An experimental investigation is made to characterize the thermal insulation properties of different compounds of local natural low cost reinforcements with polyurethane foam forming the matrix (foam only, foam and hay, foam and cane). Several rectangular enclosures were produced with walls made from this composite material. Heat was transferred mainly by natural convection and radiation from the heat source inside the enclosure to the walls. The temperature field was monitored and recorded in the three-dimensional space. The variations across the vertical and horizontal walls in temperature were obtained. The results showed that the compounds will produce two-fold improvement in the insulation properties when compared with pure polyurethane foam (increase the thermal resistance) and a significant decrease in the cost of thermal insulation. In our study, the foam + hay compound will give the best thermal insulation and cost reduction results. Presenting the data in a non-dimensional form showed that the non-dimensional temperature distribution is not a function of the input source power. This shows that the effect of thermal radiation is not significant.