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Building thermal envelope opaque assemblies shall comply with the requirements of Sections C402.2 and C402.4 based on the climate zone specified in Chapter 3. For opaque portions of the building thermal envelope intended to comply on an insulation component R-value basis, the R-values for cavity insulation and continuous insulation shall be not less than that specified in Table C402.1.3. Where cavity insulation is installed in multiple layers, the cavity insulation R-values shall be summed to determine compliance with the cavity insulation R-value requirements. Where continuous insulation is installed in multiple layers, the continuous insulation R-values shall be summed to determine compliance with the continuous insulation R-value requirements. Cavity insulation R-values shall not be used to determine compliance with the continuous insulation R-value requirements in Table C402.1.3. Commercial buildings or portions of commercial buildings enclosing Group R occupancies shall use the R-values from the "Group R" column of Table C402.1.3. Commercial buildings or portions of commercial buildings enclosing occupancies other than Group R shall use the R-values from the "All other" column of Table C402.1.3.
TABLE C402.1.3
OPAQUE THERMAL ENVELOPE INSULATION COMPONENT MINIMUM REQUIREMENTS, R-VALUE METHODa
CLIMATE ZONE 0 AND 1 2 3 4 EXCEPT MARINE 5 AND MARINE 4 6 7 8
All other Group R All other Group R All other Group R All other Group R All other Group R All other Group R All other Group R All other Group R
Roofs
Insulation entirely
above roof deck
R-20ci R-25ci R-25ci R-25ci R-25ci R-25ci R-30ci R-30ci R-30ci R-30ci R-30ci R-30ci R-35ci R-35ci R-35ci R-35ci
Metal buildingsb R-19 +
R-11 LS
R-19 +
R-11 LS
R-19 +
R11 LS
R-19 +
R-11 LS
R-19 +
R-11 LS
R-19 +
R-11 LS
R-19 +
R-11 LS
R-19 +
R-11 LS
R-19 +
R-11 LS
R-19 +
R-11 LS
R-25 +
R-11 LS
R-30 + R-11 LS R-30 +
R-11 LS
R-30 +
R-11 LS
R-25 + R-11 + R-11 LS R-25 + R-11 + R-11 LS
Attic and other R-38 R-38 R-38 R-38 R-38 R-38 R-49 R-49 R-49 R-49 R-49 R-49 R-60 R-60 R-60 R-60
Walls, above grade
Massf R-5.7cic R-5.7cic R-5.7cic R-7.6ci R-7.6ci R-9.5ci R-9.5ci R-11.4ci R-11.4ci R-13.3ci R-13.3ci R-15.2ci R-15.2ci R-15.2ci R-25ci R-25ci
Metal building R-13 +
R-6.5ci
R-13 +
R-6.5ci
R13 +
R-6.5ci
R-13 +
R-13ci
R-13 +
R-6.5ci
R-13 +
R-13ci
R-13 +
R-13ci
R-13 + R-14ci R-13 + R-14ci R-13 + R-14ci R-13 + R-14ci R-13 + R-14ci R-13 + R-17ci R-13 +
R-19.5ci
R-13 + R-19.5ci R-13 +
R-19.5ci
Metal framed R-13 +
R-5ci
R-13 +
R-5ci
R-13 +
R-5ci
R-13 +
R-7.5ci
R-13 +
R-7.5ci
R-13 +
R-7.5ci
R-13 +
R-7.5ci
R-13 +
R-7.5ci
R-13 + R-10ci R-13 + R-10ci R-13 + R-12.5ci R-13 + R-12.5ci R-13 + R-12.5ci R-13 +
R-15.6ci
R-13 + R-18.8ci R-13 + R-18.8ci
Wood framed and
other
R-13 +
R-3.8ci or
R-20
R-13 +
R-3.8ci or
R-20
R-13 +
R-3.8ci or
R-20
R-13 +
R-3.8ci or
R-20
R-13 +
R-3.8ci or
R-20
R-13 +
R-3.8ci or
R-20
R-13 +
R-3.8ci or
R-20
R-13 +
R-3.8ci or
R-20
R-13 + R-7.5ci or R20 + R3.8ci
R-13 +
R-7.5ci or
R-20 +
R-3.8ci
R-13 +
R-7.5ci or
R-20 +
R-3.8ci
R-13 +
R-7.5ci or
R-20 +
R-3.8ci
R-13 +
R-7.5ci or
R-20 +
R-3.8ci
R-13 +
R-7.5ci or
R-20 +
R-3.8ci
R-13 + R-18.8ci R-13 + R-18.8ci
Walls, below grade
Below-grade walld NR NR NR NR NR NR R-7.5ci R-10ci R-7.5ci R-10ci R-10ci R-15ci R-15ci R-15ci R-15ci R-15ci
Floors
Masse NR NR R-6.3ci R-8.3ci R-10ci R-10ci R-14.6ci R-16.7ci R-14.6ci R-16.7ci R-16.7ci R-16.7ci R-20.9ci R-20.9ci R-23ci R-23ci
Joist/framing R-13 R-13 R-30 R-30 R-30 R-30 R-30 R-30 R-30 R-30 R-38 R-38 R-38 R-38 R-38 R-38
Slab-on-grade floors
Unheated slabs NR NR NR NR NR R-10 for 24" below
R-15 for 24" below
R-15 for 24" below
R-15 for 24" below
R-20 for 24" below
R-20 for 24" below
R-20 for 48" below
R-20 for 24" below
R-20 for 48" below
R-20 for 48" below
R-25 for 48" below
Heated slabsg R-7.5 for
12" below
+ R-5 full slab
R-7.5 for
12" below
+ R-5 full slab
R-7.5 for
12" below
+ R-5 full slab
R-7.5 for
12" below
+ R-5 full slab
R-10 for
24" below
+ R-5 full slab
R-10 for
24" below
+ R-5 full slab
R-15 for
24" below
+ R-5 full slab
R-15 for
24" below
+ R-5 full slab
R-15 for
36" below
+ R-5 full slab
R-15 for
36" below
+ R-5 full slab
R-15 for
36" below
+ R-5 full slab
R-20 for
48" below
+ R-5 full slab
R-20 for
48" below
+ R-5 full slab
R-20 for
48" below
+ R-5 full slab
R-20 for
48" below
+ R-5 full slab
R-20 for
48" below
+ R-5 full slab
For SI: 1 inch = 25.4 mm, 1 pound per square foot = 4.88 kg/m2, 1 pound per cubic foot = 16 kg/m3.
ci = Continuous Insulation, NR = No Requirement, LS = Liner System.
  1. Assembly descriptions can be found in ANSI/ASHRAE/IESNA 90.1 Appendix A.
  2. Where using R-value compliance method, a thermal spacer block shall be provided, otherwise use the U-factor compliance method in Table C402.1.4.
  3. R-5.7ci is allowed to be substituted with concrete block walls complying with ASTM C90, ungrouted or partially grouted at 32 inches or less on center vertically and 48 inches or less on center horizontally, with ungrouted cores filled with materials having a maximum thermal conductivity of 0.44 Btu-in/h-f2 °F.
  4. Where heated slabs are below grade, below-grade walls shall comply with the exterior insulation requirements for heated slabs.
  5. "Mass floors" shall be in accordance with Section C402.2.3.
  6. "Mass walls" shall be in accordance with Section C402.2.2.
  7. The first value is for perimeter insulation and the second value is for full, under-slab insulation. Perimeter insulation is not required to extend below the bottom of the slab.

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