"Water Efficiency" is a code section found in many green, high performance building standards like ASHRAE 189.1, the International Green Construction Code (IGCC), LEED(R) Green Building Rating System, California Title 24-2013, and is the sole focus of the proposed ASHRAE 191 Standard for the Efficient Use of Water.

The Water Efficiency sections in the above codes and standards address the areas of irrigation of the landscape, the use of efficient plumbing fixtures, and water metering. The effects of these fixtures and devices are well understood and have quantifiable impacts on water usage. This conference paper examines the "Water Efficiency" requirements for evaporative heat rejection equipment used in HVAC systems according to ANSI/ASHRAE/USGBC/IES Standard 189.1-2011 Standard for the Design of High-Performance Green Buildings and the International Green Construction Code (IGCC). The goals of these cooling tower water efficiency requirements are to conserve the potable make-up water used in the evaporative cooling process while maintaining system heat transfer efficiency and longevity.