Microstructure analyses in non-autoclaved aerated concrete (Non-AAC) and autoclaved aerated concrete (AAC) were conducted using optical microscopic and scanning electron microscopic (SEM) methods, while their chemical analyses were also carried out using X-ray diffraction (XRD). Laboratory investigation including physiothermal properties and field tests using four lab-scale houses built with the Non-AAC and AAC blocks were also compared. It could be observed that the AAC exhibited properties superior to that of the Non-AAC. Interestingly, the AAC blocks could provide lower humidity accumulation than the Non-AAC blocks, resulting in possibility to prevent mold growth in such construction materials.