Question-and-Answer Resource for the Building Energy Modeling Community
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I'm puzzled by this question. It seems you're assuming the predominant driver in daylighting potential is the latitude, which is true only in the crudest sense, because there are many other factors such as the atmospheric turbidity and the amount of clouds. Instead of using latitude, I would pick a range of solar radiation as shown in the map posted earlier, and if you want only 3 locations to get a range, just pick locations with average, high, and low amounts of radiation :-)
Keep in mind the following when doing your analysis: (1) the illuminances in the weather files are all calculated based on the solar radiation, so take them with a grain of salt, (2) the illuminances shown have to be converted to the amounts entering vertical surfaces, i.e., windows, and can be expected to change greatly, (3) for India, ISHRAE released in early 2014 a new set of typical year weather files for 59 Indian locations with decent solar radiation calibrated against satellite-derived values (I was involved in that work); please contact Vikram Murthy at vikrammur@gmail.com on how to obtain those files.
