A fiber blend comprising a staple fiber formed from cellulose acetate and a binder fiber. The staple fiber has a crimp frequency of 10 to 30 crimps per inch (CPI), a cut length of 55 mm or less, and a non-round cross-sectional shape. The blend can be made into nonwoven webs for heat-bonding and subsequent use as thermal insulation in, e.g., outerwear, bedding, etc. The cellulose acetate fibers provide superior thermal insulation clo value relative to at equivalent loft.