Model/datatypes/epc/domain
Khalim Conn-Kowlessar bd25a3c774 mapper: disambiguate SY system-built from B basement wall (both share code 6)
RdSAP10 `wall_construction == 6` is canonically WALL_SYSTEM_BUILT — a
WALL TYPE — but the gov-EPC basement heuristic hijacked it: Elmhurst
lodges both "SY System build" and "B Basement wall" as code 6, and the
API lodges basements as code 6 too, so a system-built wall was
mis-flagged `main_wall_is_basement` → wrong RdSAP §5.17 / Table 23
u_basement_wall/u_basement_floor overrides, and downstream the solid-wall
Recommendation Generator couldn't offer EWI/IWI on system-built walls.

System-built stays the wall type on its canonical code 6; the basement
signal moves OFF code 6 to a dedicated `is_basement` (SapAlternativeWall)
/ `wall_is_basement` (SapBuildingPart) Optional[bool] flag:
- Elmhurst: `_elmhurst_wall_is_basement` sets it from the distinct
  "SY"/"B" labels (False for SY, True for B, None otherwise).
- gov-EPC API: per-wall code 6 can't be told apart at lodging time, so
  `from_api_response` post-processes via `_clear_basement_flag_when_
  system_built` — when the cert addendum marks the dwelling system-built,
  the code-6 basement heuristic is cleared. A genuine basement (no
  addendum signal) keeps the code-6 fallback.
- `main_wall_is_basement` / `is_basement_wall` honour the flag when set,
  else fall back to the code-6 heuristic — so untouched API basements and
  the cert 000565 "B" cohort are unchanged.

`EpcPropertyData.system_build` is a derived property over the wall type:
the MAIN wall is system-built iff `wall_construction == 6` and it is not
flagged basement. System-built lives on `wall_construction`; the basement
attribute is separate.

Acceptance: a system-built main wall (Elmhurst SY, or API addendum
system_build) → wall_construction == 6, main_wall_is_basement is False,
system_build is True; a genuine basement main wall → main_wall_is_basement
is True, system_build is False. Full §4 suite green (2404 passed).

Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>
2026-06-04 19:39:18 +00:00
..
tests S0380.222: map API roof_construction codes 6 (thatched) + 7 (dwelling 2026-06-04 15:16:49 +00:00
__init__.py fix broken imports and rename mapper class 2026-04-13 16:36:13 +00:00
epc.py added ucl corrected peui 2026-05-16 14:39:24 +00:00
epc_codes.csv slice 8a: window physics and orientation aggregates 2026-05-16 15:32:45 +00:00
epc_property_data.py mapper: disambiguate SY system-built from B basement wall (both share code 6) 2026-06-04 19:39:18 +00:00
field_mappings.py insulation thickness can be string 🟥 2026-04-15 14:26:09 +00:00
historic_epc.py demo generated for use in address2uprn 2026-05-08 14:48:15 +00:00
historic_epc_matching.py rank address similiarity 2026-05-12 16:02:01 +00:00
mapper.py mapper: disambiguate SY system-built from B basement wall (both share code 6) 2026-06-04 19:39:18 +00:00