Architectural design involves not only functional aspects with respect to structural and space utilization but also environmental aspects and energy considerations. Architectural design is influenced by the actual thermal behaviour of building components, and this depends not only on their steady and periodic thermal characteristics but also on exposure effects, orientation, surface colour and the climate parameters of the location. All these parameters enter into heat transfer computations in a complex manner. The design data and criteria should be produced in a rational way for each location, so that architects and engineers can confidently apply them in their design calculations, and to enable precise evaluation of the influence of various design parameters on the overall thermal performance of buildings.The present work is carried out with an objective of first,evaluating:the thermal characteristics and behavior of parts of the grand space of the mosque "Musalla" envelope,theimpact of sol-air temperatures,and heat gain factors components.Secondly,the generational architectural criteria for appropriate thermal design of grand space.