// CODE SNIPPET
C402.1.4 Assembly U-factor, C-Factor or F-Factor-Based Method
JUMP TO FULL CODE CHAPTER
(Equation 4-1)
Building thermal envelope opaque assemblies shall meet the requirements of Sections C402.2 and C402.4 based on the climate zone specified in Chapter 3. Building thermal envelope opaque assemblies intended to comply on an assembly U-, C- or F-factor basis shall have a U-, C- or F-factor not greater than that specified in Table C402.1.4. Commercial buildings or portions of commercial buildings enclosing Group R occupancies shall use the U-, C- or F-factor from the "Group R" column of Table C402.1.4. Commercial buildings or portions of commercial buildings enclosing occupancies other than Group R shall use the U-, C- or F-factor from the "All other" column of Table C402.1.4
OPAQUE THERMAL ENVELOPE ASSEMBLY MAXIMUM REQUIREMENTS, U-FACTOR METHODa, b
CLIMATE ZONE | 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 | U-0.048 | U-0.039 | U-0.039 | U-0.039 | U-0.039 | U-0.039 | U-0.032 | U-0.032 | U-0.032 | U-0.032 | U-0.032 | U-0.032 | U-0.028 | U-0.028 | U-0.028 | U-0.028 |
Metal buildings | U-0.044 | U-0.035 | U-0.035 | U-0.035 | U-0.035 | U-0.035 | U-0.035 | U-0.035 | U-0.035 | U-0.035 | U-0.031 | U-0.031 | U-0.029 | U-0.029 | U-0.029 | U-0.029 |
Attic and other | U-0.027 | U-0.027 | U-0.027 | U-0.027 | U-0.027 | U-0.027 | U-0.027 | U-0.027 | U-0.027 | U-0.021 | U-0.021 | U-0.021 | U-0.021 | U-0.021 | U-0.021 | U-0.021 |
Walls, above grade | ||||||||||||||||
Massg | U-0.151 | U-0.151 | U-0.151 | U-0.123 | U-0.123 | U-0.104 | U-0.104 | U-0.090 | U-0.090 | U-0.080 | U-0.080 | U-0.071 | U-0.071 | U-0.071 | U-0.061 | U-0.061 |
Metal building | U-0.079 | U-0.079 | U-0.079 | U-0.079 | U-0.079 | U-0.052 | U-0.052 | U-0.052 | U-0.052 | U-0.052 | U-0.052 | U-0.052 | U-0.052 | U-0.039 | U-0.052 | U-0.039 |
Metal framed | U-0.077 | U-0.077 | U-0.077 | U-0.064 | U-0.064 | U-0.064 | U-0.064 | U-0.064 | U-0.064 | U-0.064 | U-0.064 | U-0.064 | U-0.064 | U-0.052 | U-0.064 | U-0.045 |
Wood framed and otherc | U-0.064 | U-0.064 | U-0.064 | U-0.064 | U-0.064 | U-0.064 | U-0.064 | U-0.064 | U-0.064 | U-0.064 | U-0.051 | U-0.051 | U-0.051 | U-0.051 | U-0.036 | U-0.036 |
Walls, below grade | ||||||||||||||||
Below-grade wallc | C-1.140e | C-1.140e | C-1.140e | C-1.140e | C-1.140e | C-1.140e | C-0.119 | C-0.119 | C-0.119 | C-0.119 | C-0.119 | C-0.119 | C-0.092 | C-0.092 | C-0.092 | C-0.092 |
Floors | ||||||||||||||||
Massd | U-0.322e | U-0.322e | U-0.107 | U-0.087 | U-0.076 | U-0.076 | U-0.076 | U-0.074 | U-0.074 | U-0.064 | U-0.064 | U-0.064 | U-0.055 | U-0.051 | U-0.055 | U-0.051 |
Joist/framing | U-0.066e | U-0.066e | U-0.033 | U-0.033 | U-0.033 | U-0.033 | U-0.033 | U-0.033 | U-0.033 | U-0.033 | U-0.033 | U-0.033 | U-0.033 | U-0.033 | U-0.033 | U-0.033 |
Slab-on-grade floors | ||||||||||||||||
Unheated slabs | F-0.73e | F-0.73e | F-0.73e | F-0.73e | F-0.73e | F-0.73e | F-0.54 | F-0.54 | F-0.54 | F-0.54 | F-0.54 | F-0.52 | F-0.40 | F-0.40 | F-0.40 | F-0.40 |
Heated slabsf | F-1.02 0.74 | F-1.02 0.74 | F-1.02 0.74 | F-1.02 0.74 | F-0.90 0.74 | F-0.90 0.74 | F-0.86 0.64 | F-0.86 0.64 | F-0.79 0.64 | F-0.79 0.64 | F-0.79 0.55 | F-0.69 0.55 | F-0.69 0.55 | F-0.69 0.55 | F-0.69 0.55 | F-0.69 0.55 |
Opaque doors | ||||||||||||||||
Swinging door | U-0.61 | U-0.61 | U-0.61 | U-0.61 | U-0.61 | U-0.61 | U-0.61 | U-0.61 | U-0.37 | U-0.37 | U-0.37 | U-0.37 | U-0.37 | U-0.37 | U-0.37 | U-0.37 |
Garage door <14% glazing | U-0.31 | U-0.31 | U-0.31 | U-0.31 | U-0.31 | U-0.31 | U-0.31 | U-0.31 | U-0.31 | U-0.31 | U-0.31 | U-0.31 | U-0.31 | U-0.31 | U-0.31 | U-0.31 |
For SI: 1 pound per square foot = 4.88 kg/m2, 1 pound per cubic foot = 16 kg/m3.
- Where assembly U-factors, C-factors, and F-factors are established in ANSI/ASHRAE/IESNA 90.1 Appendix A, such opaque assemblies shall be a compliance alternative where those values meet the criteria of this table, and provided that the construction, excluding the cladding system on walls, complies with the appropriate construction details from ANSI/ASHRAE/ISNEA 90.1 Appendix A.
- Where U-factors have been established by testing in accordance with ASTM C1363, such opaque assemblies shall be a compliance alternative where those values meet the criteria of this table. The R-value of continuous insulation shall be permitted to be added to or subtracted from the original tested design.
- Where heated slabs are below grade, below-grade walls shall comply with the U-factor requirements for above-grade mass walls.
- "Mass floors" shall be in accordance with Section C402.2.3.
- These C-, F- and U-factors are based on assemblies that are not required to contain insulation.
- The first value is for perimeter insulation and the second value is for full slab insulation.
- "Mass walls" shall be in accordance with Section C402.2.2.
U-factors of walls with cold-formed steel studs shall be permitted to be determined in accordance with Equation 4-1

where:
Rs = The cumulative R-value of the wall components along the path of heat transfer, excluding the cavity insulation and steel studs.
ER = The effective R-value of the cavity insulation with steel studs as specified in Table C402.1.4.1.
EFFECTIVE R-VALUES FOR STEEL STUD WALL ASSEMBLIES
NOMINAL STUD DEPTH (inches) | SPACING OF FRAMING (inches) | CAVITY R-VALUE (insulation) | CORRECTION FACTOR (Fc) | EFFECTIVE R-VALUE (ER) (Cavity R-Value × Fc) |
31/2 | 16 | 13 | 0.46 | 5.98 |
15 | 0.43 | 6.45 | ||
31/2 | 24 | 13 | 0.55 | 7.15 |
15 | 0.52 | 7.80 | ||
6 | 16 | 19 | 0.37 | 7.03 |
21 | 0.35 | 7.35 | ||
6 | 24 | 19 | 0.45 | 8.55 |
21 | 0.43 | 9.03 | ||
8 | 16 | 25 | 0.31 | 7.75 |
24 | 25 | 0.38 | 9.50 |
Related Code Sections
C402.1.4 [CE] Commercial Energy Efficiency, Assembly U -Factor, C -Factor or F -Factor-Based Method
3. Building thermal envelope opaque assemblies intended to comply on an assembly U- , C - or F -factor basis shall have a U- , C - or F ...
Energy Conservation Code 2021 of Colorado > 4 [CE] Commercial Energy Efficiency > C402 Building Envelope Requirements > C402.1 General > C402.1.4 Assembly U -Factor, C -Factor or F -Factor-Based Method
C402.1.4 [CE] Commercial Energy Efficiency, Assembly U-factor, C-Factor or F-Factor-Based Method
with Section C402.2.3. These C -, F - and U -factors are based on assemblies that are not required to contain insulation. The first value ...
Energy Conservation Code 2018 of Colorado > 4 [CE] Commercial Energy Efficiency > C402 Building Envelope Requirements > C402.1 General (Prescriptive) > C402.1.4 Assembly U-factor, C-Factor or F-Factor-Based Method
C402.1.4 [CE] Commercial Energy Efficiency, Assembly U-factor, C -Factor or F -Factor-Based Method
of floor surface area where the material weight is not more than 120 pounds per cubic foot.
These C -, F - and U -factors are based on assemblies ...
Energy Conservation Code 2015 of Colorado > 4 [CE] Commercial Energy Efficiency > C402 Building Envelope Requirements > C402.1 General (Prescriptive) > C402.1.4 Assembly U-factor, C -Factor or F -Factor-Based Method
C402.1.4.1.2 [CE] Commercial Energy Efficiency, Suspended Ceilings
Insulation installed on suspended ceilings having removable ceiling tiles shall not be considered part of the assembly U -factor of the roof ...
Energy Conservation Code 2021 of Colorado > 4 [CE] Commercial Energy Efficiency > C402 Building Envelope Requirements > C402.1 General > C402.1.4 Assembly U -Factor, C -Factor or F -Factor-Based Method > C402.1.4.1 Roof/ C Eiling a Ssembly > C402.1.4.1.2 Suspended Ceilings
C402.1.4.1.3 [CE] Commercial Energy Efficiency, Joints Staggered
Continuous insulation board shall be installed in not less than two layers, and the edge joints between each layer of insulation shall be staggered ...
Energy Conservation Code 2021 of Colorado > 4 [CE] Commercial Energy Efficiency > C402 Building Envelope Requirements > C402.1 General > C402.1.4 Assembly U -Factor, C -Factor or F -Factor-Based Method > C402.1.4.1 Roof/ C Eiling a Ssembly > C402.1.4.1.3 Joints Staggered