Traditional tools in the domains of thermal design and control of building systems usually rely on a deterministic approach. Building systems, on the other hand, are strongly influenced by meteorological variables, which obviousy are characterized by a stochastic nature. Due to this mismatch, traditional tools can neither evaluated properly the fluctuations of the solar and heat load intensities for design puroposes, nor anticipate their stochastic behavior to optimize the thermal control of building systems. The aim of this research is the application of stochastic methods to overcome this difficulty.