3.3.3.1. Gypsum content at 1%. Fig. 12 shows the relationship between gypsum content and thermal conductivity at 1% fibre content. The figure shows that thermal conductivity slightly increased with increasing gypsum content. The results showed no significance difference (P < 0.05) between bricks reinforced with wheat and barley straw fibres. The average thermal conductivity of unfired wheat straw reinforced earth bricks are 0.596, 0.622 and 0.638 W/m K for the gypsum contents of 0%, 5% and 10%, respectively. The thermal conductivity for barley straw reinforced bricks are 0.620, 0.624 and 0.640 W/m K, for cement contents of 0%, 5% and 10%, respectively.