Model/domain/modelling/contingencies.py
Khalim Conn-Kowlessar ae7e6a0c42 feat(modelling): composite per-dwelling boiler + tune-up costing (ADR-0027)
Replace the flat placeholder scalars (boiler £3000; tune-up £500/£900) with a
per-dwelling composite cost, mirroring the ASHP architecture (ADR-0025): a
`HeatingRates` table (data, `heating_rates.json`), typed `BoilerCostInputs` /
`TuneUpCostInputs`, pure `Products.boiler_bundle_cost` / `tune_up_cost`, and
modelling-layer interpreters that read the dwelling into those inputs.

The cost mirrors the Simulation Overlay component-for-component, sharing the
controls + cylinder pricing across both options:

- tune-up (standard) = standard controls + cylinder fixes
- tune-up (zone)     = zone controls + cylinder fixes
- boiler upgrade     = £3200 all-in + standard controls (only when the upgrade
  fired a controls change) + cylinder fixes

Standard controls are priced INCREMENTALLY — only the parts missing to reach
SAP 2106 (programmer £120 / room thermostat £150 / TRV £35×radiators), read
from a Table 4e Group-1 feature map so a dwelling that already has a room
thermostat + TRVs is only charged the programmer. Zone controls are a full
smart kit (hub £205 + smart TRV £50×radiators) — the smart TRV is itself the
room sensor, so there is no separate per-room sensor line. Cylinder fixes:
jacket £50 (when under-insulated) + thermostat £150 (when absent). The boiler
is a like-for-like wet swap (no radiators/flue/pipework — eligibility already
requires an existing wet boiler), so those dead-code extras are not modelled.

Figures are research-validated 2025/26 UK installed costs (legacy Costs.py
lineage); fully-loaded totals with one contingency on top (Model B, not the
legacy VAT/preliminaries engine). Contingency: boiler 0.26; tune-ups 0.10
(was a 0.15 placeholder). ADR-0027 records the design; CONTEXT.md's Heating
Eligibility entry updated to cover the partial boiler/tune-up family + composed
cost. Products cost pins (delta<=1e-9) + interpreter tests + generator
composite-cost assertions.

Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>
2026-06-10 19:41:06 +00:00

38 lines
1.3 KiB
Python

"""Per-Measure-Type contingency rates.
The one cost component carried separately from a Product's fully-loaded total
(CONTEXT.md). Mirrors the legacy `recommendations/Costs.py::Costs.CONTINGENCIES`;
extended as each measure type lands.
"""
_CONTINGENCY_RATES: dict[str, float] = {
"cavity_wall_insulation": 0.10,
"loft_insulation": 0.10,
"sloping_ceiling_insulation": 0.10,
"flat_roof_insulation": 0.10,
"suspended_floor_insulation": 0.20,
"solid_floor_insulation": 0.26,
"mechanical_ventilation": 0.26,
"external_wall_insulation": 0.26,
"internal_wall_insulation": 0.26,
"double_glazing": 0.15,
"secondary_glazing": 0.15,
"low_energy_lighting": 0.26,
"high_heat_retention_storage_heaters": 0.10,
"air_source_heat_pump": 0.25,
"gas_boiler_upgrade": 0.26,
"system_tune_up": 0.10,
"system_tune_up_zoned": 0.10,
"solar_pv": 0.15,
}
def contingency_rate(measure_type: str) -> float:
"""Return the contingency rate for a Measure Type, raising if unknown
(strict — do not silently default, per the repo's strict-raise convention)."""
try:
return _CONTINGENCY_RATES[measure_type]
except KeyError as exc:
raise ValueError(
f"no contingency rate configured for measure type {measure_type!r}"
) from exc