3.3.3.2. Gypsum content at 3% fibre. The average thermal conductivities of earth bricks reinforced with wheat straw are 0.310, 0.415 and 0.461 W/m K for gypsum contents of 0%, 5% and 10%, respec- tively; while the thermal conductivity for barley straw reinforced bricks are 0.314, 0.424 and 0.476 W/m K for gypsum contents of 0%, 5% and 10%, respectively. Fig. 13 shows the relationship between gypsum content and thermal conductivity with 3% fibre content. The figure showed that the thermal conductivity increased slightly with increasing gypsum content. The results showed no significance difference between bricks reinforced with wheat and barley straw fibres (P < 0.05). The results revealed that increasing gypsum percentages from 0% to 10% caused thermal conductivity to increase from 0% to 48.7% in comparison to brick materials without gypsum and with 3% wheat reinforcement fibres. For barley straw fibres, increasing gypsum percentages from 0% to 10% caused thermal conductivity percentages to increase from 0% to 51.6% with the same fibre content. This trend is due to gypsum and its formation. Thus at 3% fibre content, high porosity and many gaps exist between fibres and soil particles. Cement fills these gaps. The figure also showed that the thermal conductivity for barley straw reinforced bricks is higher than wheat straw reinforced bricks.