Multifamily Restructuring

Proposal Description

The multifamily restructuring CASE Report will propose changes to envelope and HVAC requirements that differ under 2022 Title 24, Part 6 between multifamily buildings up to three habitable stories and multifamily buildings four or more habitable stories.

• Slab Perimeter Insulation
• Visible Transmittance
• Skylight Properties (Additions and Alterations)
• Central Ventilation Shaft Sealing
• Additions and Alterations Clean-Up
• Snapshot Quality Insulation Installation (QII)
• Verification (HERS/ATT) Clean-Up

Data may be provided anonymously. To participate or provide information, please email Lucy Albin ([email protected]) directly and cc [email protected].

Slab Perimeter Insulation

This proposed measure would extend the multifamily prescriptive requirement for slab perimeter insulation, currently only required for applicable multifamily buildings with three or fewer habitable stories, to multifamily buildings with any number of habitable stories.

The proposed measure would also clarify one metric used for compliance, from “U-factor” as is currently stated, to “F-factor” as is the correct term for this metric.

Visible Transmittance

This cleanup measure would change application of VT requirements for fenestration in multifamily buildings to align with the original intent of the requirement. Instead of applying to buildings four or more habitable stories, it would apply to fenestration in common use areas in multifamily buildings, regardless of number of stories. This change would apply to new construction, additions, and alterations. It does not modify field verification or require updates to the compliance software.

See the Multifamily Envelope topic for information on alignment of SHGC requirements by climate zone and window type (curtain wall, AW, or other) across all multifamily buildings.

Fenestration Properties

The fenestration properties measure would define consistent SHGC requirements by climate zone and window type (curtain wall, AW, or other) across all multifamily buildings. The measure would add SHGC requirements where not required in 2022 Title 24, Part 6 for buildings up to three habitable stories in Climate Zones 1, 3, 5, and 16. This measure would also define consistent Visual Transmittance (VT) requirements, considering interaction with the daylighting requirements applicable to common use areas.

Data Needs/Stakeholder Information Requests

Data needs include:

• Prevalence of daylit zones in multifamily dwelling units and common use areas

Skylight Properties (Additions and Alterations)

This proposed measure would change the categories that determine the required performance specifications for skylight alterations in multifamily buildings. Instead of requirements of altered or added skylights differing based on the number of habitable stories in the multifamily building, this proposed measure would apply the requirements for maximum U-Factor, maximum Solar Heat Gain Coefficient (SHGC), and minimum VT for multifamily buildings with four or more habitable stories to apply instead to all multifamily buildings with any number of stories. This proposed measure also modifies and clarifies exceptions for added and replaced skylights under a certain amount of square feet.

This change would address an oversight in the standards that requires a level of fenestration performance stringency that is not widely available for skylights, and which may not be technically feasible other than in the form of certain small tubular skylights.

Central Ventilation Shaft Sealing

This measure would extend the central ventilation shaft sealing for multifamily buildings with four or more habitable stories to all multifamily buildings with central ventilation, including buildings with three habitable stories or fewer. The measure would require acceptance testing of central ventilation duct leakage using a fan pressurization test to ensure that leakage does not exceed six percent of the central (e.g., rooftop) fan airflow rate at 50 Pa (0.2 inches of water column (w.c.)) for central ventilation duct serving more than six dwelling units, and fan airflow rate at 25 Pa (0.1 inches w.c.) for central ventilation duct serving six or fewer dwelling units.

Additions and Alterations Clean-Up

2022 multifamily restructuring left some gaps and misalignments in the additions and alterations chapter, as well as opportunity for streamlining code language. This clean-up measure will:

• Restructure requirements for consistency with the multifamily chapters for new construction, including organization by:
  • Addition vs. Alteration
  • Mandatory, Prescriptive, Performance
  • Building systems (envelope, IAQ, HVAC, DHW, etc.)
  • Dwelling unit vs. common use area
• Limit reference to other chapters and eliminate circular references; and
• Add clarifying language on the scope or circumstances under which the requirements apply.

Data Needs/Stakeholder Information Requests

Data needs include:

• Anticipated challenges with the 2022 Multifamily Additions, Alterations, and Repairs chapter, and areas for improvement.

Data may be provided anonymously. To participate or provide information, please email Lucy Albin—[email protected]—directly and CC [email protected].

Snapshot Quality Insulation Installation (QII)

QII is currently a prescriptive requirement for multifamily buildings with three or fewer habitable stories. This measure would maintain the prescriptive quality insulation installation (QII) requirements and verification protocol for multifamily buildings of three or fewer habitable stories.

The measure proposes a snapshot QII procedure which would apply prescriptively for multifamily buildings with four or more habitable stories, and as a compliance option for multifamily buildings with three or fewer habitable stories. Snapshot QII is designed to be possible to fulfill in a single visit to the building and includes QII inspection of all open envelope cavities during the visit(s), rather than requiring inspection of 100 percent of the envelope, for multifamily buildings with staged construction.

The proposed change would apply to additions greater than 700 square feet of conditioned floor area based on the building’s number of habitable stories. The proposed change does not apply to alterations or to buildings using curtainwall assembly types.

An exception for Climate Zone 7, which currently exists for buildings up to three habitable stories, would apply to all multifamily buildings (both full and snapshot QII).

Data Needs/Stakeholder Information Requests

The Statewide CASE Team has the following questions for stakeholders:

• What technical challenges prevent buildings from pursuing or complying with the existing QII requirement in multifamily buildings, if any?
• Would requiring insulation installers to undergo training for QII increase insulation installation quality?
• How could we time visits so that the building is in the right phase of construction to verify air sealing and insulation quality?

Data may be provided anonymously. To participate or provide information, please email Lucy Albin—[email protected]—directly and CC [email protected].

Verification (HERS/ATT) Clean-Up

This measure would extend HERS compliance credits to all applicable multifamily buildings, regardless of number of habitable stories, for:

1. Low Leakage Air-handling Units: Verify low leakage air handler and ducts installed and system leakage rate meets or exceeds rate specified on certificate of compliance
2. Variable Capacity Heat Pump (VCHP) Compliance Option: Verify system equipment is listed in CEC low-static pressure systems, non-continuous fan operation, refrigerant charge, low leakage ducts in conditioned space, ductless system in conditioned space, airflow to all habitable spaces, wall-mounted thermostats for zones >150 ft2, ducted airflow, and air filter pressure drop

The measure would remove verification requirements for buildings with three or fewer habitable stories, so that the compliance options can be claimed without verification for all applicable multifamily buildings, regardless of number of habitable stories, for:

1. Verified Energy Efficiency Ratio (EER/EER2): Verify system equipment is listed in approved directory and necessary information is provided
2. Verified Seasonal Energy Efficiency Ratio (SEER/SEER2): Verify system equipment is listed in approved directory and necessary information is provided
3. Verified Heating Seasonal Performance Factor (HSPF/HSPF2): Verify system equipment is listed in approved directory and necessary information is provided
4. Rated Heat Pump Capacity Verification: Verify system equipment is listed in approved directory and heating capacities are greater than or equal to values specified on certificate of compliance

The measure would also remove compliance options that are not applicable or common in multifamily buildings, including:

1. Evaporatively Cooled Condensers – Verify low leakage ducts, refrigerant charge, time delay response, listed equipment, and system efficiencies
2. Whole House Fan: Verify airflow rate and watt draw. Calculate efficacy (w/cfm). Confirm airflow rate and efficacy meet or exceed requirements of certificate of compliance
3. Central Fan Ventilation Cooling System: Verify system airflow and fan efficacy meet or exceed requirements of certificate of compliance

The measure would not modify the process for conducting the verification tests, and would not affect additions or alterations.
The measure would replace mention of “low-rise residential” and “high-rise residential” in the Residential and Nonresidential Appendices with “single-family” and “multifamily” and appropriate mention of multifamily buildings up to three habitable stories and four or more habitable stories.

Data Needs/Stakeholder Information Requests

Data needs include:

• Technical feasibility of technologies and prevalence of the compliance options in multifamily buildings.
• Barriers to removing and extending compliance options, and removing verification for proposed compliance options.
• Cost and labor time required to perform each verification test per dwelling unit.

Data may be provided anonymously. To participate or provide information, please email Lucy Albin—[email protected]—directly and CC [email protected].

Relevant Documents

Round Two Utility-Sponsored Stakeholder Meeting Materials

• Proposal Summary – Multifamily Restructuring, Envelope & HVAC (May 22, 2023)
• Proposal Summary – Multifamily Restructuring, Snapshot QII (Apr. 25, 2023)
• Proposal Summary – Multifamily Restructuring, Verification Clean-Up (Apr. 25, 2023)
• Presentation – Multifamily Restructuring, Verification Clean-Up (May 22, 2023)

Round One Utility-Sponsored Stakeholder Meeting Materials

• Stakeholder Meetings Introduction
• Multifamily Restructuring – Snapshot QII – Presentation (Feb. 14, 2023)
• Multifamily Restructuring – Snapshot QII – Proposal Summary (Feb. 3, 2023)
• February 14, 2023 Meeting Notes
• Multifamily Restructuring: Envelope & HVAC – Presentation (Feb. 21, 2023)
• Multifamily Restructuring: Envelope & HVAC – Proposal Summary (Feb. 15, 2023)
• February 21, 2023 Meeting Notes