We explore the general properties of convection in a solar surface layer. Our three-dimensional simulations use a tabulated equation of state that includes excitation and ionization of hydrogen and other abundant atoms, and the formation of H2 molecules. The radiative energy exchange is determined by solving the radiative transfer equation. This is particularly important in the upper cooling layer, where the observed granulation pattern is created. Our hydrodynamic runs simulate a region 6 × 6 × 3 Mm, extending vertically from the temperature minimum at 0.5 Mm above the visible surface, down to 2.5 Mm below it. We have run a new simulation at twice the resolution (25 km horizontally, and 15 - 35 km vertically) of a previous run. The bulk properties of the convection are very similar in both runs.