We report the results of a study of IR emissivity of aluminium films as a function of impurity level, film thickness and sputtering conditions. Preliminary work suggests that for a given level of film impurities and deposition conditions, the JJR emissivity can be minimized with a certain film thickness. The influence of impurity level, film thickness, and sputter pressure on IR emissivity has been correlated with the resistivity and the surface roughness (measured by atomic force microscopy). The results are discussed in the general context of the Drude theory with allowances for the observed roughness.