  We perform a self-consistent calculation of the thermal structure in the
crust of a superbursting neutron star. In particular, we follow the
nucleosynthetic evolution of an accreted fluid element from its deposition into
the atmosphere down to a depth where the electron Fermi energy is 20 MeV. We
include temperature-dependent continuum electron capture rates and realistic
sources of heat loss by thermal neutrino emission from the crust and core. We
show that, in contrast to previous calculations, electron captures to excited
states and subsequent gamma-emission significantly reduce the local heat loss
due to weak-interaction neutrinos. Depending on the initial composition these
reactions release up to a factor of 10 times more heat at densities < 10^{11}
g/cc than obtained previously. This heating reduces the ignition depth of
superbursts. In particular, it reduces the discrepancy noted by Cumming et al.
between the temperatures needed for unstable 12C ignition on timescales
consistent with observations and the reduction in crust temperature from Cooper
pair neutrino emission.
