  This paper is a contribution to the understanding of the thermal properties
of aging systems where statistically independent degrees of freedom with
largely separated timescales are expected to coexist. Focusing on the
prototypical case of quenched ferromagnets, where fast and slow modes can be
respectively associated to fluctuations in the bulk of the coarsening domains
and to their interfaces, we perform a set of numerical experiments specifically
designed to compute the heat exchanges between different degrees of freedom.
Our studies promote a scenario with fast modes acting as an equilibrium
reservoir to which interfaces may release heat through a mechanism that allows
fast and slow degrees to maintain their statistical properties independent.
