This tool calculates the solar heat gain through vertical windows in temperate latitudes. From Sustainable by Design
Christopher Gronbeck, developer of the Sustainable By Design tools and calculators, updated this tool June 2011. The accuracy of the calculation has been improved, and the outputs were changed from a simple list of monthly values to a more comprehensive table of hourly and monthly values, so you can see when heat gain is being realized throughout the day. He also added a feature (found in several other of his tools) that lets you e-mail yourself the output data for off-line viewing or import into a spreadsheet.