A system of blinds comprising louvers that are inclined in such a way as to maximize the direct solar illumination received during the winter months and to minimize same during the summer months is described. The inclinations are determined according to the terrestrial latitude of the building supporting these blinds, and the orientation of the surface of the building that is to be protected. The longitudinal slope of the louvers is determined such that the longitudinal direction of the louvers is substantially parallel to the straight line of intersection of the plane of the surface and the equatorial plane seen from the building. The transverse tilt of the louvers is determined such that these louvers face in a direction comprised between 12° and 24° below the direction of the equatorial plane.