Due to the rapid increase in population growth, energy and synthetic material consumption, the materials which reduce energy consumption like isolation structures have been gaining an importance after results of many innovative researches. So far, the most part of energy reducing materials have been produced by synthetic chemicals and therefore have a detrimental effect on the natural world and living organisms. Rigid polyurethane foam (PUF) is mainly manufactured by synthetic raw materials and widely used as an isolation material for different applications. Here, we present a novel composite PUFs contain different amount of natural materials as fiberglass, straw and basalt fibers between 0.5% and 2% by weight. Thermal conductivity is varied from 0.02109 to 0.02260 W/(m.K) by using 1% and 2% for fiberglass and straw, respectively. Furthermore, there is no significant change for the compression strengths of the resulted composites when compare with virgin PUF except 2% fiberglass which demonstrates about 70 kPa performance. We strongly believe that lowering synthetic raw materials content for PUF by incorporating natural materials will have a proportionately less harmful impact on the ecology and natural sustainability while keep similar thermal and physical properties to those of the current 100% synthetic PUFs.