855773644-LEED-v5-BD-C-Reference-Guide-Launch-Edition - Page 204

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Minimum Water Efficiency, Minimum Outdoor Water Use Efficiency, Option 2. Efficient Irrigation must prove the reduction from the calculated baseline using the annual TIR.

Include all landscaped areas in the irrigation calculations. However, teams may exclude irrigation for vegetated playgrounds, athletic fields, food gardens, and urban agricultural areas from the calculations.

AND/OR

Option 5. Optimize Process Water Use

Cooling towers and industrial processes use a significant amount of potable water. Projects that include these systems must consider opportunities to reduce concentration cycles or optimize water use for cooling or select alternative water sources.

Process water uses include, but are not limited to, cooling, humidification, sterilization, dishwashers, clothes washers, and pools. This option offers three pathways, which depend on the type of process water use. Path 3 also requires that process water use meets a minimum percentage of the total building water use.

PATH 1. LIMIT COOLING TOWER CYCLES

This path prioritizes water conservation for cooling towers by limiting the cycles of concentration from the equipment. A cycle of concentration is the number of times water can circulate through the system without creating performance or operational problems. A low cycle of concentration means more single-use water passes through the system, resulting in excess water consumption. However, as we reuse water, dissolved solids remain, which increases the concentration levels of calcium, silicon dioxide (SiO2), and chloride. Higher cycles of concentration may result in scaling and corrosion issues.

The intent of the credit is not to impact system operations, but to inform designers on alternative solutions for reducing water consumption for cooling processes. Finding the correct balance of cooling tower blowdown and chemical treatment maintains system efficiency, reduces maintenance, and conserves potable water.

For each cooling process, conduct a potable water analysis to determine set points for the chemical treatment system and the associated cycles of concentration. Teams must confirm that the systems will operate at the specified cycles of concentration and not exceed parameters outlined in Table 18.

U.S. Green Building Council LEED v5 Reference Guide for Building Design and Construction, April 2025 Launch Edition 194