Water efficiency moves earlier in home design

By Jesse Sanchez. 

Updated water-efficiency standards give irrigation contractors a greater role in planning systems before construction begins. 

Outdoor water use is becoming a more important part of residential building design, according to the Irrigation Association, creating opportunities for irrigation contractors to contribute earlier in the planning process. The National Association of Home Builders (NAHB) updated its Matrix of Water Efficiency Rating Systems to reflect changes in the 2025 ICC 700 National Green Building Standard (NGBS)®. The matrix leads to a Water Rating Index (WRI) score that helps builders, designers and contractors evaluate projected indoor and outdoor water use before construction. 

“These updated water efficiency requirements require that all indoor and outdoor water features, including irrigation systems, must be addressed as part of the project’s water performance plan,” said Amy Manz, program manager of sustainability and green building for NAHB. 

Irrigation strategies considered under the framework include smart controllers, rain sensors, soil moisture sensors, efficient nozzles and emitters, system zoning and integration with building management systems. 

The updated WRI also applies to existing buildings, expanding opportunities for irrigation professionals working on renovations and retrofits. 

“The 2025 edition of the NGBS expands the WRI to apply to both new and existing buildings, allowing certification of total indoor and outdoor water use against a code-minimum baseline,” Amy said. “This means irrigation contractors can now contribute to reduced WRI scores for retrofits and renovations, not just new construction.” 

WRI scores range from 0 to 100, with lower scores representing greater water efficiency. The calculation considers a home’s size, design, water-saving features and outdoor conservation measures, including irrigation, rainwater collection and graywater reuse. 

Understanding the framework can help contractors compare system designs, estimate water demand and recommend components that align with a project’s efficiency goals. Early modeling can also help builders plan for local requirements, water reuse and stressed water-supply scenarios. Amy noted, “To achieve these enhanced irrigation efficiency measures, contractors are encouraged to take steps to plan early in the design phase, verify compliance, coordinate with landscape architects, document performance data diligently and train installers on maintenance needs.” 

Learn more about how the Water Rating Index can support efficient irrigation planning during new construction, renovations and retrofits!