This paper presents the unsteady thermal response characteristics such as, admittance, transmittance, decrement factor, time lag, surface factor, surface factor time lag and areal thermal heat capacity of hollow bricks with different materials and varying air gap in hollow bricks for reducing heat gain into the buildings. A computer simulation program was developed which employs a cyclic admittance method. The results showed that thermal admittance, surface factor time lag, decrement factor time lag and areal thermal heat capacity values increase and thermal transmittance and decrement factor decrease with the increase in the number of air gaps in hollow bricks.