![]() ![]() In winter, the distance D between the window head and the underside of the eave or overhang, is critical to the window’s performance. This figure ( A) is the required depth of the overhang: A = H x F heightĮxample: For the Wellington region, if the height ( H) of the eave or sunshade above the window sill is 2.0 m, multiply 2.0 m by 0.32 ( F height) = 0.64 m – so the overhang should be 640 mm deep. To calculate the overhang, multiply the height ( H) from the window sill to the eave or sunshade by the factor F height for the nearest main centre location. Use this to calculate the amount of overhang required to exclude midday summer sun but admit midday winter sun. The following table gives height and shading factors based on sun path diagrams for the main centres in New Zealand. ![]() They must be sized correctly to exclude summer sun but still admit winter sun. EavesĮaves or other fixed overhangs are the simplest way to provide protection against solar gain. To be effective, external shading must be considered along with other passive design features such as location, orientation and layout, window size and placement, and thermal mass. It’s important that each is designed to take account of the sun paths at the site at different times of the year. There are many options for external shade. Providing shade over building openings and outdoor spaces can reduce temperatures and save energy. External shading prevents solar access and so helps to keep a building cool. ![]()
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