As a typical thermochromic material, vanadium dioxide (VO2) has the potential to serve as a smart regulator of building energy consumption. However, a selection of currently used VO2 glazing types were found to lack such smart regulation capacity due to their increased solar absorptivity after entering the metallic state, and the cooling energy consumption of a room containing such VO2 glazing increased as the transition temperature decreased. This study presents a comprehensive discussion of this glazing's smart regulation capacity. It is observed that the VO2 glazing's smart regulation capacity is influenced by property variations in its solar absorptivity and transmittance after the transition process. Smart Index (SI) is proposed to evaluate the "smart level" of VO2 glazing, and a contour map of SI is plotted to provide a concise method of determining how "smart" VO2 glazing can be. (C) 2013 Elsevier B.V. All rights reserved.