3.2   Opaque Envelope Assembly

This section addresses the requirements for thermal control of the opaque portion of the building shell or envelope.

3.2.1    General Envelope Requirements

This section contains mandatory measures that are not specific to one envelope component.

3.2.1.1  Mandatory Requirements

A.   Certification of Insulation Materials

Manufacturers must certify that insulating materials comply with California Quality Standards for Insulating Materials, which became effective January 1, 1982. It ensures that insulation sold or installed in the state performs according to the stated R-values and meets minimum quality, health, and safety standards.

Builders may not install insulating materials, unless the product has been certified by the Department of Consumer Affairs, Bureau of Electronic and Appliance Repair, Home Furnishing and Thermal Insulation. Builders and enforcement agencies shall use the Department of Consumer Affairs Directory of Certified Insulation Materials to verify certification of the insulating material. If an insulating product is not 'listed in the most recent edition of the directory, contact the Department of Consumer Affairs, Bureau of Bureau of Electronic and Appliance Repair, Home Furnishing and Thermal Insulation Program, at (916) 999-2041 or by e-mail: HomeProducts@dca.ca.gov.

Where applicable, the R-value of cavity and/or continuous insulation, or the overall assembly U-factor, may be used to demonstrate compliance with required insulation levels. Reference insulation values are provided in the Reference Appendix JA4, where assembly U-factors are shown for various assemblies and components. U-factors represent the actual thermal conductance of the assembly, including air film coefficients, framing factors, and all layers used to construct the assembly. Assemblies not listed in JA4 tables may calculate U-factors using the assembly calculator in the public domain software, CBECC-COM.

B.   Urea Formaldehyde Foam Insulation

The mandatory measures restrict the use of urea formaldehyde foam insulation. The restrictions are intended to limit human exposure to formaldehyde, which is a volatile organic chemical known to be harmful to humans.

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 barrier must be placed in the wall construction to isolate the insulation from the interior of the space. The barrier must be 4-mil (0.1 mm) thick polyethylene or equivalent.

C.   Flame Spread Rating of Insulation

The California Quality Standards for Insulating Materials also require that all exposed installations of faced mineral fiber and mineral aggregate insulations use fire retardant facings that have been tested and certified not to exceed a flame spread of 25 and a smoke development rating of 450. Insulation facings that do not touch a ceiling, wall, floor surface, and faced batts on the underside of roofs with an air space between the ceiling and facing are considered exposed applications.

Flame spread ratings and smoke density ratings are shown on the insulation or packaging material or may be obtained from the manufacturer.

D.   Infiltration and Air Leakage

All joints and other openings in the building envelope that are potential sources of air leakage must be caulked, gasketed, weatherstripped, or otherwise sealed to limit air leakage into or out of the building. This applies to penetrations for pipes and conduits, ducts, vents, and other openings. It means that all gaps between wall panels, around doors, and other construction joints must be well sealed. Ceiling joints, lighting fixtures, plumbing openings, doors, and windows should all be considered as potential sources of unnecessary energy loss due to infiltration.

No special construction requirements are necessary for suspended (T-bar) ceilings, provided they meet the requirements of §110.8(e). Standard construction is typically adequate for meeting the infiltration/exfiltration requirements unless an air barrier is required. (See Section 3.2.1.2).

E.   Mandatory Insulation Requirements (Newly Constructed Buildings)

Newly constructed nonresidential and high-rise residential buildings and hotels/motels must meet mandatory insulation requirements for opaque portions of the building that separate conditioned spaces from unconditioned spaces or ambient air. The U-factor for each assembly type shall not exceed the values listed in Table 3-2. Determining the total weight-averaged U-factor is allowed for all assembly types except for light and heavy mass walls. Joint Appendix JA-4 of the Reference Appendices illustrates the allowed procedure for calculating U-factors. The representative constructions that meet these requirements are shown in parentheses. U-factors allow greater flexibility in the design choice of components making up a given assembly that meet the maximum U-factor requirement and design conditions of the envelope.

An exception is specified that exempts buildings designed as data centers with high, constant server loads from the mandatory minimum requirements. To qualify for this exception, it should have a design computer room process load of 750 kW or greater.

3.2.1.2  Prescriptive Requirements

A.      Air Barrier

Table cB of the Energy Standards specifies requirements for air barriers in nonresidential buildings. Air barrier requirements apply to nonresidential buildings, but not relocatable public school buildings, and are effectively mandatory requirements, since they cannot be traded off in the performance approach. These requirements reduce the overall building air leakage rate. The reduction in air leakage can be met with a continuous air barrier that seals all joints and openings in the building envelope and is composed of one of the following:

1.       Materials having a maximum air permeance of 0.004 cfm/ft2 (see Table 3-1 below).

2.       Assemblies of materials and components having an average air leakage not exceeding 0.04 cfm/ft2.

3.       An entire building having an air leakage rate not exceeding 0.40 cfm/ft².

The air leakage requirements stipulated in §140.3 must be met, either by demonstrating that component air leakage or whole-building air leakage of 0.4 cfm/ft2 is not exceeded. This requirement must be met regardless of the compliance path chosen, so it is effectively mandatory.

Table 3-1: Materials Deemed to Comply As Air Barrier

3.2.2    Roofs

3.2.2.1  Mandatory Measures

A.      Roof/Ceiling Insulation

1.       Metal Building: Weighted average U-factor of U-0.098 (R-19 screw down roof, no thermal blocks).

2.       Wood-Framed and Others: Weighted average U-factor of U-0.075 (2x4 rafter, R-19 insulation).

B.      Insulation Placement on Roof/Ceilings

Insulation installed on top of suspended (T-bar) ceilings with removable ceiling panels may not be used to comply with the Energy Standards unless the installation meets the criteria described in the Exception to §120.7(a)3 below. Insulation may be installed in this location for other purposes such as for sound control, but it will have no value in terms of meeting roof/ceiling insulation requirements of the Energy Standards.

Acceptable insulation installations include placing the insulation in direct contact with a continuous roof or ceiling that is sealed to limit infiltration and exfiltration as specified in §110.7, including, but not limited to, placing insulation either above or below the roof deck or on top of a drywall ceiling.

When insulation is installed at the roof in nonresidential buildings, the space between the ceiling and the roof is considered to be either directly or indirectly conditioned space. Therefore, this space must not include fixed vents or openings to the outdoors or to unconditioned spaces. This space is not considered an attic for complying with California Building Code (CBC) attic ventilation requirements. Vents that do not penetrate the roof deck and that are designed for wind resistance for roof membranes are acceptable.

Exception to §120.7(a)3: When there are conditioned spaces with a combined floor area no greater than 2,000 square feet in an otherwise unconditioned building, and when the average height of the space between the ceiling and the roof over these spaces is greater than 12 feet, insulation placed in direct contact with a suspended ceiling with removable ceiling panels shall be an acceptable method of reducing heat loss from a conditioned space and shall be accounted for in heat loss calculations.

C.      Wet Insulation Systems

Wet insulation systems are roofing systems where the insulation is installed above the roof’s waterproof membrane. 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 before choosing the table column in Reference Appendix JA4 for determining assembly U-factor. See the footnotes in the Reference Appendix JA4 for Tables 4.2.1 through 4.2.7.

D.      Roofing Products: Solar Reflectance and Thermal Emittance

Roofing products must be tested and labeled by the Cool Roof Rating Council (CRRC), and liquid-applied products must meet minimum standards for performance and durability per §110.8(i)4. Installing cool roofs is not a mandatory measure. However, to receive credit for product performance, the reflectance and thermal emittance of a roofing product must be tested and certified according to CRRC procedures. If a CRRC rating is not obtained for roofing products, default values for reflectance and emittance must be used.

1.       Rating and Labeling

When a cool roof is installed to meet the prescriptive requirement or when it is used for compliance credit, the products must be tested and labeled by the CRRC as specified in §10-113. The CRRC is the supervisory entity responsible for certifying cool roof products. The CRRC test procedure is documented in CRRC-1, the CRRC Product Rating Program Manual. This test procedure includes tests for both solar reflectance and thermal emittance. See Figure 3-2 for an example of an approved CRRC product label.

Figure 3-2: Sample CRRC Product Label and Information

2.       Solar Reflectance, Thermal Emittance, and Solar Reflectance Index (SRI)

To demonstrate compliance with the Energy Standards, all cool roofing products must be certified and labeled according to CRRC procedures. The CRRC certification includes solar reflectance and thermal emittance. There are three kinds of solar reflectance listed in the CRRC’s Rated Product Directory:

1. Initial solar reflectance.

2. 3-year aged solar reflectance.

3. Accelerated aged solar reflectance.

All requirements of the Energy Standards are based on the 3-year aged solar reflectance. However, if the aged value for the reflectance is not available in the CRRC’s Rated Product Directory, then the aged value shall be derived from the CRRC initial value or an accelerated testing process. Until the appropriate aged rated value for the reflectance is posted in the directory, the equation below can be used to calculate the aged rated solar reflectance or a new method of testing is used to find the accelerated solar reflectance.

Aged Reflectance_calculated=(0.2+ β[ρ_initial – 0.2])

Where,

ρ_initial = Initial Reflectance listed in the CRRC Rated Product Directory

β= 0.65 for Field Applied Coating, or 0.70 for Not a Field-Applied Coating

The Energy Standards do not distinguish between initial and aged thermal emittance, meaning that either value can be used to demonstrate compliance with the Energy Standards. If a manufacturer fails to obtain CRRC certificate for its roofing products, the following default aged solar reflectance and thermal emittance values must be used for compliance:

a.       For asphalt shingles, 0.08/0.75.

b.       For all other roofing products, 0.10/0.75.

The temperature of a surface depends on the solar radiation incident, surface reflectance, and emittance. The SRI measures the relative steady-state surface temperature of a surface with respect to standard white (SRI=100) and standard black (SRI=0) under the standard solar and ambient condition. A calculator has been produced by Lawrence Berkeley National Laboratory that calculates the SRI by designating the solar reflectance and thermal emittance of the desired roofing material. The calculator can be found at http://www.energy.ca.gov/title24/2016standards/documents/solar_reflectance/. To calculate the SRI, the 3-year aged value of the roofing product must be used. By using the SRI calculator, a cool roof may prescriptively comply with an emittance lower than 0.85, as long as the aged solar reflectance is higher or a lower aged solar reflectance with a much higher than 0.85 emittance.

3.       Field-Applied Liquid Coatings

Liquid roof coatings applied to low-sloped roofs in the field as the top surface of a roof covering shall comply with the following mandatory requirements and descriptions. There are several liquid products, including elastomeric coatings and white acrylic coatings that qualify for field-applied liquid coatings. The Energy Standards specify minimum performance and durability requirements for field-applied liquid coatings in Table 110.8-C. These requirements do not apply to industrial coatings that are factory-applied, such as metal roof panels. The requirements address elongation, tensile strength, permeance, and accelerated weathering. The requirements depend on the type of coating and are described in greater detail below.

a.       Aluminum-Pigmented Asphalt Roof Coatings

Aluminum-pigmented coatings are silver-colored coatings that are commonly applied to modified bitumen and other roofing products. The coating has aluminum pigments that float to the surface of the coating and provides a shiny, surface. Because of the shiny surface and the physical properties of aluminum, these coatings have a thermal emittance below 0.75, which is the minimum rating for prescriptive compliance. The performance approach is typically used to achieve compliance with these coatings.

This class of field-applied liquid coatings shall be applied across the entire surface of the roof and meet the dry mil thickness or coverage recommended by the coating manufacturer, taking into consideration the substrate on which the coating will be applied. Also, the aluminum-pigmented asphalt roof coatings shall be manufactured in accordance with ASTM D2824. Standard specification is also required for aluminum-pigmented asphalt roof coatings, nonfibered, asbestos-fibered, and fibered without asbestos that are suitable for applying to roofing or masonry surfaces by brush or spray. Use ASTM D6848, Standard Specification for Aluminum Pigmented Emulsified Asphalt used as a Protective Coating for Roofing, installed in accordance with ASTM D3805, Standard Guide for Application of Aluminum-Pigmented Asphalt Roof Coatings.

b.       Cement-Based Roof Coatings

This class of coatings consists of a layer of cement and has been used for a number of years in California’s Central Valley and other regions. These coatings may be applied to almost any type of roofing product. Cement-based coatings shall be applied across the entire roof surface to meet the dry mil thickness or coverage recommended by the manufacturer. Also, cement-based coatings shall be manufactured to contain no less than 20 percent Portland cement and meet the requirements of ASTM D822, ASTM C1583, and ASTM D5870.

c.       Other Field-Applied Liquid Coatings

Other field-applied liquid coatings include elastomeric and acrylic-based coatings. These coatings must be applied across the entire surface of the roof to meet the dry mil thickness or coverage recommended by the coating manufacturer, taking into consideration the substrate on which the coating will be applied. The field-applied liquid coatings must be tested to meet performance and durability requirements as specified in Table 110.8-C of the Energy Standards or the minimum performance requirements of ASTM C836, D3468, D6083, or D6694, whichever are appropriate to the coating material.

3.2.2.2  Prescriptive Measures

A.   Insulation Requirements − Exterior Roofs and Ceilings

Under the prescriptive requirements, roofs or ceilings must have an assembly U-factor equal to or lower than the U-factor criterion for nonresidential or high-rise residential buildings. (See Table 3-2The U-factor values for exterior roofs and ceilings from Reference Appendix JA4 must be used to determine compliance with the maximum assembly U-factor requirements.  Alternatively, the assembly calculator that is incorporated into CBECC-COM, the public domain program, can be used to determine U-factors for assemblies and/or components not listed in JA4 tables.

The metal building roof prescriptive requirement has been updated in the 2016 Energy Standards to require a filled cavity insulation technique for improved performance. In the past, a common technique for standing seam metal roofs is to drape a layer of insulation over the purlins, using thermal blocks where the insulation is compressed at the supports. (See Figure 3-3.)

Table 3-2: Roof/Ceiling U-Factor Requirements

Summary of Tables 140.3-B, 140.3-C, and 140.3-D of the Energy Standards

Figure 3-3 – Standing Seam Metal Building Roof With Single Insulation Layer

Source: North American Insulation Manufacturers Association (NAIMA)

Recent studies show that the thermal performance of this assembly is not as good as estimated. Therefore, there are significant benefits to using the “filled cavity” approach, shown below.

Figure 3-3A – Filled Cavity Insulation for Metal Building Roofs

Source: North American Insulation Manufacturers Association (NAIMA)

A rigid polyisoyanurate (“polyiso”) thermal block with a minimum R-value of R-3.5 should be installed at the supports (a 1-inch-thick thermal block is recommended). The first rated R-value of the insulation is for faced insulation installed between the purlins. The second rated R-value of insulation represents unfaced insulation installed above the first layer, perpendicular to the purlins and compressed when the metal roof panels are attached. A supporting structure retains the bottom of the first layer at the prescribed depth required for the full thickness of insulation.

The bottom layer of insulation should completely fill the space between the purlins, and the support bands should be installed tightly to prevent the insulation from sagging.

The configuration above, which corresponds to two layers of R-19 and R-10 insulation, corresponds to the prescriptive requirement of U-0.041, but other insulation combinations exceeding the minimum requirement are readily achievable.

B.   Thermal Emittance and Solar Reflectance

The prescriptive requirements call for roofing products to meet the solar reflectance and thermal emittance in both low-sloped and steep-sloped roof applications for nonresidential buildings. A qualifying roofing product under the prescriptive approach for a nonresidential building must have an aged solar reflectance and thermal emittance greater than or equal to that the values indicated in Table 3-3 below. Table 3-4 is for high-rise residential buildings and hotel/motel guest rooms, and Table 3-5 is for relocatable public school buildings where the manufacturer certifies use in all climate zones.

Table 3-3: Prescriptive Criteria for Roofing Products for Nonresidential Buildings

Energy Standards Table 140.3-B

Table 3-4: Prescriptive Criteria for Roofing Products for
High-Rise Residential Buildings and Guest Rooms of Hotel/Motel Buildings
(Energy Standards Table 140.3-C)

Energy Standards Table 140.3-C

Table 3-5: Prescriptive Criteria for Roofing Products for Relocatable Public School Buildings, Where Manufacturer Certifies Use in All Climate Zones

If the aged value for the solar reflectance is not available in the CRRC Rated Product Directory, then the equation in Section 3.2.2.1D (Aged Reflectance_calculated=(0.2+ β[ρ_initial – 0.2])) can be used until the aged rated value for the reflectance is posted in the directory.

There are three exceptions to the minimum prescriptive requirements for solar reflectance and thermal emittance:

1.    Roof area covered by building-integrated photovoltaic panels and building-integrated solar thermal panels is not required to meet the cool roof requirements.

2.    If the roof construction has a thermal mass like gravel, concrete pavers, stone, or other materials with a weight of at least 25 lb/ft² over the roof membrane, then it is exempt from the above requirements for solar reflectance and thermal emittance.

3.    Wood-framed roofs in climate zones 3 and 5 with a U- factor of 0.034 are exempt from the low-sloped cool roof requirement.

Where a low-sloped nonresidential roof’s aged reflectance is less than the prescribed requirement, insulation tradeoffs are available. By increasing the insulation level of a roof, a roofing product with a lower reflectance than the prescriptive requirements can be used to meet the cool roof requirements. The appropriate U-factor can be determined from Table 3-6 for nonresidential buildings based on roof type, climate zone and aged reflectance of at least 0.25.

Table 3-6: Roof/Ceiling Insulation Tradeoff for Aged Solar Reflectance

Energy Standards Table 140.3

3.2.2.3  Performance Approach – Compliance Options

The compliance options process allows the Energy Commission to review and gather public input regarding the merits of new compliance techniques, products, materials, designs, or procedures to demonstrate compliance for newly constructed buildings and additions and alterations to existing buildings.

A.   Aggregate Default Roof Reflectance Properties

Some low-sloped roofs of nonresidential buildings use aggregate material made of gravel or crushed stone that is 3/4" or smaller, as the surface layer under a ballasted roof. Such roofing cannot be accurately tested via CRRC procedures because some of the aggregate can become damaged in transit, affecting the performance.

The Energy Commission has stipulated aged reflectance and emittance values that can be used for these types of products that have been tested via ASTM procedures. The default reflectance and emittance values may be used below in the performance compliance approach or prescriptive tradeoff with increased insulation (Table 140.3 of the Energy Standards).

Table 3-7: Default Solar Reflectance on Thermal Emittance
for Aggregate Materials Based on Size

For example, aggregate with size 2-4 meeting the requirements must have a tested solar reflectance of at least 0.45 to use a default aged reflectance value of 0.40 in the performance method.

Eligibility criteria for aggregate used as the surface layer of low-sloped roofs:

1. Aggregate shall have a tested initial solar reflectance that meets or exceeds 0.50 for built-up roofs and 0.45 for ballasted roofs using the ASTM E1918 test procedure conducted by an independent laboratory meeting the requirement of §10-113(d)4

2. Aggregate shall have a label on bags or containers of the aggregate material stating

(a) the tested initial solar reflectance of the material conforming to ASTM D1863, and (b) the size of the material conforming to ASTM D448.

3.2.3    Exterior Walls

3.2.3.1  Mandatory Requirements

A.   Wall Insulation 

1.    Metal Building:  Weighted average U-factor of U-0.113 (single layer of R-13 batt insulation).

2.    Metal-Framed: Weighted average U-factor of U-0.151 (R-8 continuous insulation, or R-13 batt insulation between studs and 1/2” of continuous rigid insulation of R-2). It may be possible to meet the area-weighted average U-factor without continuous insulation, if the appropriate siding materials are used.

3.    Light Mass Walls: 6 inches or greater hollow core concrete masonry unit having a U-factor not exceeding 0.440 (partially grouted with insulated cells).

4.    Heavy Mass Walls: 8 inches or greater hollow core concrete masonry unit having a U-factor not exceeding 0.690 (solid grout concrete, normal weight, 125 lb/ft3).

5.    Wood-Framed and Others: Weighted average U-factor of U-0.110 (R-11 batt insulation).

6.    Glass Spandrel Panels and Glass Curtain Wall: Weighted average U-factor of U-0.280.

Exception: Buildings designed as data centers with high, constant server loads from the mandatory minimum requirements are exempt. To qualify for this exception, it should have a design computer room process load of 750 kW or greater.

3.2.3.2  Prescriptive Requirements

Under the prescriptive requirements, exterior walls must have an assembly U-factor equal to or lower than the U-factor criterion for nonresidential and high-rise residential buildings in Table 3-8.

The U-factor for exterior walls from Reference Appendix JA4 must be used to determine compliance with the assembly U-factor requirements. The Energy Standards no longer allow using the R-value of the cavity or continuous insulation alone to demonstrate compliance with the insulation values of Reference Appendix JA4; only U-factors may be used to demonstrate compliance.

For metal-framed walls with insulation between the framing sections, continuous insulation may need to be added to meet the U-factor requirements of the Energy Standards. For light mass walls, insulation is not required for buildings in South Coast climates but is required for other climates. For heavy mass walls, insulation is not required for buildings in Central Coast or South Coast climates but is required for other climates.

Table 3-8: Wall U-Factor Requirements

The U-factor criteria for walls depend on the class of construction. U-factors used for compliance must be selected from Reference Appendix JA4.  Alternatively, the assembly calculator that is incorporated into CBECC-COM can be used to determine U-factors for assemblies and/or components not listed in JA4 tables.

There are five classes of wall constructions: wood-framed, metal-framed, metal building walls, light mass, and heavy mass. The following provides additional information about each type of wall system:

1.  Wood-framed walls: As defined by the 2013 California Building Code, Type IV buildings typically have wood-framed walls. Framing members typically consist of 2x4 or 2x6 framing members spaced at 24 inch or 16 inch OC. Composite framing members and engineered wood products also qualify as wood framed walls if the framing members are nonmetallic. Structurally insulated panels (SIPs) are another construction type that qualifies as wood-framed. SIPs panels typically consist of rigid foam insulation sandwiched between two layers of oriented strand board (OSB). Reference Appendix JA4, Table 4.3.1 has data for conventional wood-framed walls, and Table 4.3.2 has data for SIPs panels.

2.  Metal-framed walls: Many nonresidential buildings and high-rise residential buildings require noncombustible construction, and this is achieved with metal-framed walls. Often metal-framed walls are not structural and are used as infill panels in rigid framed steel or concrete buildings. Batt insulation is less effective for metal-framed walls (compared to wood-framed walls) because the metal framing members are more conductive. In most cases, continuous insulation is required to meet prescriptive U-factor requirements. Reference Appendix JA4, Table 4.3.3, has data for metal-framed walls. 

For 2016, the continuous insulation requirements for steel-framed walls have increased for climate zones 1, 6, and 7. Two inches of rigid polyisocyanurate insulation (with no cavity insulation) will meet the new requirement.

3.  Metal building walls: Metal building walls consist of a metal building skin that is directly attached to metal framing members. The framing members are typically positioned in a horizontal direction and spaced at about 4 ft. A typical method of insulating metal building walls is to drape the insulation over the horizontal framing members and to compress the insulation when the metal exterior panel is installed.

4.  Light-mass walls: Light-mass walls have a heat capacity (HC) greater or equal to 7.0 but less than 15.0 Btu/°F-ft². See the definition below for heat capacity. From Reference Appendix JA4, Tables 4.3.5 and 4.3.6 have U-factor, C-factor, and heat capacity data for hollow unit masonry walls, solid unit masonry and concrete walls, and concrete sandwich panels.

5.  Heavy-mass walls: Have an HC equal to or greater than 15.0 Btu/°F-ft². See Reference Appendix JA4 for HC data on mass walls.

Note: For light- and high-mass walls, heat capacity (HC) is the amount of heat required to raise the temperature of the material by 1 degree F. In the Energy Standards, it is defined as the product of the density (lb/ft3), specific heat (Btu/lb-F), and wall thickness (ft). For instance, a 6” medium weight concrete hollow unit masonry wall has a heat capacity of 11.4 and is considered a light mass wall. The same masonry wall with solid grout that is 10 inches thick has a heat capacity of 19.7 and is considered a heavy mass wall.

6.  Furred walls: Are a specialty wall component, commonly applied to a mass wall type.  See Figure 3-4 below. The Reference Appendix JA4 Table 4.3.5, 4.3.6, or other masonry tables list alternative walls. Additional continuous insulation layers are selected from Reference Appendix JA4 Table 4.3.13 and calculated using either Equation 4-1 or 4-4 from the JA4. The effective R-value of the furred component depends upon the framing thickness, type, and insulation level.

Figure 3-4: Brick Wall With Furring Details

7.  Spandrel panels and glass curtain walls: These wall types consist of metalized or glass panels often hung outside structural framing to create exterior wall elements around fenestration and between floors. See Reference Appendix JA4, Table 4.3.8 for U-factor data.

8.  Continuous insulation: For some climate zones, mass walls and metal-framed walls require continuous insulation to meet the prescriptive U-factor requirements. When this is the case, the effect of the continuous insulation is estimated by Equation 4-1 in Reference Appendix JA4.

U_prop = 1 / [ (1/U_col,A) + R_cont,insul]

Figure 3-5: Classes of Wall Construction

Framed or block walls can also have insulation installed between interior or exterior furring strips. The effective continuous R-value of the furring/insulation layer is shown in Table 4.3.13 of Reference Appendix JA4.

3.2.4    Demising Walls

3.2.4.1  Mandatory Insulation for Demising Walls

Demising walls separate conditioned space from enclosed unconditioned space. The insulation requirements include:

•    Wood-framed: minimum of R-13 insulation (or have an equivalent U-factor of 0.099) between framing members.

•    Metal-framed: minimum R-13 insulation (or a U-factor no greater than 0.151) between framing members plus R-2 continuous insulation.

•    If it is not a framed assembly (constructed of brick, concrete masonry units, or solid concrete), then no insulation is required.

This requirement applies to buildings meeting compliance with either the prescriptive or performance approach.

3.2.5    Doors

3.2.5.1  Mandatory Requirements

Manufactured exterior doors shall have an air infiltration rate not exceeding:

•    0.3 cfm/ft2 of door area for nonresidential single doors (swinging and sliding).

•    1.0 cfm/ft2 of door area for nonresidential double doors (swinging).

3.2.5.2  Prescriptive Requirements

The Energy Standards define prescriptive requirements for exterior doors in Tables 140.3-B and 140.3-C. For swinging doors, the maximum U-factor is 0.70, and for nonswinging doors, the maximum allowed U-factor is 1.45 in Climate Zones 2 through 15 and 0.50 in Climate Zones 1 and 16. (See Table 3-9)

The swinging door requirement corresponds to uninsulated double-layer metal swinging doors. The 1.45 swinging door U-factor requirement corresponds to insulated single-layer metal doors or uninsulated single-layer metal roll-up doors and fire-rated doors. The 0.50 U-factor requirement for Climate Zones 1 and 16 corresponds to wood doors with a minimum nominal thickness of 1 ¾ inches. For more information, consult Reference Appendix JA4, Table 4.5.1.

When glazing area exceeds one-half of the entire door area, it is then defined as a fenestration product in the Energy Standards, and the entire door area is modeled as a fenestration unit. (See Section 3.3.2.) If the glazing area is less than half the door area, the glazing must be modeled as the glass area plus 2 inches in each direction of the opaque door surface (to account for a frame). However, exterior doors are part of the gross exterior wall area and must be considered when calculating the window-wall-ratio. 

Table 3-9: Door Requirements Summary

Energy Standards Table 140.3-B, 140.3-C, and 140.3-D

3.2.6    Floors

3.2.6.1  Mandatory Requirements

A.   Insulation Requirements for Heated Slab Floors

Heated slab-on-grade floors must be insulated according to the requirements in Table 110.8-A of the Energy Standards (Table 3-10). The top of the insulation must be protected with a rigid shield to prevent intrusion of insects into the building foundation, and the insulation must be capable of withstanding water intrusion.

A common location for the slab insulation is on the foundation perimeter. 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.

Another option is to install the insulation inside the foundation wall and between the heated slab. In this case insulation must extend downward to the top of the footing and then extend horizontally inward, under the slab, a distance of 4 ft 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.

Figure 3-6: Perimeter Slab Insulation

Table 3-10: Slab Insulation Requirements for Heated Slab Floors

Energy Standards Table 110.8-A

B.     Floor and Soffit Insulation

1.  Raised Mass Floors: A minimum of 3 inches of lightweight concrete over a metal deck or the weighted average U-factor of the floor assembly shall not exceed U-0.269.

2.  Other Floors:  Weighted average U-factor of U-0.071.

3.  Heated Slab Floor: A heated slab floor shall be insulated to meet the requirements of §110.8(g). See Section 3.2.6.1A above for more information.

3.2.6.2  Prescriptive Requirements

A.     Exterior Floors and Soffits

Under the prescriptive requirements, exterior floors and insulated soffits must have an assembly U-factor equal to or lower than the U-factor criterion for nonresidential, high-rise residential buildings and relocatable public school buildings in Table 3-11 below. The U-factor for exterior floors and soffits from Reference Appendix JA4 shall be used to determine compliance with the maximum assembly U-factor requirements. The Energy Standards no longer allow using the R-value of the cavity or continuous insulation to demonstrate compliance with the insulation values of the Reference Appendix JA4; only U-factors may be used to demonstrate compliance. For metal-framed floors, batt insulation between framing section may need continuous insulation to be modeled and installed on the interior or exterior to meet the U-factor requirements of the Energy Standards.

Table 3-11: Floor/Soffit U-Factor Requirements

Summary from Energy Standards Tables 140.3-B, 140.3-C, and 140.3-D

The U-factor criteria for concrete raised floors depend on whether the floor is a mass floor or not. A mass floor is one constructed of concrete with a heat capacity (HC) greater than or equal to 7.0 Btu/°F-ft².

Insulation levels for nonresidential concrete raised floors with HC ≥ 7.0 using
U-factor for compliance, from Reference Appendix JA4, Table 4.4.6, are equivalent to no insulation in Climate Zones 3-10 and associated U-factors to continuous insulation of R-8 in Climate Zones 1, 2, 11 through 15; and R-15 in Climate Zone 16.

To determine the U-factor insulation levels for high-rise residential concrete raised floors, use the U-factors that are associated with R-8 continuous insulation in Climate Zones 7 through 9; R-15 in Climate Zones 3-5 and 11-13; with additional insulation required in the desert and mountain Climate Zones 1, 2, 14 and 16.

Table 4.4.6 from Reference Appendix JA4 is used with mass floors while Tables 4.4.1 through 4.4.5 are used for nonmass floors. (See Figure 3-8.)

Figure 3-7: Requirements for Floor/Soffit Surfaces

Figure 3-8: Classes of Floor Constructions