Abstract: The amount of solar radiation through the fenestration of a building into the interior space is a key factor in assessing the indoor comfort and the eventual energy used in cooling off these spaces. In predominantly hot humid regions like Ghana which receives sunlight all year around, buildings and for that matter windows should be oriented to minimize solar gain and maximize natural ventilation. Windows are possibly the most complex and interesting elements in every habitable structure. Heat loss and heat gain through a window will not only depend on the type of window and its properties alone but also the size and the position of the same. This paper describes an investigation into the consequence of window sizes (varied wall-to window –ratio) and it’s positioning on indoor thermal comfort for residential buildings in Ghana. A typical room of 3m x 4m was parametrically simulated using the Tas tool. Various window sizes with diverse WWR were then probed into with varying positions (low, middle and high). The result showed that the ideal window to wall ratio for achieving almost comfortable indoor conditions should be between 10 to 40%. Meanwhile, the various positions of the windows did not seem to have any effect on the indoor temperature values since all the values were the same. The study should lead to an improved residential design with appropriate window sizes and correct positions which will ensure indoor comfort and thereby reducing the total energy used in cooling.

Keywords: Window size, Thermal Comfort, Passive, WWR, Tropical region.