Straw bales provide a decent thermal insulation values of 0.067 W/mK that abundant less than the wood and other building raw material (Goodhew and Griffiths, 2005). Most studies dealing with insulation material (cork, bark, rice straw, hemp, etc.
) shows that the low densities between 170 kg/m³ and 260 kg/m³ and low thermal conductivity coefficients between 0.0475 W/mK and 0.0697 W/mK. (Kain et al.
, 2013; Wei et al., 2015; Ali and Alabdulkarem, 2017). Besides that, an experiment of low density boards with a mix of wheat straw and corn pith of has been done. Different experiment has been done shows that the bale density ranges from 54.
6 kg/m³ -78.3 kg/m³ for barley straw bales and 81 kg/m³ -106.3 kg/m³ for each oat and wheat straw bales (Watts et al., 1995). Furthermore, another experiment result shows that the equilibrium moisture content is not affected by the density of the sample.
From the experiment, the results shows that the thickness swell is larger than linear growth because of the orientation of fibres, parallel to the faces board (Wang, D. Sun, 2002).