Supplemental air conditioning system for building

A supplemental air conditioning system for a space in a building to lower the costs of using the building condenser water, used to cool the condensers of water cooled air conditioning units, said building having a core and a plurality of floor spaces and supplying said condenser water and cooled air, each floor space having a ceiling plenum formed by a drop ceiling, air conditioning ducts within the ceiling plenum to conduct said cooled air from the building core to the floor spaces, and air return means to draw heated air from the ceiling plenum and conduct said heated air to the building core, said building having a supply of said condenser water, characterized in that the supplemental air conditioning system comprises at least one air-cooled air conditioner unit and at least one water-cooled air conditioner unit having a condenser cooled by said building condenser water and located within said floor space to lower the temperature thereon in the range of 2.degree.-10.degree. F., each of said units blowing out cold air, with the ratio of tons of air conditioning capacity between said respective units being in the range of 85:15 to 70:30 and with the water-cooled unit blowing cold air into the ceiling plenum and the air-cooled unit blowing cold air to the floor space below said drop ceiling.