A good estimate of the cooling load is one vital aspect for achieving the optimal level of comfort and energy effiency in buildings. Due to its relative simplicity, the Cooling Load Temperature Diffrence (CLTD) method is still used both in education and industry for cooling load calculations. However, one downside of using this method is the limited number of walls and roofs which do not represent effctively all commonly used wall and roof constructions. In this research, a transient heat

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... er model was developedto fid the (CLTD) values, for the most common external walls of buildings that have widespread use in Tripoli, Libya. Th Finite diffrence method was used to solve the governing partial diffrential equations with appropriate initial and boundary conditions. A MATLAB program has been developed and used to solve the system of algebraic equations produced by applying the fiite diffrence method to the governing diffrential equations. A comparison has been made between the computed results and ASHRAE CLTDvalues. At standard conditions specifid in ASHRAE handbooks for the same wall with a default composition, a reasonably good agreement was found between computed and ASHRAE CLTD values for this wall. CLTD values have been generated for three diffrent types of walls; Hollow concrete block, Limestone block, and Hollow brick. With these values, the cooling load calculation of buildings can be easily and manually performed with more accuracy. It is also concluded from the transient analysis that the limestone block walls provide the best therm.