Title 24 · California Energy Code

Continuous insulation R‑value requirements to allow interior vapor retarders (1404.3 tables)

If you install an interior Class I or II vapor retarder over a framed wall with exterior foam sheathing, the California code requires a minimum amount of exterior continuous insulation (R‑values vary by climate zone and 2×4 vs 2×6 framing) listed in Table 1404.3(4); if you omit an interior vapor retarder you must meet the larger R‑values in Table 1404.3(5) and meet notes about interior R limits and exterior vapor control. All thresholds and installation rules are set out in **§ 1404.3** and Tables **1404.3(4)** and **1404.3(5)** .

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Last reviewed: July 6, 2026

What the code requires — 2–4 sentences

The interior vapor‑retarder rules for frame walls are set by § 1404.3 and the continuous‑insulation R‑value thresholds in Tables 1404.3(4) and 1404.3(5). In plain English: if you use an interior Class I or Class II vapor retarder in combination with exterior continuous foam insulation, that exterior continuous insulation must meet the minimum R‑values in Table 1404.3(4); alternatively, if you omit an interior vapor retarder the exterior continuous insulation must meet the larger minimums in Table 1404.3(5) (and other conditions apply). See § 1404.3 and the tables for the precise climate‑zone values and related conditions .

The most important rule: to permit an interior Class I or II vapor retarder with exterior foam sheathing you must provide the minimum exterior continuous‑insulation R‑value required for your climate zone in Table 1404.3(4); if no interior vapor retarder is used, use the larger R‑values in Table 1404.3(5) .

Requirements in detail

Key definitions and controls (first mentions are bold)

  • Class I, Class II, Class III vapor retarders — material classes defined in § 1404.3 (see Table 1404.3(1)) and used to determine what is permitted in each climate zone .
  • Responsive vapor retarder — a permitted option for interior placement; when a Class I or II vapor retarder is used with exterior foam it must be a responsive vapor retarder per the table notes and § 1404.3 guidance .
  • Climate zone selection for these tables follows the IECC/CA mapping rules referenced in § 1404.3.3 (comparison tables are in Chapter 12) — use the correct IEC C/California mapping when selecting the climate zone for a project .
  • Spray‑applied foam rules: spray foam with a maximum permeance of 1.5 perms at installed thickness can be treated as meeting the continuous‑insulation moisture‑control requirement if its R‑value alone, or combined with continuous insulation, equals or exceeds the table value (see § 1404.3.1) .

Minimum continuous‑insulation R‑values (decision table)

The table below consolidates the decision‑relevant dimensions: climate zone, wall framing (where applicable), the minimum exterior continuous R required to allow an interior Class I/II vapor retarder (Table 1404.3(4)) or to allow no interior vapor retarder (Table 1404.3(5)), and the code reference.

Climate zone Wall type / condition Minimum continuous insulation R‑value to allow an interior Class I/II vapor retarder (Table 1404.3(4)) Minimum continuous insulation R‑value to allow no interior vapor retarder (Table 1404.3(5)) Code Reference
3 any frame R‑2 N/A § 1404.3; Table 1404.3(4)
4, 5, 6 2×4 frame R‑3 (over 2×4) R‑4.5 (zone 4) / R‑6.5 (zone 5) / R‑8.5 (zone 6) § 1404.3; Tables 1404.3(4) & 1404.3(5)
4, 5, 6 2×6 frame R‑5 (over 2×6) same zone values as above § 1404.3; Tables 1404.3(4) & 1404.3(5)
7 2×4 frame R‑5 (over 2×4) R‑11.5 § 1404.3; Tables 1404.3(4) & 1404.3(5)
7 2×6 frame R‑7.5 (over 2×6) R‑11.5 § 1404.3; Tables 1404.3(4) & 1404.3(5)
8 2×4 frame R‑7.5 (over 2×4) R‑14 § 1404.3; Tables 1404.3(4) & 1404.3(5)
8 2×6 frame R‑10 (over 2×6) R‑14 § 1404.3; Tables 1404.3(4) & 1404.3(5)

Notes:

  • The values above are extracted directly from Table 1404.3(4) (when an interior Class I/II responsive vapor retarder is used) and Table 1404.3(5) (when there is no interior vapor retarder) as published under § 1404.3 .
  • For climate zones not listed in Table 1404.3(5) (e.g., Zones 1–3) an interior vapor retarder is generally not required; consult § 1404.3 for exceptions and full applicability .

Mandatory related conditions (short table)

Condition Requirement Code reference
Interior insulating layers to the interior side of the exterior continuous insulation Total R‑value must not exceed R‑5; if interior R > R‑5 an approved design is required Table 1404.3(5) notes; § 1404.3
Exterior vapor control layer when no interior retarder A water‑vapor control material with permeance ≤ 1 perm (ASTM E96 Procedure A dry cup) must exist on the exterior side and to the interior side of the exterior continuous insulation; exterior CI may serve if it is Class I or II at installed thickness or with an interior facer Table 1404.3(5) notes
Spray foam used interior to sheathing If spray foam has ≤ 1.5 perms permeance and its R‑value alone or combined meets the table requirement, it can satisfy the continuous‑insulation moisture‑control requirement (see § 1404.3.1) § 1404.3.1
Vapor retarder installation Install per manufacturer instructions or an approved design; if it functions as an air barrier, it must meet the California Energy Code air‑barrier requirements (see § 1404.3.2) § 1404.3.2

Exceptions & special cases

  • A vapor retarder is not required in Climate Zones 1, 2, and 3 (exceptions listed in § 1404.3) — do not add one unless required for another reason .
  • Basement walls and below‑grade portions of walls are excepted from these interior vapor‑retarder requirements (see § 1404.3 exceptions) .
  • Where a Class I vapor retarder exists on the exterior side of the wall, using a Class I on the interior that is not a responsive vapor retarder requires an approved design (see table notes) .
  • If interior spray foam (≤1.5 perms) is used, the spray foam can be accepted in lieu of separate continuous insulation only if the spray foam’s R‑value alone or combined R (spray foam + exterior CI) meets the Table requirement—see § 1404.3.1 .
  • The exterior continuous insulation may be allowed to serve as the required exterior vapor control layer only where the installed CI (or with a facer) is a Class I or II vapor retarder (Table 1404.3(5) note) .

If a condition or material you plan to use is not explicitly covered by these tables or notes, you must provide an approved design (hygrothermal analysis) as allowed under § 1404.3 .

Common mistakes

  • Confusing IECC climate zones with California Energy Code climate zones — § 1404.3.3 clarifies the mapping; pick the correct zone before reading the tables .
  • Using the smaller R‑values from Table 1404.3(4) when no interior vapor retarder is actually present — if there is no interior retarder you must use Table 1404.3(5) (the required R's are larger) .
  • Forgetting the interior insulation limit: even if exterior CI meets Table 1404.3(5), the total R of materials interior to the exterior CI must not exceed R‑5 unless an approved design is provided (Table 1404.3(5) note) .
  • Assuming any foam sheathing automatically provides the vapor control layer — only when the installed CI (or with facer) is a Class I or II vapor retarder may it serve as the vapor control layer per Table 1404.3(5) notes .
  • Misapplying spray‑foam allowances: to use the spray‑foam equivalency the spray foam must have permeance ≤ 1.5 perms and meet the R‑value test in § 1404.3.1 .

Worked example — concrete scenario

Scenario: You are building a wood‑frame house in Climate Zone 6 with 2×4 framing. You plan to install foam plastic insulating sheathing as exterior continuous insulation and want to use an interior Class II vapor retarder.

  • Step 1 — Table selection: for an interior Class I/II responsive retarder, use Table 1404.3(4) under § 1404.3 .
  • Step 2 — Read the R‑value: for Zones 4, 5, 6 over a 2×4 wall the required exterior continuous insulation is R‑3 (see Table 1404.3(4)) — so provide at least R‑3 of exterior continuous insulation to allow the interior Class II retarder .
  • Alternative (no interior vapor retarder): if you decide NOT to install any interior vapor retarder, consult Table 1404.3(5) — for Zone 6 the required exterior continuous insulation is R‑8.5, and you must also meet the interior R ≤ R‑5 limitation and the external vapor control/permeance conditions .
  • Spray foam note: if you use interior spray foam (≤1.5 perms) that by itself provides R‑3 or the combined R (spray foam + exterior CI) equals R‑3, it can satisfy Table 1404.3(4) per § 1404.3.1 .

Related provisions

  • § 1404.3 — Vapor retarders and Tables 1404.3(1)–(5) (primary control) .
  • § 1404.3.1 — Spray foam acceptance rules (≤1.5 perms and R‑value combination test) .
  • § 1404.3.2 — Vapor retarder installation and when the retarder is also an air barrier (installation per manufacturer or approved design) .
  • § 1404.3.3 — Climate zone mapping (IECC vs California Energy Code) used to determine applicable table values .
  • Table 1404.3(4) — Continuous insulation minimum R‑values when an interior Class I or II responsive vapor retarder is used .
  • Table 1404.3(5) — Continuous insulation minimum R‑values for walls without an interior Class I/II/III vapor retarder (and associated notes about permeance, interior R ≤ R‑5, etc.) .

If you need, I can convert this into a one‑page decision flowchart (climate zone → interior retarder present? → select table → verify notes) or check a specific wall assembly and list exactly which materials and thicknesses meet the R requirements — tell me the climate zone, framing (2×4 or 2×6), and whether you will use interior spray foam (and its R and permeance).

Code references

Grounded in the retrieved California Energy Code — click a citation to read the verbatim passage:

  • § 1404.3 High relevance — show source text

    Where a Class I or II vapor retarder is used in combination with foam plastic insulating sheathing installed as continuous insulation on the exterior side of frame walls, the
    continuous insulation shall comply with Table 1404.3(4) and the Class I or II vapor retarder shall be a responsive vapor retarder.|a. A responsive vapor retarder shall be allowed on the interior side of any frame wall in all climate zones.
    b. In frame walls with a Class I vapor retarder on the exterior side, use of a Class I interior vapor retarder that is not a responsive vapor retarder shall require an_approved_ design.
    c. Where a Class I or II vapor retarder is used in combination with foam plastic insulating sheathing installed as continuous insulation on the exterior side of frame walls, the
    continuous insulation shall comply with Table 1404.3(4) and the Class I or II vapor retarder shall be a responsive vapor retarder.|a. A responsive vapor retarder shall be allowed on the interior side of any frame wall in all climate zones.
    b. In frame walls with a Class I vapor retarder on the exterior side, use of a Class I interior vapor retarder that is not a responsive vapor retarder shall require an_approved_ design.
    c. Where a Class I or II vapor retarder is used in combination with foam plastic insulating sheathing installed as continuous insulation on the exterior side of frame walls, the
    continuous insulation shall comply with Table 1404.3(4) and the Class I or II vapor retarder shall be a responsive vapor retarder.|

    TABLE 1404.3(3)—CLASS III VAPOR RETARDERS Col2
    ZONE CLASS III VAPOR RETARDERS PERMITTED FOR:a, b
    4 Vented cladding over wood structural panels
    Vented cladding over fiberboard
    Vented cladding over gypsum
    Continuous insulation with_R_-value ≥ R-2.5 over 2 × 4 wall
    Continuous insulation with_R_-value ≥ R-3.75 over 2 × 6 wall
    5 Vented cladding over wood structural panels
    Vented cladding over fiberboard
    Vented cladding over gypsum
    Continuous insulation with_R_-value ≥ R-5 over 2 × 4 wall
    Continuous insulation with_R_-value ≥ R-7.5 over 2 × 6 wall
    6 Vented cladding over fiberboard
    Vented cladding over gypsum
    Continuous insulation with_R_-value ≥ R-7.5 over 2 × 4 wall
    Continuous insulation with_R_-value ≥ R-11.25 over 2 × 6 wall
    7 Continuous insulation with_R_-value ≥ R-10 over 2 × 4 wall
    Continuous insulation with_R_-value ≥ R-15 over 2 × 6 wall
    8 Continuous insulation with_R_-value ≥ R-12.5 over 2 × 4 wall
    Continuous insulation with_R_-value ≥ R-20 over 2 × 6 wall
    a. Vented cladding shall include vinyl lap siding, polypropylene, horizontal aluminum siding, brick veneer with airspace as specified in this code, rainscreen systems and other
    approved vented claddings.
    b. The requirements in this table apply only to insulation used to control moisture in order to permit the use of Class III vapor retarders. The insulation materials used to satisfy
    this option also contribute to but do not supersede the building thermal envelope requirements of the_California Energy Code_.    		 a.
  • § 1404.3 High relevance — show source text

    The requirements in this table apply only to insulation used to control moisture in order to permit the use of Class I or II vapor retarders. The insulation materials used to
    satisfy this option also contribute to but do not supersede the building thermal envelope requirements of the_California Energy Code_.|

    TABLE 1404.3(5)—CONTINUOUS INSULATION ON WALLS WITHOUT A CLASS I, II, OR III INTERIOR VAPOR RETARDERa Col2
    CLIMATE ZONE PERMITTED CONDITIONSb,c
    4 Continuous insulation with_R_-value ≥ 4.5
    5 Continuous insulation with_R_-value ≥ 6.5
    6 Continuous insulation with_R_-value ≥ 8.5
    7 Continuous insulation with_R_-value ≥ 11.5
    8 Continuous insulation with_R_-value ≥ 14
    a. The total insulating value of materials to the interior side of the exterior continuous insulation, including any cavity insulation, shall not exceed R-5. Where the_R_-value of
    materials to the interior side of the exterior continuous insulation exceeds R-5, an_approved_ design shall be required.
    b. A water vapor control material layer having a permeance of not greater than 1 perm in accordance with ASTM E96, Procedure A (dry cup) shall be placed on the exterior side
    of the wall and to the interior side of the exterior continuous insulation. The exterior continuous insulation shall be permitted to serve as the vapor control layer where, at its
    installed thickness or with a facer on its interior face, the exterior continuous insulation is a Class I or II vapor retarder.
    c. The requirements of this table apply only to continuous insulation used to control moisture in order to allow walls without a Class I, II or III interior vapor retarder. The insula-
    tion materials used to satisfy this option also contribute to but do not supersede the_building_ thermal envelope requirements of the_California Energy Code_.    		 a. The total insulating value of materials to the interior side of the exterior continuous insulation, including any cavity insulation, shall not exceed R-5. Where the_R_-value of
    materials to the interior side of the exterior continuous insulation exceeds R-5, an_approved_ design shall be required.
    b. A water vapor control material layer having a permeance of not greater than 1 perm in accordance with ASTM E96, Procedure A (dry cup) shall be placed on the exterior side
    of the wall and to the interior side of the exterior continuous insulation. The exterior continuous insulation shall be permitted to serve as the vapor control layer where, at its
    installed thickness or with a facer on its interior face, the exterior continuous insulation is a Class I or II vapor retarder.
    c. The requirements of this table apply only to continuous insulation used to control moisture in order to allow walls without a Class I, II or III interior vapor retarder. The insula-
    tion materials used to satisfy this option also contribute to but do not supersede the_building_ thermal envelope requirements of the_California Energy Code_.

    �

    EXTERIOR WALLS

  • § 14-7 High relevance — show source text

    Vented cladding shall include vinyl lap siding, polypropylene, horizontal aluminum siding, brick veneer with airspace as specified in this code, rainscreen systems and other
    approved vented claddings.
    b. The requirements in this table apply only to insulation used to control moisture in order to permit the use of Class III vapor retarders. The insulation materials used to satisfy
    this option also contribute to but do not supersede the building thermal envelope requirements of the_California Energy Code_.|

    2025 CALIFORNIA BUILDING CODE 14-7

    on Jul 18, 2025 11:14 AM (CDT) THEREUNDER.

    TABLE 1404.3(4)—CONTINUOUS INSULATION WITH A CLASS I OR II RESPONSIVE VAPOR RETARDER Col2
    CLIMATE ZONE PERMITTED CONDITIONSa
    3 Continuous insulation with_R_-value ≥ R-2
    4, 5, 6 Continuous insulation with_R_-value ≥ R-3 over 2 × 4 wall
    Continuous insulation with_R_-value ≥ R-5 over 2 × 6 wall
    7 Continuous insulation with_R_-value ≥ R-5 over 2 × 4 wall
    Continuous insulation with_R_-value ≥ R-7.5 over 2 × 6 wall
    8 Continuous insulation with_R_-value ≥ R-7.5 over 2 × 4 wall
    Continuous insulation with_R_-value ≥ R-10 over 2 × 6 wall
    a. The requirements in this table apply only to insulation used to control moisture in order to permit the use of Class I or II vapor retarders. The insulation materials used to
    satisfy this option also contribute to but do not supersede the building thermal envelope requirements of the_California Energy Code_.    		 a. The requirements in this table apply only to insulation used to control moisture in order to permit the use of Class I or II vapor retarders. The insulation materials used to
    satisfy this option also contribute to but do not supersede the building thermal envelope requirements of the_California Energy Code_.
    TABLE 1404.3(5)—CONTINUOUS INSULATION ON WALLS WITHOUT A CLASS I, II, OR III INTERIOR VAPOR RETARDERa Col2
    CLIMATE ZONE PERMITTED CONDITIONSb,c
    4 Continuous insulation with_R_-value ≥ 4.5
    5 Continuous insulation with_R_-value ≥ 6.5
    6 Continuous insulation with_R_-value ≥ 8.5
    7 Continuous insulation with_R_-value ≥ 11.5
    8 Continuous insulation with_R_-value ≥ 14
    a. The total insulating value of materials to the interior side of the exterior continuous insulation, including any cavity insulation, shall not exceed R-5. Where the_R_-value of
    materials to the interior side of the exterior continuous insulation exceeds R-5, an_approved_ design shall be required.
    b. A water vapor control material layer having a permeance of not greater than 1 perm in accordance with ASTM E96, Procedure A (dry cup) shall be placed on the exterior side
    of the wall and to the interior side of the exterior continuous insulation. The exterior continuous insulation shall be permitted to serve as the vapor control layer where, at its
    installed thickness or with a facer on its interior face, the exterior continuous insulation is a Class I or II vapor retarder.
    c.
  • § 2.5 High relevance — show source text

    b**| |4|Vented cladding over wood structural panels
    Vented cladding over fiberboard
    Vented cladding over gypsum
    Continuous insulation with_R_-value ≥ R-2.5 over 2 × 4 wall
    Continuous insulation with_R_-value ≥ R-3.75 over 2 × 6 wall| |5|Vented cladding over wood structural panels
    Vented cladding over fiberboard
    Vented cladding over gypsum
    Continuous insulation with_R_-value ≥ R-5 over 2 × 4 wall
    Continuous insulation with_R_-value ≥ R-7.5 over 2 × 6 wall| |6|Vented cladding over fiberboard
    Vented cladding over gypsum
    Continuous insulation with_R_-value ≥ R-7.5 over 2 × 4 wall
    Continuous insulation with_R_-value ≥ R-11.25 over 2 × 6 wall| |7|Continuous insulation with_R_-value ≥ R-10 over 2 × 4 wall
    Continuous insulation with_R_-value ≥ R-15 over 2 × 6 wall| |8|Continuous insulation with_R_-value ≥ R-12.5 over 2 × 4 wall
    Continuous insulation with_R_-value ≥ R-20 over 2 × 6 wall| |a. Vented cladding shall include vinyl lap siding, polypropylene, horizontal aluminum siding, brick veneer with airspace as specified in this code, rainscreen systems and other
    approved vented claddings.
    b. The requirements in this table apply only to insulation used to control moisture in order to permit the use of Class III vapor retarders. The insulation materials used to satisfy
    this option also contribute to but do not supersede the building thermal envelope requirements of the_California Energy Code_.|a. Vented cladding shall include vinyl lap siding, polypropylene, horizontal aluminum siding, brick veneer with airspace as specified in this code, rainscreen systems and other
    approved vented claddings.
    b. The requirements in this table apply only to insulation used to control moisture in order to permit the use of Class III vapor retarders. The insulation materials used to satisfy
    this option also contribute to but do not supersede the building thermal envelope requirements of the_California Energy Code_.|

    2025 CALIFORNIA BUILDING CODE 14-7

    on Jul 18, 2025 11:14 AM (CDT) THEREUNDER.

    TABLE 1404.3(4)—CONTINUOUS INSULATION WITH A CLASS I OR II RESPONSIVE VAPOR RETARDER Col2
    CLIMATE ZONE PERMITTED CONDITIONSa
    3 Continuous insulation with_R_-value ≥ R-2
    4, 5, 6 Continuous insulation with_R_-value ≥ R-3 over 2 × 4 wall
    Continuous insulation with_R_-value ≥ R-5 over 2 × 6 wall
    7 Continuous insulation with_R_-value ≥ R-5 over 2 × 4 wall
    Continuous insulation with_R_-value ≥ R-7.5 over 2 × 6 wall
    8 Continuous insulation with_R_-value ≥ R-7.5 over 2 × 4 wall
    Continuous insulation with_R_-value ≥ R-10 over 2 × 6 wall
    a. The requirements in this table apply only to insulation used to control moisture in order to permit the use of Class I or II vapor retarders.
  • § 1404.3 High relevance — show source text
    TABLE 1404.3(2)—VAPOR RETARDER OPTIONS Col2 Col3 Col4
    CLIMATE ZONE VAPOR RETARDER CLASS VAPOR RETARDER CLASS VAPOR RETARDER CLASS
    CLIMATE ZONE Ia IIa III
    1, 2 Not permitted Not Permitted Permitted
    3 Not permitted Permittedc Permitted
    4 (except Marine) Not permitted Permittedc See Table 1404.3(3)
    Marine 4, 5, 6, 7, 8 Permittedb, c Permittedc See Table 1404.3(3)
    a. A responsive vapor retarder shall be allowed on the interior side of any frame wall in all climate zones.
    b. In frame walls with a Class I vapor retarder on the exterior side, use of a Class I interior vapor retarder that is not a responsive vapor retarder shall require an_approved_ design.
    c. Where a Class I or II vapor retarder is used in combination with foam plastic insulating sheathing installed as continuous insulation on the exterior side of frame walls, the
    continuous insulation shall comply with Table 1404.3(4) and the Class I or II vapor retarder shall be a responsive vapor retarder.    		 a. A responsive vapor retarder shall be allowed on the interior side of any frame wall in all climate zones.
    b. In frame walls with a Class I vapor retarder on the exterior side, use of a Class I interior vapor retarder that is not a responsive vapor retarder shall require an_approved_ design.
    c. Where a Class I or II vapor retarder is used in combination with foam plastic insulating sheathing installed as continuous insulation on the exterior side of frame walls, the
    continuous insulation shall comply with Table 1404.3(4) and the Class I or II vapor retarder shall be a responsive vapor retarder.    		 a. A responsive vapor retarder shall be allowed on the interior side of any frame wall in all climate zones.
    b. In frame walls with a Class I vapor retarder on the exterior side, use of a Class I interior vapor retarder that is not a responsive vapor retarder shall require an_approved_ design.
    c. Where a Class I or II vapor retarder is used in combination with foam plastic insulating sheathing installed as continuous insulation on the exterior side of frame walls, the
    continuous insulation shall comply with Table 1404.3(4) and the Class I or II vapor retarder shall be a responsive vapor retarder.    		 a. A responsive vapor retarder shall be allowed on the interior side of any frame wall in all climate zones.
    b. In frame walls with a Class I vapor retarder on the exterior side, use of a Class I interior vapor retarder that is not a responsive vapor retarder shall require an_approved_ design.
    c. Where a Class I or II vapor retarder is used in combination with foam plastic insulating sheathing installed as continuous insulation on the exterior side of frame walls, the
    continuous insulation shall comply with Table 1404.3(4) and the Class I or II vapor retarder shall be a responsive vapor retarder.
    TABLE 1404.3(3)—CLASS III VAPOR RETARDERS Col2
    ZONE **CLASS III VAPOR RETARDERS PERMITTED FOR:a,
  • § 7-8 High relevance — show source text

    The insulation materials used to satisfy
    this option also contribute to but do not supersede the thermal envelope requirements of Chapter 11.|

    7-8 2025 CALIFORNIA RESIDENTIAL CODE

    on Jul 18, 2025 11:14 AM (CDT) THEREUNDER.

    WALL COVERING

    TABLE R702.7(4)—CONTINUOUS INSULATION WITH CLASS I OR II RESPONSIVE VAPOR RETARDER Col2
    CLIMATE ZONE PERMITTED CONDITIONSa
    3 Continuous insulation with_R_-value ≥ 2.
    4, 5 and 6 Continuous insulation with_R_-value ≥ 3 over 2 × 4 wall.
    Continuous insulation with_R_-value ≥ 5 over 2 × 6 wall.
    7 Continuous insulation with_R_-value ≥ 5 over 2 × 4 wall.
    Continuous insulation with_R_-value ≥ 7.5 over 2 × 6 wall.
    8 Continuous insulation with_R_-value ≥ 7.5 over 2 × 4 wall.
    Continuous insulation with_R_-value ≥ 10 over 2 × 6 wall.
    a. The requirements in this table apply only to insulation used to control moisture in order to permit the use of Class II vapor retarders. The insulation materials used to satisfy
    this option also contribute to but do not supersede the thermal envelope requirements of Chapter 11.    		 a. The requirements in this table apply only to insulation used to control moisture in order to permit the use of Class II vapor retarders. The insulation materials used to satisfy
    this option also contribute to but do not supersede the thermal envelope requirements of Chapter 11.
    TABLE R702.7(5)—CONTINUOUS INSULATION ON WALLS WITHOUT A CLASS I, II OR III INTERIOR VAPOR RETARDERa Col2
    CLIMATE ZONE PERMITTED CONDITIONSb, c
    4 Continuous insulation with_R_-value ≥ 4.5
    5 Continuous insulation with_R_-value ≥ 6.5
    6 Continuous insulation with_R_-value ≥ 8.5
    7 Continuous insulation with_R_-value ≥ 11.5
    8 Continuous insulation with_R_-value ≥ 14
    a. The total insulating value of materials to the interior side of the exterior continuous insulation, including any cavity insulation, shall not exceed R-5. Where the R-value of
    materials to the interior side of the exterior continuous insulation exceeds R-5, an approved design shall be required.
    b. A water vapor control material layer having a permeance not greater than 1 perm in accordance with ASTM E96 Procedure A (dry cup) shall be placed on the exterior side of
    the wall and to the interior side of the exterior continuous insulation. The exterior continuous insulation shall be permitted to serve as the vapor control layer where, at its
    installed thickness or with a facer on its interior face, the exterior continuous insulation is a Class I or II vapor retarder.
    c. The requirements in this table apply only to insulation used to control moisture in order to allow walls without a Class I, II or III interior vapor retarder. The insulation materi-
    als used to satisfy this option also contribute to but do not supersede the thermal envelope requirements of the_California Energy Code_.    		 a. The total insulating value of materials to the interior side of the exterior continuous insulation, including any cavity insulation, shall not exceed R-5.
  • § 1404.3.1 High relevance — show source text

    The exterior continuous insulation shall be permitted to serve as the vapor control layer where, at its
    installed thickness or with a facer on its interior face, the exterior continuous insulation is a Class I or II vapor retarder.
    c. The requirements of this table apply only to continuous insulation used to control moisture in order to allow walls without a Class I, II or III interior vapor retarder. The insula-
    tion materials used to satisfy this option also contribute to but do not supersede the_building_ thermal envelope requirements of the_California Energy Code_.|a. The total insulating value of materials to the interior side of the exterior continuous insulation, including any cavity insulation, shall not exceed R-5. Where the_R_-value of
    materials to the interior side of the exterior continuous insulation exceeds R-5, an_approved_ design shall be required.
    b. A water vapor control material layer having a permeance of not greater than 1 perm in accordance with ASTM E96, Procedure A (dry cup) shall be placed on the exterior side
    of the wall and to the interior side of the exterior continuous insulation. The exterior continuous insulation shall be permitted to serve as the vapor control layer where, at its
    installed thickness or with a facer on its interior face, the exterior continuous insulation is a Class I or II vapor retarder.
    c. The requirements of this table apply only to continuous insulation used to control moisture in order to allow walls without a Class I, II or III interior vapor retarder. The insula-
    tion materials used to satisfy this option also contribute to but do not supersede the_building_ thermal envelope requirements of the_California Energy Code_.|

    �

    EXTERIOR WALLS

    1404.3.1 Spray foam plastic insulation for moisture control with Class II and III vapor retarders. For purposes of compliance with Tables 1404.3(3) and 1404.3(4), spray foam with a maximum permeance of 1.5 perms at the installed thickness applied to the interior side of wood structural panels, fiberboard, insulating sheathing or gypsum shall be deemed to meet the continuous insulation moisture control requirement in accordance with one of the following conditions:

    1. The spray foam R -value meets or exceeds the specified continuous insulation R-value.
    2. The combined R -value of the spray foam and continuous insulation is equal to or greater than the specified continuous insulation R -value.

    1404.3.2 Vapor retarder installation. Vapor retarders shall be installed in accordance with the manufacturer’s instructions or an approved design. Where a vapor retarder also functions as a component of a continuous air barrier, the vapor retarder shall be installed as an air barrier in accordance with the California Energy Code . 1404.3.3 California Energy Code and International Energy Conservation Code Climate Zones. The IECC climate zones used by this section differ from those used by the California Energy Code to determine applicability of energy efficiency measures. Comparison of IECC and California Energy Code climate zones is shown in Chapter 12, Table 1202.3.1. 1404.4 Flashing. Flashing shall be installed in such a manner so as to prevent moisture from entering the exterior wall or to redirect that moisture to the surface of the exterior wall covering or to a water-resistive barrier complying with Section 1403.2 and that is part of a means of drainage complying with Section 1402.2.

  • § 0.5 High relevance — show source text

    Wood siding of thicknesses less than 0.5 inch shall be placed over sheathing that conforms to Section 2304.6.
    b. Exclusive of texture.
    c. As measured at the bottom of decorative grooves.
    d. 16 ounces per square foot for cold-rolled copper and lead-coated copper, 12 ounces per square foot for copper shingles, high-yield copper and lead-coated high-yield copper.|

    14-6 2025 CALIFORNIA BUILDING CODE

    on Jul 18, 2025 11:14 AM (CDT) THEREUNDER.

    EXTERIOR WALLS

    1404.3 Vapor retarders. Vapor retarder materials shall be classified in accordance with Table 1404.3(1). A vapor retarder shall be provided on the interior side of frame walls in accordance with Table 1404.3(2) and Tables 1404.3(3) or 1404.3(4) as applicable, or an approved design using accepted engineering practice for hygrothermal analysis. Vapor retarders shall be installed in accordance with Section 1404.3.2. The appropriate climate zone shall be selected in accordance with the California Energy Code .

    Exceptions:

    1. Basement walls.

    2. Below-grade portion of any wall.

    3. Construction where accumulation, condensation or freezing of moisture will not damage the materials.

    4. A vapor retarder shall not be required in Climate Zones 1, 2, and 3.

    5. In Climate Zones 4 through 8, a vapor retarder on the interior side of frame walls shall not be required where the assembly complies with Table 1404.3(5).

    TABLE 1404.3(1)—VAPOR RETARDER MATERIALS AND CLASSES Col2
    VAPOR RETARDER CLASS ACCEPTABLE MATERIALS
    I Sheet polyethylene, nonperforated aluminum foil, or other approved materials with a perm rating of less than or
    equal to 0.1
    II Kraft-faced fiberglass batts or vapor retarder paint or other approved materials, applied in accordance with the
    manufacturer’s instructions for a perm rating greater than 0.1 and less than or equal to 1.0
    III Latex paint, enamel paint, or other approved materials, applied in accordance with the manufacturer’s instruc-
    tions for a perm rating of greater than 1.0 and less than or equal to 10
    TABLE 1404.3(2)—VAPOR RETARDER OPTIONS Col2 Col3 Col4
    CLIMATE ZONE VAPOR RETARDER CLASS VAPOR RETARDER CLASS VAPOR RETARDER CLASS
    CLIMATE ZONE Ia IIa III
    1, 2 Not permitted Not Permitted Permitted
    3 Not permitted Permittedc Permitted
    4 (except Marine) Not permitted Permittedc See Table 1404.3(3)
    Marine 4, 5, 6, 7, 8 Permittedb, c Permittedc See Table 1404.3(3)
    a. A responsive vapor retarder shall be allowed on the interior side of any frame wall in all climate zones.
    b.
  • § 7.1 High relevance — show source text

    The total insulating value of materials to the interior side of the exterior continuous insulation, including any cavity insulation, shall not exceed R-5. Where the R-value of
    materials to the interior side of the exterior continuous insulation exceeds R-5, an approved design shall be required.
    b. A water vapor control material layer having a permeance not greater than 1 perm in accordance with ASTM E96 Procedure A (dry cup) shall be placed on the exterior side of
    the wall and to the interior side of the exterior continuous insulation. The exterior continuous insulation shall be permitted to serve as the vapor control layer where, at its
    installed thickness or with a facer on its interior face, the exterior continuous insulation is a Class I or II vapor retarder.
    c. The requirements in this table apply only to insulation used to control moisture in order to allow walls without a Class I, II or III interior vapor retarder. The insulation materi-
    als used to satisfy this option also contribute to but do not supersede the thermal envelope requirements of the_California Energy Code_.|a. The total insulating value of materials to the interior side of the exterior continuous insulation, including any cavity insulation, shall not exceed R-5. Where the R-value of
    materials to the interior side of the exterior continuous insulation exceeds R-5, an approved design shall be required.
    b. A water vapor control material layer having a permeance not greater than 1 perm in accordance with ASTM E96 Procedure A (dry cup) shall be placed on the exterior side of
    the wall and to the interior side of the exterior continuous insulation. The exterior continuous insulation shall be permitted to serve as the vapor control layer where, at its
    installed thickness or with a facer on its interior face, the exterior continuous insulation is a Class I or II vapor retarder.
    c. The requirements in this table apply only to insulation used to control moisture in order to allow walls without a Class I, II or III interior vapor retarder. The insulation materi-
    als used to satisfy this option also contribute to but do not supersede the thermal envelope requirements of the_California Energy Code_.|

    R702.7.1 Spray foam plastic insulation for moisture control with Class II and III vapor retarders. For purposes of compliance with Tables R702.7(3) and R702.7(4), spray foam with a maximum permeance of 1.5 perms at the installed thickness applied to the interior side of wood structural panels, fiberboard, insulating sheathing or gypsum shall be deemed to meet the continuous insulation moisture control requirement in accordance with one of the following conditions:

    1. The spray foam R -value is equal to or greater than the specified continuous insulation R -value.
    2. The combined R -value of the spray foam and continuous insulation is equal to or greater than the specified continuous insulation R -value.

    R702.7.2 Vapor retarder installation. Vapor retarders shall be installed in accordance with the manufacturer’s instructions, accepted installation methods or an approved design. Where a vapor retarder also functions as a component of a continuous air barrier, the vapor retarder shall be installed as an air barrier in accordance with Section N1102.5.1.1.

    R702.7.3 California Energy Code and International Energy Conservation Code Climate Zones. The IECC climate zones used by this section differ from those used by the California Energy Code to determine applicability of energy efficiency measures. Comparison of IECC and California Energy Code climate zones is shown in Table R702.7.3.

    |TABLE R702.7.3—IECC VS.

  • § 0.625 High relevance — show source text

    875b| |Unit masonry|0.625b| |Cast-in-place or precast concrete|0.625b| |Two-coat work over:|| |Unit masonry|0.5b| |Cast-in-place or precast concrete|0.375b| |Terra cotta (anchored)|1| |Terra cotta (adhered)|0.25| |Vinyl siding|0.035| |Wood shingles|0.375| |Wood siding (without sheathing)a|0.5| |For SI: 1 inch = 25.4 mm, 1 ounce = 28.35 g, 1 square foot = 0.093 m2.
    a. Wood siding of thicknesses less than 0.5 inch shall be placed over sheathing that conforms to Section 2304.6.
    b. Exclusive of texture.
    c. As measured at the bottom of decorative grooves.
    d. 16 ounces per square foot for cold-rolled copper and lead-coated copper, 12 ounces per square foot for copper shingles, high-yield copper and lead-coated high-yield copper.|For SI: 1 inch = 25.4 mm, 1 ounce = 28.35 g, 1 square foot = 0.093 m2.
    a. Wood siding of thicknesses less than 0.5 inch shall be placed over sheathing that conforms to Section 2304.6.
    b. Exclusive of texture.
    c. As measured at the bottom of decorative grooves.
    d. 16 ounces per square foot for cold-rolled copper and lead-coated copper, 12 ounces per square foot for copper shingles, high-yield copper and lead-coated high-yield copper.|

    14-6 2025 CALIFORNIA BUILDING CODE

    on Jul 18, 2025 11:14 AM (CDT) THEREUNDER.

    EXTERIOR WALLS

    1404.3 Vapor retarders. Vapor retarder materials shall be classified in accordance with Table 1404.3(1). A vapor retarder shall be provided on the interior side of frame walls in accordance with Table 1404.3(2) and Tables 1404.3(3) or 1404.3(4) as applicable, or an approved design using accepted engineering practice for hygrothermal analysis. Vapor retarders shall be installed in accordance with Section 1404.3.2. The appropriate climate zone shall be selected in accordance with the California Energy Code .

    Exceptions:

    1. Basement walls.

    2. Below-grade portion of any wall.

    3. Construction where accumulation, condensation or freezing of moisture will not damage the materials.

    4. A vapor retarder shall not be required in Climate Zones 1, 2, and 3.

    5. In Climate Zones 4 through 8, a vapor retarder on the interior side of frame walls shall not be required where the assembly complies with Table 1404.3(5).

  • § 403.4.7 High relevance — show source text

    Smoke exhaust 910 Smoke removal, high-rise buildings 403.4.7 Smokeproof enclosure 909.20.3, 909.20.5, 1023.12 Spray rooms and spaces 416.2.2, 416.3 Stages 410.2.5, 410.2.7 Under-floor ventilation 202.4 Vents, Penetration Protection 714 Vermiculite, Fire Resistant 721 Vertical Opening Protection Atriums 404.6

    Duct penetrations 717.1 Elevators 713.14, 3007.6.1, 3008.6.1 Exceptions 1019, 1023.2 Group I-3 408.5 High-rise 403.2.1.2, 403.2.2, 403.5.1 Live/work units 508.5.6 Open parking garages 406.5.9 Permitted vertical openings 712 Shaft enclosure 713, 1019, 1023.2 Vestibules, Exit Discharge 1028.2 Vinyl Expanded 803.7, 803.8 Rigid 1404.15 Violations 114 Voice Alarm (see Alarms, Voice) Walkway 402.4.3.1, 3104 During construction 3306 Encroachment, public right-of-way 3202.3.4

    Fire resistance Table 601

    Live load Table 1607.1 Materials per construction type Chapter 6 Opening protection 716, 717, 1026.2 Wall, Exterior 705, 1401 Bearing Chapter 6

    California Energy Code and International Energy Conservation Code Climate Zones 1404.3.3 Combustible wall covering 1405 Coverings 1404 Drawings 107.2.4 Exterior insulation and finish systems (EIFS) 1407 Exterior structural members 704.9

    Fire district D102.2.6, D102.1 Fire-resistance ratings 703, 705.5, Table 705.5, 706.5.1, 707.4, 1402.4 Flashing, veneered walls 1404.11.1, 1404.4

    Foam plastic insulation 2603.4.1.4, 2603.5 Glazing, rated 715.8 Joints 705.10, 714 Light-transmitting plastic panels 2607 Materials 705.4, 1403.1, 1405 Metal composite material (MCM) 1406 Nonbearing Chapter 6 Opening protection 705.11, 705.9, 716.2.5.4

    Parapets 705.12 Performance requirements 1402 Projections 705.2 Structural stability 705.7 Vapor retarders 1404.3 Veneer (see Veneer) Weather resistance 1402.2, 1404.2, 1406.6, 1407.4 Weather-resistant barriers 1404.2 Wall, Fire (see Fire Walls) Wall, Foundation (see Foundations) Wall, Interior Finishes 803, 1210.2 Opening protection 716, 717 Wall, Interior Nonbearing (See Partitions) Wall, Masonry 202 Wood Contact 2304.12.1.3,

Frequently asked questions

When do I use Table 1404.3(4) vs Table 1404.3(5)?

Use Table 1404.3(4) when an interior Class I or Class II responsive vapor retarder is provided and the exterior has foam continuous insulation; use Table 1404.3(5) when there is no interior Class I/II/III vapor retarder (see § 1404.3 and both tables) .

What if my interior cavity insulation plus interior finishes exceed R‑5?

Table 1404.3(5) requires the total insulating value of materials to the interior side of the exterior CI to not exceed R‑5; if it does exceed R‑5 you must provide an approved design (hygrothermal analysis) as noted in Table 1404.3(5) .

Can exterior continuous insulation serve as the vapor control layer?

Yes — only when the installed exterior continuous insulation (or with an interior facer) is a Class I or II vapor retarder at the installed thickness, per the notes to Table 1404.3(5) .

How does spray polyurethane foam affect the tables?

Per § 1404.3.1, spray foam with max 1.5 perms at installed thickness applied interior to sheathing is deemed to meet the continuous‑insulation moisture‑control requirement if its R‑value alone or combined with the exterior CI equals or exceeds the table R requirement .

Which climate zone mapping should I use?

Use the IECC/California comparison rules referenced in § 1404.3.3 (Chapter 12 mapping table) to determine the correct climate zone for applying Tables 1404.3(4) and 1404.3(5) .

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Vapor retarder installation requirements and spray foam criteria for moisture control

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California Energy Code