Compact Hot Water Distribution Design

Residential Water Heating

Codes and Standards Enhancement (CASE) Report

The Statewide CASE Team 2019 Title 24, Part 6 Final CASE Report is available below. The Final CASE Report incorporates feedback received during utility-sponsored stakeholder meetings, Energy Commission Pre-Rulemaking workshops, and personal communication with stakeholders. We encourage stakeholders to email feedback on the Final CASE Report to You can also participate in the 2019 Title 24, Part 6 Standards updated by attending the Energy Commission workshops and submitting written comments to the rulemaking docket. Refer to the Pre-Rulemaking and Rulemaking Workshop Notices for instructions on how to submit comments to the Energy Commission’s docket (available here).

Measure Description

The Compact Hot Water Distribution proposal is intended to provide builders a compliance option credit for designing residential buildings with hot water use fixtures located close to the water heater, saving both energy and water. A compliance option represents a voluntary measure available to builders to help meet or exceed the performance level defined by the Standard Design. The measure is intended to apply only to single family homes and low-rise multifamily apartments where each dwelling unit is served by a dedicated water heater. As a compliance option, it is a voluntary measure rewarding builders who wish to pursue the credit. The proposed measure is for new construction only.

The Compact Hot Water Distribution measure currently exists in 2016 Title 24, Part 6. The 2016 measure involves a Home Energy Rating System (HERS) verification process to demonstrate that the measured length of the hot water supply line from the water heater to the furthest fixture is less than a maximum specified pipe length, which varies with the conditioned floor area of the dwelling unit. Recent CalCERTS registry data collected over a 16-month period showed that only 0.1 percent of homes used this credit, and feedback from builders indicated the low uptake was due to the credit being not worth the added effort of an extra HERS verification effort. The proposed 2019 update is intended to provide added compliance flexibility to the measure by offering two compact credit options:

  1. A Basic Credit option that eliminates any HERS verification requirement, and
  2. An Expanded Credit option offering greater energy credits, but does require limited HERS verification.

Request for Feedback

The Statewide Utility Team encourages participation in the CASE Report development process through the submission of data—both primary sources and references to existing data. We are requesting data on areas such as energy savings, costs, market impacts, industry practices, barriers to code compliance, etc. from stakeholders. The data will inform the energy savings estimates, cost-effectiveness analysis, compliance and enforcement, and market impacts that will be presented in CASE Reports.

Do you have feedback or data to share? Send us an email at