Lightweight concrete has lower thermal conductivity and a lower coefficient of thermal expansion. This project aims to develop Eco-friendly thermally insulated lightweight concrete by using fibers. Hemp and sisal are natural fibers that play a major role in the reduction of thermal conductivity. Vermiculite is a naturally available material that can be used for lightweight concrete furthermore provides good thermal insulation. Reducing the thermal conductivity by adding fibers in different proportions (1%,1.5%,2%) in concrete where Vermiculite is partially replaced with fine aggregate and Fly ash is partially replaced with cement in which shows a reduction in thermal conductivity and also it can be used for lightweight concrete. The thermal conductivity of the concrete is tested for different mix proportions. Then the mechanical property and durability of the concrete are tested for different proportions. The thermal conductivity of the fiber-reinforced lightweight concrete is tested and the results show that when the amount of fiber increased the thermal conductivity is low. Thus, the low thermal conductivity is obtained by natural fibers. The mechanical strength of the different proportions of mixes are carried out and results show that the increase in fiber reduces the strength. The plate and wall panel are analyzed in Abaqus for the control mix and low thermal conductivity fiber-reinforced lightweight concrete mix which gives the minimum thermal conductivity and appropriate strength. The results from these experiments are found out that the natural fibers and vermiculite can be a good solution for thermally insulated Eco-friendly building construction