LEED v4 Water Efficiency Credits: Indoor, Outdoor, Cooling Tower and Metering (v4, 2019 addenda)

For LEED v4 BD+C New Construction, the Water Efficiency (WE) category has three prerequisites and four credits worth 11 points: Indoor Water Use Reduction 6, Outdoor Water Use Reduction 2, Cooling Tower Water Use 2 and Water Metering 1. This article covers LEED v4 BD+C (July 2019 addenda); LEED v4.1 is a separate version and is not covered. LEED v5 has also been released (USGBC) and is not covered. Page numbers refer to the LEED v4 BD+C rating system, July 2019 addenda.

What are the WE prerequisites and credits?

Building-level water metering is a prerequisite, not a credit. The 11 points are 2 + 6 + 2 + 1 (pp. 55, 56, 59, 61).

What does the indoor water prerequisite require?

Reduce aggregate water consumption of the fixtures and fittings in Table 1 by 20% from the baseline, using the volumes and flow rates in that table. All newly installed toilets, urinals, private lavatory faucets and showerheads eligible for a label must be WaterSense labeled (or a local equivalent outside the U.S.). Source: p. 51.

The prerequisite also sets appliance and process requirements: for example ENERGY STAR for residential clothes washers and dishwashers, CEE Tier 3A for commercial clothes washers, prerinse spray valves at 1.3 gpm or less, no once-through cooling with potable water for equipment that rejects heat, and cooling towers and evaporative condensers equipped with makeup water meters, conductivity controllers with overflow alarms and efficient drift eliminators (drift at most 0.002% of recirculated water volume for counterflow towers and 0.005% for cross-flow towers). Healthcare, Retail, Schools and Hospitality projects have additional kitchen and process tables (pp. 51-53).

How are indoor water reduction points scored?

The credit asks for further reduction from the same Table 1 baseline, and alternative water sources can add savings beyond the prerequisite level. Source: p. 56.

For Schools, Retail, Hospitality and Healthcare the percentage table stops at 45% (5 points), and one further point is earned for meeting all requirements of any one appliance and process table (pp. 56-58); Schools, Retail and Healthcare can earn a second such point for meeting two tables, for 7 in total.

How does outdoor water reduction earn points?

The prerequisite is met by showing the landscape needs no permanent irrigation system beyond a two-year establishment period, or by reducing the landscape water requirement by at least 30% from the calculated baseline for the site’s peak watering month, using plant selection and irrigation efficiency as calculated in the EPA WaterSense Water Budget Tool. Nonvegetated surfaces are excluded from landscape area calculations (p. 50).

For the credit (p. 55): Option 1, no irrigation required beyond the two-year establishment period, earns 2 points. Option 2, reduced irrigation, earns 1 point at a 50% reduction from the baseline and 2 points at 100%; the first 30% of the reduction must come from plant species selection and irrigation efficiency (as calculated in the EPA WaterSense Water Budget Tool), and only additional reductions beyond 30% may use any combination of efficiency, alternative water sources and smart scheduling technologies.

What does the Cooling Tower Water Use credit require?

For cooling towers and evaporative condensers, do a one-time potable water analysis of at least five control parameters, then calculate cooling tower cycles as the maximum allowed concentration of each parameter divided by its concentration in the makeup water (pp. 59-60).

One point is earned for the maximum number of cycles achievable without exceeding any of the limits, up to 10 cycles. Two points are earned by achieving at least 10 cycles by increasing treatment of the condenser or makeup water, or by meeting the 1-point cycles and using at least 20% recycled nonpotable water.

What do the water metering requirements say?

The Building-Level Water Metering prerequisite requires permanent meters for the total potable water use of the building and associated grounds, with meter data compiled into monthly and annual summaries (manual or automated readings), and a commitment to share whole-project water data with USGBC for five years (p. 54).

The Water Metering credit (1 point, p. 61) requires permanent meters on two or more of these subsystems, as applicable: irrigation (systems serving at least 80% of the irrigated landscaped area); indoor plumbing fixtures and fittings (at least 80%); domestic hot water (at least 80% of installed heating capacity); boilers with projected annual water use of 100,000 gallons or more or above 500,000 BtuH; reclaimed water; and other process water (at least 80% of expected daily consumption). Healthcare projects must also meter any five of a further list of systems.

Which mistakes cost points on these credits?

• Using the wrong baseline. The baseline is the Table 1 values (1.6 gpf toilet, 2.5 gpm showerhead, 2.2 gpm private lavatory, 0.5 gpm public lavatory). Calculating against a WaterSense value understates the real reduction.
• Treating the metering prerequisite as a credit. Building-level metering is required for every project and earns nothing; the 1 metering point needs two or more subsystem meters.
• Skipping the cooling tower. Cooling towers have both prerequisite requirements (meters, conductivity controllers, drift eliminators) and a 2-point credit; omit them from the water model and both are missed.
• Starting the indoor credit at 30%. The first point is at 25%.
• Applying the private lavatory flow rate to public restrooms. Public lavatory faucets use the 0.5 gpm baseline.
• Planning submeters late. The credit counts only permanent meters on two or more subsystems, so provide the rough-in during MEP design.