I recently installed a new bathroom exhaust fan, replacing a loud and underpowered one with a quieter and more powerful (110cfm) fan. Because of the existing framing and roof vent location, I was somewhat forced to install the fan in the particular orientation that you see (I'm sure with enough ingenuity I could have figured out a way to rotate the fan, but this is in a spot of my attic with very little room to work so I took the easy route). Because of this, I ended up with an unideal 180 degree bend in the ductwork. I am wondering if there is a way I can optimize this to make it "less unideal" if you will. I have considered a couple of solutions that I would appreciate some feedback on:
- Using 6" semi-rigid ducting (the fan exhaust port is only 4", so I would need an adapter/reducer of some sort) to reduce the strain caused by the bend
- Using two 90 degree rigid elbows to make the 180 degree bend (I've heard these are better to make bends with than semi-rigid duct)
- Combining 1 and 2: using two 90 degree 6" rigid elbows + some semi-rigid duct to get it to the roof.
As you can see, the total duct length is about 6 feet or so, so it's possible I am overthinking this and it would be fine as-is. The fan is at an acceptable noise level and does a good job of ventilating (it's "oversized" for the room it's in), so I'm mostly concerned about potentially burning out the motor by straining it too much.
P.S: I know it's recommended to insulate exhaust fan ductwork. I don't think that's common practice where I live because it never gets below freezing or cold enough for that to be a concern.