California Association of Building Energy Consultants

2019 Title 24 Part 6 Prescriptive Requirements for Additions

The information below offers one method for additions to meet Title 24 Part 6 Energy Code. Documentation is required to submit to the building department.

An ADDITION is any change to a building that increases conditioned floor area and conditioned volume. Addition is also any change that increases the floor area and volume of an unconditioned building of an occupancy group or type regulated by Part 6. Addition is also any change that increases the illuminated area of an outdoor lighting application regulated by Part 6.

From the 2019 Residential Compliance Manual

9.4 Prescriptive and Mandatory Measures

The prescriptive requirements apply to additions in the same way they apply to new buildings and must be documented on the CF1R-ADD-01 or CF1R-NCB-01 Form. Except as noted, all applicable prescriptive requirements for additions must be met when using the prescriptive approach. Otherwise, the building must comply using the performance approach.

For prescriptive additions, a certificate of compliance (CF1R-ADD-01 or CF1R-NCB-01) form must be completed and submitted for permit. If any mandatory or prescriptive measures require HERS verification and/or testing, the certificate of compliance for the project must be completed and registered online with a HERS Provider before submittal to the enforcement agency. Refer to Section 2.2.2 and Section 2.5.

There are three prescriptive paths available for additions based on the total conditioned floorarea (CFA) of the addition. The total CFA of the addition may include floor areas representing several physically separate additions to the building under the same permit.

Table 9-2 summarizes the key features of the prescriptive envelope requirements for the three prescriptive addition options in §150.2(a)1. Envelope requirements unique to that type of prescriptive addition are shown in bold.

The prescriptive requirements for additions are listed in §150.2(a)1. Unless otherwise noted, the prescriptive requirements contained in §150.1(c) also apply. [See prescriptive requirements of §150.1(c); in Know the Prescriptive Package Energy Home Design for the 2019 Title 24 Part 6 Energy Code.]

  1. Additions ≤ 400 ft²: All prescriptive requirements must be met except:
    1. Total glazing area up to 75 ft² or 30 percent of the conditioned floor area, whichever is greater.
    2. Total glazing area maximum for west-facing glazing is 60 ft² or 5 percent in ClimateZones 2, 4, and 6-15.
    3. QII does not apply.
    4. Rafter roof insulation of R-22.
    5. Ceiling insulation of R-38 in Climate Zones 1 and 11-16, or R-30 in Climate Zones 2-10.
    6. Radiant barrier in Climate Zones 2-15.
    7. Extensions of existing wood-framed walls (Figure 9-1) may retain the dimensions of the existing walls and require the following cavity insulation:
      1. In 2x4 wood-frame walls, insulation shall be R-15.
      2. In 2x6 or greater wood-frame walls, insulation shall be R-21.
    8. Existing wood-framed walls where existing exterior siding (or cladding) will not be removed, do not need continuous insulation and require only cavity insulation:
      1. In 2x4 wood-framed walls, insulation shall be R-15.
      2. In 2x6 or greater wood-framed walls, insulation shall be R-21.
  2. Additions > 400 ft² and ≤ 700 ft²: All prescriptive requirements must be met except:
    1. Total glazing area up to 120 ft² or 25 percent of the conditioned floor area.
    2. Total glazing area maximum for west-facing glazing is 60 ft² or 5 percent in Climate Zones 2, 4, and 6-15.
    3. QII does not apply.
    4. Rafter roof insulation of R-22.
    5. Ceiling insulation of R-38 in Climate Zones 1 and 11-16 or R-30 in Climate Zones 2-10.
    6. Radiant barrier in Climate Zones 2-15.
    7. Extensions of existing wood-framed walls may retain the dimensions of the existing walls and require the following cavity insulation:
      1. In 2x4 wood-framed walls, insulation shall be R-15.
      2. In 2x6 or greater wood-framed walls, insulation shall be R-21.
    8. Existing wood-framed walls, where existing exterior siding (or cladding) will not be removed, do not need continuous insulation and require only cavity insulation:
      1. In 2x4 wood-framed walls, insulation shall be R-15.
      2. In 2x6 or greater wood-framed walls, insulation shall be R-21.
  3. Additions > 700 ft²:
    1. Total glazing area up to 175 ft² or 20 percent of the conditioned floor area, whichever is greater.
    2. Total glazing area maximum for west-facing glazing is 70 ft² or 5 percent in Climate Zones 2, 4, and 6-15.
    3. Extensions of existing wood-framed walls may retain the dimensions of the existing walls and require the following cavity insulation:
      1. In 2x4 wood-framed walls, insulation shall be R-15.
      2. In 2x6 or greater wood-framed walls, insulation shall be R-21.
    4. Existing wood-framed walls, where existing exterior siding (or cladding) will not be removed, do not need continuous insulation and require only cavity insulation:
      1. In 2x4 wood-framed walls, insulation shall be R-15.
      2. In 2x6 or greater wood-framed walls, insulation shall be R-21.
    5. QII applies to the addition.
    6. When an addition greater than 700 ft² is an existing unconditioned space converted to conditioned space, the QII requirements do not include:
      1. Window and door header insulation.
      2. Air sealing if the existing air barrier is not removed or replaced.

Figure 9-1 provides a visual description of a wall extension.

Wall Extension

Figure 9-3 provides a visual for Prescriptive Addition Requirements:

Prescriptive Addition Envelope Requirements

As always, I am available to discuss the process of meeting the California Energy Code for any building project. Contact me …