Model/domain/sap10_calculator/worksheet
Khalim Conn-Kowlessar 5317175dd3 fix(water-heating): count electric showers in Noutlets for mixer demand (App J)
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>
2026-06-13 23:31:02 +00:00
..
__init__.py refactor: lift-and-shift packages/domain/src/domain/sap → domain/sap10_calculator 2026-05-26 12:22:37 +00:00
appendix_h_solar.py Slice S0380.74: Appendix H (H7) U3.3 monthly-integrated convention closes 1.81× over-count 2026-05-29 18:02:35 +00:00
dimensions.py refactor: lift-and-shift packages/domain/src/domain/sap → domain/sap10_calculator 2026-05-26 12:22:37 +00:00
energy_requirements.py S0380.200: SAP 10.2 §9a two-main-heating split (203)/(205)/(207)/(213) 2026-06-03 13:09:43 +00:00
fabric_energy_efficiency.py refactor: lift-and-shift packages/domain/src/domain/sap → domain/sap10_calculator 2026-05-26 12:22:37 +00:00
fuel_cost.py Slice S0380.47: wire β-split into cost cascade per SAP 10.2 Appendix M1 §6 2026-05-28 19:01:38 +00:00
heat_transmission.py fix(fabric): honour the gov-EPC lodged per-element U-values (RdSAP §5.1) 2026-06-11 13:51:26 +00:00
internal_gains.py S0380.202: SAP 10.2 Table 5a note a) second main-system pump gain (70) 2026-06-03 14:35:08 +00:00
mean_internal_temperature.py S0380.205: SAP 10.2 p.186 two-systems-different-parts MIT (weighted R + elsewhere blend) 2026-06-03 16:02:56 +00:00
mev.py Slice S0380.100: MEV SFPav + (230a) cascade helpers (SAP 10.2 §2.6.4 + Table 4f) 2026-05-30 15:28:59 +00:00
photovoltaic.py Slice S0380.44: SAP 10.2 Appendix M1 §3-4 PV β-factor calculator (no wiring) 2026-05-28 18:11:56 +00:00
rating.py refactor: lift-and-shift packages/domain/src/domain/sap → domain/sap10_calculator 2026-05-26 12:22:37 +00:00
solar_gains.py Slice S0380.42: Decimal HALF_UP per-window areas per RdSAP10 §15 — closes cert 1536 2026-05-28 17:11:39 +00:00
space_cooling.py refactor: lift-and-shift packages/domain/src/domain/sap → domain/sap10_calculator 2026-05-26 12:22:37 +00:00
space_heating.py refactor: lift-and-shift packages/domain/src/domain/sap → domain/sap10_calculator 2026-05-26 12:22:37 +00:00
utilisation_factor.py refactor: lift-and-shift packages/domain/src/domain/sap → domain/sap10_calculator 2026-05-26 12:22:37 +00:00
ventilation.py refactor: lift-and-shift packages/domain/src/domain/sap → domain/sap10_calculator 2026-05-26 12:22:37 +00:00
water_heating.py fix(water-heating): count electric showers in Noutlets for mixer demand (App J) 2026-06-13 23:31:02 +00:00