Abstract
The external heat load of residential buildings in summer is the dominant parameter of the required cooling load and refrigeration capacity of air conditioning systems. The consumed energy of air conditioning system is proportional to the outside conditions and intensity of solar radiation. The maximum heat load of building may occur at 3 O'clock PM, although the peak of solar radiation occurs at noon. The construction materials of building is playing an important rolls of heat transmission through buildings outside walls and glazing windows. The walls thermal insulation can be effective in energy conservation by reducing the cooling load and required electrical energy. The building is constructed from common materials with 0 similar to 12 cm thermal insulation in outside walls, ceilings, and double layers glazing windows. The building heat loads are calculated for two models of walls. The optimum thickness of thermal insulation is also determined and is found between 6 similar to 8 cm for insulation of thermal conductivity of 0.039 W/m.K the energy saving is 50.45% at 6 cm insulation thickness.