The decisions and personal preferences of the designer are vital for all aspects and stages of the design. To elaborate, the designer has the central role in creation, development, detailing and construction of the built forms. Also, the scientific/engineering evaluations of the design models are carried out under the directions and decisions of the designer. The paper explores the concept of ‘ desirability factor’ as a method for incorporating the decisions and preferences of the designers within the digital design media. Desirability factors are assigned to the models and explicitly express the views of the designer on the level of desirability of various aspects of the design. The desirability factors direct the process of selection of design variants (that are obtained from the sole scientific/engineering analyses) in the direction favoured by the designer. The examples in the paper illustrate the methods of definition and application of desirability factors to architectural design. The concept may be used for various engineering disciplines encountered in architectural design.