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.]