The city of Memphis adopted an ordinance in spring 2009 to improve the energy efficiency of the rental housing stock throughout the city. The ordinance establishes minimum energy efficiency standards that must be met in rental housing when the tenants pay the utility bills. Specifically, the ordinance requires that the building envelope of a residential unit have acceptable windows, sealing, weather stripping, and sufficient insulation. It requires functional heating and cooling equipment and installation as well as leak-free plumbing.