I am in the process of replacing my bathroom fan. The original fan is quite old and I tried just buying a replacement motor, but that motor only lasted a couple of months. The old fan was undersized so I bought the proper size for the size of our bathroom. I installed the fan last night, in the ceiling, but the directions and the prior installation don't really say anything about sealing the end of the fan housing to the ceiling. Does anyone put any type of tape or anything. The fan has a flange that sits on the drywall for the ceiling, but I was wondering if anyone recommended anything to create a proper seal. The old fan was also not vented outside and was just vented into the attic. I wanted to fix this. Is it best to just vent it out the roof? My house is from the 50's so the roof is not covered in plywood, but individual boards instead. Do I need to be careful at all with where I place the vent cap? I did a reading and for mounting the fan on the room I see I cut away the shingles for size of the cap, but the roof cap flange I need to try and tuck under the remaining shingles. Is roofing cement good enough for the seams? This will be my first attempt on anything on my roof.
Silicone caulk works fine for sealing the fan. You could use foam in a can if there are some large gaps.
You could vent through the side of the attic-- basically a tiny gable vent. You would have to either use insulated hose or wrap insulation around it when you're done. This is to keep the water vapor that remains trapped in the pipe from rapidly condensing and allowing mold to grow. It would seem more straightforward to vent through the roof, but this method avoids roof leaks (and that's how they did it in my house).