||Nowadays, the architectural profession is seeking a better energy saving in the design of buildings. The fear of energy shortage in the very near future, together with the rapid rise in energy prices, put pressure on researchers on this field to develop buildings with more efficient heating systems and energy systems. This work is concerned mainly with the development of a software program analyzing comfort in buildings integrated in CAD architectural systems. The problem of presenting the computer with information concerning the building itself has been overcome through integration of thermal analysis with the building capabilities of CAD system. Mainly, such experience concerns the rules for calculating heat loss and heat gain of buildings in Algeria, The program has been developed in order to demonstrate the importance of the innovation of the computer aided-architectural-design field (CAAD) in the technology of buildings such as the three dimensional modeling offering environmental thermal analysis. CAAD is an integrated architectural design system which can be used to carry out many tasks such as working drawings, perspectives and thermal studies, etc., all from the same data. Results are obtained in tabular form or in graphical output on the visual display. The principle of this program is that all input data should be readily available to the designer at the early stages of the design before the user starts to run the integrated model. Particular attention is given to the analysis of thermal aspects including solar radiation gains. Average monthly energy requirement predictions have been estimated depending on the building design aspect. So, this integrated model (CAAD and simulation comfort) is supposed to help architects to decide on the best options for improving the design of buildings. Some of these options may be included at the early design stages analysis. Indications may also be given on how to improve the design. The model stored on CAAD system provides a valuable data base for all sort analytical programs to be integrated into the system. The amount of time and expertise required to use complex analytical methods in architectural practice can be successfully overcome by integration with CAAD system.