Section C402.1.4—Assembly U-factor, C-factor, or F-factor-based method.
C402.1.4 Assembly U-factor, C-factor, or F-factor-based method. Building thermal envelope opaque assemblies shall meet the requirements of Section C402.2 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. The U-factors for typical construction assemblies are included in Appendix A. These values shall be used for all calculations. Where proposed construction assemblies are not represented in Appendix A, values shall be calculated in accordance with the ASHRAE Handbook—Fundamentals using the framing factors listed in Appendix A where applicable and shall include the thermal bridging effects of framing materials.
C402.1.4.1 Thermal resistance of cold-formed steel stud 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:
U = 1/[Rs + (ER)] |
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. |
[Statutory Authority: RCW
19.27A.020,
19.27A.025,
19.27A.160 and chapter
19.27 RCW. WSR 19-24-040, § 51-11C-40214, filed 11/26/19, effective 7/1/20. Statutory Authority: RCW
19.27A.025,
19.27A.045,
19.27A.160, and
19.27.074. WSR 16-24-070, § 51-11C-40214, filed 12/6/16, effective 5/1/17. Statutory Authority: RCW
19.27A.025,
19.27A.160, and
19.27.074. WSR 16-03-072, § 51-11C-40214, filed 1/19/16, effective 7/1/16. Statutory Authority: RCW
19.27A.020,
19.27A.025 and chapters
19.27 and
34.05 RCW. WSR 13-04-056, § 51-11C-40214, filed 2/1/13, effective 7/1/13.]
Reviser's note: The brackets and enclosed material in the text of the above section occurred in the copy filed by the agency.