Daylighting has been a part of built forms throughout architectural history. Interest in using daylighting as a major design element has varied with the social and economic forces of the time. Since 1973, interest in daylighting has increased as a result of oil embargo and the understanding that electric lighting represents a major energy consumer. Energy savings achieved through the use of daylight also translate into energy cost savings from reduced electricity consumption for lighting and cooling as well as from reduced needs during peak demand periods in many building. The objective of this paper is to explain the great importance for daylighting and the role played in design process for the building and the participation in the design from the first step which effects the designer decision for dimensions, position for the opening and the building orientation, etc... Which give the psychological comfort for building user and how to control the heat transfer throw opening by using different materials and using simulation programs which give to the designer a clear image for what will be a situation all the year around.