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Draft PDS-03, BSR/RESNET/ICC 1101-201x, Water Rating Index

Proposed Standard BSR/RESNET/ICC 1101-201x, Water Rating Index, establishes a uniform methodology for evaluating, rating and labeling the water use performance of single family and duplex dwelling units.

The Standard provides a consistent, uniform methodology for evaluating, quantifying, and labeling the water use performance of one- and two-family dwellings. The methodology compares the water use performance of an actual home (rated home) with the water use performance of a reference home of the same geometry, resulting in a relative Water Use Rating called the Water Rating Index (WRI). Where the water use performance of the actual home and the reference home are equal, the Water Rating Index is 100.

The Reference Home used for this comparative analysis has the attributes of a standard home built circa 2006. The underpinnings of the indoor Reference Home model are based on ANSI/RESNET/ICC Standard 301-2014, Addendum A. The outdoor Reference Home model is adapted using data from the Water Research Foundation’s Residential End Uses of Water Study II. Both the indoor and outdoor calculation models are grounded in actual field water use data. It is the opinion of the Standard Development Committee that alternatives not included in the calculation of the Water Rating Index did not have sufficient data to develop an equation (on par with the existing indoor and outdoor model) to confidently and accurately predict their water consumption.

One such element that did not make it into this Preliminary Draft Standard is the use of alternative water sources to displace potable water use. The committee considered this issue, and there was agreement that eventually this standard should account for the impact of alternative water sources, like gray water and harvested rainwater. However, the committee decided that, at this point, there was insufficient reliable data on how these alternative water systems impact water use under a variety of field conditions to develop a calculation to quantify their impact on a home’s potable water use. Therefore, in order to maintain the technical rigor of the calculations in the rest of the standard, alternative water sources do not provide water use reductions in a rated home in this current draft. RESNET and ICC are interested in performance and usage data on alternative water sources and systems, and request such data to be submitted through the public comment process.

It should be noted that Section 6.2 does allow Water Rating providers to petition for adjustment to the Water Rating Index for a Rated Home with features or technologies not addressed by Approved Software Rating Tools or this Standard. This process for innovative design requests will allow for technologies or features, not specifically covered in the standard, to petition for credit.

A WRI rating includes water use for: toilets, kitchen faucets, lavatory faucets, showerheads, clothes washers, dishwashers, water softeners, outdoor/landscape irrigation systems and pools/spas. There are additional factors that also influence the rating, including: excess water pressure, house size, geographic location, number of bedrooms, lot and landscape size and hot water distribution layout. The following components are not included in the standard, due to a lack of data: whole house humidifiers, water filtration systems and alternative water sources.

The first draft, PDS-01, of BSR/RESNET/ICC 1101-201x was submitted for public comment in August 2018. The comments were considered and resulting changes were incorporated in draft PDS-02 and shown with strike-through/underline red print.

The second draft, PDS-02, of BSR/RESNET/ICC 1101-201x was submitted for public comment March 15, 2019. The comments were considered and result in substantive changes to two equations in section 4.5.6. Comments will be accepted only on the text indicated by strike-through/underline in red print. To review and comment on the changes in section 4.5.6 follow the links below.


Draft PDS-03, BSR/RESNET/ICC 1101-201x

Comment on Draft PDS-03 BSR/RESNET/ICC 1101-201x

View comments on Draft PDS-03, BSR/RESNET/ICC 1101-201x


The public comment period will be open for 30 days beginning July 26, 2019 through August 25, 2019. Comments will be accepted only on text indicated by strike-through/underline red print.