The NAHB Water Efficiency Rating Matrix Can Be a Valuable Tool for Builders
NAHB’s Sustainability & Green Building team has updated its Matrix of Water Efficiency Rating Systems to reflect the release of the new ICC 700-National Green Building Standard® (NGBS).
The matrix provides information on the applicability, requirements, costs and scope for different water efficiency certification programs. It allows builders to quickly evaluate and compare the features and requirements of several above-code water efficiency and conservation programs to assist in decision-making if a project is looking for green certification.
The matrix is also a useful tool for home builders in drought-prone or water-scarce areas. Even though local rules might not require water efficiency certification, many home owners who are located in these areas are increasingly seeking out methods of limiting water usage.
The new water matrix incorporates the 2025 version of the NGBS, maintains information for the 2020 version, and removes the 2015 version, which is no longer a certification option through Home Innovation Research Labs, the sole national certification agency of the standard. Similar to the previous version, the matrix details how a Water Rating Index (WRI) score can be pursued independently from the NGBS Green certification.
WRI assesses a property’s total indoor and outdoor water use compared to a code-minimum baseline. With a certified WRI score, a builder or developer can easily communicate overall water use with investors, prospective home buyers or renters, and local officials, which helps planners better understand overall water use in new developments.
The 2025 NGBS allows the WRI to be used for both new and existing buildings. This version also features a more comprehensive Water Rating Index performance pathway and refines the calculations used by verifiers to accurately model expected indoor and outdoor water use against rising utility rates and supply risks.
The 2025 NGBS also introduces refined water efficiency requirements focusing on high-performance, resilient residential construction. Key 2025 updates include:
- Streamlined water performance paths
- Updated EPA WaterSense standards for indoor plumbing
- Enhanced irrigation controls, maintaining rigorous Bronze to Emerald certification levels
Certifying a home building project to an above-code, voluntary water efficiency rating system provides independent confirmation of the water-saving practices used.
The matrix is one of many NAHB Green Resources available to builders and developers. Check out more at nahb.org/green, including the Builders Toolkit for Water.