Title 24 · California Energy Code

How to determine fenestration U‑factor, SHGC and VT (NFRC, CMA, CMAST)

Q: What if my window is NFRC‑rated but the manufacturer didn’t provide a permanent label?

You must provide either the temporary label at inspection or a label certificate when using CMA; permanent labels are required when NFRC procedures are used (see § 110.6(a)5 ).

Q: Can I use CMA/CMAST ratings instead of NFRC physical test data?

Yes — the Code recognizes CMA and CMAST as NFRC‑approved modeling/certification approaches for certain nonresidential products, but you must have the appropriate label/certificate and follow the NFRC process. See the Code definitions and labeling requirements. file

Q: My project has site‑built or field‑fabricated windows — what values do I use?

Field‑fabricated or unrated site‑built fenestration must be demonstrated compliant using the default values in Table 110.6‑A and Table 110.6‑B (and must be caulked/weatherstripped for field‑fabricated). § 110.6(b) .

Q: How do I handle divided lites or spacers when using default U‑factors?

Table 110.6‑A notes require you to add 0.05 to the listed U‑factors for dual‑glazed products with certain dividers/spacers and for true divided lites.

Q: Is VT always required to be NFRC 200?

VT may be derived from NFRC 200 or ASTM E972 ; tubular daylighting devices use NFRC 203 . If VT is outside those standards’ scope, Reference NA6 provides the calculation method per the Code. file

The Energy Code requires you to use NFRC ratings for window U‑factor, SHGC and VT when available, or otherwise use the default values in Table 110.6‑A/B; for single‑family prescriptive compliance you must show the area‑weighted average U‑factor and SHGC meet Table 150.1‑A, determined per **§ 110.6** and **§ 150.1(c)3**. file

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Last reviewed: July 6, 2026

What the code requires — in plain English

The California Energy Code requires that fenestration thermal and solar performance be rated using NFRC procedures where available, or else assigned the default values in Tables 110.6‑A and 110.6‑B. Specifically, § 110.6 sets the required rating methods for U‑factor, SHGC, and VT and also requires labels/certificates and acceptance for site‑built products.

For single‑family prescriptive compliance the installed fenestration’s area‑weighted average U‑factor and SHGC must meet the values in Table 150.1‑A and be determined following § 110.6(a)2 and § 110.6(a)3.

Use NFRC-certified ratings (or approved equivalent methods such as the CMA/CMAST process) for U‑factor, SHGC and VT when available; otherwise use the default Table 110.6‑A/B values called out in § 110.6.

Requirements in detail

What method to use (short decision tree)

If the product is NFRC‑rated, use the NFRC rating.
- U‑factor → NFRC 100. § 110.6(a)2.
- SHGC → NFRC 200. § 110.6(a)3.
- VT → NFRC 200 or ASTM E972 (tubular devices → NFRC 203). § 110.6(a)4.
If the product is not NFRC‑rated (site‑built or field‑fabricated and not otherwise test‑rated), use the default values in Table 110.6‑A for U‑factor and Table 110.6‑B for SHGC, and Reference Appendix NA6 for VT calculations where noted. § 110.6(a)2‑4.
For nonresidential custom products, use the CMA (Component Modeling Approach) and CMAST where allowed — CMA is an NFRC certification method that generates ratings via modeling rather than full physical test data. (Definition: CMA and CMAST)

Key defined terms (first mention bolded)

U‑factor (thermal transmittance) — rated per NFRC 100 or default Table 110.6‑A. § 110.6(a)2.
SHGC (Solar Heat Gain Coefficient) — rated per NFRC 200 or default Table 110.6‑B. § 110.6(a)3.
VT (Visible Transmittance) — rated per NFRC 200 or ASTM E972; tubular devices use NFRC 203. § 110.6(a)4.
CMA / CMAST — NFRC’s Component Modeling Approach and approved software tool for modeled product ratings; allowed alternative for certain nonresidential products. (Definitions appear in the Code’s definitions section.)

Decision‑relevant dimensions and rules

Decision item	What to use or check	Code Reference
Method for U‑factor	Use NFRC 100 rating; if not available, use Table 110.6‑A default values.	§ 110.6(a)2
Method for SHGC	Use NFRC 200 rating; if not available, use Table 110.6‑B default values.	§ 110.6(a)3
Method for VT	Use NFRC 200 or ASTM E972; tubular devices → NFRC 203; otherwise NA6.	§ 110.6(a)4
Field‑fabricated fenestration	Must demonstrate compliance using Table 110.6‑A/B values for compliance documentation.	§ 110.6(b)
Labeling & certificates	Temporary label or label certificate required; permanent label/label certificate when NFRC rating or CMA is used.	§ 110.6(a)5
Area‑weighted compliance for single‑family	Installed fenestration must meet area‑weighted average U‑factor and SHGC per Table 150.1‑A, determined per § 110.6(a)2/3.	§ 150.1(c)3(A)
Adjustments for divided lites	Add +0.05 to dual‑glazed U‑factors for certain divider/spacer conditions and for true divided lites.	Table 110.6‑A notes / § 110.6

(See full tables in Table 110.6‑A and Table 110.6‑B for the default numeric values.)

Exceptions & special cases

Skylights under nonresidential standards with < 200 ft²: default U‑factor/SHGC/VT may be calculated using Reference Nonresidential Appendix NA6 (exceptions to § 110.6(a)2–4).
Field‑fabricated fenestration: allowed only if compliance documentation uses Table 110.6‑A/B values; must be caulked and weatherstripped. § 110.6(b).
Chromogenic (dynamic) glazing: for certain compliance paths chromogenic glazing must be treated separately (lower rated labeled values used with automatic controls); see exceptions in § 150.1(c)3.
Site‑built or unrated fenestration in dwelling units: may use Reference Appendix NA6 or default tables as allowed by § 150.1(c)3 exceptions.

If a specific numeric requirement (for example the target area‑weighted U‑factor in Table 150.1‑A) is needed, consult Table 150.1‑A directly — that table sets the actual prescriptive limits by climate zone and occupancy.

Common mistakes

Relying on manufacturer literature instead of the NFRC label or label certificate (labels are required; see § 110.6(a)5).
Using an NFRC rating for a product but failing to include the label certificate or temporary label at inspection. § 110.6(a)5.
Forgetting to apply the +0.05 U‑factor adjustment for dual‑glazed products with certain divider/spacer configurations or true divided lites (see Table 110.6‑A notes).
Treating CMA modeled values as acceptable without verifying that the NFRC CMA/CMAST process was used and that a label certificate is issued (CMA requires label/certificate practice per Code definitions and labeling requirements). file
For prescriptive single‑family compliance, failing to use area‑weighted averages when multiple window types are installed (the Code requires area‑weighted averaging per § 150.1(c)3).

Worked example — practical calculation (concrete numbers)

Scenario: A homeowner installs three new NFRC‑rated windows in one dwelling unit; sizing and labels are known. The project will use the prescriptive single‑family requirement in § 150.1(c)3 and the installer must show the area‑weighted U‑factor and SHGC meet Table 150.1‑A.

Given:

Window A: area = 18 ft², NFRC U = 0.28, NFRC SHGC = 0.25
Window B: area = 30 ft², NFRC U = 0.32, NFRC SHGC = 0.20
Window C: area = 12 ft², NFRC U = 0.25, NFRC SHGC = 0.30

Step 1 — compute total fenestration area:

Total area = 18 + 30 + 12 = 60 ft²

Step 2 — area‑weighted average U‑factor:

Weighted U = (18×0.28 + 30×0.32 + 12×0.25) / 60
= (5.04 + 9.6 + 3.0) / 60 = 17.64 / 60 = 0.294

Step 3 — area‑weighted average SHGC:

Weighted SHGC = (18×0.25 + 30×0.20 + 12×0.30) / 60
= (4.5 + 6.0 + 3.6) / 60 = 14.1 / 60 = 0.235

Step 4 — compare to prescriptive table:

Compare average U = 0.294 and average SHGC = 0.235 to the applicable limits in Table 150.1‑A for the dwelling’s climate zone. If both meet or are lower (for U and SHGC) than the Table’s limit, the prescriptive fenestration requirement is satisfied. The Code requires determination per § 110.6(a)2 & (a)3.

Notes:

If any window were unrated, substitute the default values from Table 110.6‑A/B for that product before area‑weighting (per § 110.6).

Related provisions (quick reference)

§ 110.6(a)2–4 — Methods for rating U‑factor, SHGC, VT (NFRC or defaults).
§ 110.6(b) — Installation/compliance documentation rule for field‑fabricated fenestration.
§ 150.1(c)3 — Single‑family requirement: area‑weighted U and SHGC and link to § 110.6.
Table 110.6‑A — Default U‑factors (numeric defaults and adjustment notes).
Table 110.6‑B — Default SHGC values.
Definitions: CMA / CMAST / NFRC 100/200/203 — Code definitions for modeling approaches and referenced NFRC standards. file
Reference Nonresidential Appendix NA6 — Procedures to calculate default VT/U/SHGC for some exceptions (skylights, site‑built).

Code references

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

§ 110.6 High relevance — show source text
Exception 1 to Section 110.6(a)2: If the fenestration product is a skylight in a building covered by the nonresidential standards with less than 200 square feet of skylight area, the default U -factor may be calculated as set forth in Reference Nonresidential Appendix NA6.

Exception 2 to Section 110.6(a)2: If the fenestration product is an alteration consisting of any area replacement of glass in a skylight product in a building covered by the nonresidential standards, the default U -factor may be calculated as set forth in Reference Nonresidential Appendix NA6. 3. Solar heat gain coefficient SHGC. The fenestration product’s SHGC shall be rated in accordance with NFRC 200, or use the applicable default SHGC set forth in Table 110.6-B.

Exception 1 to Section 110.6(a)3: If the fenestration product is a skylight in a building covered by the nonresidential standards with less than 200 square feet of skylight area, the default SHGC may be calculated as set forth in Reference Nonresidential Appendix NA6.

Exception 2 to Section 110.6(a)3: If the fenestration product is an alteration consisting of any area replacement of glass in a skylight product in a building covered by the nonresidential standards, the default SHGC may be calculated as set forth in Reference Nonresidential Appendix NA6. 4. Visible transmittance (VT). The fenestration product’s VT shall be rated in accordance with NFRC 200 or ASTM E972. For tubular daylighting devices VT shall be rated using NFRC 203.

Exception 1 to Section 110.6(a)4: If the fenestration product is a skylight in a building covered by the nonresidential standards with less than 200 square feet of skylight area, the default VT may be calculated as set forth in Reference Nonresidential Appendix NA6.

Exception 2 to Section 110.6(a)4: If the fenestration product is an alteration consisting of any area; replacement of glass in a skylight product in a building covered by the nonresidential standards, the default VT may be calculated as set forth in Reference Nonresidential Appendix NA6. 5. Labeling. Fenestration products and exterior doors shall: A. Have a temporary label for manufactured fenestration products and exterior doors or a label certificate when the component modeling approach (CMA) is used and for site-built fenestration meeting the requirements of Section 10-111(a)1. The temporary label shall not be removed before inspection by the enforcement agency; and B. Have a permanent label or label certificate when the component modeling approach (CMA) is used and for sitebuilt fenestration meeting the requirements of Section 10-111(a)2 if the product is rated using NFRC procedures. 6. Fenestration acceptance requirements. Before an occupancy permit is granted site-built fenestration products in other than single-family buildings shall be certified as meeting the Acceptance Requirements for Code Compliance, as specified in the Reference Nonresidential Appendix NA7 to ensure that site-built fenestration meets Standards requirements, including a matching label certificate for product(s) installed and be readily accessible at the project location. A certificate of accep

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§ 0.3 High relevance — show source text
1. Air leakage. Manufactured fenestration products and exterior doors shall have air infiltration rates not exceeding 0.3 cfm/ft [2] of window area, 0.3 cfm/ft [2] of door area for residential doors, 0.3 cfm/ft [2] of door area for nonresidential single doors (swinging and sliding), and 1.0 cfm/ft [2] for nonresidential double doors (swinging), when tested according to NFRC400 or ASTM E283 at a pressure differential of 75 pascals (or 1.57 pounds/ft [2] ), incorporated herein by reference.
NOTES TO SECTION 110.6(a)1: Pet doors must meet 0.3 cfm/ft [2] when tested according to ASTM E283 at 75 pascals (or 1.57 pounds per square foot).

AAMA/WDMA/CSA 101/I.S.2/A440-2011 specification is equivalent to ASTM E283 at a pressure differential of 75 pascals (or 1.57 pounds per square foot) and satisfies the air leakage certification requirements of this section.

Exception to Section 110.6(a)1: Field-fabricated fenestration and field-fabricated exterior doors.
1. U -factor. The fenestration product and exterior door’s U -factor shall be rated in accordance with NFRC 100, or use the applicable default U -factor set forth in Table 110.6-A.
Exception 1 to Section 110.6(a)2: If the fenestration product is a skylight in a building covered by the nonresidential standards with less than 200 square feet of skylight area, the default U -factor may be calculated as set forth in Reference Nonresidential Appendix NA6.

Exception 2 to Section 110.6(a)2: If the fenestration product is an alteration consisting of any area replacement of glass in a skylight product in a building covered by the nonresidential standards, the default U -factor may be calculated as set forth in Reference Nonresidential Appendix NA6. 3. Solar heat gain coefficient SHGC. The fenestration product’s SHGC shall be rated in accordance with NFRC 200, or use the applicable default SHGC set forth in Table 110.6-B.

Exception 1 to Section 110.6(a)3: If the fenestration product is a skylight in a building covered by the nonresidential standards with less than 200 square feet of skylight area, the default SHGC may be calculated as set forth in Reference Nonresidential Appendix NA6.

Exception 2 to Section 110.6(a)3: If the fenestration product is an alteration consisting of any area replacement of glass in a skylight product in a building covered by the nonresidential standards, the default SHGC may be calculated as set forth in Reference Nonresidential Appendix NA6. 4. Visible transmittance (VT). The fenestration product’s VT shall be rated in accordance with NFRC 200 or ASTM E972. For tubular daylighting devices VT shall be rated using NFRC 203.

§ 110.6 High relevance — show source text

(b) Installation of field-fabricated fenestration and exterior doors. Field-fabricated fenestration and field-fabricated exterior doors may be installed only if the compliance documentation has demonstrated compliance for the installation using U factors from Table 110.6-A and SHGC values from Table 110.6-B. Field-fabricated fenestration and field-fabricated exterior doors shall be caulked between the fenestration products or exterior door and the building, and shall be weatherstripped.

Exception to Section 110.6(b): Unframed glass doors and fire doors need not be weatherstripped or caulked.

TABLE 110.6-A—DEFAULT FENESTRATION PRODUCT U-FACTORS	Col2	Col3	Col4	Col5
FRAME1,2	PRODUCT TYPE	SINGLE PANE3, 4 U-FACTOR	DOUBLE PANE1, 3, 4 U-FACTOR	GLASS BLOCK2, 3 U-FACTOR
Metal	Operable	1.28	0.79	0.87
Metal	Fixed	1.19	0.71	0.72
Metal	Greenhouse/garden window	2.26	1.40	NA
Metal	Glazed doors	1.25	0.77	NA
Metal	Skylight	1.98	1.3	NA
Metal, thermal break	Operable	NA	0.66	NA
Metal, thermal break	Fixed	NA	0.55	NA
Metal, thermal break	Greenhouse/garden window	NA	1.12	NA
Metal, thermal break	Glazed doors	NA	0.59	NA
Metal, thermal break	Skylight	NA	1.11	NA
Nonmetal	Operable	0.99	0.58	0.60
Nonmetal	Fixed	1.04	0.55	0.57
Nonmetal	Greenhouse/garden window	0.99	0.53	NA
Nonmetal	Glazed doors	1.94	1.06	NA
Nonmetal	Skylight	1.47	0.84	NA
1. For all dual-glazed fenestration products, adjust the listed_U_-factors as follows: a. Add 0.05 for products with dividers between panes if spacer is less than7/16 inch wide. b. Add 0.05 to any product with true divided lite (dividers through the panes). 2. Translucent or transparent panels shall use glass block values when not rated by NFRC 100. 3. Visible Transmittance (VT) shall be calculated by using Reference Nonresidential Appendix NA6. 4. Windows with window film applied that is not rated by NFRC 100 shall use the default values from this table.	1. For all dual-glazed fenestration products, adjust the listed_U_-factors as follows: a. Add 0.05 for products with dividers between panes if spacer is less than7/16 inch wide. b. Add 0.05 to any product with true divided lite (dividers through the panes). 2. Translucent or transparent panels shall use glass block values when not rated by NFRC 100. 3.

§ 0.05 High relevance — show source text

Add 0.05 to any product with true divided lite (dividers through the panes).
2. Translucent or transparent panels shall use glass block values when not rated by NFRC 100.
3. Visible Transmittance (VT) shall be calculated by using Reference Nonresidential Appendix NA6.
4. Windows with window film applied that is not rated by NFRC 100 shall use the default values from this table.|

TABLE 110.6-B—DEFAULT SOLAR HEAT GAIN COEFFICIENT (SHGC)	Col2	Col3	Col4	Col5	Col6
FRAME TYPE	PRODUCT	GLAZING	FENESTRATION PRODUCT SHGC	FENESTRATION PRODUCT SHGC	FENESTRATION PRODUCT SHGC
FRAME TYPE	PRODUCT	GLAZING	Single Pane2, 3 SHGC	Double Pane2, 3 SHGC	Glass Block1, 2 SHGC
Metal	Operable	Clear	0.80	0.70	0.70
Metal	Fixed	Clear	0.83	0.73	0.73
Metal	Operable	Tinted	0.67	0.59	NA
Metal	Fixed	Tinted	0.68	0.60	NA
Metal, thermal break	Operable	Clear	NA	0.63	NA
Metal, thermal break	Fixed	Clear	NA	0.69	NA
Metal, thermal break	Operable	Tinted	NA	0.53	NA
Metal, thermal break	Fixed	Tinted	NA	0.57	NA
Nonmetal	Operable	Clear	0.74	0.65	0.70
Nonmetal	Fixed	Clear	0.76	0.67	0.67
Nonmetal	Operable	Tinted	0.60	0.53	NA
Nonmetal	Fixed	Tinted	0.63	0.55	NA
1. Translucent or transparent panels shall use glass block values when not rated by NFRC 200. 2. Visible Transmittance (VT) shall be calculated by using Reference Nonresidential Appendix NA6. 3. Windows with window film applied that is not rated by NFRC 200 shall use the default values from this table.	1. Translucent or transparent panels shall use glass block values when not rated by NFRC 200. 2. Visible Transmittance (VT) shall be calculated by using Reference Nonresidential Appendix NA6. 3. Windows with window film applied that is not rated by NFRC 200 shall use the default values from this table.	1. Translucent or transparent panels shall use glass block values when not rated by NFRC 200. 2. Visible Transmittance (VT) shall be calculated by using Reference Nonresidential Appendix NA6. 3. Windows with window film applied that is not rated by NFRC 200 shall use the default values from this table.	1. Translucent or transparent panels shall use glass block values when not rated by NFRC 200. 2. Visible Transmittance (VT) shall be calculated by using Reference Nonresidential Appendix NA6. 3.

§ 0.05 High relevance — show source text

Visible Transmittance (VT) shall be calculated by using Reference Nonresidential Appendix NA6.
4. Windows with window film applied that is not rated by NFRC 100 shall use the default values from this table.|1. For all dual-glazed fenestration products, adjust the listed_U_-factors as follows:
a. Add 0.05 for products with dividers between panes if spacer is less than7/16 inch wide.
b. Add 0.05 to any product with true divided lite (dividers through the panes).
2. Translucent or transparent panels shall use glass block values when not rated by NFRC 100.
3. Visible Transmittance (VT) shall be calculated by using Reference Nonresidential Appendix NA6.
4. Windows with window film applied that is not rated by NFRC 100 shall use the default values from this table.|1. For all dual-glazed fenestration products, adjust the listed_U_-factors as follows:
a. Add 0.05 for products with dividers between panes if spacer is less than7/16 inch wide.
b. Add 0.05 to any product with true divided lite (dividers through the panes).
2. Translucent or transparent panels shall use glass block values when not rated by NFRC 100.
3. Visible Transmittance (VT) shall be calculated by using Reference Nonresidential Appendix NA6.
4. Windows with window film applied that is not rated by NFRC 100 shall use the default values from this table.|1. For all dual-glazed fenestration products, adjust the listed_U_-factors as follows:
a. Add 0.05 for products with dividers between panes if spacer is less than7/16 inch wide.
b. Add 0.05 to any product with true divided lite (dividers through the panes).
2. Translucent or transparent panels shall use glass block values when not rated by NFRC 100.
3. Visible Transmittance (VT) shall be calculated by using Reference Nonresidential Appendix NA6.
4. Windows with window film applied that is not rated by NFRC 100 shall use the default values from this table.|

TABLE 110.6-B—DEFAULT SOLAR HEAT GAIN COEFFICIENT (SHGC)	Col2	Col3	Col4	Col5	Col6
FRAME TYPE	PRODUCT	GLAZING	FENESTRATION PRODUCT SHGC	FENESTRATION PRODUCT SHGC	FENESTRATION PRODUCT SHGC
FRAME TYPE	PRODUCT	GLAZING	Single Pane2, 3 SHGC	Double Pane2, 3 SHGC	Glass Block1, 2 SHGC
Metal	Operable	Clear	0.80	0.70	0.70
Metal	Fixed	Clear	0.83	0.73	0.73
Metal	Operable	Tinted	0.67	0.59	NA
Metal	Fixed	Tinted	0.68	0.60	NA
Metal, thermal break	Operable	Clear	NA	0.63	NA
Metal, thermal break	Fixed	Clear	NA	0.69	NA
Metal, thermal break	Operable	Tinted	NA	0.

§ 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
Exception 1 to Section 170.2(a)3Aiiib: An area-weighted average relative solar heat gain coefficient of 0.56 or less shall be used for windows:

I. That are in the first story of exterior walls that form a display perimeter; and II. For which codes restrict the use of overhangs to shade the windows. Exception 2 to Section 170.2(a)3Aiiib: For vertical glazing containing chromogenic type glazing:

I. the lower-rate labeled RSHGC 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 II. chromogenic glazing shall be considered separately from other glazing; and III. area-weighted averaging with other glazing that is not chromogenic shall not be permitted.

NOTE: Demising walls are not exterior walls, and therefore fenestration in demising walls is not subject to SHGC requirements. (Equation 170.2-A) RSHGC = SHGC × [1 + a × (2.72 [-PF] – 1) × (sin(b × Az) + c)]

where:

COMPONENT a b c

Overhang 0.150 0.008727 5.67

Exterior Horizontal Slat 0.144 0.008727 5.13

RSHGC = Relative solar heat gain coefficient.

SHGC = Solar heat gain coefficient of the vertical fenestration.

Az = Azimuth of the vertical fenestration in degrees.

PF = Projection factor as calculated by Equation 140.3-C. iv. Vertical fenestration shall have an area-weighted average visible transmittance (VT) no less than the applicable value in Table 170.2-A, or Equation 170.2-B, as applicable.

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MULTIFAMILY BUILDINGS—PERFORMANCE AND PRESCRIPTIVE COMPLIANCE APPROACHES

Exception 1 to Section 170.2(a)3Aiv: When the window’s primary and secondary sidelit daylit zones are completely overlapped by one or more skylit daylit zones, then the window need not comply with Section 170.2(a)3Aivw. Exception 2 to Section 170.2(a)3Aiv: If the window’s VT is not within the scope of NFRC 200 or ASTM E972, then the VT shall be calculated according to Reference Nonresidential Appendix NA6. Exception 3 to Section 170.2(a)3Aiv: For vertical windows containing chromogenic type glazing: a. The higher rated labeled VT shall be used with automatic controls to modulate the amount of light transmitted into the space in multiple steps in response to daylight levels or solar intensity; 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. Exception 4 to Section 170.2(a)3Aiv: Fenestration in dwelling units is not required to comply with the VT requirements.

NOTE: Demising walls are not exterior walls, and therefore windows in demising walls are not subject to VT requirements.

(Equation 170.2-B) VT ≥ 0.11/WWR

where:
§ 10-111 High relevance — show source text
1 NFRC-100 10-111(a)1B, 110.6(b) NFRC-200 10-111(a)1B, 110.6(a)3-4, Table 110.6-B, 140.3(a)5D, 170.2(a)3A NFRC-203 10-111(a)1B, 110.6(a)4 NFRC-400 10-111(a)1B, 110.6(a)1 Operable shading 140.3(d)1D, 150.1(c)4B Relative Solar Heat Gain Coefficient (RSHGC) 140.3(a)5C-D, Table 140.3-B, Table 140.3-C, 141.0(b)2A, Table 141.0-A, 141.0(b)3A, Table 141.0-E, 170.2(a)3A, Table 170.2-A, 180.2(b)1C, Table 180.2-B Site-built fenestration 110.6(a)5-6, 150.1(c)3A, 170.2(a)3A Skylight products 150.0(q), 160.1(e) Skylight Roof Ratio (SRR) 140.3(a)6A, Table 140.3-B, Table 140.3-C, Table 140.3-D, 170.2(a)3B Solar Heat Gain Coefficient (SHGC) 10-111, 10-112(a), 110.6(a)3, 110.6(b), Table 110.6-B, 140.3(a)5CD, 140.3(a)6C, Table 140.3-B, Table140.3-C, Table 140.3-D, Table 140.3-E, 140.4(b)5, 150.1(c)3, 150.1(c)4, Table 150.1-A, 150.2(b)1A, 150.2(b)1B, Table 150.2-D, 170.2(a)3A, 170.2(a)3B South-facing 140.3(d)1A, 140.3(d)3B, 150.1(c)4D Spandrel panel 120.7(b)6, 141.0(b)1B, 160.1(b)6, 180.2(a)2D

2025 CALIFORNIA ENERGY CODE 307

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INDEX

120.7(a)3C, 130.1(d), 140.3(a)9C, 140.3(c), 140.4(g), 140.6(c)1D, 140.6(c)2D, 140.6(c)3D, 140.6(c)3H-I, 140.10(a), Table 140.10-A, 141.0(b)2D, Equation 150.0-B, 150.0(q)1, Table 150.0-G, 150.1(c)3, 150.1(c)8, 150.1(c)12, Equation 150.1-C, 150.2(a)1, 160.1(e)1, Equation 160.2-B, 160.2(c)2, Equation 160.2-C, 160.2(c)5D,

COMPONENT	a	b	c
Overhang	0.150	0.008727	5.67
Exterior Horizontal Slat	0.144	0.008727	5.13

§ 180.2 High relevance — show source text

i. Fenestration installed to replace existing fenestration of the same total area shall meet either a or b: a. The maximum U- factor, RSHGC and VT requirements of Table 180.2-B, or b. The area-weighted U- factor and RSHGC of Table 170.2-A. Exception 1 to Section 180.2(b)1Ci: In an alteration, where 150 square feet or less of the entire building's vertical fenestration is replaced, RSHGC and VT requirements of Table 180.2-B shall not apply. ii. Alterations that add vertical fenestration and skylight area shall meet the total fenestration area requirements of Section 170.2(a)3 and the RSHGC and VT requirements of Table 180.2-B. Exception 1 to Section 180.2(b)1Cii: Alterations that add vertical fenestration area of up to 50 square feet shall not be required to meet the total fenestration area requirements of Sections 170.2(a)3, nor the RSHGC and VT requirements of Table 180.2-B. Exception 2 to Section 180.2(b)1Cii: Alterations that add up to 16 square feet of new skylight area per dwelling unit with a maximum U- factor of 0.55 and a maximum RSHGC of 0.30 shall not be required to meet the total fenestration area requirements of Section 170.2(a)3. D. Exterior doors. Alterations that add exterior door area shall meet the U- factor requirement of Section 170.2(a)4.

TABLE 180.2-B—ALTERED FENESTRATION MAXIMUM U-FACTOR AND MAXIMUM SHGC AND RSHGC, MINIMUM VT	Col2	Col3	Col4	Col5	Col6	Col7	Col8	Col9	Col10	Col11	Col12	Col13	Col14	Col15	Col16	Col17	Col18
BUILDING TYPE	FEATURE	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
Curtainwall/Storefront/ Window Wall1	U-factor	0.38	0.41	0.41	0.41	0.41	0.41	0.41	0.41	0.41	0.41	0.41	0.41	0.41	0.41	0.41	0.38
Curtainwall/Storefront/ Window Wall1	RSHGC	NR	0.26	NR	0.26	NR	0.26	0.26	0.26	0.26	0.26	0.26	0.26	0.26	0.26	0.26	NR
Curtainwall/Storefront/ Window Wall1	VT2	0.46	0.46	0.

§ 170.2 High relevance — show source text
2025 CALIFORNIA ENERGY CODE 239

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MULTIFAMILY BUILDINGS—PERFORMANCE AND PRESCRIPTIVE COMPLIANCE APPROACHES

Exception 1 to Section 170.2(a)3Aiv: When the window’s primary and secondary sidelit daylit zones are completely overlapped by one or more skylit daylit zones, then the window need not comply with Section 170.2(a)3Aivw. Exception 2 to Section 170.2(a)3Aiv: If the window’s VT is not within the scope of NFRC 200 or ASTM E972, then the VT shall be calculated according to Reference Nonresidential Appendix NA6. Exception 3 to Section 170.2(a)3Aiv: For vertical windows containing chromogenic type glazing: a. The higher rated labeled VT shall be used with automatic controls to modulate the amount of light transmitted into the space in multiple steps in response to daylight levels or solar intensity; 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. Exception 4 to Section 170.2(a)3Aiv: Fenestration in dwelling units is not required to comply with the VT requirements.

NOTE: Demising walls are not exterior walls, and therefore windows in demising walls are not subject to VT requirements.

(Equation 170.2-B) VT ≥ 0.11/WWR

where:

WWR = Window Wall Ratio, the ratio of (i) the total window area of the entire building to (ii) the total gross exterior wall area of the entire building. If the WWR is greater than 0.40, then 0.40 shall be used as the value for WWR in Equation 170.2-B.

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.
California Energy Code High relevance — show source text
ALTERED COMPONENT is a new fenestration component that has undergone an alteration other than a repair and is subject to all applicable standards requirements.

BAY WINDOW is a combination assembly which is composed of three or more individual windows either joined side by side or installed within opaque assemblies and which projects away from the wall on which it is installed. Center windows, if used, are parallel to the wall on which the bay is installed, the end panels or two side windows, are angled with respect to the center window. Common angles are 30° and 45°, although other angles may be employed.

CHROMOGENIC GLAZING is a class of switchable glazing that includes active materials (e.g., electrochromic) and passive materials (e.g., photochromic and thermochromic) permanently integrated into the glazing assembly. Their primary function is to switch reversibly from a high transmission state to a low transmission state with associated changes in VT and SHGC.

CLERESTORY FENESTRATION is fenestration installed above a roofline greater than or equal to 60 degrees from the horizontal, or any portion of exterior vertical glazing greater than 8 feet per floor above the finished floor of a space.

CMA (component modeling approach) is a fenestration product certification program from the National Fenestration Rating Council (NFRC) that enables energy-related performance ratings for nonresidential fenestration products, including the thermal performance U -factor, solar heat gain coefficient, and visible transmittance.

2025 CALIFORNIA ENERGY CODE 15

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ALL OCCUPANCIES—GENERAL PROVISIONS

CMAST (component modeling approach software tool) is an NFRC approved software that allows a user to create a fenestration product “virtually” and generate its energy-related performance ratings, including the thermal performance U -factor, solar heat gain coefficient, and visible transmittance.

CURTAIN WALL/STOREFRONT is an external non-bearing wall intended to separate the exterior nonconditioned and interior conditioned spaces. It also consists of any combination of framing materials, fixed glazing, opaque glazing, operable windows or other in-fill materials.

Note: Window wall is also included as part of the curtain wall/storefront fenestration category.

DUAL-GLAZED GREENHOUSE WINDOWS is a double glass pane separated by an air or other gas space that adds conditioned volume but not conditioned floor area to a building.

DYNAMIC GLAZING SYSTEMS are glazing systems that have the ability to reversibly change their performance properties, including U -factor, Solar Heat Gain Coefficient (SHGC) and/or Visible Transmittance (VT) between well-defined end points. These may include, but are not limited to, chromogenic glazing systems and integrated shading systems (defined below). Dynamic Glazing systems do not include internally mounted or externally mounted shading devices that attach to the window framing/glazing that may or may not be removable.

FENESTRATION ALTERATION is any change to an existing building’s exterior fenestration product that is not a repair (see “fenestration repair”) that: i. Replaces existing fenestration in an existing wall or roof with no net area added; or ii. Replaces existing fenestration and adds new net area in the existing wall or roof; or iii. Adds a new window that increases the net fenestration area to an existing wall or roof.
§ 606-8448 High relevance — show source text
Available from:

Cool Roof Rating Council 2435 N. Lombard Street Portland, OR 97217 (503) 606-8448 www.coolroofs.org

STANDARDS AND DOCUMENTS REFERENCED IN THE ENERGY CODE

ANSI/IES LM-79-19 Approved Method: Optical and Electrical Measurements of Solid-State Lighting Products an American National Standard

ANSI/IES LS-1-20 Lighting Science: Nomenclature and Definitions for Illuminating Engineering

ANSI/IES TM-15-20 Technical Memorandum: Luminaire Classification System for Outdoor Luminaires an American National Standard

Available from: Illuminating Engineering Society 120 Wall Street, 17th Floor New York, NY 10005-4026 (212) 248-5000 www.ies.org INTERNATIONAL ASSOCIATION OF PLUMBING AND MECHANICAL OFFICIALS

California Mechanical Code

Available from: International Association of Plumbing and Mechanical Officials 4755 E. Philadelphia St. Ontario, CA 91761 (800) 85-IAPMO (854-2766) www.iapmo.org

INTERNATIONAL CODE COUNCIL

California Building Code

Available from: International Code Council Western Regional Office 3060 Saturn St. Brea, CA 92821 (888) 422-7233 www.iccsafe.org

INTERNATIONAL ORGANIZATION FOR STANDARDIZATION

ISO 5801:2017 Fans—Performance testing using standardized airways

ISO 13256-1:1998 (RA 2012) Water-Source Heat Pumps—Testing and Rating for Performance—Part 1: Water-to-Air and Brine-to-Air Heat Pumps

ISO 13256-2:1998 (RA 2012) Water-Source Heat pumps—Testing and rating for Performance—Part 2: Water-to-Water and Brine-to-Water Heat Pumps

ISO/IEC 17025:2017 General Criteria for the Competence of Testing and Calibration Laboratories

Available from: ISO

Chemin de Blandonnet 8

CP 401

1214 Vernier Geneva, Switzerland

INTERNATIONAL WINDOW FILM ASSOCIATION

Architectural Visual Inspection Standard Window Film (reendorsed 2018)

Available from: International Window Film

Association 1103 A Brookdale St. Martinsville, VA 24112 276-666-4932

NATIONAL ELECTRICAL MANUFACTURERS ASSOCIATION

NEMA LSD 57-2023 Polyurethane Foam Application: Lighting Equipment

NEMA SSL 7A-2015 (R2021) Phase Cut Dimming for Solid State Lighting: Basic Compatibility

Available from: 1300 North 17th Street, Suite 1752 Rosslyn, VA 22209 708-841-3200

www.nema.org

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STANDARDS AND DOCUMENTS REFERENCED IN THE ENERGY CODE

NATIONAL FENESTRATION RATING COUNCIL

ANSI/NFRC 100-2023 Procedure for Determining Fenestration Product U -factors

ANSI/NFRC 200-2023 Procedure for Determining Fenestration Product Solar Heat Gain Coefficients and Visible Transmittance at Normal Incidence

ANSI/NFRC 202-2023 Procedure for Determining Translucent Fenestration Product Visible Transmittance at Normal Incidence

Frequently asked questions

What if my window is NFRC‑rated but the manufacturer didn’t provide a permanent label?

You must provide either the temporary label at inspection or a label certificate when using CMA; permanent labels are required when NFRC procedures are used (see § 110.6(a)5).

Can I use CMA/CMAST ratings instead of NFRC physical test data?

Yes — the Code recognizes CMA and CMAST as NFRC‑approved modeling/certification approaches for certain nonresidential products, but you must have the appropriate label/certificate and follow the NFRC process. See the Code definitions and labeling requirements. file

My project has site‑built or field‑fabricated windows — what values do I use?

Field‑fabricated or unrated site‑built fenestration must be demonstrated compliant using the default values in Table 110.6‑A and Table 110.6‑B (and must be caulked/weatherstripped for field‑fabricated). § 110.6(b).

How do I handle divided lites or spacers when using default U‑factors?

Table 110.6‑A notes require you to add 0.05 to the listed U‑factors for dual‑glazed products with certain dividers/spacers and for true divided lites.

Is VT always required to be NFRC 200?

VT may be derived from NFRC 200 or ASTM E972; tubular daylighting devices use NFRC 203. If VT is outside those standards’ scope, Reference NA6 provides the calculation method per the Code. file

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Related in the California Energy Code

Requirements for field‑fabricated, site‑built and field‑installed fenestration

Default ratings, window film, and acceptance values for un‑rated fenestration

Dynamic glazing systems, curtain walls/storefronts and glazed door performance rules

Fenestration ratings, installation, and special glazing systems

California Energy Code