Warning that no floor exists in Zone

Program Version,EnergyPlus 1.2.1.022, 4/9/2008 3:09 AM,IDD_Version 1.2.1.022
** Warning ** No floor exists in Zone=ZONE01
************* Testing Individual Branch Integrity
************* All Branches passed integrity testing
************* Testing Individual Supply Air Path Integrity
************* All Supply Air Paths passed integrity testing
************* Testing Individual Return Air Path Integrity
************* All Return Air Paths passed integrity testing
************* No node connection errors were found.
************* EnergyPlus Completed Successfully-- 4 Warning; 0 Severe Errors; Elapsed