• Batt and blanket insulation are made of mineral fiber and mineral wool (processed fiberglass, rock, slag wool); animal wool or cotton-based products; or cellulose materials. These products are used to insulate below floors, above ceilings, below roofs, and within walls. They offer ease of installation with R-values set by the manufacturer based on size and thickness. They are available with facings, some serve as vapor retarders, and have flanges to aid in installation to framed assemblies. Many are available as unfaced material and can be easily friction-fitted into framed cavities.
• Batt and blanket insulation allow easy inspection, and installation errors can readily be identified and remedied, including breeches in the air barrier system that allow air leakage.

Note for Contractors/Installers: Care should always be taken to install insulation properly, filling the entire cavity and butting ends or sides of the batt material to ensure uniformity of installation. Batt and blanket insulation material must be delaminated or cut to allow for wiring, plumbing, and other penetrations within the cavity. See Section 3.5.

Figure 3-15: Cellulose-Insulated

Loose-fill is insulation that has a pneumatic or blown installation process, including cellulose, fiberglass, mineral wool and natural wool (animal or cotton-based products). Blown wall insulation can be an effective way to deal with the irregularities of wall cavities, especially the spaces around pipes, electric cables, junction boxes, and other equipment embedded in wall cavities (see Figure 3-15). The R-value of blown wall insulation material installed in closed cavities is determined by the installed thickness and density. This differs from manufactured products such as fiberglass or mineral wool batts for which the R-value has been tested and arrives at the construction site in preformed lengths and thicknesses with set R-values.

When installed in floors, walls, and other assemblies, these fibrous insulations are held in place in one of three ways:

1. Preinstalled netting or fabric
2. Use of existing cavity walls
3. Use of integral adhesives

Note for Building Inspectors: Blown wall insulation must be thoroughly checked to ensure the R-value is achieved. R-value depends on the installed density of the material at the building site, and the building official should ensure that the installed density meets manufacturer specifications. See Section 3.5.

In closed cavities:

• A line of sight down a wall section can hide imperfections in the installation, leading to underachieving stated R-values.
• Depressions and voids within the insulated cavity are areas lacking in R-value performance.
• Where netting is used, overspraying can result in a higher installed density (higher R-value) but can be troublesome for attaching gypsum board to wall framing.
• Where cavities have been underfilled, there may be voids or “soft” areas under the netting. These areas must be corrected by adding insulation, or the area must be removed, and new material must be blown into the cavity.

In open cavities (attic floor or open wall):

• No netting or preexisting wall cladding is needed (Figure 3-16).
• In open horizontal applications, such as attic floors, no adhesives are used, and the R-value is verified by the weight per square foot.
• In open vertical applications, integral adhesives are used to hold the fibers in place. Water-activated adhesives are used for moist-spray cellulose, and water or polymer adhesives are used for fiberglass loose-fill applications. The fiber and/or adhesive formulation cause the insulation to adhere to itself and stick to surfaces of the wall cavity.
• Excess insulation that extends past the wall cavity is scraped off and recycled.

Figure 3-16: Attic Floor

Source: California Energy Commission

• SPF is a two-part, liquid-foamed thermoset plastic (such as polyurethane). Polyurethane is formed by the reaction of an isocyanate and a polyol. Blowing agents, catalysts, and surfactants are added to develop a cellular structure before the polyurethane mixture cures. At application, the SPF material forms in place to provide insulation, an air seal, and, in closed-cell SPF, an integral vapor retarder and water barrier.
• SPF insulation is a two-component reactive system mixed at a spray gun or a single-component system that cures by exposure to humidity. The liquid is sprayed through a nozzle into the wall, roof, ceiling, and floor cavities. SPF insulation can be formulated to have specific physical properties, such as density, compressive strength, fire resistance, and R-value.
• SPF insulation is spray-applied to adhere fully to the substrate and other framing faces to form a complete air seal within the construction cavities.

Note for Contractors/Installers: SPF must be separated from the interior of the building, including attic spaces, by an approved thermal barrier complying with Section 316.4 of the California Residential Code (CRC).

• There are two common types of SPF insulation:

Figure 3-17: Open-Cell SPF Installed in Wall Cavity

Source: SPFA

1. Low-Density Open-Cell SPF (ocSPF) Insulation: A spray-applied polyurethane foam insulation having an open cellular structure resulting in an installed nominal density of 0.4 to 1.5 pounds per cubic foot (pcf), ocSPF has been assigned a default R-value of 3.6 per inch for compliance, but some products can achieve higher R-values. The ocSPF insulation is sprayed then expands to fill the framed cavity (Figure 3-17). Excess insulation may be trimmed by a special tool to simplify interior cladding installation. The average thickness of the foam insulation must meet or exceed the required R-value. Depressions in the foam insulation surface shall not be greater than ½-inch of the required thickness, provided these depressions do not exceed 10 percent of the surface area being insulated. Note: If using the default R-value of 3.6 per inch, the entire wall cavity must be filled to achieve the mandatory minimum wall insulation requirements for 2x4 and 2x6 framing.

Figure 3-18: Closed-Cell SPF Installation in a Wall Cavity

Source: SPFA

1. B. Medium-Density Closed-Cell SPF (ccSPF) Insulation: A spray-applied polyurethane foam insulation having a closed cellular structure resulting in an installed nominal density of greater than 1.5 to less than 2.5 pounds per cubic foot (pcf), ccSPF has been assigned a default R-value of 5.8 per inch for compliance, but some products can achieve higher R-values. The average thickness of the foam insulation must meet or exceed the required R-value. Depressions in the surface of the foam insulation shall not be greater than ½-inch of the required thickness at any given point of the surface area being insulated. ccSPF is not required to fill the cavity (Figure 3-18).

Note for Building Inspectors: SPF R-value depends on the installed thickness, and the building official should ensure the thickness and uniformity of the SPF material within each cavity of framed assemblies meets manufacturer specifications.

• Rigid board insulation sheathing is made from fiberglass, mineral wool, expanded polystyrene (EPS), extruded polystyrene (XPS), polyisocyanurate (ISO), or polyurethane (PUR). It varies in thickness, and some products can provide up to R-6 per inch of thickness.

Figure 3-19: Properly Installed Rigid Insulation with Sealant Tape

Source: U.S. Environmental Protection Agency

This type of insulation is used for above-roof decks, exterior walls, cathedral ceilings, basement walls; as perimeter insulation at concrete slab edges; and to insulate special framing situations such as window and door headers and around metal seismic bracing. Rigid board insulation may also be integral to exterior siding materials. Properly sealed rigid insulation can be used continuously across an envelope surface to reduce air infiltration and exfiltration, and thermal bridging at framing.

Note for Contractors/installers: Proper installation of continuous rigid insulation may include button cap nails, furring strips, flashing, sealant tape, and design of the drainage plane. See Figure 3-19.

The 2022 California Building Code (CBC) provides guidance on fastener penetration depth, diameter, and spacing for exterior foam sheathing in Section R703.11.2. California Residential Code (CRC) Table 703.15.1 shows the fastener spacing for cladding attachment over foam sheathing to wood framing.

The mandatory requirements restrict the use of urea formaldehyde foam insulation. The restrictions are intended to limit human exposure to formaldehyde, a volatile and harmful organic chemical.

If foam insulation is used that has urea formaldehyde, it must be installed on the exterior side of the wall (not in the cavity of framed walls), and a continuous vapor retarder must be placed in the wall construction to isolate the insulation from the interior of the space. The vapor retarder must be 4-mil- thick (0.1 mm) polyethylene or equivalent.

The California Quality Standards for Insulating Materials requires that exposed facings on insulation material be fire resistant and tested and certified not to exceed a flame spread index of 25 and a smoke development index of 450. Insulation facings must be in contact with the finished assembly surface or they are considered exposed applications and cannot be installed. Flame spread indexes and smoke development indexes are shown on the insulation or packaging material or may be obtained from the manufacturer.

Loose fill insulation must be blown in evenly, and insulation levels must be documented on the certificate of installation (CF2R). The insulation level can be verified by checking that the depth of insulation conforms to the manufacturer’s coverage chart for achieving the required R-value. The insulation also must meet the manufacturer’s specified minimum weight per ft² for the corresponding R-value.

Note for Contractors/Installers: When installing loose fill insulation, the following guidelines should be followed:

1. For wood trusses that provide a flat ceiling and a sloped roof, the slope of the roof should be 4:12 or greater to provide adequate access for installing the insulation. Insulation thickness near the edge of the attic will be reduced with all standard trusses, but this is acceptable as long as the average thickness is adequate to meet the minimum insulation requirement.
2. If the ceiling is sloped (for instance, with scissor trusses), loose fill insulation can be used as long as the slope of the ceiling is no more than 4:12. If the ceiling slope is greater than 4:12, loose fill should be used only if the insulation manufacturer will certify the installation for the slope of the ceiling.
3. At the apex of the truss, a clearance of at least 30 inches should be provided to simplify installation and inspection.

Wet insulation systems are roofing systems where the insulation is installed above the waterproof membrane of the roof. Water can penetrate this insulation material and affect the energy performance of the roofing assembly in wet and cool climates. In climate zones 1 and 16, the insulating R-value of continuous insulation materials installed above the waterproof membrane of the roof must be multiplied by 0.8, and installers must use the resulting value in choosing the table column in Reference Appendices, Joint Appendix JA4 for determining assembly U-factor (when using the Joint Appendix JA4 table to comply). See the footnotes for Tables 4.2.1 through 4.2.7 in the Reference Appendices, Joint Appendix JA4.

Luminaires recessed in insulated ceilings can create thermal bridging through the assembly. Not only does this degrade the performance of the ceiling assembly, but it can permit condensation on a cold surface of the luminaire if exposed to moist air, as in a bathroom. Refer to the Lighting Chapter 6 for more information regarding the applicable requirements for recessed luminaires.

Luminaires recessed in insulated ceilings must meet three requirements.

1. They must be listed as defined in the Article 100 of the California Electric Code for zero clearance insulation contact (IC) by Underwriters Laboratories or other testing/rating laboratories recognized by the International Code Council (ICC). This enables insulation to be in direct contact with the luminaire.
2. The luminaire must have a label certified as per §150.0(k)1Cii for airtight (AT) construction. Airtight construction means that leakage through the luminaire will not exceed 2.0 cfm when exposed to a 75 Pa pressure difference, when tested in accordance with ASTM E283.
3. The luminaire must be sealed with a gasket or caulk between the housing and ceiling.

Figure 3-21: IC-Rated Luminaire (Light Fixture)

   Source: California Energy Commission

Wood-framed roof/ceiling construction assemblies must have at least R-22 insulation or a maximum U-factor of 0.043 based on 16-inch-on-center wood-framed rafter roofs, as determined from Reference Appendices, Joint Appendix JA4. Some areas of the roof/ceiling can be greater than the maximum U-factor if other areas have a U-factor lower than the requirement and the weighted average U-factor for the overall ceiling/roof is 0.043 or less.

Metal-framed and roof/ceiling constructions other than wood-framed must have a U-factor of 0.043 or less to comply with the mandatory requirement. If the insulation is not penetrated by framing, such as rigid insulation laid over a structural deck, then the rigid insulation can actually have a rated R-value of less than R-22 so long as the total roof/ceiling assembly U-factor is not greater than U-0.043.

Newly constructed attics must have roof deck insulation in climate zones 4 and 8 through 16. Insulation may either be above or below the roof deck so long as the area-weighted average U-factor of the roof assembly is not greater than 0.184. This is equivalent to R-3 or R-4 insulation depending on the location of the insulation (above or below the roof deck) and the roof type. See Table 3-10 for examples of assemblies that can be constructed to meet the requirement. Exceptions to the mandatory roof deck insulation include: (1) if the space conditioning system air handler and ducts are located entirely in conditioned space (NOTE: Duct systems located in conditioned space can be uninsulated if specific conditions are met, as explained in Section 4.4.1 (§150.0(m)1B), or (2) if no greater than 12 linear feet of supply duct, including the air handler and plenum are located in unconditioned space.

¹U-factor based on 2x4 at 24 inch on-center roof framing.

Source: California Energy Commission

The 2022 Energy Code is designed to offer flexibility to the builders and designers of residentialnewly constructed buildings in terms of achieving the intended energy efficiency targets. As such, the Energy Code offers several options for achieving one of two design objectives related to improving energy performance of homes built with ventilated attics in climate zones 4, 8-16, as shown in Figure 3-22.

Figure 3-22: Ventilated Attic Prescriptive Compliance Choices

Source: California Energy Commission

High Performance Ventilated Attic (HPVA). This approach reduces temperature differences between the attic space and the conditioned air being transported through ductwork in the attic. The package consists of insulation below the roof deck (Option B) in addition to insulation at the ceiling, R-6 or R-8 ducts, and 5 percent total duct leakage of the nominal air handler airflow.

Ducts in Conditioned Space (DCS). Ducts and air handlers are within the thermal and air barrier envelope of the building.

Note for Contractors/Installers: The Ducts in Conditioned Space (Option C) requires field verification by a HERS Rater to meet the prescriptive requirement.

All the prescriptive requirements for HPVA or DCS are based on the assumption that the home is built with the following construction practices:

1. The attic is ventilated with an appropriate free vent area as described below.
2. The roof is constructed with standard wood rafters and trusses.
3. For HPVA, the outermost layer of the roof construction is either tiles or a roofing product installed with an air gap between it and the roof deck.
4. The air handler and ducts are in the ventilated attic for HPVA and are in conditioned space for DCS.
5. The air barrier is located at the ceiling (excludes “cathedral” sealed attic roof/ceiling systems).

If a building design does not meet all of these specifications, it must comply through the performance approach.

Example 3-14: Cathedral Ceilings

Question: If 5 percent of a roof will be a cathedral ceiling, can it still comply under the prescriptive requirements?

Answer: No. The entire attic must be a ventilated space with the building air barrier located at the ceiling with standard wood rafter trusses to comply with the prescriptive requirements. This project must comply through the performance approach.

Example 3-15: Unventilated Attics

Question: Does an unventilated attic with insulation at the roof deck comply under the prescriptive requirements?

Answer: No. The entire attic must be a ventilated space with the building air barrier located at the ceiling with standard wood rafter trusses to comply with the prescriptive requirements. This project must comply through the performance approach.

Example 3-16: Insulation Above the Roof Deck

Question: Does a ventilated attic with insulation above the roof deck comply under the prescriptive requirements?

Answer: No. The insulation must be located below the roof deck between the roof rafters to comply with the prescriptive requirements. If insulation is above the roof deck, the project must comply through the performance approach.

Example 3-17: Asphalt Shingles

Question: A home with asphalt shingle roofing, having no air gap, has a ventilated attic with insulation installed below the roof deck between the roof rafters (HPVA) and at the ceiling meeting prescriptive insulation levels. Does this home comply with the prescriptive requirements?

Answer: No. The roofing product must be of a type that is installed with an air gap between the product and the roof deck, such as concrete tile, to comply with the prescriptive requirements. If a roofing product with no air gap between the product and the roof deck is installed, the project must comply through the performance approach.

Example 3-18: Gable Ends in High Performance Ventilated Attics

Question: In addition to the roof underdeck, do gable end walls in high performance ventilated attics (HPVA) need to be insulated?

Answer: No. Gable end walls do not need to be insulated when designing and installing a HPVA.

Example 3-19: Attic Insulation Placement

Question: When installing roof/ceiling insulation, does the insulation need to be installed on the entire roof/ceiling, including areas over unconditioned space?

Answer: It depends. The insulation should be installed at the roof/ceiling in one of the following ways:

(1) If the attic is an open or undivided space, then the entire roof/ceiling should be insulated. This includes portions of the roof/ceiling over an unconditioned space such as a garage.

(2) If the attic has a continuous air barrier separating the attic over unconditioned space from the attic over conditioned space, then only the portions of the roof/ceiling over conditioned space should be insulated. It is recommended, but not required, that the air barrier also be insulated.

This section describes the prescriptive requirements and approaches necessary for HPVA as they relate to roof/ceiling insulation. HVAC aspects of the HPVA including duct insulation and duct leakage are described in Chapter 4. Requirements and approaches to meet the ducts in conditioned space (DCS) are described in Chapter 4 of this manual.

Section 150.1(c)1 requires different values of roof and ceiling insulation, depending on whether the HPVA (Option B) or DCS (Option C) is chosen. Figure 3-23 shows a prescriptive requirements checklist for each option based on Tables 150.1-A.

Figure 3-23: Prescriptive Insulation Options

Note: 1 Option B is the standard design used to set the energy budget for the performance approach.

Source: California Energy Commission

• Below Roof Deck Insulation Option B. In a vented attic, air-permeable or air-impermeable insulation (batt, spray foam, loose-fill cellulose, or fiberglass) should be placed directly below the roof deck between the truss members and secured in place to provide a thermal break for the attic space. Insulation must be in direct contact with the roof deck and secured by the insulation adhesion, facing, mechanical fasteners, wire systems, a membrane material, or netting. Batts supported with cabling or other mechanical methods from below shall have supports that are less than or equal to 16” apart and no farther than 8” from the end of the batt.
• When batt thickness exceeds the depth of the roof framing members, full-width batts must be used to fit snugly and allow batts to expand beyond the framing members. Full coverage of the top chord framing members by insulation is recommended as best practice but is not required.

Figure 3-24: Details of Option B Assembly

Source: California Energy Commission

Figure 3-25: Placement of Insulation Below the Roof Deck

Source: California Energy Commission

When insulation is installed below the roof deck to meet the prescriptive requirements of Option B, a radiant barrier is not required. However, a draped radiant barrier may be installed to receive performance credit.

Vapor Retarders (Option B). Attic vapor retarders are not required by the Energy Code in most climates when using spray foam, blown-in insulation, or unfaced batts, and when sufficient attic ventilation is maintained. Although not required, the use of vapor retarders can provide additional security against possible moisture buildup in attic and framed assemblies. In climate zones 14 and 16, a Class I or Class II vapor retarder must be used to manage moisture¹ as stated in California Building Code (CBC), Title 24, Part 2.5, Section R806.2.

¹ Insulation Contractors Association of America. (2004). Technical Bulletin No. 6 Use of Vapor Retarders.

Attic Ventilation (Options B and C)

Proper attic ventilation occurs at two points at the roof: the soffit (or eave) vents and the ridge (or eyebrow) vents. Ridge or eyebrow venting must be maintained, as shown in Figure 3-26.

When installing insulation below the roof deck, vent baffles and insulation barriers should be used to maintain proper ventilation space. Proper airflow through the space helps remove moisture and prevents any associated issues.

Figure 3-26: Insulation Air Baffles

Source: Building Science Corporation

Figure 3-27: Baffles at the Eave in Attics

Source: California Energy Commission

Where ceiling insulation is installed next to eave or soffit vents, a rigid baffle should be installed at the top plate to direct ventilation air up and over the ceiling insulation. (See Figure 3-27.) The baffle should extend beyond the height of the ceiling insulation and should have sufficient clearance between the baffle and roof deck at the top. There are several acceptable methods for maintaining ventilation air, including preformed baffles made of either cardboard or plastic. In some cases, plywood or rigid foam baffles are used.

The California Building Code (CBC) requires a minimum vent area to be provided in roofs with attics, including enclosed rafter roofs creating cathedral or vaulted ceilings. Check with the local building jurisdiction to determine which of the two CBC ventilation requirements are to be followed:

1. CBC, Title 24, Part 2, Vol. 1, Section 1202.2 requires that the net-free ventilating area shall not be less than 1/300 of the area of the space ventilated.
2. CBC, Title 24, Part 2.5, Section R806.2 requires that the net-free ventilating area shall not be less than 1/150 of the area of the space ventilated. This ratio may be reduced to 1/300 if a ceiling vapor retarder is installed in climate zones 14 and 16. If meeting Option 1 above, a minimum of 40 percent and not more than 50 percent of the vents must be located in the upper portion of the space being ventilated at least 3 feet above the eave or cornice vents.

Insulation shall not block the free flow of air, and a minimum 1-inch air space shall be provided between the insulation and the roof sheathing and at the location of the vent.

Ventilated openings are covered with corrosion-resistant wire cloth screening or similar mesh material. When part of the vent area is blocked by meshes or louvers, the resulting “net-free area” of the vent must be considered to determine if ventilation requirements are met.

Many jurisdictions in California are covered by Wildland Urban Interface (WUI) regulations where specific requirements for construction materials must be used to improve fire resistance for the building. These regulations require special vents that are expressly tested to resist the intrusion of flames and burning embers. Check with the building department to ensure compliance with local codes.

Example 3-20: Installation Doesn’t Match Compliant Design Option

Question: A newly constructed building project in climate zone 12 with HVAC ducts in the attic was designed to meet the prescriptive requirements for below roof deck and ceiling insulation. Due to miscommunication amongst the team, the roof deck insulation was not installed, and R-49 ceiling insulation was installed instead. Does this project still comply?

Answer: This project no longer meets the prescriptive requirements and must follow the performance approach. For future projects, clearly communicating the project expectations to all team members early in the construction process is the key to succeeding at this design strategy. Having a project initiation meeting with all subcontractors and team members is a best practice, at least for the first few projects, until the entire team is aware of the design needs.

Note: If the design was changed so that the roof deck has a radiant barrier and the HVAC equipment and ducts are verified to be in conditioned space, the altered design will meet the prescriptive requirements under Option C.

Note for Contractors/Installers: Tips for Successfully Implementing the High Performance Attics Requirements

• Commit to a compliance strategy early in the building design process.
• Have a kick-off meeting with builder, subcontractor, designer, energy consultant, and HERS Rater to set expectations and express the value of the design.
• Communicate strategy and schedule to subcontractors and other team members early.
• Include insulation specifications according to the CF1R on the building plans.
• Insulation contractor will install insulation below roof deck (ideally at the same time as ceiling insulation).
• All relevant subcontractors must be aware of where the air barrier is located and be conscious of where they make penetrations, especially if designing for verified ducts in conditioned space or reduced building envelope leakage.

Duct and Air Handlers Located in Conditioned Space Option C. Allows a project to place and verify that ducts are located in conditioned space instead of installing insulation at the roof deck. If complying with this option, ceiling and duct insulation must be installed at the values specified in Table 150.1-A for Option C, and a radiant barrier is required in most climate zones.

• HERS Verification (Option C). Simply locating ducts in conditioned space does not qualify for this requirement; a HERS Rater must test and verify for low leakage ducts within conditioned space and that the ducts are insulated to a level required in Table 150.1-A of the Energy Code.
• Note for Architects/Designers: Design strategies that can be used to prescriptively comply with Option C include dropped ceilings (dropped soffit), plenum or scissor truss to create a conditioned plenum box, and open-web floor truss. The key is that the ducts and equipment are placed within the air barrier of the building. Locating ducts within an unvented attic does not meet Option C requirements.
• Ceiling Insulation (Options B and C). Insulation coverage should extend far enough to the outside walls to cover the bottom chord of the truss. However, insulation should not block eave vents in attics because the flow of air through the attic space helps remove moisture that can build up in the attic and condense on the underside of the roof deck. This can cause structural damage and reduce the effectiveness of the insulation.

Based on area-weighted averaging, ceiling insulation may be tapered near the eave, but it must be applied at a rate to cover the entire ceiling at the specified level. An elevated truss is not required but may be desirable in some applications.

• 2x4 inch wood-framed walls above grade. Shall have a U-factor not exceeding U-0.102. In a wood-framed wall, this requirement is met with at least R-13 insulation installed in the cavities between framing members.
• 2x6 inch or greater wood-framed walls above grade. Shall have a U-factor not exceeding 0.071. In a wood-framed wall, this requirement is met with at least R-20 insulation installed in the cavities between framing members.
  Masonry walls above grade. Must be insulated to meet the prescriptive requirements in Table 150.1-A for mass walls.
  All other wall types above grade. Must meet a maximum U-factor of U-0.102.
  Demising partitions and knee walls. Demising and knee walls must meet or exceed minimum insulation requirements listed above, depending on wall type.
  Exceptions: There are several cases where the mandatory requirements for wall insulation do not apply or apply in a special way. For best practice, the following should be implemented:
  1. The mandatory requirements apply to framed foundation walls of heated basements or heated crawl spaces that are located above grade, but not to the portion that is located below grade.
  2. For additions to existing buildings, existing wood-framed walls that are not being altered and are already insulated to a U-factor of 0.110 or lower, or that have existing R-11 insulation need not comply with the mandatory R-13 wall insulation. For more on additions see Chapter 9.
  3. Rim joists between floors of a multistory building are deemed to comply with these mandatory requirements if they have R-13 insulation installed on the inside of the rim joist and are properly installed between intersecting joist members.

Demising Partitions and Knee Walls

Demising partitions and knee walls are not required to meet the prescriptive package requirements. Demising partitions and knee walls shall meet the mandatory minimum wall insulation requirements from §150.0(c).

1. Framed Walls
   The prescriptive requirements in Table 150.1-A call for a U-factor of 0.048 in climate zones 1-5 and 8-16, and a U-factor of 0.065 in climate zones 6 and 7.
   The designer may choose any wall construction from Reference Appendices, Joint Appendix JA4 (Tables 4.3.1 and 4.3.4) that has a U-factor equal to or less than 0.048 or 0.065, depending on the climate zone.
   Wood Frame. JA4 Table 4.3.4 shows that a 2x6 wood-framed wall at 16-inches-on-center can achieve a U-factor of 0.048 with R-21 batt insulation in the cavity and R-5 exterior insulation.

Figure 3-28: Wood-Framed Wall With Brick Veneer

Source: California Energy Commission

Some examples of various wood-framed wall assemblies, associated construction, and U-values are provided in Table 3-11.

Wood-framed floors over unconditioned space, regardless of whether there is a crawlspace, must have at least R-19 insulation installed between framing members, or the construction must have a U-factor of 0.037 or less. The equivalent U-factor is based on R-19 insulation in a 2x6, 16 inch on center wood-framed floor with a crawl space.

Other types of raised floors, except for concrete raised floors (concrete raised floors do not have a mandatory requirement but do have a prescriptive requirement) must also meet the maximum U-factor. In all cases, some areas of the floor can have a U-factor greater than the requirement as long as other areas have a U-factor that is lower than the requirement and the area-weighted average U-factor is less than that described above.

Raised slab floors with radiant heat (heated slab floors) must meet special insulation requirements that are described in Chapter 4 of this manual.

Note for Contractors/Installers: When a controlled ventilated or an unvented crawlspace is used, raised-floor insulation is not required, although a vapor retarder is required over the ground, and the foundation walls must be insulated.

The prescriptive requirements differ for concrete raised floors and wood-framed floors. While the requirements for framed floors are the same in all climate zones, the requirements for concrete raised floors differ.

Framed Raised Floors. Table 150.1-A (prescriptive requirements) call for a minimum of R-19 insulation installed between wood framing or a maximum area- weighted average U-factor of 0.037 for framed raised floors in all climate zones. The requirement may be satisfied by installing the specified amount of insulation in a wood-framed floor or by meeting an equivalent U-factor. U-factors for raised floor assemblies are listed in Reference Appendices, Joint Appendix JA4.4.

Slab Insulation Products

The mandatory requirements state that the insulation material must be suitable for the application. Insulation material in direct contact with soil, such as perimeter insulation, must have a water absorption rate no greater than 0.3 percent when tested in accordance with ASTM C272 Test Method A, 24-Hour Immersion, and a vapor permeance no greater than 2.0 perm/inch when tested in accordance with ASTM E96.

The insulation must be protected from physical and UV degradation by either installing a water-resistant protection board, extending sheet metal flashing below grade, choosing an insulation product that has a hard durable surface on one side, or by other suitable means.

The top of the insulation must be protected with a rigid material to prevent intrusion of insects into the building foundation.

A common location for the slab insulation is on the foundation perimeter (Figure 3-31). Insulation that extends downward to the top of the footing is acceptable. Otherwise, the insulation must extend downward from the level of the top of the slab, down 16 inches (40 cm) or to the frost line, whichever is greater.

For below-grade slabs, vertical insulation shall be extended from the top of the foundation wall to the bottom of the foundation (or the top of the footing) or to the frost line, whichever is greater.

Figure 3-31: Perimeter Slab Insulation

Source: California Energy Commission

Heated Slab Floor Insulation §110.8(g)

Heated slab-on-grade floors must be insulated according to the requirements in Table 110.8-A and Table 3-14.

One option is to install the insulation between the heated slab and foundation wall. In this case, insulation must extend downward to the top of the footing and then extend horizontally inward four feet toward the center of the slab. R-5 vertical insulation is required in all climates except climate zone 16, which requires R-10 of vertical insulation and R-7 horizontal insulation.

Source: California Energy Commission

Table 150.1-A of the Energy Code requires slab insulation only in climate zone 16 for unheated slabs. All heated slabs must meet mandatory insulation requirements in §110.8(g).

For unheated slabs in climate zone 16, a minimum of R-7 slab-edge insulation or a maximum U-factor of 0.58 must be achieved. The insulation must be installed to a minimum depth of 16 inches or to the bottom of the footing, whichever is less. The depth is measured from the top of the insulation, as near the top of slab as practical, to the bottom edge of the insulation. See Figure 3-32.

Figure 3-32: Allowed Slab Edge Insulation Placement

Source: California Energy Commission

Note for Contractors/Installers: Perimeter insulation is not required along the slab edge between conditioned space and the concrete slab of an attached unconditioned enclosed space such as a garage, covered porch, or covered patio. Neither would it be practical or necessary to insulate concrete steps attached to the outside slab edge.

Example 3-24: Heated Slab Insulation

Question: What are the slab edge insulation requirements for a hydronic-heating system with the hot water pipes in the slab?

Answer: The requirements for insulation of heated slabs can be found in §110.8(g) of the Energy Code and are described in Section 3.5.6.1 of this manual. The material and installation specifications are as follows:

An air barrier shall be installed enclosing the entire building. The air barrier must be installed in a continuous manner across all components of framed and nonframed envelope assemblies. The installer shall provide evidence with compliance documentation that the air barrier system meets one or more of the air barrier requirements. More detailed explanation is provided in Reference Appendices, Residential Appendix RA3.5. Documentation for the air barrier includes product data sheets and manufacturer specifications and installation guidelines.

Note for HERS Raters: For QII, a third-party HERS Rater is required to verify that the air barrier has been installed properly and is integral with the insulation being used throughout the building.

Note for Contractors/Installers: Continuous Air Barrier Requirements

A combination of interconnected materials and assemblies are joined and sealed together to provide a continuous barrier to air leakage through the building envelope separating conditioned from unconditioned space or adjoining conditioned spaces of different occupancies or uses. An air barrier must meet one of the following:

1. Using materials that have an air permeance not exceeding 0.004 cfm/ft2 under a pressure differential of 0.3 in. w.g. (1.57 psf) (0.02 L/s.m2 at 75 pa) when tested in accordance with ASTM E2178.
2. Using assemblies of materials and components that have an average air leakage not to exceed 0.04 cfm/ft² under a pressure differential of 0.3 in. w.g (1.57 psf) (0.2 L/s.m2 at 75 pa) when tested in accordance with ASTM E2357, ASTM E1677, ASTM E1680 or ASTM E283.
3. Testing the completed building and demonstrating that the air leakage rate of the building envelope does not exceed 0.40 cfm/ft2 at a pressure differential of 0.3 in w.g. (1.57 psf) (2.0 L/s.m2 at 75 pa) in accordance with ASTM E779 or an equivalent approved method.

The following materials meet the air permeance testing performance levels of 1 above. Manufacturers of these and other product types must provide a specification or product data sheet showing compliance to the ASTM testing requirements to be considered as an air barrier.

• Plywood – minimum 3/8 inch
• Oriented strand board – minimum 3/8 inches
• Extruded polystyrene insulation board – minimum 1/2 inch
• Foil-backed polyisocyanurate insulation board – minimum 1/2 inch
• Foil-backed urethane foam insulation – 1 inch
• Closed-cell spray polyurethane foam (ccSPF) with a minimum density of 2.0 pcf and a minimum thickness of 2.0 inches. Alternatively, ccSPF insulation shall be installed at a thickness that meets an air permeance no greater than 0.02 L/s-m² at 75 Pa pressure differential when tested in accordance with ASTM E2178 or ASTM E283.
• Open cell spray polyurethane (ocSPF) foam with a minimum density of 0.4 to1.5 pcf and a minimum thickness of 5½ inches. Alternatively, ocSPF insulation shall be installed at a thickness that meets an air permeance no greater than 0.02 L/s-m² at 75 Pa pressure differential when tested in accordance with ASTM E2178 or ASTM E283.
• Exterior or interior gypsum board – minimum 1/2 inch
• Cement board – minimum 1/2 inch
• Built-up roofing membrane
• Modified bituminous roof membrane
• Particleboard – minimum 1/2 inch
• Fully adhered single-ply roof membrane
• Portland cement/sand parge, or gypsum plaster – minimum 5/8 inch
• Cast-in-place and precast concrete
• Fully grouted uninsulated and insulated concrete block masonry
• Sheet steel or aluminum

Materials and assemblies of materials that can demonstrate compliance with the air barrier testing requirements must be installed according to the manufacturer's instructions, and a HERS Rater shall verify the integrity of the installation.