`profile_corpus_error.py` and `dive_cert.py` compared our PE/CO2 against
the lodged EPC figures using the UK-average RATING cascade, but the EPC
lodges CO2/PE on the postcode DEMAND cascade (SAP 10.2 Appendix U p.124,
now wired into Sap10Calculator.calculate in fc7c4d2d). That confounded the
DEMAND-vs-COST triage: a cert whose demand actually reproduced on local
weather looked "PE off" purely from the climate difference and was
mislabelled DEMAND-side. Switching the PE/CO2 lens to `cert_to_demand_
inputs` (SAP still from the rating cascade) re-classifies the corpus
outside-0.5 set 261/42 -> 211/92 DEMAND/COST — ~50 certs are genuinely
cost-side (e.g. 10091578598: SAP +7.81 but PE +1.6 / CO2 -0.04). Sharpens
the hunt for the subtle widespread SAP term.
Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>
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