I'm interested in installing a bathroom extractor fan where there was a previously small regular fan, but there isn't an attic above the bathroom.
The switch is already wired from the previous fan which saves me from having to snake it, but I have questions about how to run the ducting from the fan, and about installing the fan itself.
The duct is 4", and I plan on running it through the roof to a proper exhaust vent right next to the bathroom. I'm not entirely sure how to know where a good position to make the 5" hole with the hole saw would be (since I can't see from the inside or put a marker like a nail for marking a place to drill), or how to get the ducting to a place where I could reach it and attach it to the vent.
What tactics should I use to locate a good place to drill using the hole saw?