A cooling method that transfers heat from the inside of a building to the outside atmosphere. Typically used in commercial buildings in conjunction with other air conditioning units, the system uses water chilled by a chemical process. The condenser water absorbs heat as it circulates through the building's pipes and is carried to a cooling tower located on the roof of the building. The condenser water gives up the heat to the atmosphere as it evaporates while passing through the cooling tower. Depending on the negotiated terms of the lease, condenser water charges can be expensive.