This paper presents an optimization study of the design parameters for houses using rammed earth walls, including window sizes, window shading, the amount of thermal mass and the amount of insulation in the external walls. The optimization is based on two objectives: (1) energy use reduction and (2) life-cycle cost minimization. It was found that, in general, the thicker the walls/insulation was applied, the less the energy load, but the higher the life-cycle cost. In hot arid climates, small windows and large window shadings lead to a lower energy load while the minimum life-cycle cost was achieved with the smallest window and window shading. In warm temperate climates, the optimum size of north facing window was 30% and 40% of the wall area to achieve the minimum energy load and life-cycle cost while the sizes of the windows on the other walls as well as the window shading needed to be as small as possible. In cool temperate climates, small south facing windows and large windows in the other walls would result in the lowest energy load; however, to achieve the minimum life-cycle cost, all the windows and window shadings should be as small as possible. (C) 2014 Elsevier B.V. All rights reserved.