Flame retardancy is an important characteristic in the flame and fire safety field to both prevent and limit the effects of material ignition and flame consumption. The preparation and characterization of Unsaturated Polyester Resin (UPR) filled recycled Expanded Polystyrene (EPS) composite systems were systematically investigated. Additives such as organic nanocrystal (ONC) and silica aerogel powder were added to the composite for imparting suitable characteristics to the composite. The result obtained from comparing the current study against its predecessor reveals Liquid Natural Rubber (LNR) is significantly more flammable than Styrene Butadiene Rubber (SBR) by more than doubled but aerogel utilization can negate this effect. It can be concluded that the use of additive could affect flame retardancy and thermal properties. Further studies of the material can be done in determining and/or confirming the actual mechanisms which ONC and aerogel produces this effect on flammability.