LEED v4/4.1 highlight: Tips in Water Efficiency
Green Building Team on July 28, 2021
Pilot ACP Whole Project Water Use Reduction allows project teams to demonstrate achievements using a water balance approach that documents overall water use reduction. This approach benefits projects with designs which target significant water savings beyond the uses included in the indoor and outdoor water use credit categories (e.g., process water). LEED v4 and v4.1 projects are welcome to substitute this ACP. Projects must meet the requirements of all Water Efficiency prerequisites separately, and the ACP replaces the points available cumulatively in the WE credits Outdoor Water Use Reduction, Indoor Water Use Reduction, and Cooling Tower Water Use. WEc Water Metering may be pursued separately. To pursue this pathway, project teams must develop a water use baseline and create a proposed use model. Points are achieved based on reductions from the baseline.
LEED Canada NC/CS 2009 projects are also welcomed to consider this pilot ACP, see CIR 1350 for details.
With the revised credit WE Optimize Process Water Use, LEED v4.1 has expanded the applicability of WE credit Cooling Tower to projects without cooling towers, giving more options and flexibility to project teams. This credit under the LEED v4.1 BD+C rating system is available for substitution for all LEED v4 BD+C projects. Under Option 3 Process Water Use, projects can demonstrate that they use a minimum of 20% for one point (or 30% for two points) recycled alternative water to meet their process water demand. Eligible subsystems include boilers, humidification systems and other subsystems using process water. (Note that process water uses eligible for achievement of Option 3 must represent at least 10% of total building regulated water use and may not include water used for cooling.) Additionally, core and shell projects can earn up to three points for using recycled alternative water to meet process water demand. Alternative water sources include municipally supplied reclaimed wastewater (“purple pipe” water), graywater, rainwater, stormwater, treated seawater, water recovered from condensate, foundation dewatering water, treated blowdown from process water, reverse osmosis reject water, and other recycled water sources. Well water, groundwater, and naturally occurring surface bodies of water (such as streams, lakes, or rivers) do not contribute to recycled alternative water sources.
The LEED Guide to Water Metering supports project teams in implementing water submetering. The guide summarizes the various versions of water metering credits and prerequisites in LEED v4 and v4.1, explains the key concepts behind the water metering credits, offers suggestions for submetering strategies and includes detailed FAQ’s. For example, this guide highlights that healthcare projects that do not have the minimum five additional subsystems required in their project scope, can meet the intent by metering the major water subsystems that are applicable to the project scope. See the guide for more details on this allowance.
Check out the February 2021 LEED Technical Bulletin for more helpful tips for this credit.