This paper presents the effect of natural aging upon the performance of the poly meric insulat ion materials made fro m Epo xy resins, Polydimethylsilo xane (PDMS), and Rice husk ash compound. The sa mples of epo xy resin insulation material consist of Dig lycidyl Ether of Bisphenol A (DGEBA ), Meta Phenylene Diamine (MPDA) as curing agent, and 325 mesh Rice Husk Ash (RHA) as filler, treated with variat ion of PDMS content. The research aims are to observe the Equivalent Salt Deposit Density (ESDD), crit ical leakage current, and flashover voltage on the insulation material surface that has undergone a natural aging. Experimental method was carried out through the following procedure. The samples were placed outdoor for natural aging test, outside the building of electrical engineering and informat ion technology of Gadjah Mada University in Indonesia. Then the ESDD, crit ical leakage current, flashover voltage on the sample surface was measured every 2 weeks. The experiment results show that the performance of insulator material fluctuates during 52 weeks. The higher PDMS with RHA filler content the lower ESDD and surface leakage current. Furthermore the flashover voltage increases.