Compartmentalization and Balanced Ventilation / Indoor Air Quality (IAQ)
Measure descriptions are subject to change.
The 2019 and 2022 version of Title 24 requires multifamily units to comply with either of the following: providing balanced ventilation or meeting a compartmentalization maximum of 0.3 cfm/sf @50 Pa. This proposed measure would add a mandatory measure for all multifamily units to:
- Use supply-only or balanced ventilation as a whole dwelling unit strategy. In other words, use of exhaust-only ventilation could not be used for whole dwelling unit ventilation.
- Require a mandatory compartmentalization at a maximum of level of 0.3 cfm/sf @50Pa.
Local exhaust systems should still be used to meet local exhaust requirements, such as in bathrooms, kitchens, and dryers, and exhaust fans could be used as part of a balanced ventilation approach. The proposed requirement would affect all new construction multifamily units.
In addition to these changes to the mandatory requirements, the Statewide CASE Team proposes the following changes to the prescriptive requirements and compliance options to promote energy savings:
- Revising the prescriptive requirement in the 2022 Title 24, Part 6 that requires multifamily dwelling units in Climate Zones 1, 2, and 11-16 that use the balanced ventilation path to include an HRV or ERV. The proposed change is to prescriptively require all multifamily dwelling units in Climate Zones 1, 2, 4, 11 through 14, and 16 to use balanced ventilation with an HRV or ERV. Multifamily dwelling units in these climate zones that use a performance path could use supply-only or ventilation without heat recovery, but would need to compensate by exceeding code requirements for another measure.
- Adding a mandatory requirement that the supply air filter be accessible (such that the filter access panel is within 10 feet of a walking surface), and a prescriptive requirement for an accessible outdoor air intake and a fault indicator display (FID). Projects that do not meet these prescriptive requirements could use the performance path and incur a 10% fan energy penalty and – for projects with a heat recovery ventilator (HRV) — incur a 10% reduction in the sensible recovery efficiency.
While the focus of this proposed measure is multifamily IAQ, the proposed changes for the filter accessibility, outdoor air intake accessibility, and FID are proposed for both single-family and multifamily buildings. These requirements follow ACM requirements for the 2022 Title 24, Part 6.
The primary purpose for the proposed mandatory measure (compartmentalization and balanced / supply-only ventilation) is to promote good indoor air quality (IAQ). Compartmentalization reduces pollutant transfer between units and particle infiltration. A mechanical source of supply air for ventilation is important for IAQ as a unit’s envelope is tightened to ensure adequate outdoor air. The two components of the measure also work hand-in-hand. Because compartmentalization tightens a unit’s envelope on all sides—with the exterior, and with adjacent spaces (e.g., corridor, adjacent units, trash chutes, etc.), the measure also saves energy by reducing leakage to the exterior, thereby reducing heating and cooling energy. In addition, compartmentalization reduces noise transfer between units and with the exterior.
The prescriptive H/ERV requirement is proposed for energy savings, and is cost effective in the proposed climate zones.
The proposal does not make changes for additions or alterations. But since the additions and alterations sections reference the new construction requirements, the Statewide CASE Team proposes revised language so the technical requirements remain the same for additions and alterations.
Data Needs/Stakeholder Information Requests
Data needs may include:
- Energy Savings – quantifiable savings (in BTUs, kW, etc.) that can be attributed to each measure.
- Technical Feasibility – how well-established the technology or practice is in the industry
- Market Readiness – availability in the market, and certainty regarding performance, reliability and cost
- Non-energy Benefits – consumer or societal benefits such as improved health and safety, reduced water use, and GHG emission reductions
- Costs –
- Life cycle costs
- First costs
- Operational costs
- FID costs
- Economic Impacts – job creation, environment and social justice, equity
Data may be provided anonymously. To participate or provide information, please email Marian Goebes ([email protected]) directly and CC [email protected]
Submit feedback and view the Energy Commission's proceedings and available proposed code language by visiting their 2025 Building Energy Efficiency Standards page.
This measure page will be updated as the 2025 code cycle progresses. For questions or suggestions, email [email protected]. Please include the measure name in the subject line.
Round Two Utility-Sponsored Stakeholder Meeting Materials
- Multifamily Compartmentalization and Balanced Ventilation: Indoor Air Quality (IAQ) – Proposal Summary
- IAQ System Accessibility & FID Requirements – Presentation (May 17, 2023)
Round One Utility-Sponsored Stakeholder Meeting Materials
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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.