Title 24 · California Energy Code

Raised floor and slab perimeter insulation requirements

For a homeowner: crawlspace (raised) floors must be insulated to the performance shown in Table 150.1‑A (or by using the in‑framing R‑value option); slab edge insulation must meet the same Table 150.1‑A targets and be installed down **16 inches or to the footing depth, whichever is less** — check your climate zone’s values in Table 150.1‑A and protect slab insulation from moisture and damage.

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Last reviewed: July 6, 2026

What the code requires — plain English

Raised (crawlspace) floors must be insulated so the floor assembly meets the assembly U‑factor or the in‑framing R‑value shown in Table 150.1‑A. Slab perimeter insulation must meet the U‑factor or R‑value in Table 150.1‑A and be installed to a minimum depth of 16 inches or the depth of the building footing, whichever is less. These prescriptive rules are in § 150.1(c)1C and § 150.1(c)1D of the California Energy Code.

The single most important rule: Insulate raised floors and slab edges to the performance values shown in Table 150.1‑A — and always install slab edge insulation down 16 in. or to the footing depth, whichever is less. § 150.1(c)1C–D

Requirements in detail

Scope and options

  • Raised floors separating conditioned space from unconditioned space or ambient air must meet either:
    • an assembly U‑factor ≤ the value in Table 150.1‑A, or
    • insulation placed between wood framing with an R‑value ≥ the value in Table 150.1‑A. § 150.1(c)1C
  • Slab floor perimeter insulation must meet a U‑factor ≤ or R‑value ≥ the value listed in Table 150.1‑A. The minimum installation depth for concrete slab perimeter insulation is 16 inches or the depth of the footing, whichever is less. § 150.1(c)1D

Note: The prescriptive numeric U‑factor and R‑value targets are climate‑zone dependent and are provided in Table 150.1‑A (not reproduced here). § 150.1(c)1C–D

Decision‑relevant dimensions and values

Feature Decision dimension (what you must check) Typical compliance option Code reference
Raised floor assembly Assembly U‑factor or R‑value between wood framing Meet the assembly U or install framing insulation to the R in Table 150.1‑A § 150.1(c)1C
Raised floor numeric example (mandatory section) Example U / R used elsewhere in the code for raised wood floors U‑0.037 or R‑19 (wood framed example shown in § 150.0(d)) — this appears in the mandatory features section, not in Table 150.1‑A § 150.0(d)
Slab perimeter insulation Minimum depth: 16 in. or footing depth (whichever is less); must meet U or R in Table 150.1‑A Vertical (and where applicable horizontal) insulation per Table 150.1‑A; for heated slabs see Table 110.8‑A for heated‑slab detail § 150.1(c)1D; heated slab reference § 110.8
Slab edge material requirements Durability & moisture specs for materials Water absorption ≤ 0.3% (24‑hr ASTM C272), vapor permeance ≤ 2.0 perm/in. (ASTM E96); protect from damage/UV § 150.0(f)

If you need the exact U‑factor or R‑value numbers for your project, consult Table 150.1‑A (climate‑zone dependent) in the code — Table 150.1‑A contains the prescriptive R and U targets that the text in § 150.1(c)1C–D refers to.

Installation quality & related verification

  • When Table 150.1‑A requires Quality Insulation Installation (QII), follow the QII verification and field inspection requirements in Reference Appendix RA3.5. § 150.1(c)1E (QII cross‑reference)

Exceptions & special cases

  • Raised‑floor insulation may be omitted when all of the following are true:
    • foundation walls are insulated to meet the wall minima in Table 150.1‑A;
    • a Class I or II vapor retarder covers the entire crawlspace floor;
    • crawlspace vents are fitted with automatically operated, temperature‑actuated louvers; and
    • the requirements of Reference Residential Appendix RA4.5.1 are met. (This is the exception to § 150.1(c)1C.)
  • The prescriptive numeric targets in Table 150.1‑A also may be met by demonstrating equivalent performance using an approved U‑factor calculation method that accounts for all assembly elements — see the exception language in § 150.1(c)1.
  • Heated slabs have additional, specific insulation placement and R‑value rules (see Table 110.8‑A and § 110.8(g)). Use those when the slab is heated.

Common mistakes

  • Assuming a single numeric R‑value applies statewide. The code’s prescriptive R/U targets are climate‑zone dependent in Table 150.1‑A — always check your climate zone. § 150.1(c)1C–D
  • Installing slab edge insulation shallower than the code minimum. The minimum depth is 16 in. or footing depth, whichever is less — do not use an arbitrary shallower depth. § 150.1(c)1D
  • Confusing the mandatory raised‑floor values shown in other sections (for example § 150.0(d) which lists U‑0.037 / R‑19 for raised wood floors) with the prescriptive Table 150.1‑A values for a particular prescriptive package; verify which section/table applies to your compliance path.
  • Failing to protect slab edge insulation: slab edge insulation must meet material durability requirements (water absorption, permeance) and be protected from physical/UV damage. § 150.0(f)

Worked example — concrete scenario

Scenario: A single‑family house in a climate zone where the Table 150.1‑A prescriptive target for raised wood floors equals an R‑value of R‑19 (for illustration). The house has a crawlspace with a concrete footing that is 12 inches deep.

Step 1 — Raised floor:

  • Option used: install R‑19 batt insulation between wood floor joists. This meets the wood‑framed framing option when Table 150.1‑A requires R‑19 (or matches the assembly U‑factor alternative). Cite: § 150.1(c)1C; example numeric target appears in the mandatory section as U‑0.037 / R‑19 in § 150.0(d).

Step 2 — Slab perimeter:

  • The slab has footings 12 in. deep. The code requires slab perimeter insulation depth = min(16 in., footing depth). Because the footing is 12 in., the minimum required insulation depth down the slab edge is 12 in. (footing depth), not 16 in. § 150.1(c)1D
  • Next, install vertical slab edge insulation to the R‑value or U‑factor from Table 150.1‑A for the house’s climate zone (look up the exact R or U in Table 150.1‑A). § 150.1(c)1D

Note: the example uses a presumed Table 150.1‑A R‑19 target for illustrative purposes. Always verify the actual Table 150.1‑A value for your specific climate zone and prescriptive package.

Related provisions

  • § 150.1(c)1C — Raised floors: assembly U‑factor or in‑framing R‑value options (prescriptive text pointing to Table 150.1‑A).
  • § 150.1(c)1D — Slab floor perimeter insulation: U/R requirement and minimum depth rule (16 in. or footing depth).
  • § 150.0(d) — Mandatory raised‑floor numeric example (U‑0.037 / R‑19 in wood framed assemblies) — appears in the mandatory features text.
  • § 150.0(f) — Slab edge insulation material and durability requirements (water absorption, vapor permeance, protection).
  • Table 150.1‑A — The prescriptive climate‑zone‑dependent U and R targets referenced by § 150.1(c)1C–D (consult the table in the code book for exact values).
  • Table 110.8‑A / § 110.8(g) — Heated slab insulation requirements and placement (when slab is heated).
  • Reference Residential Appendix RA4.5.1 — Required when using the raised‑floor insulation omission exception (crawlspace control).

Code references

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

  • § 150.1 High relevance — show source text

    i. Framed exterior walls shall be insulated such that the exterior wall has an assembly U -factor equal to or less than that shown in Table 150.1-A. The U -factors shown are maximum U -factors for the exterior wall assembly. ii. Mass walls above grade and below grade shall be insulated such that the wall has an assembly U -factor equal to or less than that shown in Table 150.1-A, or walls shall be insulated with continuous insulation that has an R value equal to or greater than that shown in Table 150.1-A. “Interior” denotes continuous insulation installed on the inside surface of the wall, and “exterior” denotes continuous insulation installed on the outside surface of the wall.

    iii. Other unframed exterior walls, excluding mass walls, shall meet the requirements for framed walls shown in Table 150.1-A.

    C. Raised floors shall be insulated such that the floor assembly has an assembly U -factor equal to or less than shown in Table 150.1-A, or shall be insulated between wood framing with insulation having an R- value equal to or greater than that shown in Table 150.1-A.

    Exception to Section 150.1(c)1C: Raised-floor insulation may be omitted if the foundation walls are insulated to meet the wall insulation minimums shown in Table 150.1-A, and a vapor retarder is placed over the entire floor of the crawl space, and the vents are fitted with automatically operated louvers, and the requirements of Reference Residential Appendix RA4.5.1 are met. D. Slab floor perimeter insulation shall be installed with a U -factor equal to or less than, or R -value equal to or greater than, shown in Table 150.1-A. The minimum depth of concrete-slab floor perimeter insulation shall be 16 inches or the depth of the footing of the building, whichever is less. Exception to Section 150.1(c)1: The insulation requirements of Table 150.1-A may also be met by ceiling, roof deck, wall, or floor assemblies that meet the required maximum U -factors using a U -factor calculation method that considers the thermal effects of all elements of the assembly and is approved by the executive director. E. All buildings shall comply with the quality insulation installation (QII) requirements shown in Table 150.1-A. When QII is required, insulation installation shall meet the criteria specified in Reference Appendix RA3.5.

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    SINGLE-FAMILY RESIDENTIAL BUILDINGS—PERFORMANCE AND PRESCRIPTIVE COMPLIANCE APPROACHES

    1. Radiant barrier. A radiant barrier required in Table 150.1-A shall meet the requirements specified in Section 110.8(j) and shall meet the installation criteria specified in the Reference Residential Appendix RA4.

    2. Fenestration.

    A. Installed fenestration products, including glazed doors, shall have an area weighted average U -factor and Solar Heat Gain Coefficient (SHGC) meeting the applicable fenestration value in Table 150.1-A and shall be determined in accordance with Sections 110.6(a)2 and 110.6(a)3. Exception 1 to Section 150.1(c)3A: New dwelling units with a conditioned floor area of 500 square feet or less in Climate Zone 5 may comply with a maximum U -factor of 0.30.

  • § 170.2 High relevance — show source text

    VT = Visible transmittance of framed window.

    B. Skylights shall: i. Have an area no greater than 5 percent of the gross exterior roof area Skylight Roof Ratio (SRR); and Exception 1 to Section 170.2(a)3Bi: Buildings with an atrium over 55 feet high shall have a skylight area no greater than 10 percent of the gross exterior roof area. ii. Have an area-weighted performance rating U -factor no greater than the applicable value in Table 170.2-A. Exception 2 to Section 170.2(a)3Bii: For each dwelling unit up to 16 square feet of new skylight area with a maximum U-factor of 0.55 and a maximum SHGC of 0.30.

    iii. Solar heat gain coefficient. Have an area-weighted performance rating solar heat gain coefficient no greater than the applicable value in Table 170.2-A. Exception to Sections 170.2(a)3Bii and 170.2(a)3Biii: For skylights containing chromogenic type glazing:

    a. The lower-rated labeled SHGC shall be used with automatic controls to modulate the amount of heat flow into the space in multiple steps in response to daylight levels or solar intensity; and b. Chromogenic glazing shall be considered separately from other glazing; and c. Area-weighted averaging with other glazing that is not chromogenic shall not be permitted. iv. Haze value. Have a glazing material or diffuser that has a measured haze value greater than 90 percent, determined according to ASTM D1003 or other test method approved by the Energy Commission. Exception to Section 170.2(a)3Biv: Skylights designed and installed to exclude direct sunlight entering the occupied space by the use of fixed or automated baffles or the geometry of the skylight and light well. 4. All exterior doors, excluding glazed doors, that separate conditioned space from unconditioned space or from ambient air shall have a U -factor not greater than the applicable value in Table 170.2-A. Glazed doors must comply with the requirements of Section 170.2(a)3A. Exception to Section 170.2(a)4: Swinging doors that are required to have fire protection are not required to meet the applicable door value in Table 170.2-A. 5. Floors shall meet the following requirements: A. Raised floors shall be insulated such that the floor assembly has an assembly U -factor equal to or less than shown in Table 170.2-A, or shall be insulated between wood framing with insulation having an R -value equal to or greater than shown in Table 170.2-A.

    B. Slab floors shall have perimeter insulation installed with a U -factor equal to or less than or R -value equal to or greater than shown in Table 170.2-A. The minimum depth of concrete slab floor perimeter insulation shall be 16 inches or the depth of the footing of the building, whichever is less. Exception to Section 170.2(a)5: Raised-floor insulation may be omitted if the foundation walls are insulated to meet the wall insulation minimums shown in Table 170.2-A.

  • § 0.037. High relevance — show source text

    In wood framed assemblies, compliance with U -factors may be demonstrated by installing wall insulation with an R -value of R-15 in 2x4 assemblies, and R-21 in 2x6 assemblies with 16 inches on center spacing.

    (d) Raised-floor insulation. Raised floors separating conditioned space from unconditioned space or ambient air shall have an overall assembly U -factor not exceeding U-0.037. In a wood framed assembly, compliance with the U -factor may be demonstrated by installing insulation with an R -value of 19 or greater.

    Exception to Section 150.0(d): A building with a controlled ventilation or unvented crawlspace may omit raised floor insulation if all of the following are met: i. The foundation walls are insulated to meet the wall insulation minimums as shown in Table 150.1-A; and

    ii. A Class I or Class II vapor retarder is placed over the entire floor of the crawl space; and iii. Vents between the crawlspace and outside air are fitted with automatically operated louvers that are temperature actuated; and

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    SINGLE-FAMILY RESIDENTIAL BUILDINGS— MANDATORY FEATURES AND DEVICES

    iv. The requirements in Reference Residential Appendix RA4.5.1.

    (e) Installation of fireplaces, decorative gas appliances and gas logs. If a masonry or factory-built fireplace is installed, it shall comply with Section 110.5, Section 4.503 of Part 11, and shall have the following:

    1. Closable metal or glass doors covering the entire opening of the firebox; and
    2. A combustion air intake to draw air from the outside of the building, which is at least 6 square inches in area and is equipped with a readily accessible, operable and tight-fitting damper or combustion-air control device; and Exception to Section 150.0(e)2: An outside combustion-air intake is not required if the fireplace will be installed over concrete slab flooring and the fireplace will not be located on an exterior wall.
    3. A flue damper with a readily accessible control. Exception to Section 150.0(e)3: When a gas log, log lighter or decorative gas appliance is installed in a fireplace, the flue damper shall be blocked open if required by the CMC or the manufacturer’s installation instructions.

    (f) Slab edge insulation. Material used for slab edge insulation shall meet the following minimum specifications:

    1. Water absorption rate for the insulation material alone without facings no greater than 0.3 percent when tested in accordance with Test Method A – 24-Hour-Immersion of ASTM C272.

    2. Water vapor permeance no greater than 2.0 perm/inch when tested in accordance with ASTM E96.

    3. Concrete slab perimeter insulation shall be protected from physical damage and ultraviolet light deterioration.

    4. Insulation for a heated slab floor shall meet the requirements of Section 110.8(g).

    (g) Vapor retarder.

    1. In Climate Zones 1–16, the earth floor of unvented crawl space shall be covered with a Class I or Class II vapor retarder. This requirement shall also apply to controlled ventilation crawl space for buildings complying with the Exception to Section 150.0(d).
  • § 150.1 High relevance — show source text

    viii. Building 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. ix. 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.

    (c) Prescriptive standards/component packages. Buildings 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 150.1-A. In Table 150.1-A, an NA (not allowed) means that feature is not permitted in a particular climate zone and an 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:

    1. Insulation.

    A. Roof and ceiling insulation shall be installed with an R -value equal to or greater than that shown in Table 150.1-A meeting Option i, ii or iii below. i. Option A: Reserved. ii. Option B: A minimum R -value of insulation in a ventilated attic 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 150.1(c)9A; or iii. Option C: A minimum R -value of ceiling insulation located between a ventilated attic and the conditioned space or within a cathedral ceiling assembly shall comply with Section 150.1(c)9B.

    B. Walls.

    i. Framed exterior walls shall be insulated such that the exterior wall has an assembly U -factor equal to or less than that shown in Table 150.1-A. The U -factors shown are maximum U -factors for the exterior wall assembly. ii. Mass walls above grade and below grade shall be insulated such that the wall has an assembly U -factor equal to or less than that shown in Table 150.1-A, or walls shall be insulated with continuous insulation that has an R value equal to or greater than that shown in Table 150.1-A. “Interior” denotes continuous insulation installed on the inside surface of the wall, and “exterior” denotes continuous insulation installed on the outside surface of the wall.

    iii. Other unframed exterior walls, excluding mass walls, shall meet the requirements for framed walls shown in Table 150.1-A.

    C. Raised floors shall be insulated such that the floor assembly has an assembly U -factor equal to or less than shown in Table 150.1-A, or shall be insulated between wood framing with insulation having an R- value equal to or greater than that shown in Table 150.1-A.

    Exception to Section 150.1(c)1C: Raised-floor insulation may be omitted if the foundation walls are insulated to meet the wall insulation minimums shown in Table 150.1-A, and a vapor retarder is placed over the entire floor of the crawl space, and the vents are fitted with automatically operated louvers, and the requirements of Reference Residential Appendix RA4.5.1 are met. D. Slab floor perimeter insulation shall be installed with a U -factor equal to or less than, or R -value equal to or greater than, shown in Table 150.1-A.

  • § 150.1 High relevance — show source text

    The minimum depth of concrete-slab floor perimeter insulation shall be 16 inches or the depth of the footing of the building, whichever is less. Exception to Section 150.1(c)1: The insulation requirements of Table 150.1-A may also be met by ceiling, roof deck, wall, or floor assemblies that meet the required maximum U -factors using a U -factor calculation method that considers the thermal effects of all elements of the assembly and is approved by the executive director. E. All buildings shall comply with the quality insulation installation (QII) requirements shown in Table 150.1-A. When QII is required, insulation installation shall meet the criteria specified in Reference Appendix RA3.5.

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    SINGLE-FAMILY RESIDENTIAL BUILDINGS—PERFORMANCE AND PRESCRIPTIVE COMPLIANCE APPROACHES

    1. Radiant barrier. A radiant barrier required in Table 150.1-A shall meet the requirements specified in Section 110.8(j) and shall meet the installation criteria specified in the Reference Residential Appendix RA4.

    2. Fenestration.

    A. Installed fenestration products, including glazed doors, shall have an area weighted average U -factor and Solar Heat Gain Coefficient (SHGC) meeting the applicable fenestration value in Table 150.1-A and shall be determined in accordance with Sections 110.6(a)2 and 110.6(a)3. Exception 1 to Section 150.1(c)3A: New dwelling units with a conditioned floor area of 500 square feet or less in Climate Zone 5 may comply with a maximum U -factor of 0.30. Exception 2 to Section 150.1(c)3A: For each dwelling unit, up to 3 square feet of new glazing area installed in doors and up to 3 square feet of tubular skylights area with dual-pane diffusers shall not be required to meet the U -factor and SHGC requirements of Table 150.1-A. Exception 3 to Section 150.1(c)3A: In Climate Zones 2, 4, and 6 through 15, for each dwelling unit up to 16 square feet of skylight area with a maximum U -factor of 0.40 and a maximum SHGC of 0.30. In Climate Zones 1, 3, 5, and 16, there is no SHGC requirement. Exception 4 to Section 150.1(c)3A: For fenestration containing chromogenic type glazing:

    i. The lower-rated labeled U -factor and SHGC shall be used with automatic controls to modulate the amount of solar gain and light transmitted into the space in multiple steps in response to daylight levels or solar intensity; ii. Chromogenic glazing shall be considered separately from other fenestration; and iii. Area-weighted averaging with other fenestration that is not chromatic shall not be permitted and shall be determined in accordance with Section 110.6(a). Exception 5 to Section 150.1(c)3A: For dwelling units containing unrated site-built fenestration that meets the maximum area restriction, the U -factor and SHGC can be determined in accordance with the Nonresidential Reference Appendix NA6 or use default values in Table 110.6-A and Table 110.6-B.

  • § 170.2 High relevance — show source text
    1. Floors shall meet the following requirements: A. Raised floors shall be insulated such that the floor assembly has an assembly U -factor equal to or less than shown in Table 170.2-A, or shall be insulated between wood framing with insulation having an R -value equal to or greater than shown in Table 170.2-A.

    B. Slab floors shall have perimeter insulation installed with a U -factor equal to or less than or R -value equal to or greater than shown in Table 170.2-A. The minimum depth of concrete slab floor perimeter insulation shall be 16 inches or the depth of the footing of the building, whichever is less. Exception to Section 170.2(a)5: Raised-floor insulation may be omitted if the foundation walls are insulated to meet the wall insulation minimums shown in Table 170.2-A.

    1. All buildings up to three habitable stories shall comply with the quality insulation installation (QII) requirements shown in Table 170.2-A. When QII is required, insulation installation shall meet the criteria specified in Reference Appendix RA3.5. Exception to Section 170.2(a): The insulation requirements of Table 170.2-A and Table 170.2-B may be met by ceiling, roof deck, wall or floor assemblies that meet the required maximum U -factors using a U -factor calculation method that considers the thermal effects of all elements of the assembly and is approved by the Executive Director.

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    MULTIFAMILY BUILDINGS—PERFORMANCE AND PRESCRIPTIVE COMPLIANCE APPROACHES

    TABLE 170.2-A—ENVELOPE COMPONENT PACKAGE-MULTIFAMILY STANDARD BUILDING DESIGN Col2 Col3 Col4 Col5 Col6 Col7 Col8 Col9 Col10 Col11 Col12 Col13 Col14 Col15 Col16 Col17
    BUILDING COMPONENT -
    ROOFS AND CEILINGS    		 CZ 1 CZ 2 CZ 3 CZ 4 CZ 5 CZ 6 CZ 7 CZ 8 CZ 9 CZ 10 CZ 11 CZ 12 CZ 13 CZ 14 CZ 15 CZ 16
    Option B9 Below Roof Deck
    Insulation1,
  • § 0.269. High relevance — show source text

    (c) Floor and soffit insulation. The opaque portions of floors and soffits that separate conditioned spaces from unconditioned spaces or ambient air shall meet the applicable requirements of Items 1 through 3 below:

    1. Raised mass floors shall have a minimum of 3 inches of lightweight concrete over a metal deck or the area-weighted average U- factor of the floor assembly shall not exceed 0.269.

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    MULTIFAMILY BUILDINGS—MANDATORY REQUIREMENTS

    1. Raised wood floor shall have an overall assembly U- factor not exceeding 0.037. In a wood framed assembly, compliance with the U- factor may be demonstrated by installing insulation with an R- value of 19 or greater.
    2. Other floors—The area-weighted average U- factor of the floor assembly shall not exceed 0.071.
    3. Heated slab on grade floor—A heated slab on grade floor shall be insulated to meet the requirements of Section 110.8(g). Exception to Section 160.1(c): A building with a controlled ventilation or unvented crawl space may omit raised floor insulation if all of the following are met: A. The foundation walls are insulated to meet the wall insulation minimums as shown in Table 170.2-A; and

    B. A Class I or Class II vapor retarder is placed over the entire floor of the crawl space; and C. Vents between the crawl space and outside air are fitted with automatically operated louvers that are temperature actuated; and

    D. The requirements in Reference Residential Appendix RA4.5.1.

    (d) Vapor retarder.

    1. In Climate Zones 1–16, the earth floor of unvented crawl space shall be covered with a Class I or Class II vapor retarder. This requirement shall also apply to controlled ventilation crawl space for buildings complying with the Exception to Section 160.1(c).

    2. In Climate Zones 14 and 16, a Class I or Class II vapor retarder shall be installed on the conditioned space side of all insulation in all exterior walls, vented attics and unvented attics with air-permeable insulation.

    (e) Fenestration products. Fenestration separating conditioned space from unconditioned space or outdoors shall meet the requirements of either Item 1 or 2 below:

    1. Fenestration, including skylight products, must have a maximum U- factor of 0.58. Exception 1 to Section 160.1(e)1: Up to 0.5 percent of the conditioned floor area is not required to comply with the maximum U- factor requirement. Exception 2 to Section 160.1(e)1: For dual-glazed greenhouse or garden windows, up to 30 square feet of fenestration area per dwelling unit is not required to comply with the maximum U- factor requirement.
    2. The area-weighted average U- factor of all fenestration, including skylight products, shall not exceed 0.58.

    Exception to Section 160.1(e): Fenestration installed in buildings meeting Part 7 of the California Building Code, California Wild- land-Urban Interface Code, where the building is located in Fire Hazard Severity Zones or Wildland-Urban Interface (WUI) Fire Areas as designated by the local enforcement agency.

    (f) **Installation of fireplaces, decorative gas appliances and gas logs.

  • § 0.113. High relevance — show source text

    (b) Wall insulation. Opaque portions of above grade walls separating conditioned spaces from unconditioned spaces or ambient air shall meet the following applicable requirements:

    1. Metal building—The area-weighted average U- factor of the wall assembly shall not exceed 0.113.

    2. Metal framed—The area-weighted average U- factor of the wall assembly shall not exceed 0.151.

    3. Wood framed and others—

    A. Nominal 2x4 inch framing shall have an area-weighted average U- factor of the wall assembly not exceeding 0.095. B. Nominal 2x6 inch framing shall have an area-weighted average U- factor of the wall assembly not exceeding 0.069. C. Other wall assemblies shall have an area-weighted average U- factor of the wall assembly not exceeding 0.102. 4. Light mass walls—A 6 inch or greater hollow core concrete masonry unit shall have a U- factor not to exceed 0.440. 5. Heavy mass walls—An 8 inch or greater hollow core concrete masonry unit shall have a U- factor not to exceed 0.690. 6. Spandrel panels and curtain wall—The area-weighted average U- factor of the spandrel panels and curtain wall assembly shall not exceed 0.280.

    1. Demising walls—The opaque portions of framed demising walls shall meet the requirements of Item A or B below: A. Wood framed walls shall be insulated to meet a U- factor not greater than 0.099. B. Metal framed walls shall be insulated to meet a U- factor not greater than 0.151.
    2. Bay or bow window roofs and floors shall be insulated to meet the wall insulation requirements of Table 170.2-A.

    (c) Floor and soffit insulation. The opaque portions of floors and soffits that separate conditioned spaces from unconditioned spaces or ambient air shall meet the applicable requirements of Items 1 through 3 below:

    1. Raised mass floors shall have a minimum of 3 inches of lightweight concrete over a metal deck or the area-weighted average U- factor of the floor assembly shall not exceed 0.269.

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    MULTIFAMILY BUILDINGS—MANDATORY REQUIREMENTS

    1. Raised wood floor shall have an overall assembly U- factor not exceeding 0.037. In a wood framed assembly, compliance with the U- factor may be demonstrated by installing insulation with an R- value of 19 or greater.
    2. Other floors—The area-weighted average U- factor of the floor assembly shall not exceed 0.071.
    3. Heated slab on grade floor—A heated slab on grade floor shall be insulated to meet the requirements of Section 110.8(g). Exception to Section 160.1(c): A building with a controlled ventilation or unvented crawl space may omit raised floor insulation if all of the following are met: A. The foundation walls are insulated to meet the wall insulation minimums as shown in Table 170.2-A; and

    B. A Class I or Class II vapor retarder is placed over the entire floor of the crawl space; and C. Vents between the crawl space and outside air are fitted with automatically operated louvers that are temperature actuated; and

    D. The requirements in Reference Residential Appendix RA4.5.1.

    (d) Vapor retarder.

  • § 170.2 High relevance — show source text

    iv. Haze value. Have a glazing material or diffuser that has a measured haze value greater than 90 percent, determined according to ASTM D1003 or other test method approved by the Energy Commission. Exception to Section 170.2(a)3Biv: Skylights designed and installed to exclude direct sunlight entering the occupied space by the use of fixed or automated baffles or the geometry of the skylight and light well. 4. All exterior doors, excluding glazed doors, that separate conditioned space from unconditioned space or from ambient air shall have a U -factor not greater than the applicable value in Table 170.2-A. Glazed doors must comply with the requirements of Section 170.2(a)3A. Exception to Section 170.2(a)4: Swinging doors that are required to have fire protection are not required to meet the applicable door value in Table 170.2-A. 5. Floors shall meet the following requirements: A. Raised floors shall be insulated such that the floor assembly has an assembly U -factor equal to or less than shown in Table 170.2-A, or shall be insulated between wood framing with insulation having an R -value equal to or greater than shown in Table 170.2-A.

    B. Slab floors shall have perimeter insulation installed with a U -factor equal to or less than or R -value equal to or greater than shown in Table 170.2-A. The minimum depth of concrete slab floor perimeter insulation shall be 16 inches or the depth of the footing of the building, whichever is less. Exception to Section 170.2(a)5: Raised-floor insulation may be omitted if the foundation walls are insulated to meet the wall insulation minimums shown in Table 170.2-A.

    1. All buildings up to three habitable stories shall comply with the quality insulation installation (QII) requirements shown in Table 170.2-A. When QII is required, insulation installation shall meet the criteria specified in Reference Appendix RA3.5. Exception to Section 170.2(a): The insulation requirements of Table 170.2-A and Table 170.2-B may be met by ceiling, roof deck, wall or floor assemblies that meet the required maximum U -factors using a U -factor calculation method that considers the thermal effects of all elements of the assembly and is approved by the Executive Director.

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    MULTIFAMILY BUILDINGS—PERFORMANCE AND PRESCRIPTIVE COMPLIANCE APPROACHES

    |TABLE 170.

  • § 141.0 High relevance — show source text

    G, H, 141.0(b)2M, N, O, 150.0(k)4, 170.2(e)7 Traffic sign 140.7(a), 140.7(c), 140.8(b)6 Unfiltered neon 140.8(a), 170.2(d)7 Significant Contaminant 160.2(c)8 Single Family buildings 150.0, 150.1, 150.2, 110.10(a), 110.10(b)1A, 110.10(c), 110.6(a)6, 110.8(d)1, 150.0(k)3, 150.0(s), 150.1(a), 150.1(c)1, 150.1(c)11, 150.1(c)14, 150.2(a) Phase 120.6(a)3 Pole circuit breaker space 150.0(n), 160.4(a) Pole double throw 140.6(a)1, 170.2(e)2 Side opening 160.2(c)2 Zone air conditioner 160.3(d)1 Zone central forced air system 150.0(m)13, 160.3(b)G-L Zone damper 120.1(d), 160.2(c)5 Zone heat pump 120.2(b) Zone space conditioning system 120.4(g), 140.4(a) cabinet 140.4(c)1 Site-Recovered 140.4(d), 140.4(g) Site-Solar Energy 140.4(d), 140.4(g) Sizing(Equipment) 140.4(a), 150.0(h), 160.3(b)2, 170.2(c)1 Skylight 110.6(a)3, 110.6(a)4, 130.1(d), 140.3(a)6, 140.3(c), 141.0(b)2A, 141.0(b)2G, 150.0(q), 150.1(c)3, 150.2(b)1A, 150.2(b)1B, 170.2(a)3, 180.2(b)1 Skylight Area 110.6(a)2, 110.10(b), 140.3(a), 140.3(c), 150.2(b), 170.2(b) Skylit Daylit Zone 130.1(d), 140.3(a)5, 140.3(c), 140.6(a)3, Table 140.6-A, 160.5(b)4, 170.2(b) Slab Edge Insulation 150.0(f) Slab Floor 110.8(g), Table 110.8-A, 150.0(f), 150.1(c)1, 160.1(f) Slab Floor Perimeter Insulation 170.2(a)5 Slab Insulation Requirements for Heated Slab Floor Table 110.8-A Small Duct High Velocity 150.0(m)13, 150.1(c)7, 150.2(b)1F, 160.3(b)5L, 170.2(c)3B, 180.2(b)2A Smoke Density 110.8(c)

    Smoke Test 141.0(b)2D, 150.2(b)1D, 150.

  • § 110.6 High relevance — show source text

    2(c)1 Skylight 110.6(a)3, 110.6(a)4, 130.1(d), 140.3(a)6, 140.3(c), 141.0(b)2A, 141.0(b)2G, 150.0(q), 150.1(c)3, 150.2(b)1A, 150.2(b)1B, 170.2(a)3, 180.2(b)1 Skylight Area 110.6(a)2, 110.10(b), 140.3(a), 140.3(c), 150.2(b), 170.2(b) Skylit Daylit Zone 130.1(d), 140.3(a)5, 140.3(c), 140.6(a)3, Table 140.6-A, 160.5(b)4, 170.2(b) Slab Edge Insulation 150.0(f) Slab Floor 110.8(g), Table 110.8-A, 150.0(f), 150.1(c)1, 160.1(f) Slab Floor Perimeter Insulation 170.2(a)5 Slab Insulation Requirements for Heated Slab Floor Table 110.8-A Small Duct High Velocity 150.0(m)13, 150.1(c)7, 150.2(b)1F, 160.3(b)5L, 170.2(c)3B, 180.2(b)2A Smoke Density 110.8(c)

    Smoke Test 141.0(b)2D, 150.2(b)1D, 150.2(b)1E, 180.2(b)2A Smoke Ventilation 110.10(b)1 Soffit Insulation 120.7(c), 160.1(c) Soiling Resistance 110.8(i)2, Table 110.8-B Solar Access 110.10(b)1A, 110.10(b)1B, 140.10(a)2, 170.2(g) Access Roof Area (SARA) 140.10(a), 150.1(c)14, 170.2(f), 170.2(g) Electric generation system 10-115(a), 10-115(b), 10-115(c), 110.10(b)1B, 110.10(e), 140.1(b), 150.1(b)1, 170.1(b) Energy 110.10(b)4, 110.3(c)5, 110.4(a) Gain 150.1(c)3 Heating 110.4(b) Insolation 110.10(b)1A, 110.10(b)1B, 140.10(a)2, 170.2(f), 170.2(g) Intensity 140.3(a)5, 140.3(a)6, 150.1(c)3, 170.2(a)3 Noon 150.1(c)4 Radiation 120.3(b), 120.4(f), 150.0(m)9, 160.3(b)5I, 160.3(c), 160.4(f) Rating and Certification Corporation (SRCC) 150.0(n), 160.4 Ready 110.10, 150.0(r), 160.8(a), 180.

  • § 110.7 Medium relevance — show source text
    1. Attic access doors shall have permanently attached insulation using adhesive or mechanical fasteners. The attic access shall be gasketed to prevent air leakage; and
    2. 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:

    1. 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. 2 × 6 inch or greater framing shall have an overall assembly U -factor not exceeding U-0.069.
    3. Opaque nonframed assemblies shall have an overall assembly U -factor not exceeding U-0.102.
    4. Bay or bow window roofs and floors shall be insulated to meet the wall insulation requirements of Table 150.1-A.
    5. Masonry/mass walls shall be insulated to meet the wall insulation requirements of Table 150.1-A.
    6. In wood framed assemblies, compliance with U -factors may be demonstrated by installing wall insulation with an R -value of R-15 in 2x4 assemblies, and R-21 in 2x6 assemblies with 16 inches on center spacing.

    (d) Raised-floor insulation. Raised floors separating conditioned space from unconditioned space or ambient air shall have an overall assembly U -factor not exceeding U-0.037. In a wood framed assembly, compliance with the U -factor may be demonstrated by installing insulation with an R -value of 19 or greater.

    Exception to Section 150.0(d): A building with a controlled ventilation or unvented crawlspace may omit raised floor insulation if all of the following are met: i. The foundation walls are insulated to meet the wall insulation minimums as shown in Table 150.1-A; and

    ii. A Class I or Class II vapor retarder is placed over the entire floor of the crawl space; and iii. Vents between the crawlspace and outside air are fitted with automatically operated louvers that are temperature actuated; and

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    SINGLE-FAMILY RESIDENTIAL BUILDINGS— MANDATORY FEATURES AND DEVICES

    iv. The requirements in Reference Residential Appendix RA4.5.1.

    (e) Installation of fireplaces, decorative gas appliances and gas logs. If a masonry or factory-built fireplace is installed, it shall comply with Section 110.5, Section 4.503 of Part 11, and shall have the following:

    1. Closable metal or glass doors covering the entire opening of the firebox; and

Frequently asked questions

How deep must slab edge insulation be?

Minimum depth is 16 inches or the depth of the footing, whichever is less — whichever produces the shallower required vertical extent. § 150.1(c)1D

Can I skip insulating a raised floor if I insulate the foundation wall?

Yes — raised‑floor insulation may be omitted when foundation walls meet the wall minima in Table 150.1‑A, a Class I/II vapor retarder covers the crawlspace floor, vents have automatic louvers, and RA4.5.1 requirements are met. This is the exception to § 150.1(c)1C.

Where do I find the exact R or U numbers I must meet?

The prescriptive, climate‑zone‑dependent R‑values and U‑factors are listed in Table 150.1‑A — consult that table in the code. § 150.1(c)1C–D

What materials and tests are required for slab edge insulation?

Insulation materials must have water absorption ≤ 0.3% (ASTM C272) and vapor permeance ≤ 2.0 perm/in. (ASTM E96), and must be protected from physical and UV damage. § 150.0(f)

If my slab is heated, are there different requirements?

Yes — heated slabs have specific vertical/horizontal placement and R‑value rules (see Table 110.8‑A and § 110.8(g)) in addition to the slab perimeter rule in § 150.1(c)1D.

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