This CASE Report proposes prescriptive and performance compliance pathway(s) for all-electric multifamily buildings that use electric appliances for regulated and non-regulated end uses. This topic builds on the 2019 Title 24, Part 6 Standards that allow a dual baseline strategy wherein electrically heated and water-heated buildings are compared to a code minimum electrically heated and water-heated building, whereas natural gas-based systems for heating and water heating are compared to code minimum natural gas-based systems. The limitation is that the dual baseline option for water heating is only available for multifamily buildings with individual water heaters, and the dual baseline option for heating ventilation and air conditioning (HVAC) is available only for low-rise multifamily buildings. The 2019 Title 24, Part 6 Standards did not address central water heating for both low-rise and high-rise residential buildings, HVAC, and non-regulated end uses, such as appliances and plug loads for mid-rise and high-rise residential buildings.
The Statewide CASE Team investigated suitable strategies for achieving all-electric, including electric heat pump HVAC systems, heat pump water heating (HPWH) systems, building envelope improvements, appliances and miscellaneous loads, as well as on-site renewables. For space heating, the Statewide CASE Team investigated electric heat pump HVAC systems to be the prescriptive requirement and the baseline (standard design) system for the performance approach for all multifamily buildings. The Statewide CASE Team chose single zone split system heat pumps as the proposed baseline system choice with efficiency levels required by and constrained by federal appliance standards for residential heat pump systems. For Climate Zone 16 only, the Statewide CASE Team analyzed a combined measure package that includes the limited use of natural gas. The measure included in the Climate Zone 16 package include the use of gas furnace as supplemental heating for the electric heat pump and fenestration U-factor and solar heat gain coefficient (SHGC) requirements. The fenestration requirements are presented in a separate CASE Report (Multifamily Restructuring CASE Report 2020), and incorporated into this CASE Report for completeness of the all-electric proposal. Summary values for proposed fenestration requirements are presented in Table 21. For the limited anticipated multifamily new construction in Climate Zone 16 during the 2022 code cycle, the Statewide CASE Team did not identify a cost-effective all electric space heating option. It is expected, however, that most builders will opt for the performance approach for projects in this region.
For water heating, the Statewide CASE Team reviewed options for establishing a baseline for central water heating systems utilizing heat pump water heaters. For unregulated loads, the Statewide CASE Team reviewed options for establishing appropriate modeling of electric end uses for cooking, clothes washing, clothes drying and other internal loads.
Based on the analysis of these measures and packages, the Statewide CASE Team proposes the following code changes:
- Prescriptive Requirements
- Space heating: Require the use of electric space heating for mid-rise and high-rise multifamily buildings. The prescriptive requirement would be a single zone ducted heat pump (SZHP). For Climate Zone 16, allow the use of gas furnace for supplemental heating.
- Central Water Heating: Prescriptive alternate pathway for central HPWH. The current 2019 Title 24, Part 6 prescriptive alternate pathway for individual HPWH will be retained.
- Individual DHW systems: Retain the current 2019 Title 24, Part 6 requirements.
- Performance Requirements
- HVAC System: Regardless of the proposed system fuel type, the standard design shall be single zone ducted heat pump (SZHP) for mid-rise and high-rise multifamily buildings. The electric single zone ducted heat pump (SZHP) would have minimum efficiency levels meeting applicable state and federal appliance standards. For Climate Zone 16, the SZHP shall have a gas furnace for supplemental heating.
- Central DHW system: Standard system fuel type is the same as the proposed design. The standard design shall be a central HPWH system if proposed design uses central electric water heating.
- Individual DHW systems: Retain the current 2019 Title 24, Part 6 requirements. The standard DHW system be an individual HPWH system if proposed design uses individual HPWH in multifamily buildings.
- Appliances and miscellaneous electric load (MEL) modeling rulesets for mid-rise and high-rise multifamily dwelling units shall be modified to match existing requirements for low-rise residential buildings in 2019 Title 24, Part 6 rulesets in CBECC-Res.
The proposed measure does not apply to alterations or additions.
The proposed code change would modify the following compliance documents.
- For the DHW prescriptive compliance approach, the proposed code change would add a table to an existing or create a new Worksheet (CR1R-PLB).
- For prescriptive HVAC change, update the NRCC-MCH-E to remove gas space heating option for high-rise residential buildings. Minor updates may be needed in CF1R-NCB-01-E accordingly.
- Add field verification of installed heat pump EER. Minor updates may be needed in CF1R-NCB-01-E accordingly.
The proposed changes would also require updates to the following compliance forms:
Minor updates may be needed in CF1R-PRF-E and NRCC-PRF-E accordingly.
The proposed code change would add descriptions and data fields for the field testing and visual inspection of central HPWH systems. Examples of the revised document are presented in Section 7.6.
The nonresidential grid integration CASE Report expands the HPWH demand flexibility compliance credit that is available for residential buildings that use the performance approach to comply with code so that a similar credit would also be available for nonresidential buildings including multifamily buildings with individual and central HPWH systems (Statewide CASE Team 2020). Specific revisions include updating Joint Appendix 13 – Qualification Requirements for Heat Pump Water Heating Demand Management Systems (JA13) to make the language more inclusive of HPWH systems installed in nonresidential buildings. The updated language in JA13 would align with the eligibility requirements for the Self-Generation Incentive Program (SGIP), which added HPWH as an eligible measure in January 2020. For this compliance option to become available for use, the compliance software would need to be updated to add a feature that would simulate the energy impacts of operating HPWHs with demand management capabilities enabled, which could include optimizing for utility time-of-use or critical peak pricing rates.
Measure proposals, supporting documents, and other outside references will be made public as they become available.
- CASE Study Results Report – Multifamily All Electric Package
- Final CASE Report – Multifamily All Electric Package (Updated 4/26/21)
- Final CASE Report – Multifamily All Electric Package
- Draft CASE Report – Multifamily All Electric Package
- 2019 New and Revised Multifamily Prototypes
Round Two Utility-Sponsored Stakeholder Meeting Materials
- Presentation – March 17 – Multifamily Water Heating and All Electric Package (Updated 4/13)
- Multifamily All Electric Package Submeasure Summary (Updated 4/13)
- Multifamily Central Heat Pump Water Heating Submeasure Summary
- Notes – March 17 – Multifamily Water Heating and All Electric Package
Round One Utility-Sponsored Stakeholder Meeting Materials
- Multifamily All Electric Submeasure Summary – July 30, 2019
- Multifamily Central Heat Pump Water Heating Submeasure Summary – August 22, 2019
- Presentation – Sept 10 – Grid Integration Utility-Sponsored Stakeholder Meeting
- Notes – Sept 10 – Grid Integration Utility-Sponsored Stakeholder Meeting
- Notes – Sept 5 – Nonresidential and Multifamily Outdoor Sources and Daylighting Stakeholder Meeting
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.