Acres of projected future Intermix by Fire Hazard Severity Zone (FHSZ) class. Intermix is defined as between 1 house/2 acres, and 1 house/20 acres (0.5 to 0.05 houses/acre). Landscapes with housing densities of less than 1 house per 2 acres ( 0.5 houses/acre) typically retain most of their natural vegetation fuels, and consequently are not as resilient to wildfires as denser urbanized areas. Although wildfires are fairly frequent in these types of environments, structural values (due to low housing density) are typically relatively low (as compared to urban areas).