  We calculate the outward energy transport time by convection and photon
diffusion in an inflated common envelope and find this time to be shorter than
the envelope expansion time. We conclude therefore that most of the hydrogen
recombination energy ends in radiation rather than in kinetic energy of the
outflowing envelope. We use the stellar evolution code MESA and inject energy
inside the envelope of an asymptotic giant branch star to mimic energy
deposition by a spiraling-in stellar companion. During 1.7 years the envelope
expands by a factor of more than 2. Along the entire evolution the convection
can carry the energy very efficiently outwards, to the radius where radiative
transfer becomes more efficient. The total energy transport time stays within
several months, shorter than the dynamical time of the envelope. Had we
included rapid mass loss, as is expected in the common envelope evolution, the
energy transport time would have been even shorter. It seems that calculations
that assume that most of the recombination energy ends in the outflowing gas
might be inaccurate.
