The average thermal conductivity of unfired earth bricks rein- forced with wheat straw are 0.961, 0.596 and 0.310W/mK for the fibres contents of 0%, 1% and 3%, respectively, while the ther- mal 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 com- parison 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 satis- fying. 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 increas- ing fibre content. The results showed no significance difference between bricks reinforced with wheat and barley straw fibres (P < 0.05).