In this study, the possibility of enhancing heat insulation performance of hollow bricks by filling the cavities with perlite is investigated. A conjugate heat transfer by conduction, convection and radiation in different hollow bricks are analyzed numerically to assess their thermal performance. Calculations are performed for three scenarios for each type of hollow brick: (i) cavities are filled with air, (ii) half of the cavities are filled with perlite while the other half is filled with air, (iii) all cavities are filled with perlite. The benefit of filling cavities with perlite is justified quantitatively for each investigated hollow brick type. It is concluded that the enhancement in insulation performance can be up to 15.6% and 27.5% for half-perlite and full-perlite cases, respectively, depending on the brick type.