Computational tools can be used during design to simulate building performance based on input information about the designed building envelope, lighting system, and mechanical system. Models can be used to predict energy use over the building life, solar heat and radiation distribution, air flow, and other physical phenomena within the building.[4] These tools are valuable for evaluating a design and ensuring it will perform within an acceptable range before construction begins. Many of the available computational tools have the capability to analyze building performance goals and perform design optimization.[5] The accuracy of the models is influenced by the modeler's knowledge of building science principles and by the amount of validation performed for the specific program.[6]