WAC 51-11C-61041:

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PDFWAC 51-11C-61041

Section A104.1—General.

A104.1 General. Table A104.1 lists heat loss coefficients for below-grade walls and floors.

Coefficients for below-grade walls are given as U-factors (Btu/h • ft2 • °F of wall area). Coefficients for below-grade slabs are listed as F-factors (Btu/h • ft • °F per lineal foot of slab perimeter).

Below-grade wall U-factors are only valid when used with the accompanying below-grade slab F-factor, and vice versa.

Table A104.1

Default Wall U-factors and Slab F-factors for Basements

	Below Grade Wall U-factor	Below Grade Slab F-factor
2 Foot Depth Below Grade
Uninsulated	0.331	0.58
R-11 Interior	0.063	0.67
R-11 Interior w/TB	0.065	0.59
R-19 Interior	0.042	0.68
R-19 Interior w/TB	0.045	0.59
R-21 Interior	0.040	0.68
R-21 Interior w/TB	0.042	0.59
R-21+R-5 ci Interior	0.031	0.68
R-21+R-5 Interior w/TB	0.032	0.59
R-21 plus R-7 ci Interior	0.029	0.68
R-21+R-7 Interior w/TB	0.030	0.59
R-10 Exterior	0.089	0.56
R-12 Exterior	0.061	0.60
3.5 Foot Depth Below Grade
Uninsulated	0.271	0.51
R-11 Interior	0.058	0.61
R-11 Interior w/TB	0.061	0.55
R-19 Interior	0.041	0.62
R-19 Interior w/TB	0.042	0.55
R-21 Interior	0.038	0.63
R-21 Interior w/TB	0.040	0.56
R-21+R-5 Interior	0.030	0.632
R-21+R-5 Interior w/TB	0.031	0.56
R-21 plus R-7 ci	0.027	0.63
R-21 plus R-7 ci w/TB	0.029	0.56
R-10 Exterior	0.075	0.52
R-12 Exterior	0.057	0.57
7 Foot Depth Below Grade
Uninsulated	0.185	0.43
R-11 Interior	0.051	0.541
R-11 Interior w/TB	0.053	0.49
R-19 Interior	0.036	0.54
R-19 Interior w/TB	0.037	0.50
R-21 Interior	0.035	0.56
R-21 Interior w/TB	0.035	0.50
R-21+R-5 Interior	0.027	0.56
R-21+R-5 Interior w/TB	0.028	0.51
R-21+R-7 Interior	0.025	0.57
R-21+R-7 Interior w/TB	0.026	0.51
R-10 Exterior	0.058	0.47
R-12 Exterior	0.050	0.42

TB = R-5 Thermal Break

[Statutory Authority: RCW 19.27A.020, 19.27A.045, 19.27A.160 and chapter 19.27 RCW. WSR 20-01-047, § 51-11C-61041, filed 12/9/19, effective 7/1/20. Statutory Authority: RCW 19.27A.020, 19.27A.025 and chapters 19.27 and 34.05 RCW. WSR 13-04-056, § 51-11C-61041, filed 2/1/13, effective 7/1/13.]