Ridgid is really the only way to go especially over long runs. We usually spec 4" sched. 20 PVC pipe as it comes in longer lengths than 4" metal does around here , though elbows can be tough to source sometimes. Unfortunately most contractors / HVAC guys will use flexible corrugated hose because it's cheap and fast. If it's a luxury project they'll splurge for the flex aluminum instead of the plastic kind. This type of pipe can cut a fan' effectiveness in half over long runs. Little thought is really given to these fans in most homes today. They are often undersized for a given bathroom and poorly located too. The crappy pipe detailing makes a bad situation worse. Panasonic's website has (or used to) a pretty good tutorial on how to properly size a fan, where to locate it and how to properly pipe it to the outside. I think much of the problem is cost and ignorance. Most people know you get a fan in your bath , but when pressed they won't really be able to tell you its there to expel warm moist air from your home, not smells. They assume that the $34.95 version will be fine for them and a quick & dirty install will get ya out the door for a hundred bucks. The reality is, many master baths, and some hard working kids baths need a much larger fan than 35 bucks can buy. We are often talking $100-$200 for an adequate model, more if you want features or quietness. Add the increased piping cost and labor for the proper venting needed on higher capacity fans and this can quickly become a $500 line item - which starts to look crazy for something as pedestrian looking as a bath fan. Timer switches are also a very good idea as most fans even properly sized ones need to run a while after you've left the bath to completely exhaust the moist air.

I have been searching High and Low for a replacement motor for my AUPU Bath Master Exhaust Fan - Model A716. It is the same as the Aero Pure A716. Neither AUPU nor Aero Pure have been responsive to my inquiries. If I need to replace the whole unit I will not buy an AUPU or Aero Pure.

Bathroom fans move much less air than a whole house fan. I don't think you will have a problem. If the bathroom fan is going to be used to remove moisture after a shower then I suggest wiring it to a timer. Running the fan for 20-30 minutes during and after the shower should be sufficient.

A GFCI device has two sets of terminals. Power is fed with hot and neutral to the LINE terminals. Downstream devices can be protected by the GFCI by hooking the their hot and neutral to the LOAD terminals. But it is not necessary to GFCI protect the lights and fan unless their location makes it likely a person would touch them and a grounded object (like the faucet) at the same time.