A significant amount of the solar heat gain in buildings comes through the windows, and the most effective way to reduce it is to install exterior shading devices, such as window shutters. The window shutters are typically made of foam filled aluminum rolling shutter slat. In this research, a technique of solar heat gain reduction in building through windows using phase change material (PCM) in the shutter instead of foam is investigated using finite element method. The objective of using PCM in the shutters is to utilize its high latent heat of fusion to reduce the heat gain by absorbing the heat gain before it reaches the indoor space. The thermal effectiveness of the proposed PCM shutter system is evaluated by comparing the gain at the indoor space to the heat gain of foam shutter during typical working hours. A parametric study is conducted to assess the effect of different design parameters, such as PCM's type and quantity in the shutter. The result indicates that PCM with the highest examined melting temperature shows the best thermal performance, and the heat gain through windows can be reduced as high as 23.29%. (C) 2011 Elsevier B.V. All rights reserved.