Bathroom Exhaust Fan Duct Length

[joesxm3]

I am getting my roof replaced and probably will also be replacing the skylights.

My old bathroom fan is on its last legs so I will replace that as well. There is no attic access, but it is right between the two skylights, so I figure they can replace the sheet of plywood and gain access to that area.

I figure that I should replace the duct with a brand new properly insulated run of duct tube.

The current tube runs for quite a length, at least 6 feet, maybe a bit more and comes from the inaccessible area of the attic to the accessible area and out through the root.

I had assumed that a short run would be better and was planning to ask that they install a very short duct. However, reading reviews of fans on Amazon, one comment was made that having the short duct resulted in more noise and in wind coming back into the fan more, or making more noise. The reviewer said that he also had a fan with a five foot duct and was much happier.

So, my question is whether the short duct is an improvement or should I just duplicate the current longer duct run, but replace with nicer new duct tubing and maybe a nicer exhaust port on the roof?

 

[ponyboy]

I would use the appropriate amount of duct work needed to exhaust the steam.

If duct is already in place, I would use that...unless its simple to get a new one in place. If not, let it be. Its just a flexible hose that air passes through, the house isnt going to fall down if you cant put a new one in place. Dont over think it.

 

[ERD50]

What makes you say 6' of duct is "quite a length"? Doesn't sound like anywhere too long of a run to me, I'd say it's shorter than many, and those have no problems.

Insulated could be a good thing.

-ERD50

 

[Qs Laptop]

So, my question is whether the short duct is an improvement or should I just duplicate the current longer duct run, but replace with nicer new duct tubing and maybe a nicer exhaust port on the roof?

Since you're going to replace that plywood during the skylight install I'd be inclined to replace the bathroom duct and roof vent as well. Just having insulated ductwork would be enough of a reason for me to replace. Exactly what kind of noise is being reported with a shorter duct run? Were these noisy ducts insulated ducts? If it's wind noise, do you have high winds in your area? Is that area of the roof on the side of prevailing winds? Is it the noise being caused by the flapper valve inside the vent?

Whatever you decide to do, make sure you get a new fan that is quiet. Most fans have a dB rating telling you how loud they get.

If you decide to stick with the current ductwork one trick I've learned after redoing a couple of bathrooms in the past 2 years is that only the motor part of the bathroom fan actually "needs" replacing. This is likely a $15 to $20 part. Add a new, fresh looking cover for $5 or so and you are set.