Although abondant amounts of onion skin and peanut shell wastes is produced in Turkey, after their production their leftovers cause a serious problem for farmers. They are discharged somehow, burned or used for simple heating purposes. All of these alternatives cause serious environmental problems. To circumvent these problems, the present study proposes a method of evaluating those waste materials for the insulation of buildings and prevent the harm they cause to the environment. In the direction of this aim, onion skin waste and peanut shells have been pulped and turned into insulation materials. To this end, waste onion skins and peanut shells were ground to a size of 1 millimeter and fly ash, pumice, perlite, barite, cement and gypsum were added to pro-duce samples with a size of 4 × 4 × 16 centimeters. These samples were kept in an oven for 24 h at 100◦C. Apparent specific gravities, water absorption rates, flexure and compressive strengths of the samples were determined. Moreover, thermal conductivity coefficients, ultrasonic sound penetration coefficients and radioactive permeability values were also investigated