Just had a Panasonic bathroom exhaust fan installed, which works great and is superquiet. My issue is that we felt heat radiating down from the fan area last night (yesterday was warm and humid in my area). The electrician who installed the fan replaced the fiberglass insulation around and over the fan unit, and the ductwork we used (4 inches) to vent out to the side of the house is insulated.
Is the heat coming through the inside of the vent from the outside? (its about 3-4 feet from unit to the outside) Or is the heat coming through the small amount of insulation around the duct itself and traveling down? I could try and put additional unfaced fiberglass insulation around the duct from unit to wall, but wasn't sure if that would work. We're concerned as to what this would mean in the wintertime.