Title 24 · California Energy Code

PAFs for clerestory fenestration, light shelves and horizontal slats

If your project uses clerestories, horizontal slats or light shelves and you’ve installed continuous dimming daylighting controls, you can reduce the allowed lighting watts by small factors (clerestory 5%, slats 5%, light shelves 10%) — but only if the devices meet the geometry, orientation, reflectance and labeling rules and (for multifamily/common areas) the control acceptance and certification requirements in § 170.2(e).

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Last reviewed: July 6, 2026

What the code requires — 2-4 sentences

The California Energy Code allows a small lighting Power Adjustment Factor (PAF) for luminaires in daylit zones adjacent to clerestory fenestration, horizontal slats, and light shelves — but only when the daylighting devices meet the daylighting-device requirements and the lighting has continuous dimming daylighting controls. The applicable PAF values are shown in Table 140.6‑A (nonresidential) and Table 170.2‑L (multifamily/common areas); the installation and acceptance requirements for multifamily/common-area controls are in § 170.2(e).

The single most important rule: PAFs for clerestories, slats and light shelves apply only where the daylighting devices themselves meet the daylighting-design requirements (e.g., § 140.3(d) / 170.2(b)) and continuous dimming daylighting controls are installed for the affected sidelit daylit zones.

Requirements in detail

Which PAFs are available and when

  • Clerestory fenestration PAF = 0.05 for luminaires in daylit areas adjacent to the clerestory. § 140.6 (Table 140.6‑A) / § 170.2 (Table 170.2‑L).
  • Horizontal slats PAF = 0.05 for luminaires adjacent to vertical fenestration fitted with interior or exterior horizontal slats.
  • Light shelves PAF = 0.10 for luminaires adjacent to clerestory fenestration with interior or exterior light shelves. Light-shelf PAF may be combined with clerestory PAF where allowed.

Note: PAFs apply only to luminaires in a primary or secondary sidelit daylit zone where continuous dimming daylighting controls meeting control requirements are installed (see table notes).

Decision‑relevant dimensions, thresholds and values

Item / threshold Required value / range Code Reference
Clerestory head height ≥ 10 ft above finished floor § 140.3(d)1B
Clerestory glazing height ≥ 10% of head height § 140.3(d)1C
Horizontal slats — orientation East or West facades § 140.3(d)2A
Horizontal slats — window‑wall ratio (WWR) WWR between 20% and 30% § 140.3(d)2A
Horizontal slats — projection factor As specified in Table 140.3‑E (slats: 2.0–3.0) Table 140.3‑E / Equation 140.3‑C
Horizontal slats — distance factor Minimum = 0.3 § 140.3(d)2D
Light shelves — orientation & WWR South facades; clerestory adjacent; WWR > 30% § 140.3(d)3B
Light shelves — projection factor Interior: 1.0–2.0; Exterior: 0.25–1.25 (Table 140.3‑E) Table 140.3‑E
Light shelves — distance factor Minimum = 0.3 § 140.3(d)3E
Light shelves — top surface reflectance Visible reflectance ≥ 0.50 (ASTM E903) § 140.3(d)3F
Slats — visible reflectance ≥ 0.50 (ASTM E903) § 140.3(d)2E
Slats — opacity Opaque (permitted exception: VT ≤ 0.03 by ASTM E1175) § 140.3(d)2F & exception
PAF values Clerestory = 0.05; Slats = 0.05; Light shelf = 0.10 Table 140.6‑A / Table 170.2‑L (§ 140.6 / § 170.2)
Controls required on daylit zone Continuous dimming daylighting controls (see § 130.1(d)) Table notes for 140.6‑A / 170.2‑L
Documentation / labeling Device must be shown on plans and slats/light shelves labeled (see required factory label) § 140.3(d)2I–J and 3H–J

(Projection factor and Distance factor are calculated with Equation 140.3‑C: Projection Factor = Projection / Spacing; Distance Factor = D / (HAS × Projection Factor).)

Install & control conditions

  • PAFs are limited to luminaires in the specified daylit zones and are only available where continuous dimming daylighting controls meeting the referenced control standard are installed. Table notes state the PAFs “shall only apply to lighting in a primary or secondary sidelit daylit zone where continuous dimming daylighting controls meeting the requirements of Section 130.1(d) are installed.”
  • For multifamily/common areas, lighting controls and PAFs must also comply with the acceptance, testing and installation certificate requirements in § 170.2(e) (including submission of Certificates of Acceptance and Installation Certificates as applicable).

Exceptions & special cases

  • Existing obstructions exception for slats and light shelves: where adjacent structures or natural objects block direct sunlight for fewer than a stated number of daytime hours per year, the minimum distance-factor or daylighting-hour requirements may be relaxed (examples: slats exception uses < 500 hours/year; light shelf exception uses < 750 hours/year in certain clauses — see the specific exception language). Check the exact exception text in § 140.3(d).
  • Horizontal slats may be interior or exterior; exterior slats slope level or downwards, interior slats level or sloped upwards — orientation matters for compliance.
  • A horizontal‑slat opacity exception: extremely low visible transmittance (VT ≤ 0.03 when tested per ASTM E1175) may permit a different classification.
  • Light shelves: when there is vertical fenestration area below the shelf, both interior and exterior light shelves must be installed to qualify.

If any required dimension, spacing, reflectance, orientation, or labeling is missing or the controls are not the required continuous dimming type, the PAF cannot be claimed. The tables themselves require compliance with the referenced device sections and, for multifamily, § 170.2(e) acceptance-certificate rules.

Common mistakes

  • Omitting the device dimensions on the plans. The code requires slat and light‑shelf projection and spacing dimensions shown on drawings (Equation 140.3‑C inputs).
  • Installing adjustable or removable slats/shelves and then claiming the PAF. The slats and shelves must be permanently mounted and not adjustable (unless a narrow exception applies).
  • Wrong façade/orientation or wrong WWR: slats are limited to east/west with WWR 20–30%; light shelves are for south facades with WWR > 30% (clerestory adjacency requirements also apply).
  • Forgetting the required continuous dimming daylighting controls in the specific daylit zones — PAFs are only available where those controls are installed.
  • For multifamily/common areas: not completing or submitting Acceptance and Installation Certificates per § 170.2(e) prior to occupancy.

Worked example — concrete scenario with numbers

Scenario: A 12‑ft‑high office perimeter clerestory on the south façade with a clerestory glazing height of 1.5 ft and a paired interior light shelf (exterior light shelf also installed). Continuous dimming daylighting controls are installed and verified.

  1. Verify clerestory dimensions: head height = 12 ft (≥ 10 ft) and glazing height = 1.5 ft (≥ 10% of 12 ft = 1.2 ft) → clerestory device requirement satisfied.
  2. Verify light shelf requirements: building is south‑facing with WWR > 30%, shelf projection and spacing compute to a Projection Factor that falls within Table 140.3‑E values for interior/exterior shelves (use Equation 140.3‑C to calculate). Confirm top-surface visible reflectance ≥ 0.50.
  3. Controls: continuous dimming daylighting controls are installed for the primary/secondary sidelit daylit zone per the Table 140.6‑A note. That enables PAF eligibility.

PAF calculation for a set of luminaires: assume a group of luminaires has baseline connected general lighting power of 1,000 W in the qualifying daylit zone.

  • Clerestory PAF = 0.05 → savings = 1,000 × 0.05 = 50 W.
  • Light shelf PAF = 0.10 → savings = 1,000 × 0.10 = 100 W. Table note: light-shelf PAF may be combined with clerestory PAF where allowed, so combined PAF = 0.05 + 0.10 = 0.15 (confirm project notes/authority acceptance).

Adjusted allowed lighting = 1,000 × (1 − 0.15) = 850 W allowed after PAFs. Document the devices and control acceptance test results per the plan and (for multifamily) submit the required certificates per § 170.2(e).

Related provisions

  • § 140.3(d) — Daylighting device requirements (clerestories, horizontal slats, light shelves) that the PAFs reference.
  • § 140.6 — Table 140.6‑A: PAF values and table notes for nonresidential projects.
  • § 170.2 — Table 170.2‑L: PAF values and related notes for multifamily/common‑area applications.
  • § 170.2(e) — Lighting control acceptance and installation certificate requirements (multifamily/common areas).
  • Table 140.3‑E and Equation 140.3‑C — Projection factor, distance factor, and numeric projection ranges used to verify slat/shelf geometry.
  • Definitions: HORIZONTAL SLATS, LIGHT SHELF, etc., are defined in the code glossary (see definitions).

Code references

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

  • § 130.4 High relevance — show source text

    The setting of the limit is verified by the acceptance test required by Section 130.4(a)7; and iv. The construction documents specify which lighting systems shall have their maximum light output or maximum power draw set to no greater than 85 percent of full light output or full power draw. K. To qualify for the PAF for a demand responsive control in Table 140.6-A, the general lighting wattage receiving the PAF shall not be within the scope of Section 110.12(c) and a demand responsive control shall meet all of the following requirements: i. The controlled lighting shall be capable of being automatically reduced in response to a demand response signal; and ii. General lighting shall be reduced in a manner consistent with the requirements of Section 130.1(b). L. To qualify for the PAFs for clerestory fenestration, horizontal slats, or light shelves in Table 140.6-A, the daylighting design shall meet the requirements in Section 140.3(d). The PAFs shall only apply to lighting in a primary or secondary sidelit daylit zone where continuous dimming daylighting controls meeting the requirements of Section 130.1(d) are installed.

    TABLE 140.6-A—LIGHTING POWER ADJUSTMENT FACTORS (PAF) Col2 Col3
    TYPE OF CONTROL TYPE OF AREA FACTOR
    1. Daylight continuous dimming plus
    OFF control    		 Luminaires in skylit daylit zone or primary sidelit daylit zone or secondary sidelit daylit zone 0.10
    2. Occupant sensing controls in offices
    larger than 250 square feet    		 One sensor controlling an area that is no larger than 125 square feet 0.30
    3. Occupant sensing controls in offices
    larger than 250 square feet    		 One sensor controlling an area that is 126-250 square feet 0.20
    4. Institutional tuning Luminaires in non-daylit areas:
    Luminaires that qualify for other PAFs in this table may also qualify for this tuning PAF.    		 0.10
    4. Institutional tuning Luminaires in daylit areas:
    Luminaires that qualify for other PAFs in this table may also qualify for this tuning PAF.    		 0.05
    5. Demand responsive control General lighting luminaires not in the scope of Section 110.12(c).
    If DR controls are required of Section 110.12(c), this PAF is not available for any lighting in the
    project. Luminaires that qualify for other PAFs in this table may also qualify for this demand
    responsive control PAF.    		 0.05
    6. Clerestory fenestration Luminaires in daylit areas adjacent to the clerestory.
    Luminaires that qualify for daylight dimming plus OFF control may also qualify for this PAF.    		 0.05
    7. Horizontal slats Luminaires in daylit areas adjacent to vertical fenestration with interior or exterior horizontal slats.
    Luminaires that qualify for daylight dimming plus OFF control may also qualify for this PAF.    		 0.05
    8. Light shelves Luminaires in daylit areas adjacent to clerestory fenestration with interior or exterior light
    shelves. This PAF may be combined with the PAF for clerestory fenestration.
    Luminaires that qualify for daylight dimming plus OFF control may also qualify for this PAF.    		 0.10
    a.
  • § 170.2 High relevance — show source text

    xi. To qualify for the PAF for a demand responsive control in Table 170.2-L, the general lighting wattage receiving the PAF shall not be within the scope of Section 110.12(c) and a demand responsive control shall meet all of the following requirements: a. The controlled lighting shall be capable of being automatically reduced in response to a demand response signal; and b. General lighting shall be reduced in a manner consistent with the illuminance uniformity requirements of Section 160.5(b)4B. xii. To qualify for the PAFs for clerestory fenestration, horizontal slats or light shelves in Table 170.2-L, the daylighting design shall meet the requirements in Section 170.2(b). The PAFs shall only apply to lighting in a primary or secondary sidelit daylit zone where continuous dimming daylighting controls meeting the requirements of Section 160.5(b)4D are installed.

    TABLE 170.2-L—LIGHTING POWER ADJUSTMENT FACTORS (PAF) Col2 Col3
    TYPE OF CONTROL TYPE OF AREA FACTOR
    1. Daylight Continuous
    Dimming Plus OFF Control    		 Luminaires in skylit daylit zone or primary sidelit daylit zone 0.10
    2. Occupant Sensing Controls
    in Office Spaces Larger Than
    250 Square Feet    		 In open plan offices > 250 square feet: One sensor controlling an area that is:
    No larger than 125 square feet    		 0.30
    2. Occupant Sensing Controls
    in Office Spaces Larger Than
    250 Square Feet    		 In open plan offices > 250 square feet: One sensor controlling an area that is:
    From 126 to 250 square feet    		 0.20
    3. Institutional Tuning Luminaires in nondaylit areas.
    Luminaires that qualify for other PAFs in this table may also qualify for this tuning PAF.    		 0.10
    3. Institutional Tuning Luminaires in daylit areas.
    Luminaires that qualify for other PAFs in this table may also qualify for this tuning PAF.    		 0.05
    4. Demand Responsive
    Control    		 General lighting luminaires not in the scope of Section 110.12(c). Luminaires that qualify for other
    PAFs in this table may also qualify for this demand responsive control PAF.    		 0.05
    5. Clerestory Fenestration Luminaires in daylit areas adjacent to the clerestory. Luminaires that qualify for daylight dimming
    plus OFF control may also qualify for this PAF.    		 0.05
    6. Horizontal Slats Luminaires in daylit areas adjacent to vertical fenestration with interior or exterior horizontal slats.
    Luminaires that qualify for daylight dimming plus OFF control may also qualify for this PAF.    		 0.05
    7. Light Shelves Luminaires in daylit areas adjacent to clerestory fenestration with interior or exterior light shelves.
    This PAF may be combined with the PAF for clerestory fenestration. Luminaires that qualify for
    daylight dimming plus OFF control may also qualify for this PAF.    		 0.10
    a. To qualify for any of the power adjustment factors in this table, the installation shall comply with the applicable requirements in Section 170.2(e)1Aii.
    b. Only one PAF may be used for each qualifying luminaire unless combined.
    c.
  • § 140.3 High relevance — show source text

    Exception 2 to Section 140.3(c): In buildings with unfinished interiors, future enclosed spaces for which there are plans to have: A. A floor area of less than or equal to 5,000 square feet, or B. Ceiling heights of less than or equal to 15 feet.

    This exception shall not be used for S-1 or S-2 (storage), or for F-1 or F-2 (factory) occupancies.

    Exception 3 to Section 140.3(c): Enclosed spaces having a designed general lighting system with a lighting power density less than 0.5 watts per square foot.

    Exception 4 to Section 140.3(c): Enclosed spaces where it is documented that permanent architectural features of the building, existing structures or natural objects block direct beam sunlight on at least half of the roof over the enclosed space for more than 1500 daytime hours per year between 8 a.m. and 4 p.m.

    (d) Daylighting Design Power Adjustment Factors (PAFs). To qualify for a Power Adjustment Factor (PAF) as specified in Section 140.6(a)2L, daylighting devices shall meet the following requirements:

    1. Clerestory fenestration. To qualify for a PAF, clerestory fenestration shall meet the following requirements: A. Shall be installed on east-, west-, or south-facing facades. B. Shall have a head height that is at least 10 feet above the finished floor. C. Shall have a glazing height that is greater than or equal to 10 percent of the head height. D. If operable shading is installed on the clerestory fenestration, then the clerestory fenestration shading shall be controlled separately from shading serving other vertical fenestration.
    2. Interior and exterior horizontal slats. To qualify for a PAF, horizontal slats shall meet the following requirements: A. Shall be installed adjacent to vertical fenestration on east- or west-facing facades with Window Wall Ratios between 20 and 30 percent. B. Exterior horizontal slats shall be level or sloped downwards from fenestration. Interior horizontal slats shall be level or sloped upwards from fenestration. C. Shall have a projection factor as specified in Table 140.3-E. The projection factor is calculated using Equation 140.3-C. D. Shall have a minimum distance factor of 0.3. The distance factor is calculated using Equation 140.3-C. Exception to Section 140.3(d)2D: Where it is documented that existing adjacent structures or natural objects within view of the vertical fenestration block direct sunlight onto the vertical fenestration between 8 a.m. and 5 p.m. for less than 500 daytime hours per year. E. Shall have a minimum Visible Reflectance of 0.50 when tested as specified in ASTM E903. F. Shall be opaque. Exception to Section 140.3(d)2F: Horizontal slats with a Visible Transmittance of 0.03 or less when tested as specified in ASTM E1175.

    G. Shall be permanently mounted and not adjustable. H. Shall extend the entire height of the vertical fenestration and beyond each side of the window jamb by a distance equal to or greater than their horizontal projection. Exception to Section 140.3(d)2H: Where the slats are located entirely within the vertical fenestration’s rough opening or a fin is located at the window jambs and extends vertically the entire height of the window jamb and extends horizontally the entire depth of the projection.

  • § 140.3 High relevance — show source text
    1. Interior and exterior horizontal slats. To qualify for a PAF, horizontal slats shall meet the following requirements: A. Shall be installed adjacent to vertical fenestration on east- or west-facing facades with Window Wall Ratios between 20 and 30 percent. B. Exterior horizontal slats shall be level or sloped downwards from fenestration. Interior horizontal slats shall be level or sloped upwards from fenestration. C. Shall have a projection factor as specified in Table 140.3-E. The projection factor is calculated using Equation 140.3-C. D. Shall have a minimum distance factor of 0.3. The distance factor is calculated using Equation 140.3-C. Exception to Section 140.3(d)2D: Where it is documented that existing adjacent structures or natural objects within view of the vertical fenestration block direct sunlight onto the vertical fenestration between 8 a.m. and 5 p.m. for less than 500 daytime hours per year. E. Shall have a minimum Visible Reflectance of 0.50 when tested as specified in ASTM E903. F. Shall be opaque. Exception to Section 140.3(d)2F: Horizontal slats with a Visible Transmittance of 0.03 or less when tested as specified in ASTM E1175.

    G. Shall be permanently mounted and not adjustable. H. Shall extend the entire height of the vertical fenestration and beyond each side of the window jamb by a distance equal to or greater than their horizontal projection. Exception to Section 140.3(d)2H: Where the slats are located entirely within the vertical fenestration’s rough opening or a fin is located at the window jambs and extends vertically the entire height of the window jamb and extends horizontally the entire depth of the projection. I. Shall be shown on the plans with the dimensions for the slat projection and slat spacing as specified in Equation 140.3-C. J. Shall have a conspicuous factory installed label permanently affixed and prominently located on an attachment point of the device to the building envelope, stating the following: “NOTICE: Removal of this device will require re-submittal of compliance documentation to the enforcement agency responsible for compliance with California Title 24, Part 6”. 3. Interior and Exterior Light Shelves. To qualify for a PAF, light shelves shall meet the following requirements: A. Where there is vertical fenestration area below the light shelf, both interior and exterior light shelves shall be installed. B. Shall be installed adjacent to clerestory fenestration on south-facing facades with Window Wall Ratios greater than 30 percent. The head height of the light shelves shall be no more than one foot below the finished ceiling. The clerestory fenestration shall meet the requirements of Section 140.3(d)1. C. Exterior light shelves shall be level or sloped downwards from fenestration. Interior light shelves shall be level or sloped upwards from fenestration.

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    D. Shall have a projection factor of the applicable value as specified in Table 140.3-E. The light shelf projection factor is calculated using Equation 140.3-C.

  • § 0.10 High relevance — show source text

    Institutional Tuning|Luminaires in nondaylit areas.
    Luminaires that qualify for other PAFs in this table may also qualify for this tuning PAF.|0.10| |3. Institutional Tuning|Luminaires in daylit areas.
    Luminaires that qualify for other PAFs in this table may also qualify for this tuning PAF.|0.05| |4. Demand Responsive
    Control|General lighting luminaires not in the scope of Section 110.12(c). Luminaires that qualify for other
    PAFs in this table may also qualify for this demand responsive control PAF.|0.05| |5. Clerestory Fenestration|Luminaires in daylit areas adjacent to the clerestory. Luminaires that qualify for daylight dimming
    plus OFF control may also qualify for this PAF.|0.05| |6. Horizontal Slats|Luminaires in daylit areas adjacent to vertical fenestration with interior or exterior horizontal slats.
    Luminaires that qualify for daylight dimming plus OFF control may also qualify for this PAF.|0.05| |7. Light Shelves|Luminaires in daylit areas adjacent to clerestory fenestration with interior or exterior light shelves.
    This PAF may be combined with the PAF for clerestory fenestration. Luminaires that qualify for
    daylight dimming plus OFF control may also qualify for this PAF.|0.10| |a. To qualify for any of the power adjustment factors in this table, the installation shall comply with the applicable requirements in Section 170.2(e)1Aii.
    b. Only one PAF may be used for each qualifying luminaire unless combined.
    c. Lighting controls that are required for compliance with Part 6 shall not be eligible for a PAF.|a. To qualify for any of the power adjustment factors in this table, the installation shall comply with the applicable requirements in Section 170.2(e)1Aii.
    b. Only one PAF may be used for each qualifying luminaire unless combined.
    c. Lighting controls that are required for compliance with Part 6 shall not be eligible for a PAF.|a. To qualify for any of the power adjustment factors in this table, the installation shall comply with the applicable requirements in Section 170.2(e)1Aii.
    b. Only one PAF may be used for each qualifying luminaire unless combined.
    c. Lighting controls that are required for compliance with Part 6 shall not be eligible for a PAF.|

    C. Lighting wattage excluded. The watts of the following indoor lighting applications may be excluded from Adjusted Indoor Lighting Power: i. Lighting installed by the manufacturer in walk-in coolers or freezers, vending machines and food preparation equipment. ii. Lighting that is required for exit signs subject to the CBC. Exit signs shall meet the requirements of the Appliance Efficiency Regulations. iii. Exit way or egress illumination that is normally off and that is subject to the CBC. iv. Temporary lighting systems. v. Lighting systems in qualified historic buildings, as defined in the California Historical Building Code (Title 24, Part 8), are exempt from the lighting power density allowances if they consist solely of historic lighting components or replicas of historic lighting components. If lighting systems in qualified buildings contain some historic lighting components or replicas of historic components, combined with other lighting components, only those historic or historic replica components are exempt. All other lighting systems in qualified historic buildings shall comply with the lighting power density allowances.

  • § 140.6 High relevance — show source text

    I. To qualify for the PAF for an occupant sensing control controlling the general lighting in large office areas above workstations, in accordance with Table 140.6-A, the following requirements shall be met: i. The office area shall be greater than 250 square feet; and ii. This PAF shall be available only in office areas which contain workstations; and iii. Controlled luminaires shall only be those that provide general lighting directly above the controlled area, or furniture mounted luminaires that comply with Section 140.6(a)2 and provide general lighting directly above the controlled area; and

    iv. Qualifying luminaires shall be controlled by occupant sensing controls that meet all of the following requirements, as applicable: a. Infrared sensors shall be equipped by the manufacturer, of fitted in the field by the installer, with lenses or shrouds to prevent them from being triggered by movement outside of the controlled area. b. Ultrasonic sensors shall be tuned to reduce their sensitivity to prevent them from being triggered by movements outside of the controlled area.

    c. All other sensors shall be installed and adjusted as necessary to prevent them from being triggered by movements outside of the controlled area.

    v. Occupant sensing control zones, in offices greater than 250 square feet, shall be shown on the plans. J. To qualify for the PAF for an Institutional Tuning in Table 140.6-A, the tuned lighting system shall comply with all of the following requirements: i. The lighting controls shall limit the maximum output or maximum power draw of the controlled lighting to 85 percent or less of full light output or full power draw; and ii. The means of setting the limit is accessible only to authorized personnel; and iii. The setting of the limit is verified by the acceptance test required by Section 130.4(a)7; and iv. The construction documents specify which lighting systems shall have their maximum light output or maximum power draw set to no greater than 85 percent of full light output or full power draw. K. To qualify for the PAF for a demand responsive control in Table 140.6-A, the general lighting wattage receiving the PAF shall not be within the scope of Section 110.12(c) and a demand responsive control shall meet all of the following requirements: i. The controlled lighting shall be capable of being automatically reduced in response to a demand response signal; and ii. General lighting shall be reduced in a manner consistent with the requirements of Section 130.1(b). L. To qualify for the PAFs for clerestory fenestration, horizontal slats, or light shelves in Table 140.6-A, the daylighting design shall meet the requirements in Section 140.3(d). The PAFs shall only apply to lighting in a primary or secondary sidelit daylit zone where continuous dimming daylighting controls meeting the requirements of Section 130.1(d) are installed.

    TABLE 140.6-A—LIGHTING POWER ADJUSTMENT FACTORS (PAF) Col2 Col3
    TYPE OF CONTROL TYPE OF AREA FACTOR
    1. Daylight continuous dimming plus
    OFF control    		 Luminaires in skylit daylit zone or primary sidelit daylit zone or secondary sidelit daylit zone 0.10
    2. Occupant sensing controls in offices
    larger than 250 square feet    		 One sensor controlling an area that is no larger than 125 square feet 0.30
    3.
  • § 140.3 High relevance — show source text

    I. Shall be shown on the plans with the dimensions for the slat projection and slat spacing as specified in Equation 140.3-C. J. Shall have a conspicuous factory installed label permanently affixed and prominently located on an attachment point of the device to the building envelope, stating the following: “NOTICE: Removal of this device will require re-submittal of compliance documentation to the enforcement agency responsible for compliance with California Title 24, Part 6”. 3. Interior and Exterior Light Shelves. To qualify for a PAF, light shelves shall meet the following requirements: A. Where there is vertical fenestration area below the light shelf, both interior and exterior light shelves shall be installed. B. Shall be installed adjacent to clerestory fenestration on south-facing facades with Window Wall Ratios greater than 30 percent. The head height of the light shelves shall be no more than one foot below the finished ceiling. The clerestory fenestration shall meet the requirements of Section 140.3(d)1. C. Exterior light shelves shall be level or sloped downwards from fenestration. Interior light shelves shall be level or sloped upwards from fenestration.

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    D. Shall have a projection factor of the applicable value as specified in Table 140.3-E. The light shelf projection factor is calculated using Equation 140.3-C.

    TABLE 140.3-E—DAYLIGHTING DEVICES Col2 Col3
    DAYLIGHTING DEVICE ORIENTATION OF THE VERTICAL FENESTRATION PROJECTION FACTOR
    Horizontal Slats East or West 2.0 to 3.0
    Interior Light Shelf South 1.0 to 2.0
    Exterior Light Shelf South 0.25 to 1.25

    E. Shall have a minimum Distance Factor of 0.3. The distance factor is calculated using Equation 140.3-C. Exception to Section 140.3(d)3E: Where it is documented that existing adjacent structures or natural objects within view of the vertical fenestration block direct sunlight onto the vertical fenestration between 8 a.m. and 5 p.m. for less than 750 daytime hours per year. F. Shall have a top surface with a minimum Visible Reflectance of 0.50 when tested as specified in ASTM E903. Exception to Section 140.3(d)3F : Where an exterior light shelf is installed greater than two feet below the clerestory sill.

    G. Shall extend beyond each side of the window jamb by a distance equal to or greater than their horizontal projection. H. Shall be shown on the plans with the dimensions for the light shelf projection and light shelf spacing as specified in Equation 140.3-C.

    EQUATION 140.3-C—PROJECTION AND DISTANCE FACTOR CALCULATION

    Projection Factor = Projection/Spacing

    Distance Factor = D /( H AS × Projection Factor)

    where:

    Projection = The horizontal distance between the base edge and the projected edge of the overhang, slat or light shelf.

    Spacing = For overhangs, the vertical distance between the projected edge of the overhang and sill of the vertical fenestration below it.

  • § 170.2 High relevance — show source text

    or furniture mounted luminaires that comply with Section 170.2(e)1Aii and provide general lighting directly above the controlled area; and d. Qualifying luminaires shall be controlled by occupant sensing controls that meet all of the following requirements, as applicable: I. Infrared sensors shall be equipped by the manufacturer, or fitted in the field by the installer, with lenses or shrouds to prevent them from being triggered by movement outside of the controlled

    area.

    II. Ultrasonic sensors shall be tuned to reduce their sensitivity to prevent them from being triggered by movements outside of the controlled area. III. All other sensors shall be installed and adjusted as necessary to prevent them from being triggered by movements outside of the controlled area. e. Occupant sensing control zones, in offices greater than 250 square feet, shall be shown on the plans.

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    MULTIFAMILY BUILDINGS—PERFORMANCE AND PRESCRIPTIVE COMPLIANCE APPROACHES

    x. To qualify for the PAF for an Institutional Tuning in Table 170.2-L, the tuned lighting system shall comply with all of the following requirements: a. The lighting controls shall limit the maximum output or maximum power draw of the controlled lighting to 85 percent or less of full light output or full power draw; and b. The means of setting the limit is accessible only to authorized personnel; and c. The setting of the limit is verified by the acceptance test required by Section 160.5(e)1G; and d. The construction documents specify which lighting systems shall have their maximum light output or maximum power draw set to no greater than 85 percent of full light output or full power draw. xi. To qualify for the PAF for a demand responsive control in Table 170.2-L, the general lighting wattage receiving the PAF shall not be within the scope of Section 110.12(c) and a demand responsive control shall meet all of the following requirements: a. The controlled lighting shall be capable of being automatically reduced in response to a demand response signal; and b. General lighting shall be reduced in a manner consistent with the illuminance uniformity requirements of Section 160.5(b)4B. xii. To qualify for the PAFs for clerestory fenestration, horizontal slats or light shelves in Table 170.2-L, the daylighting design shall meet the requirements in Section 170.2(b). The PAFs shall only apply to lighting in a primary or secondary sidelit daylit zone where continuous dimming daylighting controls meeting the requirements of Section 160.5(b)4D are installed.

    TABLE 170.2-L—LIGHTING POWER ADJUSTMENT FACTORS (PAF) Col2 Col3
    TYPE OF CONTROL TYPE OF AREA FACTOR
    1. Daylight Continuous
    Dimming Plus OFF Control    		 Luminaires in skylit daylit zone or primary sidelit daylit zone 0.10
    2. Occupant Sensing Controls
    in Office Spaces Larger Than
    250 Square Feet    		 In open plan offices > 250 square feet: One sensor controlling an area that is:
    No larger than 125 square feet    		 0.30
    2.
  • § 126-250 High relevance — show source text

    Occupant sensing controls in offices
    larger than 250 square feet|One sensor controlling an area that is 126-250 square feet|0.20| |4. Institutional tuning|Luminaires in non-daylit areas:
    Luminaires that qualify for other PAFs in this table may also qualify for this tuning PAF.|0.10| |4. Institutional tuning|Luminaires in daylit areas:
    Luminaires that qualify for other PAFs in this table may also qualify for this tuning PAF.|0.05| |5. Demand responsive control|General lighting luminaires not in the scope of Section 110.12(c).
    If DR controls are required of Section 110.12(c), this PAF is not available for any lighting in the
    project. Luminaires that qualify for other PAFs in this table may also qualify for this demand
    responsive control PAF.|0.05| |6. Clerestory fenestration|Luminaires in daylit areas adjacent to the clerestory.
    Luminaires that qualify for daylight dimming plus OFF control may also qualify for this PAF.|0.05| |7. Horizontal slats|Luminaires in daylit areas adjacent to vertical fenestration with interior or exterior horizontal slats.
    Luminaires that qualify for daylight dimming plus OFF control may also qualify for this PAF.|0.05| |8. Light shelves|Luminaires in daylit areas adjacent to clerestory fenestration with interior or exterior light
    shelves. This PAF may be combined with the PAF for clerestory fenestration.
    Luminaires that qualify for daylight dimming plus OFF control may also qualify for this PAF.|0.10| |a. To qualify for any of the power adjustment factors in this table, the installation shall comply with the applicable requirements in Section 140.6(a)2.
    b. Only one PAF may be used for each qualifying luminaire unless combined below.
    c. Lighting controls that are required for compliance with Part 6 shall not be eligible for a PAF.|a. To qualify for any of the power adjustment factors in this table, the installation shall comply with the applicable requirements in Section 140.6(a)2.
    b. Only one PAF may be used for each qualifying luminaire unless combined below.
    c. Lighting controls that are required for compliance with Part 6 shall not be eligible for a PAF.|a. To qualify for any of the power adjustment factors in this table, the installation shall comply with the applicable requirements in Section 140.6(a)2.
    b. Only one PAF may be used for each qualifying luminaire unless combined below.
    c. Lighting controls that are required for compliance with Part 6 shall not be eligible for a PAF.|

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    NONRESIDENTIAL AND HOTEL/MOTEL OCCUPANCIES—PERFORMANCE AND PRESCRIPTIVE

    COMPLIANCE APPROACHES FOR ACHIEVING ENERGY EFFICIENCY

    1. Lighting wattage excluded. The watts of the following indoor lighting applications may be excluded from adjusted indoor lighting power. (Indoor lighting not listed below shall comply with all applicable nonresidential indoor lighting requirements in Part 6): A. In theme parks: lighting for themes and special effects; B. Studio lighting for film or photography,
  • § 130.1 High relevance — show source text
    1. All skylit daylit zones and primary sidelit daylit zones shall be shown on building plans.
    2. General lighting in daylit zones shall be controlled in accordance with Section 130.1(d).
    3. The total skylight area is at least 3 percent of the total floor area in the space within a horizontal distance of 0.7 times the average ceiling height from the edge of rough opening of skylights; or the product of the total skylight area and the average skylight visible transmittance is no less than 1.5 percent of the total floor area in the space within a horizontal distance of 0.7 times the average ceiling height from the edge of rough opening of skylights.

    112 2025 CALIFORNIA ENERGY CODE

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    NONRESIDENTIAL AND HOTEL/MOTEL OCCUPANCIES—PERFORMANCE AND PRESCRIPTIVE

    COMPLIANCE APPROACHES FOR ACHIEVING ENERGY EFFICIENCY

    1. All skylights shall have a glazing material or diffuser that has a measured haze value greater than 90 percent, tested according to ASTM D1003 (notwithstanding its scope) or other test method approved by the Commission.
    2. Skylights for conditioned and unconditioned spaces shall have an area-weighted average visible transmittance (VT) no less than the applicable value required by Section 140.3(a)6D.

    Exception 1 to Section 140.3(c): Auditoriums, churches, movie theaters, museums and refrigerated warehouses.

    Exception 2 to Section 140.3(c): In buildings with unfinished interiors, future enclosed spaces for which there are plans to have: A. A floor area of less than or equal to 5,000 square feet, or B. Ceiling heights of less than or equal to 15 feet.

    This exception shall not be used for S-1 or S-2 (storage), or for F-1 or F-2 (factory) occupancies.

    Exception 3 to Section 140.3(c): Enclosed spaces having a designed general lighting system with a lighting power density less than 0.5 watts per square foot.

    Exception 4 to Section 140.3(c): Enclosed spaces where it is documented that permanent architectural features of the building, existing structures or natural objects block direct beam sunlight on at least half of the roof over the enclosed space for more than 1500 daytime hours per year between 8 a.m. and 4 p.m.

    (d) Daylighting Design Power Adjustment Factors (PAFs). To qualify for a Power Adjustment Factor (PAF) as specified in Section 140.6(a)2L, daylighting devices shall meet the following requirements:

    1. Clerestory fenestration. To qualify for a PAF, clerestory fenestration shall meet the following requirements: A. Shall be installed on east-, west-, or south-facing facades. B. Shall have a head height that is at least 10 feet above the finished floor. C. Shall have a glazing height that is greater than or equal to 10 percent of the head height. D. If operable shading is installed on the clerestory fenestration, then the clerestory fenestration shading shall be controlled separately from shading serving other vertical fenestration.
    2. **Interior and exterior horizontal slats.
  • § 10-111 Medium relevance — show source text

    HORIZONTAL SLATS, when referring to a daylighting device, is a set of adjacent surfaces located directly adjacent to vertical fenestration, oriented horizontally and projecting horizontally from its interior or exterior vertical surface.

    INTEGRATED SHADING SYSTEM is a class of fenestration products including an active layer: e.g., shades, louvers, blinds or other materials permanently integrated between two or more glazing layers. The U -factor and/or SHGC and VT of the insulating glass assembly can be altered by reversibly changing the enclosed active layer.

    LIGHT SHELF is an adjacent, opaque surfaced daylighting device located at the sill of clerestory glazing, oriented horizontally and projecting horizontally from an interior or exterior vertical surface.

    MANUFACTURED or KNOCKED DOWN PRODUCT is a fenestration product constructed of materials that are factory cut or otherwise factory formed with the specific intention of being used to fabricate a fenestration product. Knocked down or partially assembled products may be sold as a fenestration product when provided with temporary and permanent labels as described in Section 10-111, or as a site-built fenestration product when not provided with temporary and permanent labels as described in Section 10-111.

    NFRC 100 is the National Fenestration Rating Council document titled “Procedure for Determining Fenestration Product U factors,” (2020) (ANSI/NFRC 100-2020).

    NFRC 200 is the National Fenestration Rating Council document titled “Procedure for Determining Fenestration Product Solar Heat Gain Coefficients and Visible Transmittance at Normal Incidence,” (2020) (ANSI/NFRC 200-2020).

    NFRC 202 is the National Fenestration Rating Council document titled “Procedures for Determining Translucent Fenestration Product Visible Transmittance at Normal Incidence,” (2020) (ANSI/NFRC 202-2020).

    NFRC 203 is the National Fenestration Rating Council document titled “Procedure for Determining Visible Transmittance of Tubular Daylighting Devices,” (2020) (ANSI/NFRC 203-2020).

    16 2025 CALIFORNIA ENERGY CODE

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    ALL OCCUPANCIES—GENERAL PROVISIONS

    NFRC 400 is the National Fenestration Rating Council document titled “Procedure for Determining Fenestration Product Air Leakage,” (2020) (ANSI/NFRC 400-2020).

    OPERABLE SHADING DEVICE is a device at the interior or exterior of a building or integral with a fenestration product, which is capable of being operated, either manually or automatically, to adjust the amount of solar radiation admitted to the interior of the building.

    RELATIVE SOLAR HEAT GAIN COEFFICIENT (RSHGC) is the ratio of solar heat gain through a fenestration product (corrected for external shading) to the incident solar radiation. Solar heat gain includes directly transmitted solar heat and absorbed solar radiation, which is then reradiated, conducted or convected into the space.

    SITE-BUILT is fenestration designed to be field-glazed or field assembled units using specific factory cut or otherwise factory formed framing and glazing units that are manufactured with the intention of being assembled at the construction site. These include storefront systems, curtain walls and atrium roof systems.

    SKYLIGHT ROOF RATIO (SRR) is the ratio of the skylight area to the gross exterior roof area.

  • § 10-111 Medium relevance — show source text

    10-111(b)2C, 110.6(a), 110.6(b) Garden window 150.0(q)1, 150.2(b)2C, 160.1(e), 180.2(c)3 Glazed door Table 110.6-A, 140.3(a)7, Table 140.3-B, Table 140.3-C, Table 140.3-D, 150.1(c)3A, 150.1(c)5, 170.2(a)3A, 170.2(a)4, 170.2(a)6, Table 180.2-B Glazing 10-111(d)1, Table 110.6-B, 120.6(h)4B, 130.1(d)3D, 130.1(d)5, 140.3(a)5, 150.1(c)3B, 150.1(c)4D, 160.1(b)4D,170.2(a)3A, 170.2(a)3A, 170.2(a)3A, 170.2(a)3B Glazing area 130.1(d)5, 150.1(c)3A, 160.1(b)4D, 160.5(b)4D, 170.2(a)3A Glazing height 140.3(d)1C Glazing material 140.3(c)5, 170.2(a)3B,170.2(b)5 Greenhouse window 150.0(q)1, 150.2(b)2, 160.1(e)1, 180.2(c)3 Interior shading 140.3(a)5C, 170.2(a)3A National Fenestration Rating Council (NFRC) 100.1 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.

  • § 140.3 Medium relevance — show source text

    140.3(a)6B, 140.3(a)6C, 140.3(a)6D, 150.1(c)3A, 170.2(a)3A, 170.2(a)3A, 170.2(a)3A Clerestory fenestration 140.3(d)1, 140.3(d)3B, Table 140.3-C, Table 140.6-A, Table 170.2L Component Modeling Approach (CMA) 110.6(a)5 Curtain walls 141.0(b)1B, 180.2(a)2D Dual-glazed 150.0(q)1, 150.2(b)2C, 160.1(e)1, 180.3(c)3

    Exterior shading device 150.1(c)4 Exterior window 140.3(a)5 Fenestration area 140.3(d)3A, 150.0(q)1, 150.1(c)3B-C, 150.2(a)1A, 150.2(a)1B, 150.2(b)1A, 160.1(e)1, 170.2(a)3A, 180.1(a)1A, 180.2(b)1C Fenestration product 10-111, 100.0(g), 110.6, 150.0(q), 150.1(c)3A, 150.1(c)5, 150.2(b)1B, 160.1(e), 170.2(a)3A, 180.1(a)1B, 180.2(b)1C Field-fabricated (fenestration, doors)10111(a)2, 10-111(b)2C, 110.6(a), 110.6(b) Garden window 150.0(q)1, 150.2(b)2C, 160.1(e), 180.2(c)3 Glazed door Table 110.6-A, 140.3(a)7, Table 140.3-B, Table 140.3-C, Table 140.3-D, 150.1(c)3A, 150.1(c)5, 170.2(a)3A, 170.2(a)4, 170.2(a)6, Table 180.2-B Glazing 10-111(d)1, Table 110.6-B, 120.6(h)4B, 130.1(d)3D, 130.1(d)5, 140.3(a)5, 150.1(c)3B, 150.1(c)4D, 160.1(b)4D,170.2(a)3A, 170.2(a)3A, 170.2(a)3A, 170.2(a)3B Glazing area 130.1(d)5, 150.1(c)3A, 160.1(b)4D, 160.5(b)4D, 170.2(a)3A Glazing height 140.3(d)1C Glazing material 140.3(c)5, 170.2(a)3B,170.2(b)5 Greenhouse window 150.0(q)1, 150.2(b)2, 160.1(e)1, 180.2(c)3 Interior shading 140.3(a)5C, 170.

Frequently asked questions

What must be shown on the plans to claim a PAF?

Plans must show the daylighting device (clerestory/slat/shelf) with projection and spacing dimensions used in Equation 140.3‑C, plus any required labels called out by the code.

Can I claim both a clerestory PAF and a light‑shelf PAF for the same luminaire?

Yes — the code explicitly permits combining the light‑shelf PAF (0.10) with the clerestory PAF (0.05) where the device requirements and controls are met. Confirm documentation and enforcement‑agency acceptance.

Do horizontal slats have to be exterior?

No — slats may be interior or exterior, but exterior slats must be level or sloped downward; interior slats level or sloped upward. Other requirements (orientation, WWR, projection/distance factors, reflectance, opacity, permanence) still apply.

What control type is required to earn these daylighting PAFs?

Continuous dimming daylighting controls are required in the affected primary or secondary sidelit daylit zones (see Table 140.6‑A and Table 170.2‑L notes).

For multifamily/common areas, any additional paperwork?

Yes — lighting controls and systems that earn PAFs must meet acceptance and installation certificate requirements in § 170.2(e) (including submission of Certificates of Acceptance and Installation Certificates).

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Related in the California Energy Code

Daylit zones: defining primary/secondary sidelit and skylit daylit areas

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Daylighting design, daylight-responsive controls and daylight-related PAFs

California Energy Code