Blue curves: horizontally averaged radiative heating rates for individual bins as a function of geometrical depth in a snapshot of the  [Fe/H]  =  −3 red giant simulation computed assuming a Planckian source function and excluding the contribution of scattering to total extinction in optically thin layers. For clarity, only the relevant (upper) part of the simulation is shown; radiative heating rates at the cooling peak are unchanged when switching between scattering treatments. Red curves: horizontally averaged heating rates for the same snapshot immediately after switching to scattering as true absorption.