2025 California Title 24 Building Energy Efficiency Standards

The Effective Date for the 2025 California Building Energy Efficiency Standards is January 1st, 2026.

What’s New for 2025

The most significant change in the 2025 Building Energy Efficiency Standards affecting single- family residential buildings is the change to a single fuel baseline with heat pump being prescriptively required for both water heating and space heating.

Summary of Changes for Residential Buildings Include:

Mandatory Requirements:

• Heat pump water heaters installed with inlet air from outside must have backup heat if compressor cutout temperature is above or equal to the local Heating Winter Median of Extremes (Section 110.3(c)7A).
• Ventilation is required when installing a heat pump water heater (Section 110.3(c)7B).
• Pool- and/or spa-heating systems must be sized appropriately in newly constructed single- family buildings with heated swimming pools and spas (Section 110.4(c)).
• Heat pump pool heaters with supplementary heaters shall have controls installed to ensure that the supplementary heater does not operate when the heating load can be met by the heat pump alone (Section 110.4(d)).
• Exception to mandatory roof deck insulation in newly constructed attic systems in Climate Zones 4 and 8–16 to meet an area-weighted average U-factor no greater than 0.184 (Section 150.0(a)1), if the space-conditioning system is a ductless systems or for space- conditioning duct systems buried within insulation in an attic that complies using Section 150.1(b) and is verified according to RA 3.1.4.1.
• Increased mandatory required minimum wall insulation from R-13 to R-15 (0.095 U-factor) for 2 x 4 wood framed wall assemblies, and R-20 to R-21 (0.069 U-factor) for 2 x 6 assemblies (Section 150.0(c)).
• Clarifies that block loads (the total load for all rooms combined that are served by the central equipment) may be used for the purpose of system sizing for additions (Section 150.0(h)1).
• Provides guidance on how to use authorized load calculations in system sizing and selection. Specifically, states that heat pump heating capacity must meet minimum requirements from the California Building Code without including supplementary heating capacity; clarifies that there is no limit on minimum cooling or maximum heating capacity, and furnace heating capacity is based on ACCA Manual S-2023, Table N2.5 (Section 150.0(h)5).
• Establishes defrost requirements. Specifically, if a heat pump is equipped with a installer- adjustable defrost delay timer, the delay timer shall be set to greater than or equal to 90 minutes. This control configuration shall be tested by the installer and certified on the CF2R. Exceptions include homes in Climate Zones 6 and 7, and homes with conditioned floor area of 500 square feet or less in Climate Zones 3, 5–10, and 15 (Section 150.0(h)6).
• Requires that heat pump supplementary heating (electric resistance or gas) shall operate only above an outdoor temperature of 35°F during defrost or when the user selects emergency operation. This control configuration shall be tested by the installer and certified on the CF2R. There are exceptions for room air-conditioner heat pumps, buildings in Climate Zones 7 and 15, and buildings with a conditioned floor area less than 500 square feet (Section 150.0(h)7).
• Requires that electric resistance supplementary heat can have a capacity no larger than the heat pump nominal cooling capacity (at 95°F ambient conditions) multiplied by 2.7 kilowatts (kW) per ton, rounded up to the closest kW (Section 150.0(h)8).
• Requires that variable- or multispeed systems controlled by third-party thermostats shall be capable of responding to heating and cooling loads by modulating system compressor speed and meet thermostat requirements in Section 150.0(i)2. This control configuration shall be tested by the installer and certified on the CF2R (Section 150.0(h)9).
• Requires that thermostats controlling heat pumps with supplementary heat (electric resistance or gas) shall receive outdoor air temperature from an outdoor air temperature sensor or from an internet weather service, display the outdoor temperature, have an indicator to notify when supplementary heat or emergency heat is in use, and lock out supplementary heat when the outdoor temperature is above 35°F (alone or in conjunction with heat pump operation). This control configuration shall be tested by the installer and certified on the CF2R. There are exceptions for room air-conditioner heat pumps (Section 150.0(i)).
• Allows ducts in unvented attics to be insulated to R-4.2, less than the mandatory minimum of R-6, provided certain other requirements are met (Section 150.0(m)1Bi).
• Allows multispeed or variable-speed compressor systems with controls that vary fan speed based on the number of zones to conditioning may demonstrate compliance with airflow and fan efficacy requirements of 150.0(m)13C by operating the system at maximum compressor capacity and system fan speed, with all zones calling for conditioning (Section 150.0(m)13).
• Revises to new whole dwelling unit mechanical ventilation rates for detached and attached single-family dwellings (Section 150.0(o)1C). The revision includes accessibility requirements to facilitate servicing balanced and supply-only ventilation systems including accessibility of indoor air quality (IAQ) filters and heat recovery ventilation/energy recovery ventilator (HRV/ERV) cores, IAQ System components, and outdoor air intake location, as well as outdoor air intake design (Section 150.0(o)1Civ).
• Mandatory minimum U-factor for fenestration, including skylights, decreased to a weighted average U-factor of 0.40 (Section 150.0(q)).
• Fenestration installed in buildings located in fire hazard severity zones or wildland-urban interface (WUI) fire areas as designated by the local enforcement agency, is excepted from mandatory fenestration requirements (Section 150.0(q)).
• The battery energy storage system ready requirements have been updated to apply only for newly constructed single-family buildings that have a minimum 125 amp service panel, and an exception was added for single-family buildings that have already installed battery energy storage systems (Section 150.0(s)).

Prescriptive Compliance:

• The prescriptive maximum U-factor requirement for window assemblies in most homes was reduced to 0.27 from 0.30 in Climate Zones 1 through 5, 11 through 14, and 16; all other climate zones remain at 0.30 U-factor. This change applies to homes 500 square feet or less except in Climate Zone 5, where the prescriptive maximum U-factor for homes 500 square feet or less remains at 0.30 (Section 150.1(c)3A).
• A new alternative prescriptive compliance pathway under Option C of Table 150.1-A, for cathedral ceilings in single-family new construction. Cathedral ceilings will require a minimum R-value of 38 across all climate zones (Section 150.1(c)1A).
• Under the prescriptive compliance approach, in all climate zones, the heating equipment is required to be a heat pump or shall meet the performance compliance requirements of Section 150.1(b)1 (Section 150.1(c)6).
• Refrigerant charge verification is now required for heat pumps in all climate zones (Section 150.1(c)7A, Table 150.1-A).
• Fault indicator displays have been removed as an available method for refrigerant charge verification (Section 150.1(c)7A).
• Introduce solar access roof area (SARA) multipliers for steep-sloped and low-sloped roofs that are used to determine the PV system size in kW for a given square foot area of usable SARA roof space (Section 150.1(c)14).

Performance Compliance:

• Long-term system cost (LSC) and source energy metrics used for compliance through the performance approach (Section 150.1(b)1).

Additions and Alterations:

• Mandatory requirement for heat pump water heaters installed with inlet air from outside must have backup heat if the compressor cutout temperature is above or equal to the local heating winter median of extremes (Section 110.3(c)7A).
• Mandatory requirement for ventilation when installing a heat pump water heater (Section 110.3(c)7B).
• For additions greater than 700 square feet, the prescriptive maximum U-factor requirement for window assemblies was reduced to 0.27 from 0.30 in Climate Zones 1–5 , 11–14, and 16; the prescriptive maximum U-factor in Climate Zones 6–10 and 15 remains at 0.30. For alterations that add fenestration area, the maximum solar heat gain coefficient (SHGC) value in Climate Zone 15 is 0.23 (Section 150.2(a)1A, Table 150.1-A).
• For additions 700 square feet or less, Option C for roof insulation provides a new alternative prescriptive pathway for cathedral ceilings. Cathedral ceiling will require a minimum R-value of 38 for all climate zones (Section 150.2(a)1B, Table 150.1-A).
• In addition to the requirements in Section 150.0(h) for additions, in situations where airflow is NOT field verified to be at least 350 cubic feet per minute (cfm)/ton, maximum capacity limits are provided in Tables 150.2-A and B that depend on the relative sizes of the calculated heating design load (HL) and cooling design load (CL), the type of space conditioning system, and the duct sizing (Section 150.2(a)1E). There is an exception for ductless space-conditioning systems, as well as variable-speed and multispeed systems.
• For additions, the envelope leakage specified in the space-conditioning load calculation shall be no greater than the values shown in Table 150.2-C (“average” for many load calculation software tools). If leakage is established through field verification and diagnostic testing, the tested envelope leakage value may be used in the load calculations (Section 150.2(a)1E).
• The energy budget for additions is expressed in terms of LSC (Section 150.2(a)2).
• For altered space-conditioning systems refrigerant charge verification is required for heat pumps in all climate zones, and for air conditioners in Climate Zones 2 and 8–15 (Section 150.2(b)1F).
• Fault indicator displays have been removed as an available method for refrigerant charge verification (Section 150.2(b)1F).

(Excerpted from the CEC Title 24 Residential Compliance Manual)