Portfolio Manager Technical Reference: EPA Water Score for Multifamily Housing in the United States

Last Updated: 
10-6-2017
Technical Reference for Water Score for multifamily

The objective of the water score is to provide a fair assessment of the water use performance of a property relative to its peers, taking operational characteristics of the property and impact of climate into account. A statistical analysis is performed to identify building parameters that are significant drivers of water use using multivariate regression analysis, resulting in an equation that predicts the Water Use Intensity (WUI) of a property. The actual WUI of a property is then compared with the predicted WUI to fit a distribution in order to yield a 1 to 100 percentile ranking of performance, relative to the national population.

  • Property Type. The Water Score for multifamily housing applies to residential buildings that contain 20 or more residential living units. The score applies to single-building properties as well as properties with multiple buildings.
  • Reference Data. The analysis for multifamily housing is based on data from the Multifamily Energy and Water Market Research Survey by the Federal National Mortgage Association (“Fannie Mae”).
  • Adjustments for Weather and Business Activity. The analysis includes adjustments for:
    • Number of Units
    • Number of Bedrooms Per Unit
    • Weather and Climate (using historic evapotranspiration and precipitation based on zip code)
    • Ratio of irrigated area to the gross floor area (RIF)
  • Release Date. The EPA water score for multifamily housing was released in October 2017.

The process to develop the EPA water score follows an approach analogous to the ENERGY STAR score. A detailed description of the overall approach to develop ENERGY STAR scores is covered in the Technical Reference for the ENERGY STAR Score, available at www.energystar.gov/ENERGYSTARScore.

Fannie Mae’s Multifamily Energy and Water Market Research Survey, available at https://www.fanniemae.com/multifamily/green-initiative-market-research-survey, was used as the source data for this analysis. 

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