Each field on a roof record is one of three things: fetched from an open-data source, read from a static physics lookup, or computed from the two. The public dashboard serves a frozen 12-city artifact today; live per-scan lineage returns after backend QA.
material comes from OS NGD where present, but "metal radiates at ε≈0.45" is a constant we look up (EMITT); that assumed stock-roof emittance and the measured albedo from Sentinel-2 are balanced by ASTM E1980 physics to give a roof’s modelled temperature. Sentinel-2 SCL masks cloud, shadow, snow and no-data pixels before albedo is averaged. Nothing on a card is asserted; everything traces back to a source, a cited constant, or a labelled estimate. The Radiative cooling line’s physics (the two-band sky, the ≈68 W/m² net flux, the 0.18 clear-sky duty) is reproducible in the radiative-cooling simulator.