.34 ✓ vs ws 857.64 (Δ +4.70)
- roof_w_per_k: 34.64 → 63.72 (Δ −16.74 → +12.34)
- sap_score_continuous: 29.02 → 28.07 (Δ +0.51 → −0.44)
- sap_score (integer): 29 → 28 (temp regression
past 28.5 threshold)
- space_heating_kwh: −685 → +533
- main_heating_fuel: −403 → +321
- hot_water_kwh: ✓ 0 EXACT unchanged
Per user direction temporary continuous-SAP drift is acceptable when
fixing real spec-correct sub-component bugs; the absolute continuous-
SAP residual is now −0.44 (was +0.51) — slightly closer to zero
overall. The roof overshoot localises to:
- BP[4] Flat Ceiling 1 "Unknown PUR or PIR" lodgement (cascade 2.30
vs ws 0.15, over by +10.75 W/K) — Elmhurst-specific "Unknown +
known material" convention not yet wired
- BP[1] residual formula gives +3.68 m² over worksheet (Δ +1.29 W/K)
— Detailed-mode residual is spec-ambiguous for extensions with
non-2.45 m RR height; future slice may add a height-aware formula
Cohort safety: discriminator `has_roof_lodgement` filters out true
Detailed-mode lodgements (cohort fixtures 000474/000477/000480/
000487/000490/000516 all lodge slope/flat_ceiling/stud_wall surfaces).
Initial implementation broke 41 cohort pins; the discriminator
restores cohort behaviour exactly. Test baseline: 585 pass + 9
expected `000565` fails (was 585 + 8 — sap_score moved from passing
to failing during the slice's transient overshoot; expected per
user direction).
Pyright net-zero per touched file (test_summary_pdf_mapper_chain.py
13 → 13 preserved; heat_transmission.py 13 → 12 improved by −1).
Co-Authored-By: Claude Opus 4.7 <noreply@anthropic.com>
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|---|---|---|
| .. | ||
| fixtures | ||
| __init__.py | ||
| test_elmhurst_end_to_end.py | ||
| test_elmhurst_extractor.py | ||
| test_end_to_end.py | ||
| test_extractor.py | ||
| test_pdf.py | ||
| test_summary_pdf_mapper_chain.py | ||