assessment-model/docs/adr/0010-compliance-window-is-a-report-view-parameter.md

10. The compliance-window filter is a report-view parameter, not a Scenario constraint

Date: 2026-07-07

Status

Accepted

Context

A recurring landlord question on Reporting: "what if we don't do works on properties whose EPC keeps them compliant, from a government perspective, beyond 2030?" — i.e. exclude homes that can demonstrate the target band with an in-date certificate past a cut-off date, and see what the scenario costs without them.

Two places this could live: as a constraint on the Scenario (the optimiser never plans works for those homes) or as a filter on the report view (the modelling is unchanged; the report recomputes as if those homes' plans were dropped).

Decision

A report-view parameter on the scenario metrics endpoint (alongside hideNonCompliant and the lodged-baseline toggle), configurable in the UI:

• Membership rule: a home is "compliant beyond the window" iff its lodged certificate shows the selected band or better (default C) and remains valid past the selected date (default 1 Jan 2030). Both band and date are user-configurable. predicted homes never qualify — there is no certificate to rely on (see EPC provenance in CONTEXT.md).
• Scenario-side only: skipped homes' plans drop out of the works-list aggregates (costs, funding, benefits, homes upgraded) and they hold their current band in the after-distribution. Current-stock figures are untouched; the filter only exists when a scenario is selected.

Alternatives considered

• Scenario constraint (optimiser skips the homes): the "true" answer — the engine would redistribute budget across the remaining stock. Rejected here because Scenario configuration is immutable (ADR-0003) and adding a post-hoc exclusion would either mutate that config or mint a near-duplicate Scenario per date/band permutation. It also couples an exploratory, slider-like question to a full modelling round-trip.
• Whole-report filter: hide the homes from every figure including current stock. Rejected: the portfolio's home count would disagree with every other surface, and the landlord's question is about works, not about the stock.

Consequences

• The filtered works list is an approximation: plans were optimised with the skipped homes in scope, so shared-cost effects (e.g. scaffolding batching) are not re-optimised away. Acceptable for an exploratory filter; the exact answer is future work — a re-model with an explicit exclusion set, which would be a new Scenario capability, not this filter.
• The parameter travels in the URL, so filtered views are shareable and the PDF can reproduce them.
• If landlords start committing budgets against filtered numbers rather than exploring with them, that is the signal to build the re-model path.