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Multifamily Drainwater Heat Recovery

Measure Description

This CASE Report will look at drainwater heat recovery for both multifamily and nonresidential buildings. This CASE topic builds on a drainwater heat recovery measure added for low-rise residential in the 2019 code cycle as a compliance credit and a prescriptive alternative path for gas storage water heaters, heat pump water heaters, and solar water-heating systems. The 2019 CASE Report introduced drainwater heat recovery as a compliance credit and prescriptive alternative path and found that drainwater heat recovery was cost-effective for low-rise, multifamily buildings in all climate zones (assuming four residential units share one drainwater heat recovery unit) and would likely be cost-effective for high-rise multifamily buildings in a similar configuration.

In multifamily buildings, the proposed code change would prescriptively require drainwater heat recovery in all multifamily buildings for all hot water system types. The CASE measure may allow for exceptions for dwelling units that are slab-on-grade and may also allow for tradeoffs with other hot water compliance credits, such as compact hot water distribution. This measure would also update the prescriptive pathways in Section 150.1(c)8, refine the HERS test procedure, and update the Residential and Nonresidential Alternative Calculation Method Reference Manual calculations.

For nonresidential buildings, the features would be added to the compliance software to allow designers to receive compliance credit if they choose to install drainwater heat recovery units. The credit would be available for limited applications such as drain lines for showers in recreation centers, dishwashing stations in commercial kitchens, and clothes washers in laundry facilities. The Statewide CASE Team will evaluate appropriate verification requirements for nonresidential drainwater heat recovery units.

Provide Feedback

Participate in the Utility-Sponsored Stakeholder meeting for this topic on October 3rd, 2019! View the event here.

This measure description will be updated as research is developed to support the 2022 code cycle. For questions or suggestions, email Include the measure name in the subject line.


Relevant Documents

Measure proposals, supporting documents, and other outside references will be made public as they become available.


Give Us Your Feedback

The Statewide CASE Team values input from all stakeholders engaged in the Title 24, Part 6 code change process. We encourage the open exchange of code change comments and concerns.

  • Use the form above to provide feedback on this measure.