Building insulation materials with different perlite and pumice mixing ratios along with varying additives including planted and painted surfaces were evaluated experimentally. The purpose was to come up with high-resistance, low-cost insulation materials which also are of low density for the sake of reduced weight on the roofs. Reverse heat leak method was used in determination of R-values of all samples that are developed and fabricated within this study. An insulated test chamber was built along with a heat load at the center of the box. Temperature readings were collected from 18 different locations and were recorded with a sampling frequency of one minute for approximately nine hours for each test. Results showed that perlite and pumice based insulation boards can yield R-values close to some synthetic insulation materials such as expanded polystyrene. Uncertainty analysis with 95% confidence level was also performed for the results. The study pointed out that mixing inorganic rocks with some organic and inorganic materials can improve thermal insulation while keeping the cost and weight low. Painting was also applied on the reference sample to observe the effect of surface coating in R-value.