  Boundary layers play an important role in controlling convective heat
transfer. Their nature varies considerably between different application areas
characterized by different boundary conditions, which hampers a uniform
treatment. Here, we argue that, independent from boundary conditions,
systematic dissipation measurements in Rayleigh-B\'enard convection capture the
relevant near-wall structures. By means of direct numerical simulations with
varying Prandtl numbers, we demonstrate that such dissipation layers share
central characteristics with classical boundary layers, but, in contrast to the
latter, can be extended naturally to arbitrary boundary conditions. We validate
our approach by explaining differences in scaling behavior observed for no-slip
and stress-free boundaries, thus paving the way to an extension of scaling
theories developed for laboratory convection to a broad class of natural
systems.
