3.3   Envelope Assembly    

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

3.3.1    Mandatory Measures

A.   Certification of Insulation Materials

The California Quality Standards for Insulating Materials, which became effective on January 1, 1982, ensure that insulation sold or installed in the state performs according to the stated R-value and meets minimum quality, health, and safety standards.

Manufacturers must certify that insulating materials comply with California Quality Standards for Insulating Materials (CCR, Title 24, Part 12, Chapters 12-13), which ensure that insulation sold in the state performs according to 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 Home Furnishing and Thermal Insulation. Builders and enforcement agencies shall use the Department of Consumer Affairs Directory of Certified Insulation Material to verify the 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 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, Reference Joint Appendix JA4, where assembly U-factors is shown for various assemblies and their individual 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 EZ Frame 2013 assembly calculator.

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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.   Insulation Placement on Roof/Ceilings

Insulation installed on the top of suspended (T-bar) ceilings with removable ceiling panels may not be used to comply with the Standards unless the installation meets the criteria described in the Exception to §110.8(e)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 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 the purposes of complying with 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 §110.8(e)3:  Insulation placed in direct contact with a suspended ceiling with removable ceiling panels shall be an acceptable method when the total combined conditioned spaces with a combined floor area is no greater than 2,000 ft² in an otherwise unconditioned building., and the average height of the space between the ceiling and the roof over these conditioned spaces is greater than 12 ft.

E.   Insulation for Demising Walls

Demising walls separating conditioned space from enclosed unconditioned space must be insulated with a minimum of R-13 insulation if the wall is a wood or metal framed assembly. This requirement applies to buildings meeting compliance under the prescriptive or performance approach. This requirement assures at least some insulation in a wall where an adjoining space may remain unconditioned indefinitely. Demising walls that are constructed of brick, concrete masonry units, or solid concrete are not required to be insulated.

F.   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 Standards. 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 perimeter of the foundation. 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 downwards to the top of the footing and then extend horizontally inwards, under the slab, a distance of 4 ft towards 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 3-19 – Perimeter slab insulation

Table 3-9 -- Slab Insulation Requirements for Heated Slab Floors

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G.   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 have an effect on 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 roof’s waterproof membrane must be multiplied by 0.8 before choosing the table column in Reference Joint Appendix JA4 for determining assembly U-factor. See the footnotes for Tables 4.2.1 through 4.2.7 in the Reference Joint Appendix JA4.

H.   Roofing Products Solar Reflectance and thermal Emittance

Roofing products be tested and labeled by the Cool Roof Rating Council (CRRC) and that liquid-applied products meet minimum standards for performance and durability per §110.8(i)4 of the Standards. Note that installing cool roofs is not a mandatory measure. However, to receive compliance credit, a roofing product’s reflectance and thermal emittance 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.

I.    Rating and Labeling

When a cool roof is installed to meet the prescriptive requirement or are used for compliance credit, the products must be tested and labeled by the Cool Roof Rating Council (CRRC) as specified in §10-113 of the Standards. 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.

Figure 3-20 – Sample CRRC Product label and information

An example of an approved CRRC product label

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

To demonstrate compliance with the 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 two kinds of solar reflectance:

1.   Initial and 3-year Aged Solar Reflectance and Thermal Emittance

All requirements of the 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. The equation below can be used to calculated the aged rated solar reflectance until the appropriate aged rated value for the reflectance is posted in the directory.

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 Standards do not distinguish between initial and aged thermal emittance, meaning that either value can be used to demonstrate compliance with the Standards. If a manufacturer fails to obtain CRRC certificate for their 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

K.   Solar Reflectance Index (SRI)

The temperature of a surface depends on the solar radiation incident, surface’s 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 the staff at Lawrence Berkeley National Laboratory, which calculates the SRI by designating the Solar Reflectance and Thermal emittance of the desired roofing material. The calculator can be found at www.energy.ca.gov. SRI calculations must be based on moderate wind velocity of 2-6 meters per second. 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 comply with an emittance lower than 0.85, as long as the aged reflectance is higher and vice versa.

L.   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 a number of liquid products, including elastomeric coatings and white acrylic coatings that qualify for Field Applied Liquid Coatings. The Standards specify minimum performance and durability requirements for field-applied liquid coatings. Please note that 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.

M.  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 top surface of the coating while it is setting, providing a shiny and reflective 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 overall envelope TDV energy 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 to. 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 application 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.

N.   Cement-Based Roof Coatings

This class of coatings consists of a layer of cement and has been used for a number of years in the central valley of California and in 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% Portland Cement and meet the requirements of ASTM D822,ASTM C1583 and ASTM D5870.

O.   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 surface 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 a number of performance and durability requirements as specified in Table 110.8-C of the Standards or the minimum performance requirements of ASTM C836, D3468, D6083, or D6694, whichever are appropriate to the coating material.

P.   Infiltration and Air leakage

All joints and other openings in the building envelope that are potential sources of air leakage must be caulked, gasketed, weather-stripped, 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 3.3.5 G).

Q.   Mandatory Insulation Requirements (Newly Constructed Buildings)

Newly constructed nonresidential, high-rise residential and hotel/motel buildings 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 below.  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 individual components making up a given assembly that meet the maximum U-factor requirement and design conditions of the envelope.

R.   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).

S.   Wall Insulation  

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

2.   Metal Framed:  Weighted average U-factor U-0.105 (R-8 continuous insulation).

3.   Light Mass Walls:  6 inches or greater Hollow Core Concrete Masonry Unit having a U-factor not to exceed 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 to exceed 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).

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

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T.   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)

U.   Mandatory Insulation Requirements (Altered Buildings)

Altered buildings must meet mandatory insulation requirements for opaque portions of the building that separate conditioned spaces from unconditioned spaces or ambient air. For alterations, different mandatory insulation requirements for the building envelope apply than for newly constructed buildings (§141.0(b)1). The weighted U-factor for each assembly type shall not exceed the values 'listed below.  Joint Appendix JA-4 of the Reference Appendices illustrates the allowed procedure for calculating U-factors.  U-factors allow greater flexibility in the design choice of individual components making up a given assembly that meet the maximum U-factor requirement and design conditions of the envelope.

V.   Wall Insulation

1.   Metal Building:  Minimum R-13 or maximum weighted average U-factor U-0.113.

2.   Metal Framed:  Minimum R-13 or maximum weighted average U-factor U-0.217.

3.   Wood Framed and Others:  Minimum R-11 or maximum weighted average U-factor U-0.110.

4.   Glass Spandrel Panels and Glass Curtain Wall:  Minimum R-4 or maximum weighted average U-factor U-0.280.

5.   Light and Heavy Mass Walls:  No minimum R-value required.

W.  Floor and Soffit Insulation

1.   Raised Framed Floors:  Minimum R-11 or maximum weighted average U-factor U-0.071.

2.   Raised Mass Floors in High-rise Residential and Hotel/Motel Guest Rooms:  Minimum R-6 or maximum weighted average U-factor U-0.111.

3.   Raised Mass Floors in other Occupancies:  No minimum R-value required.

3.3.2    Prescriptive Envelope Requirements    

The prescriptive requirements include minimum insulation levels for roofs/ceilings, walls, and floors. The requirements are expressed as a maximum U-factor. The U-factor criterion are given for different classes of construction such as wood framed, metal framed, metal building, and mass assembles. The assembly U-factor and descriptions of a particular roof/ceiling, wall or floor can be found in the appropriate tables 'listed in Reference Joint Appendix JA4 or by using the EZFrame2013 assembly calculator.  Mandatory minimum insulation levels must always be met, regardless of prescriptive insulation levels prescribed by the standards.

When an assembly of the proposed building does not precisely match one of the choices in Reference Joint Appendix JA4, choose the best match which captures:  (1) the overall type of assembly (e.g., masonry, wood frame, metal frame); and (2) an insulation level in the Reference Joint Appendix JA4 assembly which is the same or less than the proposed assembly; or use the EZFrame2013 assembly calculator.

Insulation requirements vary by climate zone and occupancy type. Table 140.3-B of the standards specifies insulation levels for nonresidential buildings, including relocatable public school buildings. Table 140.3-C of the standards specifies insulation requirements for high-rise residential buildings and hotel/motel guest rooms. Requirements for nonresidential buildings are more stringent than for high-rise residential buildings and hotel/motel guest rooms because these buildings are assumed to be heated and cooled continuously. Table 140.3-D of the standards specifies insulation levels for relocatable public school buildings where the manufacturer certifies their use in all California climate zones; these criteria are not climate dependent.

A.   Exterior Roofs and Ceilings

Under the prescriptive requirements, exterior roofs or ceilings 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 (See 3-11) The U-factor values for exterior roofs and ceilings can be derived from Reference Joint Appendix JA4 and must be used to determine compliance with the maximum assembly U-factor requirements.  Alternatively, the EZFrame2013 assembly calculator can be used to determine U-factors for assemblies and/or components not 'listed in JA4 tables.

Table 3-10 – Roof/Ceiling U-Factor Requirements

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

Figure 3-21 shows acceptable means of meeting the U-factor criteria for metal roofs. For screw down metal roofs with no thermal blocks, continuous insulation will be required to meet the U-factor requirement.

The mandatory measures prohibit insulation from being installed directly over suspended ceilings (see previous section), except for limited circumstances.

The U-factor must be selected from Reference Joint Appendix JA4.  Alternatively, the EZFrame2013 assembly calculator can be used to determine U-factors for assemblies and/or components not 'listed in JA4 tables.

Figure 3-21 – Acceptable Metal-to-Metal Roof Constructions

B.   Roofing Products (Cool Roof)

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 3-11 below. Table 3-12 is for high-rise residential buildings and hotel/motel guest rooms and Table 3-13 is for relocatable public school buildings where manufacturer certifies use in all climate zones.

Table 3-11 – Prescriptive Criteria for Roofing Products for Nonresidential Buildings

Table 3-12 – Prescriptive Criteria for Roofing Products for High-rise Residential Buildings and Guest Rooms of Hotel/Motel Buildings

Table 3-13 – 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’s Rated Product Directory, then the equation in Section 3.3.1H can be used until the aged rated value for the reflectance is posted in the directory.

There are five exceptions to the minimum prescriptive requirements for solar reflectance and thermal emittance or the SRI:

1.   Wood framed roofs in climate zones 3 and 5 are exempt if the roof assembly has a U-factor of 0.039 or lower.

2.   Metal building roofs in climate zones 3 and 5 are also exempted if the roof assembly has a U-factor 0.048 or lower.

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

4.   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 or SRI.

Where a low-sloped nonresidential roof’s aged reflectance is less than the prescribed requirement, insulation trade-offs are available. By increasing a roof’s insulation level 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 3-14 for nonresidential buildings based on roof type, climate zone and aged reflectance of less than 0.63.  

Table 3-14- (Standards Table 140.3) Roof / Ceiling Insulation Tradeoff for Aged Solar Reflectance

C.   Exterior Walls

Under the prescriptive requirements, exterior walls 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 3-15 below). The U-factor for exterior walls from Reference Joint Appendix JA4 must be used to determine compliance with the maximum assembly U-factor requirements. The Standards no longer allow using the R-value of the cavity or continuous insulation to demonstrate compliance with the insulation values of the Reference Joint Appendix JA4; only U-factors may be used to demonstrate compliance.

For metal framed walls with insulation between the framing section, continuous insulation may need to be added to meet the U-factor requirements of the 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 3-15 – 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 Joint Appendix JA4.  Alternatively, the EZFrame2013 assembly calculator can be used to determine U-factors for assemblies and/or components not 'listed in JA4 tables.

There are seven classes of wall constructions: wood frame, metal frame, metal building walls, light mass, heavy mass, furred walls, and others see (Table 3-15). The “other” category is used for any wall type that does not fit into one of the other six wall classes. The following provides additional information about each type of wall system:

1.   Wood framed walls:  As defined by the 2010 California Building Code, Type IV buildings typically have wood framed walls. Framing members typically consist of 2x4 or 2x6 framing members spaced at 24 in. or 16 in. OC. Composite framing members and engineered wood products also qualify as wood framed walls if the framing members are non-metallic. 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 Joint 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 non-combustible 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. From Reference Joint Appendix JA4, Table 4.3.3 has data for metal framed walls. 

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 buildings walls is to drape the insulation over the horizontal framing members and to compress the insulation when the metal exterior panel is installed.

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

Note:  For low- and high-mass walls the heat capacity is the amount of heat required to raise the temperature of the material by one degree F. By storing heat, materials with a high heat capacity, or thermal mass, have a tendency to dampen temperature swings throughout the day. For this reason, U-factor criteria are less stringent for mass walls than for framed construction.

6.   Furred walls:  Are a specialty wall commonly applied to a mass wall type.  See figure below.  The Reference Joint Appendix JA4 Table 4.3.5, 4.3.6 or other masonry tables list alternative walls. Additional continuous insulation layers are selected from Reference Joint Appendix JA4 Table 4.3.13 and calculated using either Equation 4-1 or 4-4 from the JA4. 

Figure 3-22 – Brick wall with furring details

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

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

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

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 Joint Appendix JA4.

D.   Demising Walls

Demising walls, separating conditioned space from enclosed unconditioned space, must be insulated with a minimum of R-13 insulation if the wall is a framed assembly. If it is not a framed assembly, then no insulation is required. This applies only to the opaque portion of the wall.

The rationale for insulating demising walls is that the space on the other side may remain unconditioned indefinitely. For example, the first tenant in a warehouse building cannot know whether the future neighbor will use the adjoining space as unheated warehouse space or as an office. This requirement assures at least some insulation in the wall.

E.   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 3-16 below. The U-factor for exterior floors and soffits from Reference Joint Appendix JA4 shall be used to determine compliance with the maximum assembly U-factor requirements. The Standards no longer allow using the R-value of the cavity or continuous insulation to demonstrate compliance with the insulation values of the Reference Joint 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 Standards.

The U-factor criteria depend on whether the floor is a mass floor or not. A mass floor is one constructed of concrete and for which the HC is greater than or equal to 7.0 Btu/°F-ft².

Table 3-16– Floor/Soffit U-Factor Requirements

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 and for which the heat capacity is 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 Joint 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 Joint Appendix JA4 is used with mass floors while Tables 4.4.1 through 4.4.5 are used for non-mass floors. See also Figure 3-25.

Figure 3-23 – Classes of Wall Constructions

Figure 3-24 – Requirements for Floor/Soffit Surfaces

Figure 3-25 – Classes of Floor Constructions

E.   Exterior Doors

The Standards provide new prescriptive requirements for exterior doors. The Standards establish U-factor requirements for swinging and non-swinging doors. A maximum U-factor of 0.70 is allowed for swinging doors. For non-swinging doors the criteria depends on the climate zone as shown in the Table 3-17 below.

When glazing area exceeds one-half of the entire door area, it is then defined as a fenestration product in the Standards, and the entire door area is modeled as a fenestration unit. 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 a part of the gross exterior wall area and must be considered when calculating the window-wall-ratio. Table 3-3 from Reference Joint Appendix JA4 has U-factors for exterior doors.

Table 3-17– Door Requirements Summary (Standards Table 140.3-B and 140.3-C)

F.   Air Barrier

Table 140.3-B of the standards specifies requirements for air barriers in climate zones 10-16.  Air barrier requirements apply to nonresidential buildings, but not relocatable public school buildings.  These requirements reduce the overall building air leakage rate in climate zones that benefit from this design measure.  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:

A.   Materials having a maximum air permeance of 0.004 cfm/ft2 (see Table 3-18 below), or

B.   Assemblies of materials and components having an average air leakage not exceeding 0.05 cfm/ft2, or

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

Table 3-18 – Materials Deemed to Comply As Air Barrier