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SAP 10.2 Table 4c(3) (PDF p.169) "Factor for controls and charging method" multiplies a heat network's heat requirement by 1.05-1.10 for FLAT-RATE charging (note d: household pays a fixed amount regardless of heat used, so no incentive to economise), and by 1.0 for charging linked to use. The worksheet folds it into the heat-network requirement alongside the Table 12c distribution loss factor: (307) space = (98c) x (302) x (305) x (306) (310) DHW = (64) x (305a) x (306) Our cascade applied (306) DLF but never (305)/(305a), so every flat-rate community-heating cert under-counted demand -> over-rated SAP. Folded the factor into the 1/DLF efficiency override at the space-heating (206) and DHW (water-inherits-from-main) sites. Space column adds +0.05 for no thermostatic control (2301/2302); DHW column is 1.05 flat-rate / 1.0 linked-to-use. Corpus (RdSAP-21.0.1, 1000 certs): community cluster median +0.32 -> -0.19, within-0.5 38% -> 62% (control 2307 +0.83 -> -0.19; 2306 unchanged at factor 1.0 as spec requires). Overall gauge 65.0% -> 65.9%, MAE 1.174 -> 1.160. Ratcheted the corpus-test floor 0.62 -> 0.63 / MAE ceiling 1.25 -> 1.22. Also records (corpus-test comment + scripts/decompose_co2_pe_error.py) the disproof of the prior "CO2/PE +5% is a factor/scope bug" lead: factors are spec-exact, scope identical, and the bias is per-cert demand fidelity (corr(SAP-err, PE-diff) = -0.54), not a one-slice factor fix. Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com> |
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| data_transformation | ||
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| magicplan | ||
| modelling | ||
| property | ||
| property_baseline | ||
| sap10_calculator | ||
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| building_geometry.py | ||
| postcode.py | ||