5.2 Outdoor and Indoor Water Use Reduction Credits
Key Takeaways
- WE Credit: Outdoor Water Use Reduction earns 1 point for a 50% reduction from the calculated baseline and 2 points for a 100% reduction (no potable water used for irrigation).
- WE Credit: Indoor Water Use Reduction earns 1-6 points on a sliding scale starting at 25% reduction (1 point) and reaching 50% reduction (6 points) below the EPAct 1992 baseline.
- Indoor water calculations multiply each fixture's design flow rate by usage frequency (duration × daily uses) and FTE plus visitor occupancy, then sum across fixture groups for both baseline and design cases.
- Process water for Energy Star-rated dishwashers, clothes washers, ice machines, and food steamers can contribute to additional indoor reductions but is calculated separately from fixture water.
- WaterSense-labeled fixtures, dual-flush valves, waterless or pint urinals, and metered or sensor faucets are the highest-leverage indoor strategies for moving from the 20% prerequisite to the 6-point credit.
From Prerequisite to Credit: Going Beyond the Floor
The two reduction credits reward projects that go beyond the 20%/30% prerequisite thresholds. Together they account for 8 of the 11 WE points in LEED v4 BD+C — the largest single concentration of points in the category.
WE Credit: Outdoor Water Use Reduction (1-2 Points)
This credit uses the same EPA WaterSense Water Budget Tool methodology as the prerequisite, but raises the bar.
| Reduction from baseline LWR | Points |
|---|---|
| 50% | 1 |
| 100% (no potable water used for irrigation) | 2 |
The baseline landscape water requirement (LWR) is calculated using local evapotranspiration and the project's actual plant palette. Beyond-prerequisite strategies stack:
- Replace remaining turf with native and adapted ground cover.
- Use drip or subsurface drip irrigation (efficiency ≥0.85) rather than spray (~0.625).
- Add rain sensors, soil moisture sensors, or weather-based smart controllers (must be WaterSense-labeled controller to claim the higher efficiency assumption).
- Use captured rainwater, graywater, municipal reclaimed water, or HVAC condensate for irrigation. Any of these non-potable sources reduce potable water demand to zero and earn the 2-point threshold.
WE Credit: Indoor Water Use Reduction (1-6 Points)
| Reduction from EPAct 1992 baseline | Points |
|---|---|
| 25% | 1 |
| 30% | 2 |
| 35% | 3 |
| 40% | 4 |
| 45% | 5 |
| 50% | 6 |
The sliding scale rewards each additional 5% step.
The Calculation Methodology
For each fixture group:
Daily fixture water use = flow rate × duration × daily uses per occupant × number of occupants
For flush fixtures (water closets, urinals), "flow rate × duration" collapses to gallons per flush (gpf). For flow fixtures (faucets, showers), it's gpm × seconds ÷ 60.
LEED uses full-time equivalent (FTE) occupants plus transient visitors. Default usage assumptions from the reference guide (per occupant per day):
| Fixture | Female FTE | Male FTE | Visitor |
|---|---|---|---|
| Water closet | 3 uses | 1 use | 0.5 use |
| Urinal | 0 | 2 uses | 0.1 use |
| Lavatory faucet | 3 uses × 15 sec | 3 uses × 15 sec | 0.5 use × 15 sec |
| Shower | 0.1 use × 480 sec | 0.1 use × 480 sec | 0 |
| Kitchen sink | 1 use × 15 sec | 1 use × 15 sec | 0 |
A worked baseline example for 100 FTE occupants (50 female, 50 male) and 20 daily visitors:
- Baseline water closets: (50 × 3 + 50 × 1 + 20 × 0.5) × 1.6 gpf = 336 gal/day
- Design with 1.28 gpf WaterSense closets: same uses × 1.28 = 268.8 gal/day
- Closet reduction = (336 − 268.8) ÷ 336 = 20%
That closet-only swap only matches the prerequisite. To reach 30-50%, the team typically combines:
- Dual-flush water closets (0.8 gpf reduced flush / 1.28 gpf full)
- Pint urinals (0.125 gpf) or waterless urinals (0 gpf)
- 0.5 gpm public lavatory faucets (already baseline) plus sensor or metering valves
- 1.5 gpm WaterSense showerheads
- 1.5 gpm kitchen faucet aerators
Process Water Contribution
Separate from fixture water, process water for appliances can support additional indoor savings:
| Appliance | Energy Star / target |
|---|---|
| Residential dishwasher | ≤3.5 gal/cycle |
| Commercial dishwasher | varies by type (door-type ≤0.95 gal/rack) |
| Residential clothes washer | Water Factor (WF) ≤4.3 |
| Commercial clothes washer | WF ≤4.0 |
| Ice machine | Air-cooled, ≤25 gal per 100 lb ice |
| Food steamer | Connectionless or boilerless |
Process water from these appliances is calculated against an Energy Star or LEED-specified baseline and folded into the indoor reduction total when applicable.
Strategy Stack to Reach 50%
Prerequisite (20%)
+ WaterSense lavatories and showers (~3-5%)
+ Dual-flush water closets (~5-7%)
+ Pint or waterless urinals (~5-8%)
+ Sensor/metering valves on public faucets (~2-3%)
+ Energy Star process equipment (~2-4%)
= 35-47% (4-5 points)
Projects targeting all 6 points (50%) typically combine the above with non-potable flushing water (graywater or rainwater) — covered in Section 5.4.
An office building has 80 FTE occupants split evenly male/female and 30 daily visitors. Baseline 1.6 gpf water closets are replaced with 1.28 gpf WaterSense closets, and waterless urinals replace 1.0 gpf urinals. Using LEED default usage assumptions (3 female closet uses, 1 male closet use, 0.5 visitor closet use, 2 male urinal uses, 0.1 visitor urinal use per day), what is the approximate combined daily reduction across these two fixture types?
A project achieves a 50% reduction in calculated landscape water requirement using the EPA WaterSense Water Budget Tool by combining drip irrigation, native plantings, and a smart controller — but still uses municipal potable water for the remaining irrigation. How many points does the project earn under WE Credit: Outdoor Water Use Reduction?