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 • ft2 • °F) [W/(m2 • K)].

unheated slab-on-grade floor. A slab-on-grade floor that is not a heated slab-on-grade floor.