This research paper explains that windows, doors, glazed walls, and other fenestration products account for nearly 40% of the energy used in buildings in India. are the largest components of buildings' energy loss. It is essential to accurately evaluate the thermal performances of fenestration systems in order to improve product performance and predict the overall energy consumption of a building. Because 3-D analysis is a highly complex process that requires significantly more time, effort, and cost than 2-D analysis, it is typically used to evaluate their thermal performance. One more strategy for assessment for example actual test in a hotbox isn't feasible for every item as they are excessively costly. Fenestration products' effects on overall heat transfer must be investigated because heat transfer is a three-dimensional process. In contrast to the results obtained in two dimensions, this proposed thesis examined 3-D heat transfer effects in fenestration systems. In terms of 3-Dcmodeling of windows that included all three types of heat transfer conduction, convection, and radiation, for example—no significant work has been done previously.