PIMA Energy Code Fact Sheet
Continuous Insulation Requirements
for Exterior Above-Grade Walls
ASHRAE Climate Zone 3
Introduction
Modern energy codes – defined as the 2021 International Energy Conservation Code (IECC) and the
ASHRAE 90.1-2019 Standard – include prescriptive compliance path requirements for continuous insulation
installed on exterior above-grade walls. The requirements can differ based on the wall framing construction
as well as building type and occupancy. This fact sheet presents the continuous insulation requirements for
buildings located in ASHRAE Climate Zone 3.
Minimum R-values:
Climate Zone 8
Climate Zone 7
Climate Zone 6
Climate Zone 5
Climate Zone 4
Climate Zone 3
Climate Zone 2
Climate Zone 1
Figure 1: ASHRAE Climate Zone 3 shown. For a detailed climate zone map, visit: basc.pnnl.gov/images/
climate-zone-map-iecc-2021.
R-value Tables by Building Type
The tables below include the minimum R-value requirements for code-compliant options that include
continuous insulation by building and occupancy type. The R-values listed in the columns labeled
“minimum” and “additional options” are derived from the prescriptive tables in both the 2021 IECC
and ASHRAE 90.1, as applicable. The R-values listed in the column labeled “CI only option” have been
calculated to be equivalent to – but are not – code required minimums. Where two values are listed in the
table columns, the continuous insulation value is labeled with “ci” and the other value is cavity insulation.
Note: Other code-compliant insulation options may be available. Consult the building code
requirements enforced by the authority having jurisdiction.
Table 1. Continuous Insulation Requirements for Commercial Buildings
Commercial Buildings (other than Group R Occupancy)
Climate Zone 3: 2021 IECC/ASHRAE 90.1-2019
Building Envelope (Wall) R-value Requirements
Wall Type (Above Grade)
Mass
Minimum (R-value)
Additional Option(s)
CI Only Option4
R-7.6ci1
-
-
Metal Framed
R-13 + R-7.5ci
R-13 + R-5ci
Wood Framed and Other
R-13 + R-3.8ci
-
2
3
R-13ci5
R-12ci6
Notes:
1. 2021 IECC Table C402.1.3; ASHRAE 90.1-2019 Table 5.5-3
2. 2021 IECC Table C402.1.3
3. ASHRAE 90.1-2019 Table 5.5-3
4.Both IECC and ASHRAE 90.1 allow users to calculate and use continuous insulation (CI) only options. CI only options may differ based on wall
assembly components. Examples comply with 2021 IECC maximum assembly U-factor requirements.
5.Example calculated using Foam Sheathing Committee’s Steel Frame Wall Calculator available at: www.continuousinsulation.org/steel-wallcalculator. Example wall assembly includes MCM cladding, exterior and interior gypsum sheathing (5/8”), and 3.5” steel studs 24” on center.
6.Example calculated using Foam Sheathing Committee’s Wood Frame Wall Calculator available at: www.continuousinsulation.org/wood-wallcalculator. Example wall assembly includes fiber cement cladding, exterior OSB sheathing (7/16”), wood studs 24” on center, and interior
gypsum sheathing (1/2”).
Table 2. Continuous Insulation Requirements for Group R Occupancy Buildings
Commercial Buildings (Group R Occupancy)
Climate Zone 3: 2021 IECC/ASHRAE 90.1-2019
Building Envelope (Wall) R-value Requirements
Wall Type (Above Grade)
Minimum (R-value)1
Additional Option(s)
CI Only Option2
R-9.5ci
-
-
Metal Framed
R-13 + R-7.5ci
-
R-13ci3
Wood Framed and Other
R-13 + R-3.8ci
-
R-12ci4
Mass
Notes:
1. 2021 IECC Table C402.1.3; ASHRAE 90.1-2019 Table 5.5-3
2.Both IECC and ASHRAE 90.1 allow users to calculate and use continuous insulation (CI) only options. CI only options may differ based on wall
assembly components. Examples comply with 2021 IECC maximum assembly U-factor requirements.
3.Example calculated using Foam Sheathing Committee’s Steel Frame Wall Calculator available at: www.continuousinsulation.org/steel-wallcalculator. Example wall assembly includes MCM cladding, exterior and interior gypsum sheathing (5/8”), and 3.5” steel studs 24” on center.
4.Example calculated using Foam Sheathing Committee’s Wood Frame Wall Calculator available at: www.continuousinsulation.org/wood-wallcalculator. Example wall assembly includes fiber cement cladding, exterior OSB sheathing (7/16”), wood studs 24” on center, and interior
gypsum sheathing (1/2”).
Table 3. Continuous Insulation Requirements for Residential Buildings
Residential Buildings (IRC compliant)
Climate Zone 3: 2021 IECC
Building Envelope (Wall) R-value Requirements1
Wall Type (Above Grade)
Minimum (R-value)
Additional Option
CI Only Option
Mass2
R-8 / R-13
-
-
Wood Framed
R-13 + R-5ci
R-0 + R-15ci
-
Notes:
1. 2021 IECC Table R402.1.3
2.Mass walls must comply with Section R402.2.5. The first value applies where 50% or more of the insulation is on the exterior of the mass
wall. The second value applies where more than half of the insulation is on the interior of the mass wall.
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Additional Considerations
When specifying continuous insulation for projects, building designers may need to consider other building
code and performance requirements for a particular project. Polyisocyanurate (polyiso) insulation is uniquely
suited to deliver energy-savings performance across a wide variety of project types. More information on
polyiso continuous insulation is available at: www.polyiso.org/continuousinsulation.
Fire Safety
Exterior wall assemblies for commercial buildings may be subject to building code requirements for fire
performance such as NFPA 285. Polyiso insulation is commonly specified for exterior wall assemblies that
are required to meet the acceptance criteria of NFPA 285. Building designers should consult with product
manufacturers for more detail on NFPA 285-compiant assemblies. More information on building fire safety is
available at: www.modernbuildingalliance.us/.
Air, Moisture, and Water Control
Continuous insulation products that feature closed-cell foam cores like polyiso insulation can serve as the air
and weather barrier when properly detailed and installed in accordance with the manufacturer’s installation
instruction. Additionally, continuous insulation can improve moisture management within or through the wall
assembly helping to eliminate issues associated with condensation. More information on the performance
advantages of continuous insulation is available at: www.continuousinsulation.org/applications-continuousinsulation.
Thermal Bridging
Thermal bridges created by the framing members in exterior wall assemblies can have significant negative
effects on the overall performance of the building. Using continuous insulation can mitigate these impacts
and improve performance over wall assemblies constructed with traditional cavity insulation only. More
information on thermal bridging is available at: www.continuousinsulation.org/thermal-bridging-prevention.
About PIMA
Since 1987, PIMA has served as the voice of the North American rigid polyiso insulation industry. PIMA is a leading advocate for safe,
cost-effective, sustainable, and energy-efficient construction. The Association is comprised of polyiso manufacturers and industry suppliers,
and represents the public policy interests of its membership at the local, national, and international levels to advance high-performance
building practices.
About Polyiso Insulation
Polyiso is a rigid foam insulation used in more than 70% of commercial roof construction and offers a continuous insulation solution for
commercial and residential wall assemblies. As one of North America’s most widely used and readily available building products, polyiso is a
cost-effective insulation option for reducing building energy use and improving the overall service-life of roofs and walls.
For more information on polyisocyanurate insulation, visit www.polyiso.org
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