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Water Use & Conservation

Design and build a model home with no greater than a 40 HERSH2O Index (e.g., minimum 60% less annual water consumption than a standard benchmark house).


The organizers will use approved standards and tools to calculate a projected HERSH2O Water Efficiency Index for each competition model home. The lower the projected HERSH2O Index, the more water efficient the home. The organizers will use the approved standards and tools to develop a water efficiency model for each model home. They will use data collected from construction documents, direct measurement activities, and performance verification activities to develop the model inputs and calibrate the model outputs. As the organizers learn more about the model homes to refine model inputs, the model will become progressively more accurate in predicting annual water efficiency performance in the model home’s permanent location.

A projected HERSH2O Index less than or equal to 40 earns all available points. A projected HERSH2O Index greater than 40 and less than 60 earns reduced points, scaled linearly. A projected HERSH2O Index greater than or equal to 60 earns no points.

  • The organizers may develop custom methods for modeling innovative demand-side and supply-side water systems and strategies that are not covered by HERSH2O standard.
  • All supply-side and demand-side water systems and strategies must comply with Chapter 1 of the OCSD23 Building Code. Systems and strategies that have significant benefits but do not currently comply with Chapter 2 of the OCSD23 Building Code may be approved for demonstration on the competition site and for consideration by the juries on case-by-case basis.
  • When a team fails to provide information that is required to develop well-documented and validated model inputs, the organizers will make conservative assumptions that will tend to increase the projected HERSH2O Index.
Not applicable to this contest.