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C402.1.4 Assembly U-factor, C-Factor or F-Factor-Based Method

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

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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

TABLE C402.1.4

OPAQUE THERMAL ENVELOPE ASSEMBLY MAXIMUM REQUIREMENTS, U-FACTOR METHOD^{a, b}

CLIMATE ZONE

4
EXCEPT MARINE

5
AND MARINE 4

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-0.032

U-0.028

Metal buildings

U-0.044

U-0.035

U-0.031

U-0.029

Attic and other

U-0.027

U-0.021

Walls, above grade

Mass^g

U-0.151

U-0.123

U-0.104

U-0.090

U-0.080

U-0.071

U-0.061

Metal building

U-0.079

U-0.052

U-0.039

U-0.052

U-0.039

Metal framed

U-0.077

U-0.064

U-0.052

U-0.064

U-0.045

Wood framed and

other^c

U-0.064

U-0.051

U-0.036

Walls, below grade

Below-grade wall^c

C-1.140^e

C-0.119

C-0.092

Floors

Mass^d

U-0.322^e

U-0.107

U-0.087

U-0.076

U-0.074

U-0.064

U-0.055

U-0.051

U-0.055

U-0.051

Joist/framing

U-0.066^e

U-0.033

Slab-on-grade floors

Unheated slabs

F-0.73^e

F-0.54

F-0.52

F-0.40

Heated slabs^f

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-0.37

Garage door <14%

glazing

U-0.31

For SI: 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.

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.

C402.1.4.1 Thermal Resistance of Cold-Formed Steel Walls

U-factors of walls with cold-formed steel studs shall be permitted to be determined in accordance with Equation 4-1

(Equation 4-1)

where:

R_s = 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.

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 (F_c)	EFFECTIVE R-VALUE (ER) (Cavity R-Value × F_c)
3¹/₂	16	13	0.46	5.98
3¹/₂	16	15	0.43	6.45
3¹/₂	24	13	0.55	7.15
3¹/₂	24	15	0.52	7.80
6	16	19	0.37	7.03
6	16	21	0.35	7.35
6	24	19	0.45	8.55
6	24	21	0.43	9.03
8	16	25	0.31	7.75
8	24	25	0.38	9.50

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