Rigid or Flexible bathroom exhaust duct

Question

In my 2nd floor condominium, I need to replace bathroom ceiling and exhaust fan. Old ceiling has been removed. My contractor is going to install new ceiling. I want to replace old exhaust fan and duct work too.

I want to replace old flex plastic duct with rigid solid metal duct for smoother air flow. But I am stuck in this dilemma.

I am assuming that connecting fan with rigid duct will be easier if I install it before ceiling is in place, because once ceiling is placed, I won't be able to connect ( and seal the joint with tape) duct coming out of fan housing with rigid duct in ceiling. With some tilting even if I manage to connect both ducts, I won't be able to seal the inaccessible joint because of ceiling.

If you agree with my assumption, then it leads me to think that I should install it before new ceiling is in place, so I can connect both ducts and tape the joint. But then, my contractor has to make sure that the ceiling is installed at right level so that flanges of fan housing is flush against ceiling and the grill can be mounted flush to the ceiling. I don't have much confidence in my contractor and I don't want to end up with argument with him.

Is there an easy way to install fan after ceiling is installed and still use rigid duct work and be able to seal the joint?

I would also like to know if using rigid duct is good idea or not, if in future I need to replace the fan again, how easy it will be to push the rigid duct out of the way to remove old housing. With flex duct, you can easily push it out of the fan housing and remove it, but I can't see how it will be possible with solid duct.

Answer 1

Rigid duct is absolutely better--it's much less likely to accumulate lint and clog or create a fire hazard. However, I wouldn't be concerned about using a short length of semi-rigid (metal) duct at the fan end to allow for some install flexibility.

You could also make all the connections and rely on some pivot at the opposite end of the initial straight run to accommodate height variation. I can't imaging your builder not being able to work with that.

Answer 2

Rigid duct is a good idea. You get much air flow using it. Installing the fan before the ceiling isn't that hard. You have the existing joists already there so you mount the fan housing 3/8" or 1/2", depending on the size of the drywall being used, below the joists. When the drywall is installed it should be even with the housing.

The other solution is to use rigid for the main run and then install about two feet of the flexible duct from the fan to your rigid. That way, you can do the duct work ahead of time and then have the flexible end hanging down ready for the installation of the fan. Replacement of the fan in the future would be easier too.