Title 24 · California Energy Code
Roof and ceiling insulation options, assembly U‑factors and radiant barrier requirements
For homeowners: your roof/ceiling must either meet the table’s assembly U‑factor or be insulated to the listed R‑value option (example: R‑38 ceilings in many zones). If the table marks a radiant barrier as required for your climate zone, you must install a compliant radiant barrier and follow QII verification when the table requires it.
Last reviewed: July 6, 2026
What the code requires — plain English
Roof and ceiling assemblies must meet either a maximum assembly U‑factor or meet one of the prescribed R‑value insulation options shown in Table 150.1‑A. Where Table 150.1‑A (or Table 170.2‑A for multifamily) requires a radiant barrier, it must be installed to the standards in § 110.8(j) and the Reference Residential Appendix RA4. These prescriptive options and the requirement to show Quality Insulation Installation (QII) are set out in § 150.1(c) (single‑family/residential) and the comparable multifamily provisions in § 170.2(a).
The simplest rule: meet the table value for the assembly U‑factor or install the matching R‑value option — and if the table marks a radiant barrier as required, install it per § 110.8(j) and RA4.
Requirements in detail
Key defined terms (first mention bolded): assembly U‑factor, R‑value, radiant barrier, vented/unvented attic, QII, climate zone. See § 150.1(c) and § 170.2(a) for the controlling prescriptive rules.
How the table and options work (decision logic)
- The code provides a set of compliance options (commonly labeled Option A/B/C/D in the tables). Each option describes either:
- a required overall assembly U‑factor, or
- one or more R‑value installations (for example, insulation at the ceiling, or insulation at/under the roof deck), or
- an option for roof assemblies above conditioned spaces with no attic using a U‑factor.
- Where a radiant barrier is marked REQ in the table for a given climate zone/option, a radiant barrier must be installed and must meet Section § 110.8(j) and Appendix RA4 installation requirements.
Quick reference table — decision‑relevant dimensions
| Decision item | Typical values / meaning | Code reference |
|---|---|---|
| Assembly U‑factor option | Tables specify a maximum assembly U‑factor to meet (use calculation or certified alternative products). | § 150.1(c) |
| Ceiling/attic R‑value options | Table entries show ceiling/attic R‑values (example: R‑38, R‑30 for many wood‑framed ceilings). Use the table per climate zone. | § 150.1(c); Table 150.1‑A (see Option B/C entries) |
| Radiant barrier | If table shows REQ, install radiant barrier per § 110.8(j) and Reference Appendix RA4; above‑deck radiant barriers must meet fire & material standards (see § 1510). | § 150.1(c)2, § 110.8(j), § 1510 |
| Multifamily roof options | Multifamily prescriptive Table 170.2‑A uses the same Option B/C/D structure; radiant barrier requirements likewise referenced in § 170.2(a). | § 170.2(a) |
| Quality Insulation Installation (QII) | QII is required where noted in the table; when required, follow the field verification procedures in Reference Appendix RA3.5. | § 150.1(c)E and Table 150.1‑A |
Notes on the table content (examples drawn from the table snippets):
- Many climate zones have ceiling insulation options of R‑38 (or R‑30 in some zones) as the prescriptive ceiling insulation path (Option B/C). Radiant barrier columns in the table indicate REQ or NR by climate zone and option — follow the specific cell in Table 150.1‑A for your zone.
- Multifamily Table 170.2‑A follows the same approach and explicitly calls out Option B (below‑deck + ceiling insulation), Option C (ceiling insulation in attic), and Option D (U‑factor for roof above conditioned space).
Radiant barrier technical & installation requirements
- A radiant barrier required by the prescriptive table must comply with § 110.8(j) (product requirements) and the installation criteria in Reference Residential Appendix RA4. For above‑deck radiant barriers, follow the Building Code § 1510 material and fire‑testing provisions (ASTM C1313 for above‑deck radiant barrier material; face the low‑emittance surface to the continuous airspace).
Exceptions & special cases
- Executive‑director approved U‑factor calculations: The Table 150.1‑A insulation requirements may be met by assemblies that meet the required maximum U‑factors using an approved U‑factor calculation method that considers all assembly elements. (Exception to § 150.1(c)1.)
- Additions and small projects: Additions under certain sizes have modified requirements; for example, additions ≤ 700 ft² follow modified roof/attic U‑factor or R‑value and radiant barrier rules in the additions chapter. Check the additions exceptions in the code (see the additions/alterations text and § 150.2 / § 180.1 references).
- Solar‑reflective roof product tradeoffs: For roof solar reflectance/emittance requirements there are trade‑offs with roof deck insulation (see Table 150.2‑E / 180.2‑A). Also, roof constructions with weight ≥ 25 lb/ft² are exempt from aged reflectance/emittance SRI minimums.
- Radiant barrier placement caveat: Some equivalencies (for meeting roof reflectance rules) treat a radiant barrier as acceptable only if it is not installed directly above spaced sheathing — check the exception text that references that limitation.
Common mistakes
- Assuming a radiant barrier is optional when the table cell shows REQ — always check Table 150.1‑A or 170.2‑A for your climate zone and option before omitting it.
- Installing insulation but not meeting QII verification when QII is shown as required in the table. QII is not optional where the table requires it — use RA3.5 procedures.
- Placing insulation so it is not in direct contact where the code requires direct contact with a continuous roof or drywall ceiling (some options require insulation be in direct contact with the roof or ceiling per § 150.1(c)). Always follow the installation location called out in the option.
- Using a radiant barrier product that does not meet the material or fire‑testing standards for above‑deck installation (see §1510).
Worked example — new wood‑framed house in Climate Zone 4 with a ventilated attic
Scenario: New single‑family home, Climate Zone 4, ventilated attic, wood‑framed ceiling/attic.
- Check Table 150.1‑A for Climate Zone 4 (prescriptive options). The table shows a common prescriptive ceiling option of R‑38 for vented attics and that a radiant barrier may be required for some options in CZ4. Consult the specific table cell for CZ4 to confirm whether radiant barrier is REQ for the chosen option.
- Option path: choose ceiling insulation Option C (ceiling insulation located between attic and conditioned space) with R‑38 installed between framing members — that meets the R‑value prescriptive path where R‑38 is the table value.
- Radiant barrier: because Table 150.1‑A marks radiant barrier REQ for vented‑attic Option C in many climate zones including CZ4, install a compliant radiant barrier per § 110.8(j) and Appendix RA4. Confirm the radiant barrier material/installation meets the requirements in § 1510 if installed above deck.
- QII: If Table 150.1‑A indicates QII is required for the chosen option/zone, follow Reference Appendix RA3.5 verification procedures and keep documentation.
Result: With R‑38 installed at the ceiling, a properly installed radiant barrier (if the table requires it), and QII verification when required, the assembly complies prescriptively under § 150.1(c) for Climate Zone 4.
Related provisions
- § 150.1(c) — Single‑family prescriptive insulation table and related rules (Table 150.1‑A).
- § 170.2(a) — Multifamily prescriptive envelope requirements and Table 170.2‑A (roof options and radiant barrier references).
- § 110.8(j) — Product requirements for radiant barriers (referenced by the prescriptive tables).
- § 1510 (Building Code) — Above‑deck radiant barrier material and installation standards (fire testing and ASTM C1313).
- Reference Appendix RA3.5 — QII field verification procedures.
- Reference Residential Appendix RA4 — Radiant barrier installation criteria.
Code references
Grounded in the retrieved California Energy Code — click a citation to read the verbatim passage:
§ 170.2 High relevance — show source text
Exception 2 to Section 170.2(a)1A: Roof constructions with a weight of at least 25 lb/ft2 are not required to comply with the minimum requirements for solar reflectance and thermal emittance or SRI. B. Roof insulation. roofs shall have an overall assembly U -factor no greater than the applicable value in Table 170.2-A, meeting i, ii, iii or iv below. Where required by Sections 110.8 and 160.1(a), insulation shall be placed in direct contact with a continuous roof or drywall ceiling. i. Option A: Reserved. ii. Option B: A minimum R -value of insulation installed between the roof rafters in contact with the roof deck and an additional layer of ceiling insulation located between the attic and the conditioned space when meeting Section 170.2(c)3Biia; or iii. Option C: A minimum R -value of ceiling insulation located between the attic and the conditioned space when meeting Section 170.2(c)3Biib. iv. Option D: A minimum U -factor for roof assemblies above conditioned space without attic space. C. Radiant barrier. A radiant barrier required in Table 170.2-A shall meet the requirements specified in Section 110.8(j), and shall meet the installation criteria specified in Reference Residential Appendix RA4 .
- Wall insulation.
A. Exterior walls shall have an overall assembly U -factor no greater than the applicable value in Table 170.2-A. B. Demising walls shall meet the requirements of Section 160.1(b)7. Vertical windows in demising walls between conditioned and unconditioned spaces shall have an area-weighted average U -factor no greater than the applicable value in Table 170.2-A.
- Fenestration.
A. Vertical fenestration and glazed doors in exterior walls shall comply with Subsections i, ii and iii:
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MULTIFAMILY BUILDINGS—PERFORMANCE AND PRESCRIPTIVE COMPLIANCE APPROACHES
i. Percent fenestration area shall be limited in accordance with the applicable requirements of a and b below: a. A total fenestration area no greater than 20 percent of the conditioned floor area; and b. A total fenestration area no greater than 40 percent of the gross exterior wall area. NOTE: Demising walls are not exterior walls, and therefore demising wall area is not part of the gross exterior wall area, and fenestration in demising walls is not part of the fenestration area limitation. ii. Fenestration properties. Installed fenestration products, including glazed doors, shall have an area-weighted average U -factor, relative solar heat gain coefficient (RSHGC) and visible transmittance (VT) meeting the applicable fenestration values in Table 170.2-A and shall be determined in accordance with Sections 110.6(a)2 and 110.6(a)3. Vertical fenestration in demising walls between conditioned and unconditioned spaces is only required to comply with the area-weighted average U -factor requirement in Table 170.2-A. Exception 1 to Section 170.2(a)3Aii: For each dwelling unit, up to 3 square feet of new glazing area installed in doors shall not be required to meet the U -factor and RSHGC requirements of Table 170.2-A.
§ 0.025. High relevance — show source text
i. Roof and ceiling insulation in a ventilated attic shall meet one of the following requirements: a. In Climate Zones 1, 2, 4, and 8 through 16, achieve an overall assembly U -factor not exceeding 0.025. In wood framed assemblies, compliance with U -factors may be demonstrated by installing insulation with an R -value of R-38 or greater.
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MULTIFAMILY BUILDINGS—ADDITIONS, ALTERATIONS AND REPAIRS TO EXISTING MULTIFAMILY BUILDINGS
b. In Climate Zones 3 and 5 through 7, achieve an overall assembly U- factor not exceeding 0.031. In wood framed assemblies, compliance with U- factors may be demonstrated by installing insulation with an R- value of R-30 or greater. ii. Radiant barrier. For buildings three habitable stories or less, radiant barriers shall be installed in attics with exposed attic deck undersides in Climate Zones 2–15. iii. Extensions of existing wood-framed walls may retain the dimensions of the existing walls and shall install cavity insulation of R-15 in a 2x4 framing and R-21 in a 2x6 framing; and iv. Fenestration products must meet the U- factor, RSGHC and VT requirements of Table 180.2-B. v. Quality insulation installation (QII) requirements of Section 170.2(a)6 do not apply. Exception to Section 180.1(a)1B: Insulation in an enclosed rafter ceiling shall meet the requirements of Section 160.1(a). Exception to Section 180.1(a)1: Additions that increase the area of the roof by 2,000 square feet or less are not required to comply with the solar ready requirements of Section 160.8. 2. Mechanical ventilation for indoor air quality. Additions to existing buildings shall comply with Section 160.2 subject to the requirements specified in Subsections A and B below. When field verification and diagnostic testing are required by Section 180.1(a)2, buildings with three habitable stories or fewer shall use the applicable procedures in the Residential Appendices, and buildings with four or more habitable stories shall use the applicable procedures in Nonresidential Appendices NA1 and NA2.
Exception to Section 180.1(a)2: A dwelling unit air leakage test is not required for additions. A. Whole-dwelling unit mechanical ventilation . i. Dwelling units that meet the conditions in Subsection a or b below shall not be required to comply with the whole-dwelling unit ventilation airflow specified in Section 160.2(b)2Aiv or 160.2(b)2Av. a. Additions to an existing dwelling unit that increase the conditioned floor area of the existing dwelling unit by less than or equal to 1,000 square feet. b. Junior accessory dwelling units (JADU) that are additions to an existing building. ii. Additions to an existing dwelling unit that increase conditioned floor area by more than 1,000 square feet shall have mechanical ventilation airflow in accordance with Section 160.2(b)2Aiv or 160.2(b)2Av, as applicable. The mechanical ventilation airflow rate shall be based on the conditioned floor area of the entire dwelling unit comprising the existing dwelling unit conditioned floor area plus the addition conditioned floor area.
§ 0.23 High relevance — show source text
iii. Alterations that add fenestration area shall have a maximum SHGC value of 0.23 in Climate Zone 15.
iv. When existing siding of a wood-framed wall is not being removed or replaced, cavity insulation of R-15 in a 2 × 4 framing and R-21 in a 2 × 6 framing shall be installed and continuous insulation is not required. v. Additions that consist of the conversion of existing spaces from unconditioned to conditioned space shall not be required to perform the following as part of QII: a. Existing window and door headers shall not be required to be insulated. b. Air sealing shall not be required when the existing air barrier is not being removed or replaced. B. Additions that are 700 square feet or less shall meet the requirements of Section 150.1(c), with the following modifications: i. Roof and ceiling insulation in a ventilated attic shall meet one of the following requirements: a. In Climate Zones 1, 2, 4, and 8 through 16, achieve an overall assembly U -factor not exceeding 0.025. In wood framed assemblies, compliance with U -factors may be demonstrated by installing insulation with an R -value of R-38 or greater. b. In Climate Zones 3, and 5 through 7, achieve an overall assembly U -factor not exceeding 0.031. In wood framed assemblies, compliance with U -factors may be demonstrated by installing insulation with an R value of R-30 or greater.
ii. Radiant barriers shall be installed in Climate Zones 2-15.
iii. Extensions of existing wood-framed walls may retain the dimensions of the existing walls and shall install cavity insulation of R-15 in a 2 × 4 framing and R-21 in a 2 × 6 framing. iv. In Climate Zones 2, 4 and 6-15; the maximum allowed west-facing fenestration area shall not be greater than 60 square feet; and shall also comply with either a or b below: a. For additions that are 700 square feet or less but greater than 400 square feet, the maximum allowed fenestration area limit is the greater of 120 square feet or 25 percent of the conditioned floor area of the addition. b. For additions that are 400 square feet or less, the maximum allowed fenestration area is the greater of 75 square feet or 30 percent of the conditioned floor area of the addition. v. Quality Insulation Installation (QII) requirements of Section 150.1(c)1E do not apply. vi. When existing siding of a wood-framed wall is not being removed or replaced, cavity insulation of R-15 in a 2 × 4 framing and R-21 in a 2 × 6 framing shall be installed and continuous insulation is not required.
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SINGLE-FAMILY RESIDENTIAL BUILDINGS—ADDITIONS AND ALTERATIONS TO EXISTING RESIDENTIAL BUILDINGS
Exception to Section 150.2(a)1B: Insulation in an enclosed rafter ceiling shall meet the requirements of Section 150.0. C. Mechanical ventilation for indoor air quality. Additions to existing buildings shall comply with Section 150.0(o) subject to the requirements specified in Subsections i and ii below. i. **Whole-dwelling unit mechanical ventilation.
§ 0.184. High relevance — show source text
(a) Roof deck, ceiling and rafter roof insulation. The opaque portions of roof decks separating attic spaces from ambient air, and ceilings or rafter roofs separating conditioned spaces from unconditioned spaces or ambient air, shall meet the requirements of Items 1 through 4 below:
- In Climate Zones 4 and 8 through 16, roof decks in newly constructed attics that are above conditioned space shall be insulated to achieve an area-weighted average U -factor not exceeding U-0.184. Exception 1 to Section 150.0(a)1:
i. The space-conditioning system air handler and ducts are located entirely in conditioned space below the ceiling separating the occupiable space from the attic; or ii. The space-conditioning system air handler is located in unconditioned space and has 12 linear feet or less of supply duct, including the length of the air handler and the plenum, located in unconditioned space, with all other portions of the supply ducts located in conditioned space below the ceiling separating the occupiable space from the attic; or iii. The space-conditioning system is a ductless system. Exception 2 to Section 150.0(a)1: 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. 2. Ceilings and rafter roofs shall be insulated to achieve an area-weighted average U -factor not exceeding U-0.043 or shall be insulated between wood-framing members with insulation resulting in an installed thermal resistance of R-22 or greater for the insulation alone. For vented attics, the mandatory insulation shall be installed at the ceiling level; for unvented attics, the mandatory insulation shall be placed at either ceiling or roof level; and Exception to Section 150.0(a)2: Ceilings and rafter roofs in an alteration shall be insulated to achieve an area-weighted average U-factor not exceeding 0.054 or shall be insulated between wood-framing members with insulation resulting in an installed thermal resistance of R-19 or greater. 3. Attic access doors shall have permanently attached insulation using adhesive or mechanical fasteners. The attic access shall be gasketed to prevent air leakage; and 4. Insulation shall be installed in direct contact with a roof or ceiling which is sealed to limit infiltration and exfiltration as specified in Section 110.7, including but not limited to placing insulation either above or below the roof deck or on top of a drywall ceiling.
(b) Loose-fill insulation. When loose-fill insulation is installed, the minimum installed weight per square foot shall conform with the insulation manufacturer’s installed design weight per square foot at the manufacturer’s labeled R -value.
(c) Wall insulation. Opaque portions of above grade walls separating conditioned spaces from unconditioned spaces or ambient air shall meet the following requirements:
- 2 × 4 inch framing shall have an overall assembly U -factor not exceeding U-0.095 Exception to Section 150.0(c)1: Existing walls already insulated to a U -factor not exceeding U-0.110 or already insulated between framing members with insulation having an installed thermal resistance of R-11 or greater.
- 2 × 6 inch or greater framing shall have an overall assembly U -factor not exceeding U-0.069.
- Opaque nonframed assemblies shall have an overall assembly U -factor not exceeding U-0.102.
§ 4.4.2. High relevance — show source text
When performance compliance requires installation of a heat pump system, the heating capacity values at 47°F and 17°F shall be field verified in accordance with the procedures specified in Reference Residential Appendix RA3.4.4.2. F. Dwelling unit enclosure air leakage. When performance compliance requires a building enclosure leakage rate that is lower than the standard design, the building enclosure shall be field verified in accordance with the procedures specified in Reference Residential Appendix RA3.8. G. Quality insulation installation (QII). When performance compliance requires field verification of QII, the building insulation system shall be field verified in accordance with the procedures in Reference Residential Appendix RA3.5.
NOTE: Authority: Sections 25213, 25218, 25218.5, 25402 and 25402.1, Public Resources Code . Reference: Sections 25007, 25008, 25218.5, 25310, 25402, 25402.1, 25402.4, 25402.5, 25402.8 and 25943, Public Resources Code .
SECTION 170.2—PRESCRIPTIVE APPROACH
Multifamily buildings, including both dwelling units and common use areas, that comply with the prescriptive standards shall be designed, constructed and equipped to meet all of the requirements for the appropriate climate zone shown in Table 170.2-A. In Table 170.2-A, NA (not allowed) means that feature is not permitted in a particular climate zone and NR (no requirement) means that there is no prescriptive requirement for that feature in a particular climate zone. Installed components shall meet the following requirements:
(a) Envelope component requirements .
- Exterior roofs and ceilings . Exterior roofs and ceilings shall comply with each of the applicable requirements in this subsection:
A. Roofing products. All roofing products shall meet the requirements of Section 110.8 and the applicable minimum aged solar reflectance and thermal emittance requirements of Table 170.2-A. Exception 1 to Section 170.2(a)1A: Roof area covered with building integrated photovoltaic panels and building integrated solar thermal panels are not required to comply with the minimum requirements for solar reflectance and thermal emittance or SRI.
Exception 2 to Section 170.2(a)1A: Roof constructions with a weight of at least 25 lb/ft2 are not required to comply with the minimum requirements for solar reflectance and thermal emittance or SRI. B. Roof insulation. roofs shall have an overall assembly U -factor no greater than the applicable value in Table 170.2-A, meeting i, ii, iii or iv below. Where required by Sections 110.8 and 160.1(a), insulation shall be placed in direct contact with a continuous roof or drywall ceiling. i. Option A: Reserved. ii. Option B: A minimum R -value of insulation installed between the roof rafters in contact with the roof deck and an additional layer of ceiling insulation located between the attic and the conditioned space when meeting Section 170.2(c)3Biia; or iii. Option C: A minimum R -value of ceiling insulation located between the attic and the conditioned space when meeting Section 170.2(c)3Biib. iv. Option D: A minimum U -factor for roof assemblies above conditioned space without attic space. C. Radiant barrier. A radiant barrier required in Table 170.2-A shall meet the requirements specified in Section 110.8(j), and shall meet the installation criteria specified in Reference Residential Appendix RA4 .
- Wall insulation.
§ 203.1.2 High relevance — show source text
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APPENDIX A4 — RESIDENTIAL VOLUNTARY MEASURES
A4.203.1.2 Prerequisite options. In addition, a minimum of TWO of the efficiency measures specified in Sections A4.203.1.2.1 through A4.203.1.2.7 must be met.
A4.203.1.2.1 Roof deck insulation, or ducts in conditioned space. Meet one of the three options for the location of ducts and air handlers as well as insulation R -values and installation of a radiant barrier as specified in Title 24, Part 6, Section 150.1(c)9A or B:
Below roof deck insulation with a minimum R -value of 19; or,
Continuous above deck insulation with a minimum R-8 and with an air space present between the roofing and the roof deck; or,
All ducts and air handlers in conditioned space as specified in the Title 24, Part 6, Reference Appendix RA3.1.
A4.203.1.2.2 High performance walls. Meet the climate zone dependent U -factor or insulation R -value for either 2x6 or 2x4 framing as specified in Title 24, Part 6, Section 150.1(c)1B: maximum U -factor of 0.048.
A4.203.1.2.3 Compact hot water distribution system. Meet the requirements for installation of Compact Hot Water Distribution Systems specified in the Title 24, Part 6, Reference Appendix RA3.6.5.
A4.203.1.2.4 Drain water heat recovery. Meet the requirements for installation of Drain Water Heat Recovery specified in Title 24, Part 6, Reference Appendix RA4.4.21.
A4.203.1.2.5 High performance vertical fenestration. Meet the climate zone dependent U -factor and Solar Heat Gain Coefficient (SHGC) as rated in accordance with Title 24, Part 6, Section 110.6, and shall have a maximum U -factor of 0.21 in Climate Zones 1 − 16, maximum SHGC of 0.23 in Climate Zones 2, 4, and 6 − 14, and maximum SHGC of 0.20 in Climate Zone 15.
Exception to A4.203.1.2.5: Fenestration in Climate Zones 1, 3, 5, and 16 is not required to comply with the maximum SHGC requirements.
A4.203.1.2.6 Heat pump water heater demand management. For buildings with heat pump water heating, meet the requirements for installation of controls specified by Title 24, Part 6, Reference Appendix JA13.3.3.
A4.203.1.2.7 Battery storage system controls. For buildings with battery storage systems, meet the requirements for installation of controls specified by Title 24, Part 6, Reference Appendix JA12 for either the Time-of-Use Control or Advanced Demand Flexibility Control option.
§ 4.3.1 High relevance — show source text
Use Reference Joint Appendices JA4 Table 4.3.1, 4.3.1(a), or Table 4.3.4 to determine alternative insu-
lation products to be less than or equal to the required maximum U-factor.
4. Mass wall has a heat capacity greater than or equal to 7.0 Btu/h-ft2.
5. Product must be certified to meet the North American Fenestration Standard/Specification for an Architectural Window (AW).
6. Glazed doors must meet the fenestration requirements.
7. Requirements apply to doors included in the curtain wall/storefront construction assembly.
8. If using_F_-factor to comply, use Reference Joint Appendices JA4, Table 4.4.7 to determine alternate depth and R-value to be less than or equal to the required maximum_F_-
factor.
9. Option B meets §170.2(a)1Bii.
10. Option C meets §170.2(a)1BIiii.
11. Option D meets §170.2(a)1Biv.|1. Install the specified_R_-value with an airspace present between the roofing and the roof deck. Such as standard installation of concrete or clay tile.
2._ R_-values shown for below roof deck insulation are for wood-frame construction with insulation installed between the framing members. Alternatives including insulation
above rafters or above roof deck shall comply with the performance standards.
3. Assembly_U_-factors for exterior framed walls can be met with cavity insulation alone or with continuous insulation alone, or with both cavity and continuous insulation that
results in an assembly_U_-factor equal to or less than the_U_-factor shown. Use Reference Joint Appendices JA4 Table 4.3.1, 4.3.1(a), or Table 4.3.4 to determine alternative insu-
lation products to be less than or equal to the required maximum U-factor.
4. Mass wall has a heat capacity greater than or equal to 7.0 Btu/h-ft2.
5. Product must be certified to meet the North American Fenestration Standard/Specification for an Architectural Window (AW).
6. Glazed doors must meet the fenestration requirements.
7. Requirements apply to doors included in the curtain wall/storefront construction assembly.
8. If using_F_-factor to comply, use Reference Joint Appendices JA4, Table 4.4.7 to determine alternate depth and R-value to be less than or equal to the required maximum_F_-
factor.
9. Option B meets §170.2(a)1Bii.
10. Option C meets §170.2(a)1BIiii.
11. Option D meets §170.2(a)1Biv.|1. Install the specified_R_-value with an airspace present between the roofing and the roof deck. Such as standard installation of concrete or clay tile.
2._ R_-values shown for below roof deck insulation are for wood-frame construction with insulation installed between the framing members. Alternatives including insulation
above rafters or above roof deck shall comply with the performance standards.
3. Assembly_U_-factors for exterior framed walls can be met with cavity insulation alone or with continuous insulation alone, or with both cavity and continuous insulation that
results in an assembly_U_-factor equal to or less than the_U_-factor shown.§ 0.63 High relevance — show source text
2** (with Air
Space)|NR|NR|NR|R-19|NR|NR|NR|R-19|R-19|R-19|R-19|R-19|R-19|R-19|R-19|R-19| |Option B13
Ceiling Insulation|R-38|R-38|R-30|R-38|R-30|R-30|R-30|R-38|R-38|R-38|R-38|R-38|R-38|R-38|R-38|R-38| |Option B13
Radiant Barrier|NR|REQ|REQ|NR|REQ|REQ|REQ|NR|NR|NR|NR|NR|NR|NR|NR|NR| |Option C14
Ceiling Insulation for
Vented Attics|R-38|R-30|R-30|R-30|R-30|R-30|R-30|R-38|R-38|R-38|R-38|R-38|R-38|R-38|R-38|R-38| |Option C14
Radiant Barrier for
Vented Attics|NR|REQ|REQ|REQ|REQ|REQ|REQ|REQ|REQ|REQ|REQ|REQ|REQ|REQ|REQ|NR| |Option C
Roof Deck Insulation for
Cathedral Ceilings1,4 |R-38|R-38|R-38|R-38|R-38|R-38|R-38|R-38|R-38|R-38|R-38|R-38|R-38|R-38|R-38|R-38| |Low-Sloped Roofing
Product Aged Solar
Reflectance|NR|NR|NR|NR|NR|NR|NR|NR|NR|NR|NR|NR|0.63|NR|0.63|NR| |Low-Sloped Roofing
Product Thermal
Emittance|NR|NR|NR|NR|NR|NR|NR|NR|NR|NR|NR|NR|0.75|NR|0.75|NR| |Steep-Sloped Roofing
Product Aged Solar
Reflectance|NR|NR|NR|NR|NR|NR|NR|NR|NR|0.20|0.20|0.20|0.20|0.20|0.20|NR| |Steep-Sloped Roofing
Product Thermal
Emittance|NR|NR|NR|NR|NR|NR|NR|NR|NR|0.75|0.75|0.75|0.75|0.75|0.75|NR| |Above Grade Framed
Walls3|U-0.048|U-0.048|U-0.048|U-0.048|U-0.048|U-0.065|U-0.065|U-0.048|U-0.048|U-0.048|U-0.048|U-0.048|U-0.048|U-0.048|U-0.048|U-0.048| |Above Grade Masonry/
Mass Wall Interior5,6|U-0.077
R-13|U-0.077
R-13|U-0.077
R-13|U-0.077
R-13|U-0.077
R-13|U-0.077
R-13|U-0.077
R-13|U-0.077
R-13|U-0.077
R-13|U-0.§ 180.1 High relevance — show source text
Exception 7 to Section 180.1 : Dwelling unit space heating system. New or replacement space heating systems serving an addition may be a heat pump or gas heating system.
(a) Prescriptive approach. The envelope and lighting of the addition; any newly installed space-conditioning or ventilation system, electrical power distribution system, or water-heating system; any addition to an outdoor lighting system; and any new sign installed in conjunction with an indoor or outdoor addition shall meet the applicable requirements of Sections 110.0 through 110.12; 160.0, 160.1, and 160.2(c) and (d); and 160.3 through 170.2.
- Envelope. A. Additions that are greater than 700 square feet shall meet the requirements of Section 170.2(a), with the following modifications:
i. Framed walls extension. Extensions of existing wood-framed walls may retain the dimensions of the existing walls and shall install cavity insulation of R-15 in a 2x4 framing and R-21 in a 2x6 framing. ii. The maximum allowed fenestration area shall be the greater of 175 square feet or 20 percent of the addition floor area.
iii. When existing siding of a wood-framed wall is not being removed or replaced, cavity insulation of R-15 in a 2x4 framing and R-21 in a 2x6 framing shall be installed and continuous insulation is not required. iv. Additions that consist of the conversion of existing spaces from unconditioned to conditioned space shall not be required to perform the air sealing part of QII when the existing air barrier is not being removed or replaced. B. Additions that are 700 square feet or less shall meet the requirements of Section 170.2(a), with the following modifications.
i. Roof and ceiling insulation in a ventilated attic shall meet one of the following requirements: a. In Climate Zones 1, 2, 4, and 8 through 16, achieve an overall assembly U -factor not exceeding 0.025. In wood framed assemblies, compliance with U -factors may be demonstrated by installing insulation with an R -value of R-38 or greater.
2025 CALIFORNIA ENERGY CODE 271
on Jul 18, 2025 11:14 AM (CDT) THEREUNDER.
MULTIFAMILY BUILDINGS—ADDITIONS, ALTERATIONS AND REPAIRS TO EXISTING MULTIFAMILY BUILDINGS
b. In Climate Zones 3 and 5 through 7, achieve an overall assembly U- factor not exceeding 0.031. In wood framed assemblies, compliance with U- factors may be demonstrated by installing insulation with an R- value of R-30 or greater. ii. Radiant barrier. For buildings three habitable stories or less, radiant barriers shall be installed in attics with exposed attic deck undersides in Climate Zones 2–15. iii. Extensions of existing wood-framed walls may retain the dimensions of the existing walls and shall install cavity insulation of R-15 in a 2x4 framing and R-21 in a 2x6 framing; and iv. Fenestration products must meet the U- factor, RSGHC and VT requirements of Table 180.2-B. v. Quality insulation installation (QII) requirements of Section 170.2(a)6 do not apply. Exception to Section 180.1(a)1B: Insulation in an enclosed rafter ceiling shall meet the requirements of Section 160.1(a).
§ 2.9 High relevance — show source text
Fire district D102.2.9 Height modifications 503.1.4, 504.3 Impact resistance 1504.7 Insulation 1508 Lightning protection systems 1511.7.6 Materials 1506 Mechanical equipment screen 1511.6 Parapet walls 1503.2, 1503.3 Penthouses 713.12.1, 1511.2 Photovoltaic panels and modules 1511.10, 1511.10.1 Radiant barrier 1510
Tanks 1511.3 Towers, spires, domes and cupolas 1511.5, 3108 Weather protection 1503 Wind resistance 1504.1, 1504.3, 1504.4, 1609.6 Roof Construction Construction walkways 3306.7 Coverings (see Roof Coverings) 1609.6.2 Draftstopping 718.4 Fire resistance Table 601 Fireblocking 718.2 Live loads 1607.14, Table 1607.1,
3111.1.2
Materials Chapter 6 Penetration of fire-resistant assemblies
714 Protection from adjacent construction 3307.1
Rain loads 1611
Roof deck 1609.6.1 Signs, roof mounted H110 Slope, minimum Chapter 15
Snow load 1608 Solar systems, rooftop-mounted 3111.1, 3111.3.2 Trusses 2206.1.3, 2303.4, 2308.11.12 Ventilation 1202.2
Wood (see Roof Construction, Wood) Roof Construction, Wood 602.4, 602.5 Anchorage to walls 1604.8.2 Attic access 1209.2 Ceiling joists 2308.11.1 Diaphragms 2305.1, 2306.2 Fastening requirements 2304.10 Fire-retardant-treated Table 601,
603.1
Framing 2304.11.4, 2308.11 Rafters 2306.1.1, 2308.11.2 Sheathing 2304.8.2, 2308.11.9 Trusses 2303.4, 2308.11.12 Ventilation, attic 1202.2 Wind uplift 2308.11.4 Roof Coverings 1507 Asphalt shingles 1507.2, 1609.2.1 Built up 1507.10 Clay tile 1507.3, 1513 Concrete tile 1507.3, 1513 Fire district D102.2.4
§ 1508.2 High relevance — show source text
[BF] 1508.2 Material standards. Above-deck thermal insulation board shall comply with the standards in Table 1508.2.
[BF] TABLE 1508.2—MATERIAL STANDARDS FOR ROOF INSULATION Col2 MATERIAL STANDARD Cellular glass board ASTM C552 or ASTM C1902 Composite boards ASTM C1289, Type III, IV, V or VII Expanded polystyrene ASTM C578 Extruded polystyrene ASTM C578 Fiber-reinforced gypsum board ASTM C1278 Glass-faced gypsum board ASTM C1177 High-density polyisocyanurate board ASTM C1289, Type II, Class 4 Mineral fiber insulation board ASTM C726 Perlite board ASTM C728 Polyisocyanurate board ASTM C1289, Type I or II Wood fiberboard ASTM C208, Type II SECTION 1509—ROOF COATINGS
1509.1 General. The installation of a roof coating on a roof covering shall comply with the requirements of Section 1505 and this section.
15-20 2025 CALIFORNIA BUILDING CODE
on Jul 18, 2025 11:14 AM (CDT) THEREUNDER.
ROOF ASSEMBLIES AND ROOFTOP STRUCTURES
1509.2 Material standards. Roof coating materials shall comply with the standards in Table 1509.2.
TABLE 1509.2—ROOF COATING MATERIAL STANDARDS Col2 MATERIAL STANDARD Acrylic coating ASTM D6083 Asphaltic emulsion coating ASTM D1227 Asphalt coating ASTM D2823 Asphalt roof coating ASTM D4479 Aluminum-pigmented asphalt coating ASTM D2824 Silicone coating ASTM D6694 Moisture-cured polyurethane coating ASTM D6947 SECTION 1510—RADIANT BARRIERS INSTALLED ABOVE DECK
[BF] 1510.1 General. A radiant barrier installed above a deck shall comply with Sections 1510.2 through 1510.4.
[BF] 1510.2 Fire testing. Radiant barriers shall be permitted for use above decks where the radiant barrier is covered with an approved roof covering and the system consisting of the radiant barrier and the roof covering complies with the requirements of either FM 4450 or UL 1256.
[BF] 1510.3 Installation. The low emittance surface of the radiant barrier shall face the continuous airspace between the radiant barrier and the roof covering.
[BF] 1510.4 Material standards. A radiant barrier installed above a deck shall comply with ASTM C1313/C1313M.
SECTION 1511—ROOFTOP STRUCTURES
[BG] 1511.1 General. The provisions of this section shall govern the construction of rooftop structures.
Frequently asked questions
When does a roof require a radiant barrier?
If the prescriptive table (Table 150.1‑A for single‑family or Table 170.2‑A for multifamily) shows REQ for the selected option in your climate zone, a radiant barrier is required and must meet § 110.8(j) and RA4 installation criteria.
Can I comply by calculating an assembly U‑factor instead of installing the tabulated R‑value?
Yes — the table requirements may be met by an overall assembly U‑factor shown in the table or by using an approved U‑factor calculation method that accounts for all assembly elements (per the exception to § 150.1(c)1).
What if my roof is above conditioned space (no attic)?
Use the option in the applicable table that provides a U‑factor path for roofs above conditioned space (Option D in Table 170.2‑A and corresponding entries in Table 150.1‑A).
Do I always need QII (quality insulation installation) documentation?
Only when the table or prescriptive pathway for your project indicates QII is required. When required, follow the RA3.5 verification protocol.
Are there fire or material standards for radiant barriers?
Yes. Above‑deck radiant barriers must comply with the fire‑testing and material standards in § 1510 (including ASTM C1313) and be installed so the low‑emittance face faces the continuous airspace.
Where can I find the specific R‑value or U‑factor for my climate zone?
Consult Table 150.1‑A for single‑family work or Table 170.2‑A for multifamily; each table cell shows the assembly U‑factors, R‑value options, and whether a radiant barrier or QII is required for that climate zone.
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