The Solar disinfection system uses solar energy to disinfect food grains, by removing the moisture content present in them. This aids their preservation for a long term. A mixed mode solar dryer uses a combination of direct solar drying and hot air drying, for maximum efficiency. It is observed that, some amount of this energy is lost, through conduction in the collector body. This is avoided with the use of insulators. Different types of heat insulating materials are available. This study uses the weighted property method to decide among the various alternatives of insulating material, which is suitable for the mentioned project. Here various parameters of insulator material selection are applied and their Relative Emphasis Coefficient, Scaled Property, and Ranks (or weights) are calculated. The material with a rank of unity gets the utmost preference, and the subsequent materials are preferred in the obtained order. The tangible parameters considered in this study are: Density, Thermal conductivity, Maximum service temperature range, Specific heat capacity, and cost. In this study, Rock mineral wool, with a performance of 84.58%, was selected as the suitable material. This can be applied in the mentioned project as an insulation material, after considering other intangible factors.