Wash. Admin. Code § 51-11R-58000
Building owners may choose to use this appendix to achieve an additional 6 percent savings in building energy use. The number of additional energy efficiency credits required by Section R406.3 would be increased by the following amounts:
1.0 credit for each new single-family, two-family and townhouse dwelling unit.
0.5 credit for each new dwelling unit within an R-2 occupancy building.
0.5 credit for each addition smaller than 500 square feet to a single-family, two-family or townhouse dwelling unit.
1.0 credit for each addition of 500 square feet or larger to a single-family, two-family or townhouse dwelling unit.
Where Section R405, Simulated performance alternative, is used, the maximum allowable energy consumption shall be 92 percent of the value calculated according to Section R405.3.
Wash. Admin. Code § 51-11R-58000