Smart Buildings Act - Amends the Internal Revenue Code to allow a 20-year depreciation recovery period, calculated on a straight line basis, for property that is part of a heating, ventilation, air conditioning, or refrigeration system, or which replaces one or more components of such a system, if such system or such replacement component: (1) exceeds by at least 10 percent the applicable minimum performance standard under the National Appliance Energy Conservation Act of 1987, the Energy Policy Act of 2005, or the American Society of Heating, Refrigerating and Air-Conditioning Engineers Standard 90.1; (2) is placed in service before January 1, 2012; and (3) is installed in nonresidential or residential rental buildings.