An occupant-support base includes a seat assembly and a heater mat coupled to the seat assembly. The seat assembly includes a seat frame, a foam pad coupled to the seat frame, and a trim cover coupled to the foam pad. The trim cover is coupled to the seat assembly by one or more attachments. The heater mat is arranged between the trim cover and the foam pad and includes a carrier sheet and a heating element coupled to the carrier sheet. The heater mat is secured to the seat assembly with a fastener system.