WAC 51-11C-20221. Section C202.21 — U

U -FACTOR (THERMAL TRANSMITTANCE) . The coefficient of heat transmission (air to air) through a building component or assembly, equal to the time rate of heat flow per unit area and unit temperature difference between the warm side and cold side air films (Btu/h • ft 2 • °F) [W/(m 2 • K)]. UNCONDITIONED SPACE . An enclosed space within a building that is not a conditioned space and that is not categorized under Section C402.1.1. Crawlspaces, attics and parking garages with natural or mechanical ventilation are not considered enclosed spaces . UNHEATED SLAB-ON-GRADE FLOOR . A slab-on-grade floor that is not a heated slab-on-grade floor. UNIFORM ILLUMINATION . A quality of illumination delivered by a lighting system typically comprised of similar fixtures mounted at a regular spacing interval. This lighting system provides a uniform contrast ratio of no greater than 5:1 maximum-to-minimum ratio throughout the entire area served, including task areas.