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.]