Demixing of two polymers (polystyrene and poly(2-vinylpyridine)) in solution was studied on a substrate with a surface energy pattern for varying relative humidities and gaseous atmospheres. A good pattern transfer of laser-generated surface energy patterns could only be observed at medium relative humidity. An incomplete replication of the energy patterns at lower humidity and a netlike (nanoporous) structure, especially in the PVP phase, at higher humidity was observed. The control of the water content in the solvent (tetrahydrofuran/THF) turned out to be a second important factor for the templating process. So a fine balance including both parameters, the humidity in the process gas and the content of water in the solution, is critical for the quality of surface energy pattern transfer into polymer blends during spin-coating.