The average thermal conductivity of unfired earth bricks reinforced with wheat straw are 0.961, 0.596 and 0.310W/mK for the fibres contents of 0%, 1% and 3%, respectively, while the thermal conductivity for bricks reinforced with barley straw fibres are 0.961, 0.620 and 0.314 W/m K for reinforcement fibres contents of 0%, 1% and 3%, respectively. The mentioned results illustrate that increasing wheat straw fibre percentages from 0% to 3% caused a decreasing of thermal conductivity percentage to 54.4% in comparison to bricks without reinforcement fibres. Also, increasing barley straw fibre percentages from 0% to 3% caused a decreasing of thermal conductivity percentage to 53% in comparison to bricks without reinforcement fibres, results which are extremely satisfying. The change in thermal conductivity by altering the fibre content is shown in Fig. 9. As expected, thermal conductivity decreased with increasing fibre content. Fig. 9 also shows that the decrease in thermal conductivity was gradual with increasing fibre content. The results showed no significance difference between bricks reinforced with wheat and barley straw fibres (P < 0.05).